[PATCH][middle-end][i386][version 6]Add -fzero-call-used-regs=[skip|used-gpr-arg|used-arg|all-gpr-arg|all-arg|used-gpr|all-gpr|used|all]

[Qing Zhao via Gcc-patches]

Hi, 

This is the 6th version of the implementation of patch -fzero-call-used-regs.

The X86 part is exactly the same as 5th version. (And it has been approved by 
Uros already).

The major change compared to the previous version (5th version) are:

1. Documentation change per Richard’s suggestion;
2. Other minor changes. 
3.  general testing cases update per Richard’s suggestion;


I have tested this new GCC on both x86 and arm64, no regression. 

Richard, Please let me know whether it’s ready for stage 1 gcc11?

thanks.

Qing

In order to make it easier for you to review the change, I list the changes I 
added compared to the 5th version first, and then the whole patch followed.

*****The patch compared to 5th version:

From 3545cc92b327e11af0dde832a60161da92cc4262 Mon Sep 17 00:00:00 2001
From: qing zhao <qinz...@gcc.gnu.org>
Date: Thu, 29 Oct 2020 18:40:27 +0100
Subject: [PATCH] fix all issues raised by Richard on 10/29

---
 gcc/c-family/c-attribs.c                           |  8 +-
 gcc/common.opt                                     |  2 +-
 gcc/doc/extend.texi                                | 72 ++++++++---------
 gcc/doc/invoke.texi                                |  6 +-
 gcc/emit-rtl.h                                     |  3 -
 gcc/flag-types.h                                   |  2 +-
 gcc/function.c                                     | 56 +++++++-------
 gcc/opts.c                                         |  2 +-
 gcc/targhooks.c                                    |  2 +-
 gcc/testsuite/c-c++-common/zero-scratch-regs-11.c  | 90 +---------------------
 gcc/testsuite/c-c++-common/zero-scratch-regs-2.c   | 13 +---
 gcc/testsuite/c-c++-common/zero-scratch-regs-3.c   | 13 +---
 gcc/testsuite/c-c++-common/zero-scratch-regs-4.c   | 13 +---
 gcc/testsuite/c-c++-common/zero-scratch-regs-5.c   | 13 +---
 gcc/testsuite/c-c++-common/zero-scratch-regs-6.c   | 13 +---
 gcc/testsuite/c-c++-common/zero-scratch-regs-7.c   | 13 +---
 gcc/testsuite/c-c++-common/zero-scratch-regs-8.c   | 13 +---
 gcc/testsuite/c-c++-common/zero-scratch-regs-9.c   | 13 +---
 .../c-c++-common/zero-scratch-regs-attr-usages.c   | 10 ++-
 19 files changed, 90 insertions(+), 267 deletions(-)

diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
index 1b05e8c..8da1dc7 100644
--- a/gcc/c-family/c-attribs.c
+++ b/gcc/c-family/c-attribs.c
@@ -4979,13 +4979,15 @@ handle_zero_call_used_regs_attribute (tree *node, tree 
name, tree args,
       error_at (DECL_SOURCE_LOCATION (decl),
                "%qE attribute applies only to functions", name);
       *no_add_attrs = true;
+      return NULL_TREE;
     }
 
   if (TREE_CODE (id) != STRING_CST)
     {
       error_at (DECL_SOURCE_LOCATION (decl),
-               "attribute %qE arguments not a string", name);
+               "%qE argument not a string", name);
       *no_add_attrs = true;
+      return NULL_TREE;
     }
 
   bool found = false;
@@ -5000,8 +5002,8 @@ handle_zero_call_used_regs_attribute (tree *node, tree 
name, tree args,
   if (!found)
     {
       error_at (DECL_SOURCE_LOCATION (decl),
-               "unrecognized zero_call_used_regs attribute: %qs",
-               TREE_STRING_POINTER (id));
+               "unrecognized %qE attribute argument %qs",
+               name, TREE_STRING_POINTER (id));
       *no_add_attrs = true;
     }
 
diff --git a/gcc/common.opt b/gcc/common.opt
index 4a13f32..d716ea1 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -228,7 +228,7 @@ unsigned int flag_sanitize_coverage
 Variable
 bool dump_base_name_prefixed = false
 
-; What subset of registers should be zeroed
+; What subset of registers should be zeroed on function return
 Variable
 unsigned int flag_zero_call_used_regs
 
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index b011c17..25b3909 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -3996,22 +3996,19 @@ with a named @code{target} must be @code{static}.
 @cindex @code{zero_call_used_regs} function attribute
 
 The @code{zero_call_used_regs} attribute causes the compiler to zero
-a subset of all call-used registers at function return according to
-@var{choice}.
-This is used to increase the program security by either mitigating
-Return-Oriented Programming (ROP) or preventing information leak
+a subset of all call-used registers@footnote{A ``call-used'' register
+is a register whose contents can be changed by a function call;
+therefore, a caller cannot assume that the register has the same contents
+on return from the function as it had before calling the function.  Such
+registers are also called ``call-clobbered'', ``caller-saved'', or
+``volatile''.} at function return.
+This is used to increase program security by either mitigating
+Return-Oriented Programming (ROP) attacks or preventing information leakage
 through registers.
 
-A ``call-used'' register is a register whose contents can be changed by
-a function call; therefore, a caller cannot assume that the register has
-the same contents on return from the function as it had before calling
-the function.  Such registers are also called ``call-clobbered'',
-``caller-saved'', or ``volatile''.
-
 In order to satisfy users with different security needs and control the
-run-time overhead at the same time, GCC provides a flexible way to choose
-the subset of the call-used registers to be zeroed.
-
+run-time overhead at the same time, @var{choice} parameter provides a
+flexible way to choose the subset of the call-used registers to be zeroed.
 The three basic values of @var{choice} are:
 
 @itemize @bullet
@@ -4046,42 +4043,41 @@ together, they must appear in the order above.
 
 The full list of @var{choice}s is therefore:
 
-@itemize @bullet
-@item
-@samp{skip} doesn't zero any call-used register.
+@table @code
+@item skip
+doesn't zero any call-used register.
 
-@item
-@samp{used} only zeros call-used registers that are used in the function.
+@item used
+only zeros call-used registers that are used in the function.
 
-@item
-@samp{all} zeros all call-used registers.
+@item used-gpr
+only zeros call-used general purpose registers that are used in the function.
 
-@item
-@samp{used-arg} only zeros used call-used registers that pass arguments.
+@item used-arg
+only zeros call-used registers that are used in the function and pass 
arguments.
 
-@item
-@samp{used-gpr} only zeros used call-used general purpose registers.
+@item used-gpr-arg
+only zeros call-used general purpose registers that are used in the function
+and pass arguments.
 
-@item
-@samp{used-gpr-arg} only zeros used call-used general purpose registers that
-pass arguments.
+@item all
+zeros all call-used registers.
 
-@item
-@samp{all-gpr-arg} zeros all call-used general purpose registers that pass
-arguments.
+@item all-gpr
+zeros all call-used general purpose registers.
 
-@item
-@samp{all-arg} zeros all call-used registers that pass arguments.
+@item all-arg
+zeros all call-used registers that pass arguments.
 
-@item
-@samp{all-gpr} zeros all call-used general purpose registers.
-@end itemize
+@item all-gpr-arg
+zeros all call-used general purpose registers that pass
+arguments.
+@end table
 
-Among this list, @samp{used-gpr-arg}, @samp{used-arg}, @samp{all-gpr-arg},
-and @samp{all-arg} are mainly used for ROP mitigation.
+Of this list, @samp{used-arg}, @samp{used-gpr-arg}, @samp{all-arg},
+and @samp{all-gpr-arg} are mainly used for ROP mitigation.
 
 The default for the attribute is controlled by @option{-fzero-call-used-regs}.
-
 @end table
 
 @c This is the end of the target-independent attribute table
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index c9e3128..23834a2 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -12552,9 +12552,9 @@ Not all targets support this option.
 
 @item -fzero-call-used-regs=@var{choice}
 @opindex fzero-call-used-regs
-Zero call-used registers at function return to increase the program
-security by either mitigating Return-Oriented Programming (ROP) or
-preventing information leak through registers.
+Zero call-used registers at function return to increase program
+security by either mitigating Return-Oriented Programming (ROP)
+attacks or preventing information leakage through registers.
 
 The possible values of @var{choice} are the same as for the
 @code{zero_call_used_regs} attribute (@pxref{Function Attributes}).
diff --git a/gcc/emit-rtl.h b/gcc/emit-rtl.h
index d7bdb66..4658c4a 100644
--- a/gcc/emit-rtl.h
+++ b/gcc/emit-rtl.h
@@ -173,9 +173,6 @@ struct GTY(()) rtl_data {
         local stack.  */
   unsigned int stack_alignment_estimated;
 
-  /* How to zero call-used regsiters for this routine.  */
-  unsigned int zero_call_used_regs;
-
   /* How many NOP insns to place at each function entry by default.  */
   unsigned short patch_area_size;
 
diff --git a/gcc/flag-types.h b/gcc/flag-types.h
index 8807635..51c7e5f 100644
--- a/gcc/flag-types.h
+++ b/gcc/flag-types.h
@@ -288,7 +288,7 @@ enum sanitize_code {
 };
 
 /* Different settings for zeroing subset of registers.  */
-namespace  zero_regs_code {
+namespace zero_regs_flag {
   const unsigned int UNSET = 0;
   const unsigned int SKIP = 1UL << 0;
   const unsigned int ONLY_USED = 1UL << 1;
diff --git a/gcc/function.c b/gcc/function.c
index 77f0b5d..76a5037 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -5817,15 +5817,15 @@ make_prologue_seq (void)
   return seq;
 }
 
-/* Emit a sequence of insns to zero the call-used registers before RET.  */
-using namespace zero_regs_code;
+/* Emit a sequence of insns to zero the call-used registers before RET
+   according to ZERO_REGS_TYPE.  */
 
 static void
-gen_call_used_regs_seq (rtx_insn *ret)
+gen_call_used_regs_seq (rtx_insn *ret, unsigned int zero_regs_type)
 {
-  bool gpr_only = true;
-  bool used_only = true;
-  bool arg_only = true;
+  bool only_gpr = true;
+  bool only_used = true;
+  bool only_arg = true;
 
   /* No need to zero call-used-regs in main ().  */
   if (MAIN_NAME_P (DECL_NAME (current_function_decl)))
@@ -5836,23 +5836,25 @@ gen_call_used_regs_seq (rtx_insn *ret)
   if (crtl->calls_eh_return)
     return;
 
-  /* If gpr_only is true, only zero call-used registers that are
-     general-purpose registers; if used_only is true, only zero
+  /* If only_gpr is true, only zero call-used registers that are
+     general-purpose registers; if only_used is true, only zero
      call-used registers that are used in the current function;
-     if arg_only is true, only zero call-used registers that pass
+     if only_arg is true, only zero call-used registers that pass
      parameters defined by the flatform's calling conversion.  */
 
-  gpr_only = crtl->zero_call_used_regs & ONLY_GPR;
-  used_only = crtl->zero_call_used_regs & ONLY_USED;
-  arg_only = crtl->zero_call_used_regs & ONLY_ARG;
+  using namespace zero_regs_flag;
+
+  only_gpr = zero_regs_type & ONLY_GPR;
+  only_used = zero_regs_type & ONLY_USED;
+  only_arg = zero_regs_type & ONLY_ARG;
 
   /* For each of the hard registers, we should zero it if:
            1. it is a call-used register;
        and 2. it is not a fixed register;
        and 3. it is not live at the return of the routine;
-       and 4. it is general registor if gpr_only is true;
-       and 5. it is used in the routine if used_only is true;
-       and 6. it is a register that passes parameter if arg_only is true.  */
+       and 4. it is general registor if only_gpr is true;
+       and 5. it is used in the routine if only_used is true;
+       and 6. it is a register that passes parameter if only_arg is true.  */
 
   /* First, prepare the data flow information.  */
   basic_block bb = BLOCK_FOR_INSN (ret);
@@ -5871,12 +5873,12 @@ gen_call_used_regs_seq (rtx_insn *ret)
        continue;
       if (REGNO_REG_SET_P (live_out, regno))
        continue;
-      if (gpr_only
+      if (only_gpr
          && !TEST_HARD_REG_BIT (reg_class_contents[GENERAL_REGS], regno))
        continue;
-      if (used_only && !df_regs_ever_live_p (regno))
+      if (only_used && !df_regs_ever_live_p (regno))
        continue;
-      if (arg_only && !FUNCTION_ARG_REGNO_P (regno))
+      if (only_arg && !FUNCTION_ARG_REGNO_P (regno))
        continue;
 
