[PATCH 2/2] [RISC-V] resolve confilct between zcmp multi push/pop and shrink-wrap-separate

[Fei Gao]

Disable zcmp multi push/pop if shrink-wrap-separate is active.

So in -Os that prefers smaller code size, by default shrink-wrap-separate
is disabled while zcmp multi push/pop is enabled.

And in -O2 and others that prefers speed, by default shrink-wrap-separate
is enabled while zcmp multi push/pop is disabled. To force enabling zcmp multi
push/pop in this case, -fno-shrink-wrap-separate has to be explictly given.

The following TC shows the issues in -O2 before this patch with both
shrink-wrap-separate and zcmp multi push/pop active.
1. duplicated store of s regs.
2. cm.push pushes ra, s0-s11 in reverse order than what normal
   prologue does, causing stack corruption and failure to resotre s regs.

TC: zcmp_shrink_wrap_separate.c included in this patch.

output asm before this patch:
calc_func:
        cm.push {ra, s0-s3}, -32
        ...
        beq     a5,zero,.L2
        ...
.L2:
        ...
        sw      s1,20(sp) //issue here
        sw      s3,12(sp) //issue here
        ...
        sw      s2,16(sp) //issue here

output asm after this patch:
calc_func:
        addi    sp,sp,-32
        sw      s0,24(sp)
        ...
        beq     a5,zero,.L2
        ...
.L2:
        ...
        sw      s1,20(sp)
        sw      s3,12(sp)
        ...
        sw      s2,16(sp)

Signed-off-by: Fei Gao <gao...@eswincomputing.com>
Co-Authored-By: Zhangjin Liao <liaozhang...@eswincomputing.com>

gcc/ChangeLog:

        * config/riscv/riscv.cc
        (riscv_avoid_shrink_wrapping_separate): wrap the condition check in
          riscv_avoid_shrink_wrapping_separate.
        (riscv_avoid_multi_push): avoid multi push if shrink_wrapping_separate
          is active.
        (riscv_get_separate_components): call 
riscv_avoid_shrink_wrapping_separate
---
 gcc/config/riscv/riscv.cc | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index 26405b5978b..2cca5fbb62d 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -64,6 +64,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "cfghooks.h"
 #include "cfgloop.h"
 #include "cfgrtl.h"
+#include "shrink-wrap.h"
 #include "sel-sched.h"
 #include "fold-const.h"
 #include "gimple-iterator.h"
@@ -389,6 +390,7 @@ static const struct riscv_tune_param 
optimize_size_tune_info = {
   false,                                       /* use_divmod_expansion */
 };
 
+static bool riscv_avoid_shrink_wrapping_separate ();
 static tree riscv_handle_fndecl_attribute (tree *, tree, tree, int, bool *);
 static tree riscv_handle_type_attribute (tree *, tree, tree, int, bool *);
 
@@ -5032,6 +5034,8 @@ riscv_avoid_multi_push(const struct riscv_frame_info 
*frame)
       || cfun->machine->interrupt_handler_p
       || cfun->machine->varargs_size != 0
       || crtl->args.pretend_args_size != 0
+      || (use_shrink_wrapping_separate ()
+          && !riscv_avoid_shrink_wrapping_separate ())
       || (frame->mask & ~ MULTI_PUSH_GPR_MASK))
     return true;
 
@@ -6199,6 +6203,17 @@ riscv_epilogue_uses (unsigned int regno)
   return false;
 }
 
+static bool
+riscv_avoid_shrink_wrapping_separate ()
+{
+  if (riscv_use_save_libcall (&cfun->machine->frame)
+      || cfun->machine->interrupt_handler_p
+      || !cfun->machine->frame.gp_sp_offset.is_constant ())
+    return true;
+
+  return false;
+}
+
 /* Implement TARGET_SHRINK_WRAP_GET_SEPARATE_COMPONENTS.  */
 
 static sbitmap
@@ -6208,9 +6223,7 @@ riscv_get_separate_components (void)
   sbitmap components = sbitmap_alloc (FIRST_PSEUDO_REGISTER);
   bitmap_clear (components);
 
-  if (riscv_use_save_libcall (&cfun->machine->frame)
-      || cfun->machine->interrupt_handler_p
-      || !cfun->machine->frame.gp_sp_offset.is_constant ())
+  if (riscv_avoid_shrink_wrapping_separate ())
     return components;
 
   offset = cfun->machine->frame.gp_sp_offset.to_constant ();
-- 
2.17.1