From: Kyrylo Tkachov <[email protected]>
get_memory_rtx creates memory operands for both sources and destinations
of string operations. The memory attribute setter cannot infer the access
direction from the address expression. Its conservative default therefore
loses nontrapping information for known loads. An inline memcmp source
changes from:
(mem:QI (...) [ this ])
to:
(mem/c:QI (...) [ this ])
Add a required STORE_P argument to get_memory_rtx. Mark destinations as
stores and sources as loads at every caller. This keeps precise nontrapping
information for loads without using it for stores.
Bootstrapped and tested on aarch64-unknown-linux-gnu. Tested on
x86_64-pc-linux-gnu.
gcc/ChangeLog:
* builtins.cc (get_memory_rtx): Add STORE_P. Pass it to
set_mem_attributes.
(expand_builtin_memory_copy_args): Mark the destination as a store
and the source as a load.
(expand_movstr): Likewise.
(expand_builtin_strncpy): Mark the destination as a store.
(expand_builtin_memset_args): Likewise.
(expand_builtin_memcmp): Mark both memory operands as loads.
(expand_builtin_strcmp): Likewise.
(expand_builtin_strncmp): Likewise.
(inline_string_cmp): Mark the memory operand as a load.
* builtins.h (get_memory_rtx): Add STORE_P.
* internal-fn.cc (expand_RAWMEMCHR): Mark the memory operand as a
load.
gcc/testsuite/ChangeLog:
* g++.dg/opt/mem-notrap-load-builtin.C: New test.
Signed-off-by: Kyrylo Tkachov <[email protected]>
---
gcc/builtins.cc | 35 ++++++++++---------
gcc/builtins.h | 2 +-
gcc/internal-fn.cc | 2 +-
.../g++.dg/opt/mem-notrap-load-builtin.C | 22 ++++++++++++
4 files changed, 42 insertions(+), 19 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/opt/mem-notrap-load-builtin.C
diff --git a/gcc/builtins.cc b/gcc/builtins.cc
index 056fd20c4c6..02170d74ae9 100644
--- a/gcc/builtins.cc
+++ b/gcc/builtins.cc
@@ -1364,10 +1364,10 @@ expand_builtin_prefetch (tree exp)
/* Get a MEM rtx for expression EXP which is the address of an operand
to be used in a string instruction (cmpstrsi, cpymemsi, ..). LEN is
the maximum length of the block of memory that might be accessed or
- NULL if unknown. */
+ NULL if unknown. STORE_P is true when EXP is the destination. */
rtx
-get_memory_rtx (tree exp, tree len)
+get_memory_rtx (tree exp, tree len, bool store_p)
{
tree orig_exp = exp, base;
rtx addr, mem;
@@ -1401,7 +1401,7 @@ get_memory_rtx (tree exp, tree len)
from the original address we got, and build an all-aliasing
unknown-sized access to that one. */
if (is_gimple_mem_ref_addr (TREE_OPERAND (exp, 0)))
- set_mem_attributes (mem, exp, 0);
+ set_mem_attributes (mem, exp, 0, store_p);
else if (TREE_CODE (TREE_OPERAND (exp, 0)) == ADDR_EXPR
&& (base = get_base_address (TREE_OPERAND (TREE_OPERAND (exp, 0),
0))))
@@ -1414,7 +1414,7 @@ get_memory_rtx (tree exp, tree len)
size_zero_node,
NULL)),
exp, build_int_cst (ptr_type_node, 0));
- set_mem_attributes (mem, exp, 0);
+ set_mem_attributes (mem, exp, 0, store_p);
/* Since we stripped parts make sure the offset is unknown and the
alignment is computed from the original address. */
clear_mem_offset (mem);
@@ -3770,7 +3770,7 @@ expand_builtin_memory_copy_args (tree dest, tree src,
tree len,
if (expected_align < dest_align)
expected_align = dest_align;
- dest_mem = get_memory_rtx (dest, len);
+ dest_mem = get_memory_rtx (dest, len, true);
set_mem_align (dest_mem, dest_align);
len_rtx = expand_normal (len);
determine_block_size (len, len_rtx, &min_size, &max_size,
@@ -3804,7 +3804,7 @@ expand_builtin_memory_copy_args (tree dest, tree src,
tree len,
return dest_mem;
}
- src_mem = get_memory_rtx (src, len);
+ src_mem = get_memory_rtx (src, len, false);
set_mem_align (src_mem, src_align);
/* Copy word part most expediently. */
@@ -3873,8 +3873,8 @@ expand_movstr (tree dest, tree src, rtx target, memop_ret
retmode)
if (!targetm.have_movstr ())
return NULL_RTX;
- dest_mem = get_memory_rtx (dest, NULL);
- src_mem = get_memory_rtx (src, NULL);
+ dest_mem = get_memory_rtx (dest, NULL, true);
+ src_mem = get_memory_rtx (src, NULL, false);
if (retmode == RETURN_BEGIN)
{
target = force_reg (Pmode, XEXP (dest_mem, 0));
@@ -4150,7 +4150,7 @@ expand_builtin_strncpy (tree exp, rtx target)
dest_align, false))
return NULL_RTX;
- dest_mem = get_memory_rtx (dest, len);