       /* Now this is a register that we might want to zero.  */
@@ -6614,14 +6616,14 @@ public:
 unsigned int
 pass_zero_call_used_regs::execute (function *fun)
 {
+  using namespace zero_regs_flag;
   unsigned int zero_regs_type = UNSET;
-  unsigned int attr_zero_regs_type = UNSET;
 
-  tree attr_zero_regs
-       = lookup_attribute ("zero_call_used_regs",
-                           DECL_ATTRIBUTES (fun->decl));
+  tree attr_zero_regs = lookup_attribute ("zero_call_used_regs",
+                                         DECL_ATTRIBUTES (fun->decl));
 
-  /* Get the type of zero_call_used_regs from function attribute.  */
+  /* Get the type of zero_call_used_regs from function attribute.
+     We have filtered out invalid attribute values already at this point.  */
   if (attr_zero_regs)
     {
       /* The TREE_VALUE of an attribute is a TREE_LIST whose TREE_VALUE
@@ -6635,18 +6637,14 @@ pass_zero_call_used_regs::execute (function *fun)
        if (strcmp (TREE_STRING_POINTER (attr_zero_regs),
                     zero_call_used_regs_opts[i].name) == 0)
          {
-           attr_zero_regs_type = zero_call_used_regs_opts[i].flag;
+           zero_regs_type = zero_call_used_regs_opts[i].flag;
            break;
          }
     }
 
-  zero_regs_type = attr_zero_regs_type;
-
   if (!zero_regs_type)
     zero_regs_type = flag_zero_call_used_regs;
 
-  crtl->zero_call_used_regs = zero_regs_type;
-
   /* No need to zero call-used-regs when no user request is present.  */
   if (!(zero_regs_type & ENABLED))
     return 0;
@@ -6664,7 +6662,7 @@ pass_zero_call_used_regs::execute (function *fun)
     {
       rtx_insn *insn = BB_END (e->src);
       if (JUMP_P (insn) && ANY_RETURN_P (JUMP_LABEL (insn)))
-       gen_call_used_regs_seq (insn);
+       gen_call_used_regs_seq (insn, zero_regs_type);
     }
 
   return 0;
diff --git a/gcc/opts.c b/gcc/opts.c
index 7cd097a..8c439e4 100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -1776,7 +1776,7 @@ const struct sanitizer_opts_s coverage_sanitizer_opts[] =
   { NULL, 0U, 0UL, false }
 };
 
-using namespace zero_regs_code;
+using namespace zero_regs_flag;
 /* -fzero-call-used-regs= suboptions.  */
 const struct zero_call_used_regs_opts_s zero_call_used_regs_opts[] =
 {
diff --git a/gcc/targhooks.c b/gcc/targhooks.c
index 88eef00..4e4d100 100644
--- a/gcc/targhooks.c
+++ b/gcc/targhooks.c
@@ -1011,7 +1011,7 @@ default_zero_call_used_regs (HARD_REG_SET 
need_zeroed_hardregs)
              {
                issued_error = true;
                sorry ("%qs not supported on this target",
-                       "fzero-call-used_regs");
+                       "-fzero-call-used_regs");
              }
            delete_insns_since (last_insn);
          }
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-11.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-11.c
index 6756f57..7721e39 100644
--- a/gcc/testsuite/c-c++-common/zero-scratch-regs-11.c
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-11.c
@@ -1,92 +1,4 @@
 /* { dg-do run } */
 /* { dg-options "-O2 -fzero-call-used-regs=all" } */
 
-#include <assert.h>
-int result = 0;
-
-int 
-__attribute__((noipa))
-__attribute__ ((zero_call_used_regs("skip")))
-foo1 (int x)
-{
-  return (x + 1);
-}
-
-int 
-__attribute__((noipa))
-__attribute__ ((zero_call_used_regs("used-gpr-arg")))
-foo2 (int x)
-{
-  return (x + 2);
-}
-
-int 
-__attribute__((noipa))
-__attribute__ ((zero_call_used_regs("used-gpr")))
-foo3 (int x)
-{
-  return (x + 3);
-}
-
-int 
-__attribute__((noipa))
-__attribute__ ((zero_call_used_regs("used-arg")))
-foo4 (int x)
-{
-  return (x + 4);
-}
-
-int 
-__attribute__((noipa))
-__attribute__ ((zero_call_used_regs("used")))
-foo5 (int x)
-{
-  return (x + 5);
-}
-
-int 
-__attribute__((noipa))
-__attribute__ ((zero_call_used_regs("all-gpr-arg")))
-foo6 (int x)
-{
-  return (x + 6);
-}
-
-int 
-__attribute__((noipa))
-__attribute__ ((zero_call_used_regs("all-gpr")))
-foo7 (int x)
-{
-  return (x + 7);
-}
-
-int 
-__attribute__((noipa))
-__attribute__ ((zero_call_used_regs("all-arg")))
-foo8 (int x)
-{
-  return (x + 8);
-}
-
-int 
-__attribute__((noipa))
-__attribute__ ((zero_call_used_regs("all")))
-foo9 (int x)
-{
-  return (x + 9);
-}
-
-int main()
-{
-  result = foo1 (1);
-  result += foo2 (1);
-  result += foo3 (1);
-  result += foo4 (1);
-  result += foo5 (1);
-  result += foo6 (1);
-  result += foo7 (1);
-  result += foo8 (1);
-  result += foo9 (1);
-  assert (result == 54);
-  return 0;
-}
+#include "zero-scratch-regs-10.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-2.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-2.c
index 73c3794..25891ac 100644
--- a/gcc/testsuite/c-c++-common/zero-scratch-regs-2.c
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-2.c
@@ -1,15 +1,4 @@
 /* { dg-do run } */
 /* { dg-options "-O2 -fzero-call-used-regs=used-gpr-arg" } */
 
-volatile int result = 0;
-int 
-__attribute__((noipa))
-foo (int x)
-{
-  return x;
-}
-int main()
-{
-  result = foo (2);
-  return 0;
-}
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-3.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-3.c
index d3db757..7c3d286 100644
--- a/gcc/testsuite/c-c++-common/zero-scratch-regs-3.c
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-3.c
@@ -1,15 +1,4 @@
 /* { dg-do run } */
 /* { dg-options "-O2 -fzero-call-used-regs=used-gpr" } */
 
-volatile int result = 0;
-int 
-__attribute__((noipa))
-foo (int x)
-{
-  return x;
-}
-int main()
-{
-  result = foo (2);
-  return 0;
-}
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-4.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-4.c
index 029aa79..ba28c06 100644
--- a/gcc/testsuite/c-c++-common/zero-scratch-regs-4.c
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-4.c
@@ -1,15 +1,4 @@
 /* { dg-do run } */
 /* { dg-options "-O2 -fzero-call-used-regs=used-arg" } */
 
-volatile int result = 0;
-int 
-__attribute__((noipa))
-foo (int x)
-{
-  return x;
-}
-int main()
-{
-  result = foo (2);
-  return 0;
-}
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-5.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-5.c
index 509ce20..26679a4 100644
--- a/gcc/testsuite/c-c++-common/zero-scratch-regs-5.c
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-5.c
@@ -1,15 +1,4 @@
 /* { dg-do run } */
 /* { dg-options "-O2 -fzero-call-used-regs=used" } */
 
-volatile int result = 0;
-int 
-__attribute__((noipa))
-foo (int x)
-{
-  return x;
-}
-int main()
-{
-  result = foo (2);
-  return 0;
-}
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-6.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-6.c
index 56d8063..80f5bbb 100644
--- a/gcc/testsuite/c-c++-common/zero-scratch-regs-6.c
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-6.c
@@ -1,15 +1,4 @@
 /* { dg-do run } */
 /* { dg-options "-O2 -fzero-call-used-regs=all-gpr-arg" } */
 
-volatile int result = 0;
-int 
-__attribute__((noipa))
-foo (int x)
-{
-  return x;
-}
-int main()
-{
-  result = foo (2);
-  return 0;
-}
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-7.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-7.c
index 40378ed..159f35c 100644
--- a/gcc/testsuite/c-c++-common/zero-scratch-regs-7.c
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-7.c
@@ -1,15 +1,4 @@
 /* { dg-do run } */
 /* { dg-options "-O2 -fzero-call-used-regs=all-gpr" } */
 
-volatile int result = 0;
-int 
-__attribute__((noipa))
-foo (int x)
-{
-  return x;
-}
-int main()
-{
-  result = foo (2);
-  return 0;
-}
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-8.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-8.c
index 7bdef95..c1faaf0 100644
--- a/gcc/testsuite/c-c++-common/zero-scratch-regs-8.c
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-8.c
@@ -1,15 +1,4 @@
 /* { dg-do run } */
 /* { dg-options "-O2 -fzero-call-used-regs=all-arg" } */
 
-volatile int result = 0;
-int 
-__attribute__((noipa))
-foo (int x)
-{
-  return x;
-}
-int main()
-{
-  result = foo (2);
-  return 0;
-}
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-9.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-9.c
index 032da1a..3f14bac 100644
--- a/gcc/testsuite/c-c++-common/zero-scratch-regs-9.c
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-9.c
@@ -1,15 +1,4 @@
 /* { dg-do run } */
 /* { dg-options "-O2 -fzero-call-used-regs=all" } */
 
-volatile int result = 0;
-int 
-__attribute__((noipa))
-foo (int x)
-{
-  return x;
-}
-int main()
-{
-  result = foo (2);
-  return 0;
-}
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-attr-usages.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-attr-usages.c
index c60e946..1e75795 100644
--- a/gcc/testsuite/c-c++-common/zero-scratch-regs-attr-usages.c
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-attr-usages.c
@@ -1,10 +1,16 @@
-/* { dg-do compile} */
+/* { dg-do compile } */
 /* { dg-options "-O2" } */
 
 int result __attribute__ ((zero_call_used_regs("all"))); /* { dg-error 
"attribute applies only to functions" } */
 int
 __attribute__ ((zero_call_used_regs("gpr-arg-all")))
-foo1 (int x) /* { dg-error "unrecognized zero_call_used_regs attribute" } */
+foo1 (int x) /* { dg-error "unrecognized 'zero_call_used_regs' attribute 
argument" } */
 {
   return (x + 1);
 }
+int
+__attribute__ ((zero_call_used_regs(1)))
+foo2 (int x) /* { dg-error "argument not a string" } */
+{
+  return (x + 2);
+}
-- 
1.8.3.1


******The whole patch:

From bc91029c821ed8c3aad2023375e2ab44b0f33166 Mon Sep 17 00:00:00 2001
From: qing zhao <qing.z...@oracle.com>
Date: Thu, 1 Oct 2020 00:27:57 +0000
Subject: [PATCH] The 6th version of -fzero-call-used-regs

We will provide a new feature into GCC:

Add -fzero-call-used-regs=[skip|used-gpr-arg|used-arg|all-gpr-arg
                           |all-arg|used-gpr|all-gpr|used|all]
command-line option
and
zero_call_used_regs("skip|used-gpr-arg|used-arg|all-gpr-arg
                     |all-arg|used-gpr|all-gpr|used|all")
function attribues:

1. -fzero-call-used-regs=skip and zero_call_used_regs("skip")
2. -fzero-call-used-regs=used-gpr-arg and zero_call_used_regs("used-gpr-arg")
3. -fzero-call-used-regs=used-arg and zero_call_used_regs("used-arg")
4. -fzero-call-used-regs=all-gpr-arg and zero_call_used_regs("all-gpr-arg")
5. -fzero-call-used-regs=all-arg and zero_call_used_regs("all-arg")
6. -fzero-call-used-regs=used-gpr and zero_call_used_regs("used-gpr")
7. -fzero-call-used-regs=all-gpr and zero_call_used_regs("all-gpr")
8. -fzero-call-used-regs=used and zero_call_used_regs("used")
9. -fzero-call-used-regs=all and zero_call_used_regs("all")
---
 gcc/c-family/c-attribs.c                           |  51 ++++
 gcc/common.opt                                     |   8 +
 gcc/config/i386/i386.c                             | 294 +++++++++++++++++++++
 gcc/df-scan.c                                      |  12 +-
 gcc/df.h                                           |   1 +
 gcc/doc/extend.texi                                |  86 ++++++
 gcc/doc/invoke.texi                                |  15 +-
 gcc/doc/tm.texi                                    |  12 +
 gcc/doc/tm.texi.in                                 |   2 +
 gcc/emit-rtl.h                                     |   3 +
 gcc/flag-types.h                                   |  22 ++
 gcc/function.c                                     | 190 ++++++++++++-
 gcc/optabs.c                                       |  42 +++
 gcc/optabs.h                                       |   2 +
 gcc/opts.c                                         |  45 ++++
 gcc/opts.h                                         |   6 +
 gcc/passes.def                                     |   1 +
 gcc/recog.c                                        |  18 +-
 gcc/recog.h                                        |   1 +
 gcc/resource.c                                     |   2 +-
 gcc/target.def                                     |  15 ++
 gcc/targhooks.c                                    |  32 +++
 gcc/targhooks.h                                    |   1 +
 gcc/testsuite/c-c++-common/zero-scratch-regs-1.c   |  15 ++
 gcc/testsuite/c-c++-common/zero-scratch-regs-10.c  |  92 +++++++
 gcc/testsuite/c-c++-common/zero-scratch-regs-11.c  |   4 +
 gcc/testsuite/c-c++-common/zero-scratch-regs-2.c   |   4 +
 gcc/testsuite/c-c++-common/zero-scratch-regs-3.c   |   4 +
 gcc/testsuite/c-c++-common/zero-scratch-regs-4.c   |   4 +
 gcc/testsuite/c-c++-common/zero-scratch-regs-5.c   |   4 +
 gcc/testsuite/c-c++-common/zero-scratch-regs-6.c   |   4 +
 gcc/testsuite/c-c++-common/zero-scratch-regs-7.c   |   4 +
 gcc/testsuite/c-c++-common/zero-scratch-regs-8.c   |   4 +
 gcc/testsuite/c-c++-common/zero-scratch-regs-9.c   |   4 +
 .../c-c++-common/zero-scratch-regs-attr-usages.c   |  16 ++
 .../gcc.target/i386/zero-scratch-regs-1.c          |  12 +
 .../gcc.target/i386/zero-scratch-regs-10.c         |  21 ++
 .../gcc.target/i386/zero-scratch-regs-11.c         |  39 +++
 .../gcc.target/i386/zero-scratch-regs-12.c         |  39 +++
 .../gcc.target/i386/zero-scratch-regs-13.c         |  21 ++
 .../gcc.target/i386/zero-scratch-regs-14.c         |  19 ++
 .../gcc.target/i386/zero-scratch-regs-15.c         |  14 +
 .../gcc.target/i386/zero-scratch-regs-16.c         |  14 +
 .../gcc.target/i386/zero-scratch-regs-17.c         |  13 +
 .../gcc.target/i386/zero-scratch-regs-18.c         |  13 +
 .../gcc.target/i386/zero-scratch-regs-19.c         |  12 +
 .../gcc.target/i386/zero-scratch-regs-2.c          |  19 ++
 .../gcc.target/i386/zero-scratch-regs-20.c         |  23 ++
 .../gcc.target/i386/zero-scratch-regs-21.c         |  14 +
 .../gcc.target/i386/zero-scratch-regs-22.c         |  21 ++
 .../gcc.target/i386/zero-scratch-regs-23.c         |  29 ++
 .../gcc.target/i386/zero-scratch-regs-24.c         |  10 +
 .../gcc.target/i386/zero-scratch-regs-25.c         |  10 +
 .../gcc.target/i386/zero-scratch-regs-26.c         |  23 ++
 .../gcc.target/i386/zero-scratch-regs-27.c         |  15 ++
 .../gcc.target/i386/zero-scratch-regs-28.c         |  16 ++
 .../gcc.target/i386/zero-scratch-regs-29.c         |  10 +
 .../gcc.target/i386/zero-scratch-regs-3.c          |  12 +
 .../gcc.target/i386/zero-scratch-regs-30.c         |  12 +
 .../gcc.target/i386/zero-scratch-regs-31.c         |  12 +
 .../gcc.target/i386/zero-scratch-regs-4.c          |  14 +
 .../gcc.target/i386/zero-scratch-regs-5.c          |  20 ++
 .../gcc.target/i386/zero-scratch-regs-6.c          |  14 +
 .../gcc.target/i386/zero-scratch-regs-7.c          |  13 +
 .../gcc.target/i386/zero-scratch-regs-8.c          |  19 ++
 .../gcc.target/i386/zero-scratch-regs-9.c          |  15 ++
 gcc/tree-pass.h                                    |   1 +
 67 files changed, 1552 insertions(+), 7 deletions(-)
 create mode 100644 gcc/testsuite/c-c++-common/zero-scratch-regs-1.c
 create mode 100644 gcc/testsuite/c-c++-common/zero-scratch-regs-10.c
 create mode 100644 gcc/testsuite/c-c++-common/zero-scratch-regs-11.c
 create mode 100644 gcc/testsuite/c-c++-common/zero-scratch-regs-2.c
 create mode 100644 gcc/testsuite/c-c++-common/zero-scratch-regs-3.c
 create mode 100644 gcc/testsuite/c-c++-common/zero-scratch-regs-4.c
 create mode 100644 gcc/testsuite/c-c++-common/zero-scratch-regs-5.c
 create mode 100644 gcc/testsuite/c-c++-common/zero-scratch-regs-6.c
 create mode 100644 gcc/testsuite/c-c++-common/zero-scratch-regs-7.c
 create mode 100644 gcc/testsuite/c-c++-common/zero-scratch-regs-8.c
 create mode 100644 gcc/testsuite/c-c++-common/zero-scratch-regs-9.c
 create mode 100644 gcc/testsuite/c-c++-common/zero-scratch-regs-attr-usages.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-1.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-10.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-11.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-12.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-13.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-14.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-15.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-16.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-17.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-18.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-19.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-2.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-20.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-21.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-22.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-23.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-24.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-25.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-26.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-27.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-28.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-29.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-3.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-30.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-31.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-4.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-5.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-6.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-7.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-8.c
 create mode 100644 gcc/testsuite/gcc.target/i386/zero-scratch-regs-9.c

diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
index c779d13..8da1dc7 100644
--- a/gcc/c-family/c-attribs.c
+++ b/gcc/c-family/c-attribs.c
@@ -138,6 +138,8 @@ static tree handle_target_clones_attribute (tree *, tree, 
tree, int, bool *);
 static tree handle_optimize_attribute (tree *, tree, tree, int, bool *);
 static tree ignore_attribute (tree *, tree, tree, int, bool *);
 static tree handle_no_split_stack_attribute (tree *, tree, tree, int, bool *);
+static tree handle_zero_call_used_regs_attribute (tree *, tree, tree, int,
+                                                 bool *);
 static tree handle_argspec_attribute (tree *, tree, tree, int, bool *);
 static tree handle_fnspec_attribute (tree *, tree, tree, int, bool *);
 static tree handle_warn_unused_attribute (tree *, tree, tree, int, bool *);
@@ -437,6 +439,8 @@ const struct attribute_spec c_common_attribute_table[] =
                              ignore_attribute, NULL },
   { "no_split_stack",        0, 0, true,  false, false, false,
                              handle_no_split_stack_attribute, NULL },
+  { "zero_call_used_regs",    1, 1, true, false, false, false,
+                             handle_zero_call_used_regs_attribute, NULL },
   /* For internal use only (marking of function arguments).
      The name contains a space to prevent its usage in source code.  */
   { "arg spec",                      1, -1, true, false, false, false,
@@ -4959,6 +4963,53 @@ handle_no_split_stack_attribute (tree *node, tree name,
   return NULL_TREE;
 }
 
+/* Handle a "zero_call_used_regs" attribute; arguments as in
+   struct attribute_spec.handler.  */
+
+static tree
+handle_zero_call_used_regs_attribute (tree *node, tree name, tree args,
+                                     int ARG_UNUSED (flags),
+                                     bool *no_add_attrs)
+{
+  tree decl = *node;
+  tree id = TREE_VALUE (args);
+
+  if (TREE_CODE (decl) != FUNCTION_DECL)
+    {
+      error_at (DECL_SOURCE_LOCATION (decl),
+               "%qE attribute applies only to functions", name);
+      *no_add_attrs = true;
+      return NULL_TREE;
+    }
+
+  if (TREE_CODE (id) != STRING_CST)
+    {
+      error_at (DECL_SOURCE_LOCATION (decl),
+               "%qE argument not a string", name);
+      *no_add_attrs = true;
+      return NULL_TREE;
+    }
+
+  bool found = false;
+  for (unsigned int i = 0; zero_call_used_regs_opts[i].name != NULL; ++i)
+    if (strcmp (TREE_STRING_POINTER (id),
+               zero_call_used_regs_opts[i].name) == 0)
+      {
+       found = true;
+       break;
+      }
+
+  if (!found)
+    {
+      error_at (DECL_SOURCE_LOCATION (decl),
+               "unrecognized %qE attribute argument %qs",
+               name, TREE_STRING_POINTER (id));
+      *no_add_attrs = true;
+    }
+
+  return NULL_TREE;
+}
+
 /* Handle a "returns_nonnull" attribute; arguments as in
    struct attribute_spec.handler.  */
 
diff --git a/gcc/common.opt b/gcc/common.opt
index 292c2de..d716ea1 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -228,6 +228,10 @@ unsigned int flag_sanitize_coverage
 Variable
 bool dump_base_name_prefixed = false
 
+; What subset of registers should be zeroed on function return
+Variable
+unsigned int flag_zero_call_used_regs
+
 ###
 Driver
 
@@ -3111,6 +3115,10 @@ fzero-initialized-in-bss
 Common Report Var(flag_zero_initialized_in_bss) Init(1)
 Put zero initialized data in the bss section.
 
+fzero-call-used-regs=
+Common Report RejectNegative Joined
+Clear call-used registers upon function return.
+
 g
 Common Driver RejectNegative JoinedOrMissing
 Generate debug information in default format.
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index f684954..4360595 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -3551,6 +3551,297 @@ ix86_function_value_regno_p (const unsigned int regno)
   return false;
 }
 
+/* Check whether the register REGNO should be zeroed on X86.
+   When ALL_SSE_ZEROED is true, all SSE registers have been zeroed
+   together, no need to zero it again.
+   When NEED_ZERO_MMX is true, MMX registers should be cleared.  */
+
+static bool
+zero_call_used_regno_p (const unsigned int regno,
+                       bool all_sse_zeroed,
+                       bool need_zero_mmx)
+{
+  return GENERAL_REGNO_P (regno)
+        || (!all_sse_zeroed && SSE_REGNO_P (regno))
+        || MASK_REGNO_P (regno)
+        || (need_zero_mmx && MMX_REGNO_P (regno));
+}
+
+/* Return the machine_mode that is used to zero register REGNO.  */
+
+static machine_mode
+zero_call_used_regno_mode (const unsigned int regno)
+{
+  /* NB: We only need to zero the lower 32 bits for integer registers
+     and the lower 128 bits for vector registers since destination are
+     zero-extended to the full register width.  */
+  if (GENERAL_REGNO_P (regno))
+    return SImode;
+  else if (SSE_REGNO_P (regno))
+    return V4SFmode;
+  else if (MASK_REGNO_P (regno))
+    return HImode;
+  else if (MMX_REGNO_P (regno))
+    return V4HImode;
+  else
+    gcc_unreachable ();
+}
+
+/* Generate a rtx to zero all vector registers together if possible,
+   otherwise, return NULL.  */
+
+static rtx
+zero_all_vector_registers (HARD_REG_SET need_zeroed_hardregs)
+{
+  if (!TARGET_AVX)
+    return NULL;
+
+  for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
+    if ((IN_RANGE (regno, FIRST_SSE_REG, LAST_SSE_REG)
+        || (TARGET_64BIT
+            && (REX_SSE_REGNO_P (regno)
+                || (TARGET_AVX512F && EXT_REX_SSE_REGNO_P (regno)))))
+       && !TEST_HARD_REG_BIT (need_zeroed_hardregs, regno))
+      return NULL;
+
+  return gen_avx_vzeroall ();
+}
+
+/* Generate insns to zero all st registers together.
+   Return true when zeroing instructions are generated.
+   Assume the number of st registers that are zeroed is num_of_st,
+   we will emit the following sequence to zero them together:
+                 fldz;         \
+                 fldz;         \
+                 ...
+                 fldz;         \
+                 fstp %%st(0); \
+                 fstp %%st(0); \
+                 ...
+                 fstp %%st(0);
+   i.e., num_of_st fldz followed by num_of_st fstp to clear the stack
+   mark stack slots empty.
+
+   How to compute the num_of_st:
+   There is no direct mapping from stack registers to hard register
+   numbers.  If one stack register needs to be cleared, we don't know
+   where in the stack the value remains.  So, if any stack register
+   needs to be cleared, the whole stack should be cleared.  However,
+   x87 stack registers that hold the return value should be excluded.
+   x87 returns in the top (two for complex values) register, so
+   num_of_st should be 7/6 when x87 returns, otherwise it will be 8.  */
+
+
+static bool
+zero_all_st_registers (HARD_REG_SET need_zeroed_hardregs)
+{
+  unsigned int num_of_st = 0;
+  for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
+    if ((STACK_REGNO_P (regno) || MMX_REGNO_P (regno))
+       && TEST_HARD_REG_BIT (need_zeroed_hardregs, regno))
+      {
+       num_of_st++;
+       break;
+      }
+
+  if (num_of_st == 0)
+    return false;
+
+  bool return_with_x87 = false;
+  return_with_x87 = (crtl->return_rtx
+                    && (STACK_REG_P (crtl->return_rtx)));
+
+  bool complex_return = false;
+  complex_return = (crtl->return_rtx
+                   && COMPLEX_MODE_P (GET_MODE (crtl->return_rtx)));
+
+  if (return_with_x87)
+    if (complex_return)
+      num_of_st = 6;
+    else
+      num_of_st = 7;
+  else
+    num_of_st = 8;
+
+  rtx st_reg = gen_rtx_REG (XFmode, FIRST_STACK_REG);
+  for (unsigned int i = 0; i < num_of_st; i++)
+    emit_insn (gen_rtx_SET (st_reg, CONST0_RTX (XFmode)));
+
+  for (unsigned int i = 0; i < num_of_st; i++)
+    {
+      rtx insn;
+      insn = emit_insn (gen_rtx_SET (st_reg, st_reg));
+      add_reg_note (insn, REG_DEAD, st_reg);
+    }
+  return true;
+}
+
+
+/* When the routine exit in MMX mode, if any ST register needs
+   to be zeroed, we should clear all MMX registers except the
+   RET_MMX_REGNO that holds the return value.  */
+static bool
+zero_all_mm_registers (HARD_REG_SET need_zeroed_hardregs,
+                      unsigned int ret_mmx_regno)
+{
+  bool need_zero_all_mm = false;
+  for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
+    if (STACK_REGNO_P (regno)
+       && TEST_HARD_REG_BIT (need_zeroed_hardregs, regno))
+      {
+       need_zero_all_mm = true;
+       break;
+      }
+
+  if (!need_zero_all_mm)
+    return false;
+
+  rtx zero_mmx = NULL_RTX;
+  machine_mode mode = V4HImode;
+  for (unsigned int regno = FIRST_MMX_REG; regno <= LAST_MMX_REG; regno++)
+    if (regno != ret_mmx_regno)
+      {
+       rtx reg = gen_rtx_REG (mode, regno);
+       if (zero_mmx == NULL_RTX)
+         {
+           zero_mmx = reg;
+           emit_insn (gen_rtx_SET (reg, CONST0_RTX (mode)));
+         }
+       else
+         emit_move_insn (reg, zero_mmx);
+      }
+  return true;
+}
+
+/* TARGET_ZERO_CALL_USED_REGS.  */
+/* Generate a sequence of instructions that zero registers specified by
+   NEED_ZEROED_HARDREGS.  Return the ZEROED_HARDREGS that are actually
+   zeroed.  */
+static HARD_REG_SET
+ix86_zero_call_used_regs (HARD_REG_SET need_zeroed_hardregs)
+{
+  HARD_REG_SET zeroed_hardregs;
+  bool all_sse_zeroed = false;
+  bool all_st_zeroed = false;
+  bool all_mm_zeroed = false;
+
+  CLEAR_HARD_REG_SET (zeroed_hardregs);
+
+  /* first, let's see whether we can zero all vector registers together.  */
+  rtx zero_all_vec_insn = zero_all_vector_registers (need_zeroed_hardregs);
+  if (zero_all_vec_insn)
+    {
+      emit_insn (zero_all_vec_insn);
+      all_sse_zeroed = true;
+    }
+
+  /* mm/st registers are shared registers set, we should follow the following
+     rules to clear them:
+                       MMX exit mode         x87 exit mode
+       -------------|----------------------|---------------
+       uses x87 reg | clear all MMX        | clear all x87
+       uses MMX reg | clear individual MMX | clear all x87
+       x87 + MMX    | clear all MMX        | clear all x87
+
+     first, we should decide which mode (MMX mode or x87 mode) the function
+     exit with.  */
+
+  bool exit_with_mmx_mode = (crtl->return_rtx
+                            && (MMX_REG_P (crtl->return_rtx)));
+
+  if (!exit_with_mmx_mode)
+    /* x87 exit mode, we should zero all st registers together.  */
+    {
+      all_st_zeroed = zero_all_st_registers (need_zeroed_hardregs);
+      if (all_st_zeroed)
+       SET_HARD_REG_BIT (zeroed_hardregs, FIRST_STACK_REG);
+    }
+  else
+    /* MMX exit mode, check whether we can zero all mm registers.  */
+    {
+      unsigned int exit_mmx_regno = REGNO (crtl->return_rtx);
+      all_mm_zeroed = zero_all_mm_registers (need_zeroed_hardregs,
+                                            exit_mmx_regno);
+      if (all_mm_zeroed)
+       for (unsigned int regno = FIRST_MMX_REG; regno <= LAST_MMX_REG; regno++)
+         if (regno != exit_mmx_regno)
+           SET_HARD_REG_BIT (zeroed_hardregs, regno);
+    }
+
+  /* Now, generate instructions to zero all the other registers.  */
+
+  rtx zero_gpr = NULL_RTX;
+  rtx zero_vector = NULL_RTX;
+  rtx zero_mask = NULL_RTX;
+  rtx zero_mmx = NULL_RTX;
+
+  for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
+    {
+      if (!TEST_HARD_REG_BIT (need_zeroed_hardregs, regno))
+       continue;
+      if (!zero_call_used_regno_p (regno, all_sse_zeroed,
+                                  exit_with_mmx_mode && !all_mm_zeroed))
+       continue;
+
+      SET_HARD_REG_BIT (zeroed_hardregs, regno);
+
+      rtx reg, tmp, zero_rtx;
+      machine_mode mode = zero_call_used_regno_mode (regno);
+
+      reg = gen_rtx_REG (mode, regno);
+      zero_rtx = CONST0_RTX (mode);
+
+      if (mode == SImode)
+       if (zero_gpr == NULL_RTX)
+         {
+           zero_gpr = reg;
+           tmp = gen_rtx_SET (reg, zero_rtx);
+           if (!TARGET_USE_MOV0 || optimize_insn_for_size_p ())
+             {
+               rtx clob = gen_rtx_CLOBBER (VOIDmode,
+                                           gen_rtx_REG (CCmode,
+                                                        FLAGS_REG));
+               tmp = gen_rtx_PARALLEL (VOIDmode, gen_rtvec (2,
+                                                            tmp,
+                                                            clob));
+             }
+           emit_insn (tmp);
+         }
+       else
+         emit_move_insn (reg, zero_gpr);
+      else if (mode == V4SFmode)
+       if (zero_vector == NULL_RTX)
+         {
+           zero_vector = reg;
+           tmp = gen_rtx_SET (reg, zero_rtx);
+           emit_insn (tmp);
+         }
+       else
+         emit_move_insn (reg, zero_vector);
+      else if (mode == HImode)
+       if (zero_mask == NULL_RTX)
+         {
+           zero_mask = reg;
+           tmp = gen_rtx_SET (reg, zero_rtx);
+           emit_insn (tmp);
+         }
+       else
+         emit_move_insn (reg, zero_mask);
+      else if (mode == V4HImode)
+       if (zero_mmx == NULL_RTX)
+         {
+           zero_mmx = reg;
+           tmp = gen_rtx_SET (reg, zero_rtx);
+           emit_insn (tmp);
+         }
+       else
+         emit_move_insn (reg, zero_mmx);
+      else
+       gcc_unreachable ();
+    }
+  return zeroed_hardregs;
+}
+
 /* Define how to find the value returned by a function.
    VALTYPE is the data type of the value (as a tree).
    If the precise function being called is known, FUNC is its FUNCTION_DECL;
@@ -23229,6 +23520,9 @@ ix86_run_selftests (void)
 #undef TARGET_FUNCTION_VALUE_REGNO_P
 #define TARGET_FUNCTION_VALUE_REGNO_P ix86_function_value_regno_p
 
+#undef TARGET_ZERO_CALL_USED_REGS
+#define TARGET_ZERO_CALL_USED_REGS ix86_zero_call_used_regs
+
 #undef TARGET_PROMOTE_FUNCTION_MODE
 #define TARGET_PROMOTE_FUNCTION_MODE ix86_promote_function_mode
 
diff --git a/gcc/df-scan.c b/gcc/df-scan.c
index 93b060f..9e75c13 100644
--- a/gcc/df-scan.c
+++ b/gcc/df-scan.c
@@ -3614,6 +3614,14 @@ df_update_entry_block_defs (void)
 }
 
 
+/* Return true if REGNO is used by the epilogue.  */
+bool
+df_epilogue_uses_p (unsigned int regno)
+{
+  return (EPILOGUE_USES (regno)
+         || TEST_HARD_REG_BIT (crtl->must_be_zero_on_return, regno));
+}
+
 /* Set the bit for regs that are considered being used at the exit. */
 
 static void
@@ -3661,7 +3669,7 @@ df_get_exit_block_use_set (bitmap exit_block_uses)
      epilogue as being live at the end of the function since they
      may be referenced by our caller.  */
   for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
-    if (global_regs[i] || EPILOGUE_USES (i))
+    if (global_regs[i] || df_epilogue_uses_p (i))
       bitmap_set_bit (exit_block_uses, i);
 
   if (targetm.have_epilogue () && epilogue_completed)
@@ -3802,7 +3810,6 @@ df_hard_reg_init (void)
   initialized = true;
 }
 
-
 /* Recompute the parts of scanning that are based on regs_ever_live
    because something changed in that array.  */
 
@@ -3862,7 +3869,6 @@ df_regs_ever_live_p (unsigned int regno)
   return regs_ever_live[regno];
 }
 
-
 /* Set regs_ever_live[REGNO] to VALUE.  If this cause regs_ever_live
    to change, schedule that change for the next update.  */
 
diff --git a/gcc/df.h b/gcc/df.h
index 8b6ca8c..0f098d7 100644
--- a/gcc/df.h
+++ b/gcc/df.h
@@ -1085,6 +1085,7 @@ extern void df_update_entry_exit_and_calls (void);
 extern bool df_hard_reg_used_p (unsigned int);
 extern unsigned int df_hard_reg_used_count (unsigned int);
 extern bool df_regs_ever_live_p (unsigned int);
+extern bool df_epilogue_uses_p (unsigned int);
 extern void df_set_regs_ever_live (unsigned int, bool);
 extern void df_compute_regs_ever_live (bool);
 extern void df_scan_verify (void);
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index c9f7299..25b3909 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -3992,6 +3992,92 @@ performing a link with relocatable output (i.e.@: 
@code{ld -r}) on them.
 A declaration to which @code{weakref} is attached and that is associated
 with a named @code{target} must be @code{static}.
 
+@item zero_call_used_regs ("@var{choice}")
+@cindex @code{zero_call_used_regs} function attribute
+
+The @code{zero_call_used_regs} attribute causes the compiler to zero
+a subset of all call-used registers@footnote{A ``call-used'' register
+is a register whose contents can be changed by a function call;
+therefore, a caller cannot assume that the register has the same contents
+on return from the function as it had before calling the function.  Such
+registers are also called ``call-clobbered'', ``caller-saved'', or
+``volatile''.} at function return.
+This is used to increase program security by either mitigating
+Return-Oriented Programming (ROP) attacks or preventing information leakage
+through registers.
+
+In order to satisfy users with different security needs and control the
+run-time overhead at the same time, @var{choice} parameter provides a
+flexible way to choose the subset of the call-used registers to be zeroed.
+The three basic values of @var{choice} are:
+
+@itemize @bullet
+@item
+@samp{skip} doesn't zero any call-used registers.
+
+@item
+@samp{used} only zeros call-used registers that are used in the function.
+A ``used'' register is one whose content has been set or referenced in
+the function.
+
+@item
+@samp{all} zeros all call-used registers.
+@end itemize
+
+In addition to these three basic choices, it is possible to modify
+@samp{used} or @samp{all} as follows:
+
+@itemize @bullet
+@item
+Adding @samp{-gpr} restricts the zeroing to general-purpose registers.
+
+@item
+Adding @samp{-arg} restricts the zeroing to registers that can sometimes
+be used to pass function arguments.  This includes all argument registers
+defined by the platform's calling conversion, regardless of whether the
+function uses those registers for function arguments or not.
+@end itemize
+
+The modifiers can be used individually or together.  If they are used
+together, they must appear in the order above.
+
+The full list of @var{choice}s is therefore:
+
+@table @code
+@item skip
+doesn't zero any call-used register.
+
+@item used
+only zeros call-used registers that are used in the function.
+
+@item used-gpr
+only zeros call-used general purpose registers that are used in the function.
+
+@item used-arg
+only zeros call-used registers that are used in the function and pass 
arguments.
+
+@item used-gpr-arg
+only zeros call-used general purpose registers that are used in the function
+and pass arguments.
+
+@item all
+zeros all call-used registers.
+
+@item all-gpr
+zeros all call-used general purpose registers.
+
+@item all-arg
+zeros all call-used registers that pass arguments.
+
+@item all-gpr-arg
+zeros all call-used general purpose registers that pass
+arguments.
+@end table
+
+Of this list, @samp{used-arg}, @samp{used-gpr-arg}, @samp{all-arg},
+and @samp{all-gpr-arg} are mainly used for ROP mitigation.
+
+The default for the attribute is controlled by @option{-fzero-call-used-regs}.
 @end table
 
 @c This is the end of the target-independent attribute table
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index c049932..23834a2 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -550,7 +550,7 @@ Objective-C and Objective-C++ Dialects}.
 -funit-at-a-time  -funroll-all-loops  -funroll-loops @gol
 -funsafe-math-optimizations  -funswitch-loops @gol
 -fipa-ra  -fvariable-expansion-in-unroller  -fvect-cost-model  -fvpt @gol
--fweb  -fwhole-program  -fwpa  -fuse-linker-plugin @gol
+-fweb  -fwhole-program  -fwpa  -fuse-linker-plugin -fzero-call-used-regs @gol
 --param @var{name}=@var{value}
 -O  -O0  -O1  -O2  -O3  -Os  -Ofast  -Og}
 
@@ -12550,6 +12550,19 @@ int foo (void)
 
 Not all targets support this option.
 