+ dest_mem = get_memory_rtx (dest, len, true);
store_by_pieces (dest_mem, tree_to_uhwi (len),
builtin_strncpy_read_str,
const_cast<char *> (p), dest_align, false,
@@ -4709,7 +4709,7 @@ expand_builtin_memset_args (tree dest, tree val, tree len,
len_rtx = expand_normal (len);
determine_block_size (len, len_rtx, &min_size, &max_size,
&probable_max_size);
- dest_mem = get_memory_rtx (dest, len);
+ dest_mem = get_memory_rtx (dest, len, true);
val_mode = TYPE_MODE (unsigned_char_type_node);
if (TREE_CODE (val) != INTEGER_CST
@@ -4893,8 +4893,8 @@ expand_builtin_memcmp (tree exp, rtx target, bool
result_eq)
if (arg1_align == 0 || arg2_align == 0)
return NULL_RTX;
- rtx arg1_rtx = get_memory_rtx (arg1, len);
- rtx arg2_rtx = get_memory_rtx (arg2, len);
+ rtx arg1_rtx = get_memory_rtx (arg1, len, false);
+ rtx arg2_rtx = get_memory_rtx (arg2, len, false);
rtx len_rtx = expand_normal (fold_convert_loc (loc, sizetype, len));
/* Set MEM_SIZE as appropriate. */
@@ -4987,8 +4987,8 @@ expand_builtin_strcmp (tree exp, ATTRIBUTE_UNUSED rtx
target)
arg1 = builtin_save_expr (arg1);
arg2 = builtin_save_expr (arg2);
- rtx arg1_rtx = get_memory_rtx (arg1, NULL);
- rtx arg2_rtx = get_memory_rtx (arg2, NULL);
+ rtx arg1_rtx = get_memory_rtx (arg1, NULL, false);
+ rtx arg2_rtx = get_memory_rtx (arg2, NULL, false);
/* Try to call cmpstrsi. */
if (cmpstr_icode != CODE_FOR_nothing)
@@ -5144,8 +5144,8 @@ expand_builtin_strncmp (tree exp, ATTRIBUTE_UNUSED rtx
target,
len = fold_convert_loc (loc, sizetype, len);
len = fold_build2_loc (loc, MIN_EXPR, TREE_TYPE (len), len, len3);
}
- rtx arg1_rtx = get_memory_rtx (arg1, len);
- rtx arg2_rtx = get_memory_rtx (arg2, len);
+ rtx arg1_rtx = get_memory_rtx (arg1, len, false);
+ rtx arg2_rtx = get_memory_rtx (arg2, len, false);
rtx arg3_rtx = expand_normal (len);
result = expand_cmpstrn_or_cmpmem (cmpstrn_icode, target, arg1_rtx,
arg2_rtx, TREE_TYPE (len), arg3_rtx,
@@ -7602,7 +7602,8 @@ inline_string_cmp (rtx target, tree var_str, const char
*const_str,
{
HOST_WIDE_INT offset = 0;
rtx var_rtx_array
- = get_memory_rtx (var_str, build_int_cst (unsigned_type_node,length));
+ = get_memory_rtx (var_str, build_int_cst (unsigned_type_node, length),
+ false);
rtx var_rtx = NULL_RTX;
rtx const_rtx = NULL_RTX;
rtx result = target ? target : gen_reg_rtx (mode);
diff --git a/gcc/builtins.h b/gcc/builtins.h
index 9cca88c647c..97b79908d0d 100644
--- a/gcc/builtins.h
+++ b/gcc/builtins.h
@@ -162,7 +162,7 @@ extern char target_percent_s[3];
extern char target_percent_c[3];
extern char target_percent_s_newline[4];
extern bool target_char_cst_p (tree t, char *p);
-extern rtx get_memory_rtx (tree exp, tree len);
+extern rtx get_memory_rtx (tree exp, tree len, bool store_p);
extern internal_fn associated_internal_fn (combined_fn, tree);
extern internal_fn associated_internal_fn (tree);
diff --git a/gcc/internal-fn.cc b/gcc/internal-fn.cc
index c57b594ac59..eae0ca9bf51 100644
--- a/gcc/internal-fn.cc
+++ b/gcc/internal-fn.cc
@@ -3404,7 +3404,7 @@ expand_RAWMEMCHR (internal_fn, gcall *stmt)
create_call_lhs_operand (&ops[0], lhs_rtx, lhs_mode);
tree mem = gimple_call_arg (stmt, 0);
- rtx mem_rtx = get_memory_rtx (mem, NULL);
+ rtx mem_rtx = get_memory_rtx (mem, NULL, false);
create_fixed_operand (&ops[1], mem_rtx);
tree pattern = gimple_call_arg (stmt, 1);
diff --git a/gcc/testsuite/g++.dg/opt/mem-notrap-load-builtin.C
b/gcc/testsuite/g++.dg/opt/mem-notrap-load-builtin.C
new file mode 100644
index 00000000000..1e8bfa0c603
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/mem-notrap-load-builtin.C
@@ -0,0 +1,22 @@
+// Keep the source loads of an inline memcmp nontrapping.
+
+// { dg-do compile }
+// { dg-options "-O2 -fdelete-null-pointer-checks -fnon-call-exceptions
-finline-stringops=memcmp -fdump-rtl-expand" }
+// { dg-require-effective-target ptr32plus }
+// { dg-skip-if "" keeps_null_pointer_checks }
+
+struct blocks
+{
+ unsigned char first[16384];
+ unsigned char second[16384];
+ int compare () const;
+};
+
+int
+blocks::compare () const
+{
+ return __builtin_memcmp (first, second, sizeof (first));
+}
+
+// { dg-final { scan-rtl-dump {\(mem(?:/[a-z])*/c(?:/[a-z])*:[^\n\r]*\[ this
\]} "expand" } }
+// { dg-final { scan-assembler-not {\mmemcmp\M} } }
--
2.50.1 (Apple Git-155)