+@item -fzero-call-used-regs=@var{choice}
+@opindex fzero-call-used-regs
+Zero call-used registers at function return to increase program
+security by either mitigating Return-Oriented Programming (ROP)
+attacks or preventing information leakage through registers.
+
+The possible values of @var{choice} are the same as for the
+@code{zero_call_used_regs} attribute (@pxref{Function Attributes}).
+The default is @samp{skip}.
+
+You can control this behavior for a specific function by using the function
+attribute @code{zero_call_used_regs} (@pxref{Function Attributes}).
+
 @item --param @var{name}=@var{value}
 @opindex param
 In some places, GCC uses various constants to control the amount of
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 97437e8..18f8ad9 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -12053,6 +12053,18 @@ argument list due to stack realignment.  Return 
@code{NULL} if no DRAP
 is needed.
 @end deftypefn
 
+@deftypefn {Target Hook} HARD_REG_SET TARGET_ZERO_CALL_USED_REGS (HARD_REG_SET 
@var{selected_regs})
+This target hook emits instructions to zero the subset of @var{selected_regs}
+that could conceivably contain values that are useful to an attacker.
+Return the set of registers that were actually cleared.
+
+The default implementation uses normal move instructions to zero
+all the registers in @var{selected_regs}.  Define this hook if the
+target has more efficient ways of zeroing certain registers,
+or if you believe that certain registers would never contain
+values that are useful to an attacker.
+@end deftypefn
+
 @deftypefn {Target Hook} bool TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS (void)
 When optimization is disabled, this hook indicates whether or not
 arguments should be allocated to stack slots.  Normally, GCC allocates
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 412e22c..a67dbea 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -8111,6 +8111,8 @@ and the associated definitions of those functions.
 
 @hook TARGET_GET_DRAP_RTX
 
+@hook TARGET_ZERO_CALL_USED_REGS
+
 @hook TARGET_ALLOCATE_STACK_SLOTS_FOR_ARGS
 
 @hook TARGET_CONST_ANCHOR
diff --git a/gcc/emit-rtl.h b/gcc/emit-rtl.h
index 92ad0dd6..4658c4a 100644
--- a/gcc/emit-rtl.h
+++ b/gcc/emit-rtl.h
@@ -310,6 +310,9 @@ struct GTY(()) rtl_data {
      sets them.  */
   HARD_REG_SET asm_clobbers;
 
+  /* All hard registers that need to be zeroed at the return of the routine.  
*/
+  HARD_REG_SET must_be_zero_on_return;
+
   /* The highest address seen during shorten_branches.  */
   int max_insn_address;
 };
diff --git a/gcc/flag-types.h b/gcc/flag-types.h
index 852ea76..51c7e5f 100644
--- a/gcc/flag-types.h
+++ b/gcc/flag-types.h
@@ -20,6 +20,8 @@ along with GCC; see the file COPYING3.  If not see
 #ifndef GCC_FLAG_TYPES_H
 #define GCC_FLAG_TYPES_H
 
+#if !defined(IN_LIBGCC2) && !defined(IN_TARGET_LIBS) && !defined(IN_RTS)
+
 enum debug_info_type
 {
   NO_DEBUG,        /* Write no debug info.  */
@@ -285,6 +287,24 @@ enum sanitize_code {
                                  | SANITIZE_BOUNDS_STRICT
 };
 
+/* Different settings for zeroing subset of registers.  */
+namespace zero_regs_flag {
+  const unsigned int UNSET = 0;
+  const unsigned int SKIP = 1UL << 0;
+  const unsigned int ONLY_USED = 1UL << 1;
+  const unsigned int ONLY_GPR = 1UL << 2;
+  const unsigned int ONLY_ARG = 1UL << 3;
+  const unsigned int ENABLED = 1UL << 4;
+  const unsigned int USED_GPR_ARG = ENABLED | ONLY_USED | ONLY_GPR | ONLY_ARG;
+  const unsigned int USED_GPR = ENABLED | ONLY_USED | ONLY_GPR;
+  const unsigned int USED_ARG = ENABLED | ONLY_USED | ONLY_ARG;
+  const unsigned int USED = ENABLED | ONLY_USED;
+  const unsigned int ALL_GPR_ARG = ENABLED | ONLY_GPR | ONLY_ARG;
+  const unsigned int ALL_GPR = ENABLED | ONLY_GPR;
+  const unsigned int ALL_ARG = ENABLED | ONLY_ARG;
+  const unsigned int ALL = ENABLED;
+}
+
 /* Settings of flag_incremental_link.  */
 enum incremental_link {
   INCREMENTAL_LINK_NONE,
@@ -382,4 +402,6 @@ enum parloops_schedule_type
   PARLOOPS_SCHEDULE_RUNTIME
 };
 
+#endif
+
 #endif /* ! GCC_FLAG_TYPES_H */
diff --git a/gcc/function.c b/gcc/function.c
index c612959..76a5037 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -46,10 +46,12 @@ along with GCC; see the file COPYING3.  If not see
 #include "stringpool.h"
 #include "expmed.h"
 #include "optabs.h"
+#include "opts.h"
 #include "regs.h"
 #include "emit-rtl.h"
 #include "recog.h"
 #include "rtl-error.h"
+#include "hard-reg-set.h"
 #include "alias.h"
 #include "fold-const.h"
 #include "stor-layout.h"
@@ -5815,6 +5817,103 @@ make_prologue_seq (void)
   return seq;
 }
 
+/* Emit a sequence of insns to zero the call-used registers before RET
+   according to ZERO_REGS_TYPE.  */
+
+static void
+gen_call_used_regs_seq (rtx_insn *ret, unsigned int zero_regs_type)
+{
+  bool only_gpr = true;
+  bool only_used = true;
+  bool only_arg = true;
+
+  /* No need to zero call-used-regs in main ().  */
+  if (MAIN_NAME_P (DECL_NAME (current_function_decl)))
+    return;
+
+  /* No need to zero call-used-regs if __builtin_eh_return is called
+     since it isn't a normal function return.  */
+  if (crtl->calls_eh_return)
+    return;
+
+  /* If only_gpr is true, only zero call-used registers that are
+     general-purpose registers; if only_used is true, only zero
+     call-used registers that are used in the current function;
+     if only_arg is true, only zero call-used registers that pass
+     parameters defined by the flatform's calling conversion.  */
+
+  using namespace zero_regs_flag;
+
+  only_gpr = zero_regs_type & ONLY_GPR;
+  only_used = zero_regs_type & ONLY_USED;
+  only_arg = zero_regs_type & ONLY_ARG;
+
+  /* For each of the hard registers, we should zero it if:
+           1. it is a call-used register;
+       and 2. it is not a fixed register;
+       and 3. it is not live at the return of the routine;
+       and 4. it is general registor if only_gpr is true;
+       and 5. it is used in the routine if only_used is true;
+       and 6. it is a register that passes parameter if only_arg is true.  */
+
+  /* First, prepare the data flow information.  */
+  basic_block bb = BLOCK_FOR_INSN (ret);
+  auto_bitmap live_out;
+  bitmap_copy (live_out, df_get_live_out (bb));
+  df_simulate_initialize_backwards (bb, live_out);
+  df_simulate_one_insn_backwards (bb, ret, live_out);
+
+  HARD_REG_SET selected_hardregs;
+  CLEAR_HARD_REG_SET (selected_hardregs);
+  for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
+    {
+      if (!crtl->abi->clobbers_full_reg_p (regno))
+       continue;
+      if (fixed_regs[regno])
+       continue;
+      if (REGNO_REG_SET_P (live_out, regno))
+       continue;
+      if (only_gpr
+         && !TEST_HARD_REG_BIT (reg_class_contents[GENERAL_REGS], regno))
+       continue;
+      if (only_used && !df_regs_ever_live_p (regno))
+       continue;
+      if (only_arg && !FUNCTION_ARG_REGNO_P (regno))
+       continue;
+
+      /* Now this is a register that we might want to zero.  */
+      SET_HARD_REG_BIT (selected_hardregs, regno);
+    }
+
+  if (hard_reg_set_empty_p (selected_hardregs))
+    return;
+
+  /* Now that we have a hard register set that needs to be zeroed, pass it to
+     target to generate zeroing sequence.  */
+  HARD_REG_SET zeroed_hardregs;
+  start_sequence ();
+  zeroed_hardregs = targetm.calls.zero_call_used_regs (selected_hardregs);
+  rtx_insn *seq = get_insns ();
+  end_sequence ();
+  if (seq)
+    {
+      /* Emit the memory blockage and register clobber asm volatile before
+        the whole sequence.  */
+      start_sequence ();
+      expand_asm_reg_clobber_mem_blockage (zeroed_hardregs);
+      rtx_insn *seq_barrier = get_insns ();
+      end_sequence ();
+
+      emit_insn_before (seq_barrier, ret);
+      emit_insn_before (seq, ret);
+
+      /* Update the data flow information.  */
+      crtl->must_be_zero_on_return |= zeroed_hardregs;
+      df_set_bb_dirty (EXIT_BLOCK_PTR_FOR_FN (cfun));
+    }
+}
+
+
 /* Return a sequence to be used as the epilogue for the current function,
    or NULL.  */
 
@@ -6486,7 +6585,96 @@ make_pass_thread_prologue_and_epilogue (gcc::context 
*ctxt)
 {
   return new pass_thread_prologue_and_epilogue (ctxt);
 }
-

+
+namespace {
+
+const pass_data pass_data_zero_call_used_regs =
+{
+  RTL_PASS, /* type */
+  "zero_call_used_regs", /* name */
+  OPTGROUP_NONE, /* optinfo_flags */
+  TV_NONE, /* tv_id */
+  0, /* properties_required */
+  0, /* properties_provided */
+  0, /* properties_destroyed */
+  0, /* todo_flags_start */
+  0, /* todo_flags_finish */
+};
+
+class pass_zero_call_used_regs: public rtl_opt_pass
+{
+public:
+  pass_zero_call_used_regs (gcc::context *ctxt)
+    : rtl_opt_pass (pass_data_zero_call_used_regs, ctxt)
+  {}
+
+  /* opt_pass methods: */
+  virtual unsigned int execute (function *);
+
+}; // class pass_zero_call_used_regs
+
+unsigned int
+pass_zero_call_used_regs::execute (function *fun)
+{
+  using namespace zero_regs_flag;
+  unsigned int zero_regs_type = UNSET;
+
+  tree attr_zero_regs = lookup_attribute ("zero_call_used_regs",
+                                         DECL_ATTRIBUTES (fun->decl));
+
+  /* Get the type of zero_call_used_regs from function attribute.
+     We have filtered out invalid attribute values already at this point.  */
+  if (attr_zero_regs)
+    {
+      /* The TREE_VALUE of an attribute is a TREE_LIST whose TREE_VALUE
+        is the attribute argument's value.  */
+      attr_zero_regs = TREE_VALUE (attr_zero_regs);
+      gcc_assert (TREE_CODE (attr_zero_regs) == TREE_LIST);
+      attr_zero_regs = TREE_VALUE (attr_zero_regs);
+      gcc_assert (TREE_CODE (attr_zero_regs) == STRING_CST);
+
+      for (unsigned int i = 0; zero_call_used_regs_opts[i].name != NULL; ++i)
+       if (strcmp (TREE_STRING_POINTER (attr_zero_regs),
+                    zero_call_used_regs_opts[i].name) == 0)
+         {
+           zero_regs_type = zero_call_used_regs_opts[i].flag;
+           break;
+         }
+    }
+
+  if (!zero_regs_type)
+    zero_regs_type = flag_zero_call_used_regs;
+
+  /* No need to zero call-used-regs when no user request is present.  */
+  if (!(zero_regs_type & ENABLED))
+    return 0;
+
+  edge_iterator ei;
+  edge e;
+
+  /* This pass needs data flow information.  */
+  df_analyze ();
+
+  /* Iterate over the function's return instructions and insert any
+     register zeroing required by the -fzero-call-used-regs command-line
+     option or the "zero_call_used_regs" function attribute.  */
+  FOR_EACH_EDGE (e, ei, EXIT_BLOCK_PTR_FOR_FN (cfun)->preds)
+    {
+      rtx_insn *insn = BB_END (e->src);
+      if (JUMP_P (insn) && ANY_RETURN_P (JUMP_LABEL (insn)))
+       gen_call_used_regs_seq (insn, zero_regs_type);
+    }
+
+  return 0;
+}
+
+} // anon namespace
+
+rtl_opt_pass *
+make_pass_zero_call_used_regs (gcc::context *ctxt)
+{
+  return new pass_zero_call_used_regs (ctxt);
+}
 
 /* If CONSTRAINT is a matching constraint, then return its number.
    Otherwise, return -1.  */
diff --git a/gcc/optabs.c b/gcc/optabs.c
index 8ad7f4b..1820b91 100644
--- a/gcc/optabs.c
+++ b/gcc/optabs.c
@@ -6484,6 +6484,48 @@ expand_memory_blockage (void)
     expand_asm_memory_blockage ();
 }
 
+/* Generate asm volatile("" : : : "memory") as a memory blockage, at the
+   same time clobbering the register set specified by REGS.  */
+
+void
+expand_asm_reg_clobber_mem_blockage (HARD_REG_SET regs)
+{
+  rtx asm_op, clob_mem;
+
+  unsigned int num_of_regs = 0;
+  for (unsigned int i = 0; i < FIRST_PSEUDO_REGISTER; i++)
+    if (TEST_HARD_REG_BIT (regs, i))
+      num_of_regs++;
+
+  asm_op = gen_rtx_ASM_OPERANDS (VOIDmode, "", "", 0,
+                                rtvec_alloc (0), rtvec_alloc (0),
+                                rtvec_alloc (0), UNKNOWN_LOCATION);
+  MEM_VOLATILE_P (asm_op) = 1;
+
+  rtvec v = rtvec_alloc (num_of_regs + 2);
+
+  clob_mem = gen_rtx_SCRATCH (VOIDmode);
+  clob_mem = gen_rtx_MEM (BLKmode, clob_mem);
+  clob_mem = gen_rtx_CLOBBER (VOIDmode, clob_mem);
+
+  RTVEC_ELT (v, 0) = asm_op;
+  RTVEC_ELT (v, 1) = clob_mem;
+
+  if (num_of_regs > 0)
+    {
+      unsigned int j = 2;
+      for (unsigned int i = 0; i < FIRST_PSEUDO_REGISTER; i++)
+       if (TEST_HARD_REG_BIT (regs, i))
+         {
+           RTVEC_ELT (v, j) = gen_rtx_CLOBBER (VOIDmode, regno_reg_rtx[i]);
+           j++;
+         }
+      gcc_assert (j == (num_of_regs + 2));
+    }
+
+  emit_insn (gen_rtx_PARALLEL (VOIDmode, v));
+}
+
 /* This routine will either emit the mem_thread_fence pattern or issue a 
    sync_synchronize to generate a fence for memory model MEMMODEL.  */
 
diff --git a/gcc/optabs.h b/gcc/optabs.h
index 0b14700..bfa10c8 100644
--- a/gcc/optabs.h
+++ b/gcc/optabs.h
@@ -345,6 +345,8 @@ rtx expand_atomic_store (rtx, rtx, enum memmodel, bool);
 rtx expand_atomic_fetch_op (rtx, rtx, rtx, enum rtx_code, enum memmodel, 
                              bool);
 
+extern void expand_asm_reg_clobber_mem_blockage (HARD_REG_SET);
+
 extern bool insn_operand_matches (enum insn_code icode, unsigned int opno,
                                  rtx operand);
 extern bool valid_multiword_target_p (rtx);
diff --git a/gcc/opts.c b/gcc/opts.c
index 3bda59a..8c439e4 100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -1776,6 +1776,25 @@ const struct sanitizer_opts_s coverage_sanitizer_opts[] =
   { NULL, 0U, 0UL, false }
 };
 
+using namespace zero_regs_flag;
+/* -fzero-call-used-regs= suboptions.  */
+const struct zero_call_used_regs_opts_s zero_call_used_regs_opts[] =
+{
+#define ZERO_CALL_USED_REGS_OPT(name, flags) \
+    { #name, flags }
+  ZERO_CALL_USED_REGS_OPT (skip, SKIP),
+  ZERO_CALL_USED_REGS_OPT (used-gpr-arg, USED_GPR_ARG),
+  ZERO_CALL_USED_REGS_OPT (used-gpr, USED_GPR),
+  ZERO_CALL_USED_REGS_OPT (used-arg, USED_ARG),
+  ZERO_CALL_USED_REGS_OPT (used, USED),
+  ZERO_CALL_USED_REGS_OPT (all-gpr-arg, ALL_GPR_ARG),
+  ZERO_CALL_USED_REGS_OPT (all-gpr, ALL_GPR),
+  ZERO_CALL_USED_REGS_OPT (all-arg, ALL_ARG),
+  ZERO_CALL_USED_REGS_OPT (all, ALL),
+#undef ZERO_CALL_USED_REGS_OPT
+  {NULL, 0U}
+};
+
 /* A struct for describing a run of chars within a string.  */
 
 class string_fragment
@@ -1970,6 +1989,27 @@ parse_no_sanitize_attribute (char *value)
   return flags;
 }
 
+/* Parse -fzero-call-used-regs suboptions from ARG, return the FLAGS.  */
+
+unsigned int
+parse_zero_call_used_regs_options (const char *arg)
+{
+  unsigned int flags = 0;
+
+  /* Check to see if the string matches a sub-option name.  */
+  for (unsigned int i = 0; zero_call_used_regs_opts[i].name != NULL; ++i)
+    if (strcmp (arg, zero_call_used_regs_opts[i].name) == 0)
+      {
+       flags = zero_call_used_regs_opts[i].flag;
+       break;
+      }
+
+  if (!flags)
+    error ("unrecognized argument to %<-fzero-call-used-regs=%>: %qs", arg);
+
+  return flags;
+}
+
 /* Parse -falign-NAME format for a FLAG value.  Return individual
    parsed integer values into RESULT_VALUES array.  If REPORT_ERROR is
    set, print error message at LOC location.  */
@@ -2601,6 +2641,11 @@ common_handle_option (struct gcc_options *opts,
       /* Automatically sets -ftree-loop-vectorize and
         -ftree-slp-vectorize.  Nothing more to do here.  */
       break;
+    case OPT_fzero_call_used_regs_:
+      opts->x_flag_zero_call_used_regs
+       = parse_zero_call_used_regs_options (arg);
+      break;
+
     case OPT_fshow_column:
       dc->show_column = value;
       break;
diff --git a/gcc/opts.h b/gcc/opts.h
index 8f594b4..7d1e126 100644
--- a/gcc/opts.h
+++ b/gcc/opts.h
@@ -444,6 +444,12 @@ extern const struct sanitizer_opts_s
   bool can_recover;
 } sanitizer_opts[];
 
+extern const struct zero_call_used_regs_opts_s
+{
+  const char *const name;
+  unsigned int flag;
+} zero_call_used_regs_opts[];
+
 extern vec<const char *> help_option_arguments;
 
 extern void add_misspelling_candidates (auto_vec<char *> *candidates,
diff --git a/gcc/passes.def b/gcc/passes.def
index f865bdc..77d4676 100644
--- a/gcc/passes.def
+++ b/gcc/passes.def
@@ -492,6 +492,7 @@ along with GCC; see the file COPYING3.  If not see
       POP_INSERT_PASSES ()
       NEXT_PASS (pass_late_compilation);
       PUSH_INSERT_PASSES_WITHIN (pass_late_compilation)
+         NEXT_PASS (pass_zero_call_used_regs);
          NEXT_PASS (pass_compute_alignments);
          NEXT_PASS (pass_variable_tracking);
          NEXT_PASS (pass_free_cfg);
diff --git a/gcc/recog.c b/gcc/recog.c
index ce83b7f..b458746 100644
--- a/gcc/recog.c
+++ b/gcc/recog.c
@@ -922,7 +922,23 @@ validate_simplify_insn (rtx_insn *insn)
       }
   return ((num_changes_pending () > 0) && (apply_change_group () > 0));
 }
-

+
+/* Check whether INSN matches a specific alternative of an .md pattern.  */
+
+bool
+valid_insn_p (rtx_insn *insn)
+{
+  recog_memoized (insn);
+  if (INSN_CODE (insn) < 0)
+    return false;
+  extract_insn (insn);
+  /* We don't know whether the insn will be in code that is optimized
+     for size or speed, so consider all enabled alternatives.  */
+  if (!constrain_operands (1, get_enabled_alternatives (insn)))
+    return false;
+  return true;
+}
+
 /* Return 1 if OP is a valid general operand for machine mode MODE.
    This is either a register reference, a memory reference,
    or a constant.  In the case of a memory reference, the address
diff --git a/gcc/recog.h b/gcc/recog.h
index ae3675f..d87456c 100644
--- a/gcc/recog.h
+++ b/gcc/recog.h
@@ -113,6 +113,7 @@ extern void validate_replace_src_group (rtx, rtx, rtx_insn 
*);
 extern bool validate_simplify_insn (rtx_insn *insn);
 extern int num_changes_pending (void);
 extern bool reg_fits_class_p (const_rtx, reg_class_t, int, machine_mode);
+extern bool valid_insn_p (rtx_insn *);
 
 extern int offsettable_memref_p (rtx);
 extern int offsettable_nonstrict_memref_p (rtx);
diff --git a/gcc/resource.c b/gcc/resource.c
index 0a9d594..90cf091 100644
--- a/gcc/resource.c
+++ b/gcc/resource.c
@@ -1186,7 +1186,7 @@ init_resource_info (rtx_insn *epilogue_insn)
                               &end_of_function_needs, true);
 
   for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
-    if (global_regs[i] || EPILOGUE_USES (i))
+    if (global_regs[i] || df_epilogue_uses_p (i))
       SET_HARD_REG_BIT (end_of_function_needs.regs, i);
 
   /* The registers required to be live at the end of the function are
diff --git a/gcc/target.def b/gcc/target.def
index ed2da15..b916635 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -5080,6 +5080,21 @@ argument list due to stack realignment.  Return 
@code{NULL} if no DRAP\n\
 is needed.",
  rtx, (void), NULL)
 
+/* Generate instruction sequence to zero call used registers.  */
+DEFHOOK
+(zero_call_used_regs,
+ "This target hook emits instructions to zero the subset of 
@var{selected_regs}\n\
+that could conceivably contain values that are useful to an attacker.\n\
+Return the set of registers that were actually cleared.\n\
+\n\
+The default implementation uses normal move instructions to zero\n\
+all the registers in @var{selected_regs}.  Define this hook if the\n\
+target has more efficient ways of zeroing certain registers,\n\
+or if you believe that certain registers would never contain\n\
+values that are useful to an attacker.",
+ HARD_REG_SET, (HARD_REG_SET selected_regs),
+default_zero_call_used_regs)
+
 /* Return true if all function parameters should be spilled to the
    stack.  */
 DEFHOOK
diff --git a/gcc/targhooks.c b/gcc/targhooks.c
index 5d94fce..4e4d100 100644
--- a/gcc/targhooks.c
+++ b/gcc/targhooks.c
@@ -56,6 +56,9 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-ssa-alias.h"
 #include "gimple-expr.h"
 #include "memmodel.h"
+#include "backend.h"
+#include "emit-rtl.h"
+#include "df.h"
 #include "tm_p.h"
 #include "stringpool.h"
 #include "tree-vrp.h"
@@ -987,6 +990,35 @@ default_function_value_regno_p (const unsigned int regno 
ATTRIBUTE_UNUSED)
 #endif
 }
 
+/* The default hook for TARGET_ZERO_CALL_USED_REGS.  */
+
+HARD_REG_SET
+default_zero_call_used_regs (HARD_REG_SET need_zeroed_hardregs)
+{
+  gcc_assert (!hard_reg_set_empty_p (need_zeroed_hardregs));
+
+  for (unsigned int regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
+    if (TEST_HARD_REG_BIT (need_zeroed_hardregs, regno))
+      {
+       rtx_insn *last_insn = get_last_insn ();
+       machine_mode mode = GET_MODE (regno_reg_rtx[regno]);
+       rtx zero = CONST0_RTX (mode);
+       rtx_insn *insn = emit_move_insn (regno_reg_rtx[regno], zero);
+       if (!valid_insn_p (insn))
+         {
+           static bool issued_error;
+           if (!issued_error)
+             {
+               issued_error = true;
+               sorry ("%qs not supported on this target",
+                       "-fzero-call-used_regs");
+             }
+           delete_insns_since (last_insn);
+         }
+      }
+  return need_zeroed_hardregs;
+}
+
 rtx
 default_internal_arg_pointer (void)
 {
diff --git a/gcc/targhooks.h b/gcc/targhooks.h
index 44ab926..e0a925f 100644
--- a/gcc/targhooks.h
+++ b/gcc/targhooks.h
@@ -160,6 +160,7 @@ extern unsigned int default_function_arg_round_boundary 
(machine_mode,
                                                         const_tree);
 extern bool hook_bool_const_rtx_commutative_p (const_rtx, int);
 extern rtx default_function_value (const_tree, const_tree, bool);
+extern HARD_REG_SET default_zero_call_used_regs (HARD_REG_SET);
 extern rtx default_libcall_value (machine_mode, const_rtx);
 extern bool default_function_value_regno_p (const unsigned int);
 extern rtx default_internal_arg_pointer (void);
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-1.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-1.c
new file mode 100644
index 0000000..2463353
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-1.c
@@ -0,0 +1,15 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fzero-call-used-regs=skip" } */
+
+volatile int result = 0;
+int 
+__attribute__((noipa))
+foo (int x)
+{
+  return x;
+}
+int main()
+{
+  result = foo (2);
+  return 0;
+}
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-10.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-10.c
new file mode 100644
index 0000000..bdaf8e7
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-10.c
@@ -0,0 +1,92 @@
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+#include <assert.h>
+int result = 0;
+
+int 
+__attribute__((noipa))
+__attribute__ ((zero_call_used_regs("skip")))
+foo1 (int x)
+{
+  return (x + 1);
+}
+
+int 
+__attribute__((noipa))
+__attribute__ ((zero_call_used_regs("used-gpr-arg")))
+foo2 (int x)
+{
+  return (x + 2);
+}
+
+int 
+__attribute__((noipa))
+__attribute__ ((zero_call_used_regs("used-gpr")))
+foo3 (int x)
+{
+  return (x + 3);
+}
+
+int 
+__attribute__((noipa))
+__attribute__ ((zero_call_used_regs("used-arg")))
+foo4 (int x)
+{
+  return (x + 4);
+}
+
+int 
+__attribute__((noipa))
+__attribute__ ((zero_call_used_regs("used")))
+foo5 (int x)
+{
+  return (x + 5);
+}
+
+int 
+__attribute__((noipa))
+__attribute__ ((zero_call_used_regs("all-gpr-arg")))
+foo6 (int x)
+{
+  return (x + 6);
+}
+
+int 
+__attribute__((noipa))
+__attribute__ ((zero_call_used_regs("all-gpr")))
+foo7 (int x)
+{
+  return (x + 7);
+}
+
+int 
+__attribute__((noipa))
+__attribute__ ((zero_call_used_regs("all-arg")))
+foo8 (int x)
+{
+  return (x + 8);
+}
+
+int 
+__attribute__((noipa))
+__attribute__ ((zero_call_used_regs("all")))
+foo9 (int x)
+{
+  return (x + 9);
+}
+
+int main()
+{
+  result = foo1 (1);
+  result += foo2 (1);
+  result += foo3 (1);
+  result += foo4 (1);
+  result += foo5 (1);
+  result += foo6 (1);
+  result += foo7 (1);
+  result += foo8 (1);
+  result += foo9 (1);
+  assert (result == 54);
+  return 0;
+}
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-11.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-11.c
new file mode 100644
index 0000000..7721e39
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-11.c
@@ -0,0 +1,4 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fzero-call-used-regs=all" } */
+
+#include "zero-scratch-regs-10.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-2.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-2.c
new file mode 100644
index 0000000..25891ac
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-2.c
@@ -0,0 +1,4 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fzero-call-used-regs=used-gpr-arg" } */
+
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-3.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-3.c
new file mode 100644
index 0000000..7c3d286
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-3.c
@@ -0,0 +1,4 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fzero-call-used-regs=used-gpr" } */
+
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-4.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-4.c
new file mode 100644
index 0000000..ba28c06
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-4.c
@@ -0,0 +1,4 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fzero-call-used-regs=used-arg" } */
+
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-5.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-5.c
new file mode 100644
index 0000000..26679a4
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-5.c
@@ -0,0 +1,4 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fzero-call-used-regs=used" } */
+
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-6.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-6.c
new file mode 100644
index 0000000..80f5bbb
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-6.c
@@ -0,0 +1,4 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fzero-call-used-regs=all-gpr-arg" } */
+
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-7.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-7.c
new file mode 100644
index 0000000..159f35c
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-7.c
@@ -0,0 +1,4 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fzero-call-used-regs=all-gpr" } */
+
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-8.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-8.c
new file mode 100644
index 0000000..c1faaf0
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-8.c
@@ -0,0 +1,4 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fzero-call-used-regs=all-arg" } */
+
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-9.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-9.c
new file mode 100644
index 0000000..3f14bac
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-9.c
@@ -0,0 +1,4 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fzero-call-used-regs=all" } */
+
+#include "zero-scratch-regs-1.c"
diff --git a/gcc/testsuite/c-c++-common/zero-scratch-regs-attr-usages.c 
b/gcc/testsuite/c-c++-common/zero-scratch-regs-attr-usages.c
new file mode 100644
index 0000000..1e75795
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/zero-scratch-regs-attr-usages.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+int result __attribute__ ((zero_call_used_regs("all"))); /* { dg-error 
"attribute applies only to functions" } */
+int
+__attribute__ ((zero_call_used_regs("gpr-arg-all")))
+foo1 (int x) /* { dg-error "unrecognized 'zero_call_used_regs' attribute 
argument" } */
+{
+  return (x + 1);
+}
+int
+__attribute__ ((zero_call_used_regs(1)))
+foo2 (int x) /* { dg-error "argument not a string" } */
+{
+  return (x + 2);
+}
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-1.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-1.c
new file mode 100644
index 0000000..9f61dc4
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-1.c
@@ -0,0 +1,12 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=used" } */
+
+void
+foo (void)
+{
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
+/* { dg-final { scan-assembler-not "movl\[ \t\]*%" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-10.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-10.c
new file mode 100644
index 0000000..09048e5
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-10.c
@@ -0,0 +1,21 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=skip" } */
+
+extern int foo (int) __attribute__ ((zero_call_used_regs("all-gpr")));
+
+int
+foo (int x)
+{
+  return x;
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler "xorl\[ \t\]*%edx, %edx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %ecx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %esi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %edi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r8d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r9d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r10d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r11d" { target { ! ia32 } } 
} } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-11.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-11.c
new file mode 100644
index 0000000..4862688
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-11.c
@@ -0,0 +1,39 @@
+/* { dg-do run { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=used-gpr" } */
+
+struct S { int i; };
+__attribute__((const, noinline, noclone))
+struct S foo (int x)
+{
+  struct S s;
+  s.i = x;
+  return s;
+}
+
+int a[2048], b[2048], c[2048], d[2048];
+struct S e[2048];
+
+__attribute__((noinline, noclone)) void
+bar (void)
+{
+  int i;
+  for (i = 0; i < 1024; i++)
+    {
+      e[i] = foo (i);
+      a[i+2] = a[i] + a[i+1];
+      b[10] = b[10] + i;
+      c[i] = c[2047 - i];
+      d[i] = d[i + 1];
+    }
+}
+
+int
+main ()
+{
+  int i;
+  bar ();
+  for (i = 0; i < 1024; i++)
+    if (e[i].i != i)
+      __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-12.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-12.c
new file mode 100644
index 0000000..500251b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-12.c
@@ -0,0 +1,39 @@
+/* { dg-do run { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=all-gpr" } */
+
+struct S { int i; };
+__attribute__((const, noinline, noclone))
+struct S foo (int x)
+{
+  struct S s;
+  s.i = x;
+  return s;
+}
+
+int a[2048], b[2048], c[2048], d[2048];
+struct S e[2048];
+
+__attribute__((noinline, noclone)) void
+bar (void)
+{
+  int i;
+  for (i = 0; i < 1024; i++)
+    {
+      e[i] = foo (i);
+      a[i+2] = a[i] + a[i+1];
+      b[10] = b[10] + i;
+      c[i] = c[2047 - i];
+      d[i] = d[i + 1];
+    }
+}
+
+int
+main ()
+{
+  int i;
+  bar ();
+  for (i = 0; i < 1024; i++)
+    if (e[i].i != i)
+      __builtin_abort ();
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-13.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-13.c
new file mode 100644
index 0000000..8b058e3
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-13.c
@@ -0,0 +1,21 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=all -march=corei7" } */
+
+void
+foo (void)
+{
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler "pxor\[ \t\]*%xmm0, %xmm0" } } */
+/* { dg-final { scan-assembler-times "movaps\[ \t\]*%xmm0, %xmm\[0-9\]+" 7 { 
target { ia32 } } } } */
+/* { dg-final { scan-assembler-times "movaps\[ \t\]*%xmm0, %xmm\[0-9\]+" 15 { 
target { ! ia32 } } } } */
+/* { dg-final { scan-assembler "xorl\[ \t\]*%eax, %eax" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %ecx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %esi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r8d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r9d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r10d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r11d" { target { ! ia32 } } 
} } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-14.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-14.c
new file mode 100644
index 0000000..d4eaaf7
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-14.c
@@ -0,0 +1,19 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=all -march=corei7 -mavx" } */
+
+void
+foo (void)
+{
+}
+
+/* { dg-final { scan-assembler-times "vzeroall" 1 } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler "xorl\[ \t\]*%eax, %eax" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %ecx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %esi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r8d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r9d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r10d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r11d" { target { ! ia32 } } 
} } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-15.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-15.c
new file mode 100644
index 0000000..dd3bb90
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-15.c
@@ -0,0 +1,14 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=skip" } */
+
+extern void foo (void) __attribute__ ((zero_call_used_regs("used")));
+
+void
+foo (void)
+{
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
+/* { dg-final { scan-assembler-not "movl\[ \t\]*%" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-16.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-16.c
new file mode 100644
index 0000000..e2274f6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-16.c
@@ -0,0 +1,14 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=all" } */
+
+extern void foo (void) __attribute__ ((zero_call_used_regs("skip")));
+
+void
+foo (void)
+{
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
+/* { dg-final { scan-assembler-not "movl\[ \t\]*%" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-17.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-17.c
new file mode 100644
index 0000000..7f5d153
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-17.c
@@ -0,0 +1,13 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=used" } */
+
+int
+foo (int x)
+{
+  return x;
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" { target ia32 } } } */
+/* { dg-final { scan-assembler "xorl\[ \t\]*%edi, %edi" { target { ! ia32 } } 
} } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-18.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-18.c
new file mode 100644
index 0000000..fe13d2b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-18.c
@@ -0,0 +1,13 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=used -march=corei7" } */
+
+float
+foo (float z, float y, float x)
+{
+  return x + y;
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler "pxor\[ \t\]*%xmm1, %xmm1" { target { ! ia32 } 
} } } */
+/* { dg-final { scan-assembler "movaps\[ \t\]*%xmm1, %xmm2" { target { ! ia32 
} } } } */
+/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-19.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-19.c
new file mode 100644
index 0000000..205a532
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-19.c
@@ -0,0 +1,12 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=used -march=corei7" } */
+
+float
+foo (float z, float y, float x)
+{
+  return x;
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler "pxor\[ \t\]*%xmm2, %xmm2" { target { ! ia32 } 
} } } */
+/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-2.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-2.c
new file mode 100644
index 0000000..e046684
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-2.c
@@ -0,0 +1,19 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=all-gpr" } */
+
+void
+foo (void)
+{
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler "xorl\[ \t\]*%eax, %eax" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %ecx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %esi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r8d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r9d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r10d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r11d" { target { ! ia32 } } 
} } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-20.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-20.c
new file mode 100644
index 0000000..4be8ff6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-20.c
@@ -0,0 +1,23 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=all -march=corei7" } */
+
+float
+foo (float z, float y, float x)
+{
+  return x + y;
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler "pxor\[ \t\]*%xmm0, %xmm0" { target { ia32 } } 
} } */
+/* { dg-final { scan-assembler "pxor\[ \t\]*%xmm1, %xmm1" { target { ! ia32 } 
} } } */
+/* { dg-final { scan-assembler-times "movaps\[ \t\]*%xmm0, %xmm\[0-9\]+" 7 { 
target { ia32 } } } } */
+/* { dg-final { scan-assembler-times "movaps\[ \t\]*%xmm1, %xmm\[0-9\]+" 14 { 
target { ! ia32 } } } } */
+/* { dg-final { scan-assembler "xorl\[ \t\]*%eax, %eax" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %ecx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %esi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r8d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r9d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r10d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r11d" { target { ! ia32 } } 
} } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-21.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-21.c
new file mode 100644
index 0000000..0eb34e0
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-21.c
@@ -0,0 +1,14 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=skip -march=corei7" } */
+
+__attribute__ ((zero_call_used_regs("used")))
+float
+foo (float z, float y, float x)
+{
+  return x + y;
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler "pxor\[ \t\]*%xmm1, %xmm1" { target { ! ia32 } 
} } } */
+/* { dg-final { scan-assembler "movaps\[ \t\]*%xmm1, %xmm2" { target { ! ia32 
} } } } */
+/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-22.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-22.c
new file mode 100644
index 0000000..0258c70
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-22.c
@@ -0,0 +1,21 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=all -march=corei7 -mavx" } */
+
+void
+foo (void)
+{
+}
+
+/* { dg-final { scan-assembler "vzeroall" } } */
+/* { dg-final { scan-assembler-times "fldz" 8 } } */
+/* { dg-final { scan-assembler-times "fstp" 8 } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler "xorl\[ \t\]*%eax, %eax" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %ecx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %esi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r8d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r9d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r10d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r11d" { target { ! ia32 } } 
} } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-23.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-23.c
new file mode 100644
index 0000000..0625eb5
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-23.c
@@ -0,0 +1,29 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=all -march=corei7 -mavx512f" } */
+
+void
+foo (void)
+{
+}
+
+/* { dg-final { scan-assembler "vzeroall" } } */
+/* { dg-final { scan-assembler-times "fldz" 8 } } */
+/* { dg-final { scan-assembler-times "fstp" 8 } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler "xorl\[ \t\]*%eax, %eax" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %ecx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %esi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r8d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r9d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r10d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r11d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "kxorw\[ \t\]*%k0, %k0, %k0" { target { ! ia32 
} } } } */
+/* { dg-final { scan-assembler "kmovw\[ \t\]*%k0, %k1" { target { ! ia32 } } } 
} */
+/* { dg-final { scan-assembler "kmovw\[ \t\]*%k0, %k2" { target { ! ia32 } } } 
} */
+/* { dg-final { scan-assembler "kmovw\[ \t\]*%k0, %k3" { target { ! ia32 } } } 
} */
+/* { dg-final { scan-assembler "kmovw\[ \t\]*%k0, %k4" { target { ! ia32 } } } 
} */
+/* { dg-final { scan-assembler "kmovw\[ \t\]*%k0, %k5" { target { ! ia32 } } } 
} */
+/* { dg-final { scan-assembler "kmovw\[ \t\]*%k0, %k6" { target { ! ia32 } } } 
} */
+/* { dg-final { scan-assembler "kmovw\[ \t\]*%k0, %k7" { target { ! ia32 } } } 
} */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-24.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-24.c
new file mode 100644
index 0000000..208633e
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-24.c
@@ -0,0 +1,10 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=used-gpr-arg" } */
+
+int 
+foo (int x)
+{
+  return x;
+}
+
+/* { dg-final { scan-assembler "xorl\[ \t\]*%edi, %edi" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-25.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-25.c
new file mode 100644
index 0000000..21e82c6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-25.c
@@ -0,0 +1,10 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=used-arg" } */
+
+int 
+foo (int x)
+{
+  return x;
+}
+
+/* { dg-final { scan-assembler "xorl\[ \t\]*%edi, %edi" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-26.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-26.c
new file mode 100644
index 0000000..293d2fe
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-26.c
@@ -0,0 +1,23 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=all-arg" } */
+
+int 
+foo (int x)
+{
+  return x;
+}
+
+/* { dg-final { scan-assembler "xorl\[ \t\]*%edx, %edx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %ecx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %esi" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %edi" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r8d" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r9d" } } */
+/* { dg-final { scan-assembler "pxor\[ \t\]*%xmm0, %xmm0" } } */
+/* { dg-final { scan-assembler "movaps\[ \t\]*%xmm0, %xmm1" } } */
+/* { dg-final { scan-assembler "movaps\[ \t\]*%xmm0, %xmm2" } } */
+/* { dg-final { scan-assembler "movaps\[ \t\]*%xmm0, %xmm3" } } */
+/* { dg-final { scan-assembler "movaps\[ \t\]*%xmm0, %xmm4" } } */
+/* { dg-final { scan-assembler "movaps\[ \t\]*%xmm0, %xmm5" } } */
+/* { dg-final { scan-assembler "movaps\[ \t\]*%xmm0, %xmm6" } } */
+/* { dg-final { scan-assembler "movaps\[ \t\]*%xmm0, %xmm7" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-27.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-27.c
new file mode 100644
index 0000000..c34e6af
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-27.c
@@ -0,0 +1,15 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=all-gpr-arg" } */
+
+int 
+foo (int x)
+{
+  return x;
+}
+
+/* { dg-final { scan-assembler "xorl\[ \t\]*%edx, %edx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %ecx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %esi" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %edi" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r8d" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r9d" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-28.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-28.c
new file mode 100644
index 0000000..48b1f01
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-28.c
@@ -0,0 +1,16 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -mmmx -fzero-call-used-regs=all" } */
+/* { dg-require-effective-target ia32 } */
+
+__v2si ret_mmx (void)
+{
+  return (__v2si) { 123, 345 };
+}
+
+/* { dg-final { scan-assembler "pxor\[ \t\]*%mm1, %mm1" } } */
+/* { dg-final { scan-assembler "movq\[ \t\]*%mm1, %mm2" } } */
+/* { dg-final { scan-assembler "movq\[ \t\]*%mm1, %mm3" } } */
+/* { dg-final { scan-assembler "movq\[ \t\]*%mm1, %mm4" } } */
+/* { dg-final { scan-assembler "movq\[ \t\]*%mm1, %mm5" } } */
+/* { dg-final { scan-assembler "movq\[ \t\]*%mm1, %mm6" } } */
+/* { dg-final { scan-assembler "movq\[ \t\]*%mm1, %mm7" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-29.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-29.c
new file mode 100644
index 0000000..8b5e1cd
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-29.c
@@ -0,0 +1,10 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=all" } */
+
+long double ret_x87 (void)
+{
+  return 1.1L;
+}
+
+/* { dg-final { scan-assembler-times "fldz" 7 } } */
+/* { dg-final { scan-assembler-times "fstp" 7 } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-3.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-3.c
new file mode 100644
index 0000000..de71223
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-3.c
@@ -0,0 +1,12 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=skip" } */
+
+void
+foo (void)
+{
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
+/* { dg-final { scan-assembler-not "movl\[ \t\]*%" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-30.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-30.c
new file mode 100644
index 0000000..2a6f38f
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-30.c
@@ -0,0 +1,12 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2  -fzero-call-used-regs=all" } */
+
+_Complex long double ret_x87_cplx (void)
+{
+  return 1.1L + 1.2iL;
+}
+
+/* { dg-final { scan-assembler-times "fldz" 8 { target ia32 } } } */
+/* { dg-final { scan-assembler-times "fstp" 8 { target ia32 } } } */
+/* { dg-final { scan-assembler-times "fldz" 6 { target { ! ia32 } } } } */
+/* { dg-final { scan-assembler-times "fstp" 6 { target { ! ia32 } } } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-31.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-31.c
new file mode 100644
index 0000000..df71286
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-31.c
@@ -0,0 +1,12 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -mmmx -fzero-call-used-regs=all-arg" } */
+/* { dg-require-effective-target ia32 } */
+
+__v2si ret_mmx (void)
+{
+  return (__v2si) { 123, 345 };
+}
+
+/* { dg-final { scan-assembler "pxor\[ \t\]*%mm1, %mm1" } } */
+/* { dg-final { scan-assembler "movq\[ \t\]*%mm1, %mm2" } } */
+/* { dg-final { scan-assembler-not "movq\[ \t\]*%mm1, %mm\[34567\]" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-4.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-4.c
new file mode 100644
index 0000000..ccfa441
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-4.c
@@ -0,0 +1,14 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=skip" } */
+
+extern void foo (void) __attribute__ ((zero_call_used_regs("used-gpr")));
+
+void
+foo (void)
+{
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
+/* { dg-final { scan-assembler-not "movl\[ \t\]*%" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-5.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-5.c
new file mode 100644
index 0000000..6b46ca3
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-5.c
@@ -0,0 +1,20 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=skip" } */
+
+__attribute__ ((zero_call_used_regs("all-gpr")))
+void
+foo (void)
+{
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler "xorl\[ \t\]*%eax, %eax" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %ecx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %esi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %edi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r8d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r9d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r10d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%eax, %r11d" { target { ! ia32 } } 
} } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-6.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-6.c
new file mode 100644
index 0000000..0680f38
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-6.c
@@ -0,0 +1,14 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=all-gpr" } */
+
+extern void foo (void) __attribute__ ((zero_call_used_regs("skip")));
+
+void
+foo (void)
+{
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" } } */
+/* { dg-final { scan-assembler-not "movl\[ \t\]*%" } } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-7.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-7.c
new file mode 100644
index 0000000..534defa
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-7.c
@@ -0,0 +1,13 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=used-gpr" } */
+
+int
+foo (int x)
+{
+  return x;
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" { target ia32 } } } */
+/* { dg-final { scan-assembler "xorl\[ \t\]*%edi, %edi" { target { ! ia32 } } 
} } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-8.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-8.c
new file mode 100644
index 0000000..477bb19
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-8.c
@@ -0,0 +1,19 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=all-gpr" } */
+
+int
+foo (int x)
+{
+  return x;
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler "xorl\[ \t\]*%edx, %edx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %ecx" } } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %esi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %edi" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r8d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r9d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r10d" { target { ! ia32 } } 
} } */
+/* { dg-final { scan-assembler "movl\[ \t\]*%edx, %r11d" { target { ! ia32 } } 
} } */
diff --git a/gcc/testsuite/gcc.target/i386/zero-scratch-regs-9.c 
b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-9.c
new file mode 100644
index 0000000..a305a60
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/zero-scratch-regs-9.c
@@ -0,0 +1,15 @@
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O2 -fzero-call-used-regs=skip" } */
+
+extern int foo (int) __attribute__ ((zero_call_used_regs("used-gpr")));
+
+int
+foo (int x)
+{
+  return x;
+}
+
+/* { dg-final { scan-assembler-not "vzeroall" } } */
+/* { dg-final { scan-assembler-not "%xmm" } } */
+/* { dg-final { scan-assembler-not "xorl\[ \t\]*%" { target ia32 } } } */
+/* { dg-final { scan-assembler "xorl\[ \t\]*%edi, %edi" { target { ! ia32 } } 
} } */
diff --git a/gcc/tree-pass.h b/gcc/tree-pass.h
index 62e5b69..8afe8ee 100644
--- a/gcc/tree-pass.h
+++ b/gcc/tree-pass.h
@@ -592,6 +592,7 @@ extern rtl_opt_pass *make_pass_gcse2 (gcc::context *ctxt);
 extern rtl_opt_pass *make_pass_split_after_reload (gcc::context *ctxt);
 extern rtl_opt_pass *make_pass_thread_prologue_and_epilogue (gcc::context
                                                             *ctxt);
+extern rtl_opt_pass *make_pass_zero_call_used_regs (gcc::context *ctxt);
 extern rtl_opt_pass *make_pass_stack_adjustments (gcc::context *ctxt);
 extern rtl_opt_pass *make_pass_sched_fusion (gcc::context *ctxt);
 extern rtl_opt_pass *make_pass_peephole2 (gcc::context *ctxt);
-- 
1.8.3.1