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* [gcc r12-5363] i386: Fix wrong codegen for -mrelax-cmpxchg-loop
@ 2021-11-18 8:31 Hongyu Wang
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From: Hongyu Wang @ 2021-11-18 8:31 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:15f5e70cbb33b40c97325ef9d55557747a148d39
commit r12-5363-g15f5e70cbb33b40c97325ef9d55557747a148d39
Author: Hongyu Wang <hongyu.wang@intel.com>
Date: Thu Nov 18 14:45:23 2021 +0800
i386: Fix wrong codegen for -mrelax-cmpxchg-loop
For -mrelax-cmpxchg-loop introduced by PR 103069/r12-5265, it would
produce infinite loop. The correct code should be
.L84:
movl (%rdi), %ecx
movl %eax, %edx
orl %esi, %edx
cmpl %eax, %ecx
jne .L82
lock cmpxchgl %edx, (%rdi)
jne .L84
movl %r8d, %eax <<< retval is missing in previous impl
ret
.L82:
rep nop
jmp .L84
Adjust corresponding expander to fix such issue, and fix runtime test
so the problem would be exposed.
gcc/ChangeLog:
* config/i386/i386-expand.c (ix86_expand_atomic_fetch_op_loop):
Adjust generated cfg to avoid infinite loop.
gcc/testsuite/ChangeLog:
* gcc.target/i386/pr103069-2.c: Adjust.
Diff:
---
gcc/config/i386/i386-expand.c | 7 ++++++-
gcc/testsuite/gcc.target/i386/pr103069-2.c | 11 ++++++-----
2 files changed, 12 insertions(+), 6 deletions(-)
diff --git a/gcc/config/i386/i386-expand.c b/gcc/config/i386/i386-expand.c
index 3e4de64ec24..0d5d1a0e205 100644
--- a/gcc/config/i386/i386-expand.c
+++ b/gcc/config/i386/i386-expand.c
@@ -23143,13 +23143,14 @@ void ix86_expand_atomic_fetch_op_loop (rtx target, rtx mem, rtx val,
bool doubleword)
{
rtx old_reg, new_reg, old_mem, success, oldval, new_mem;
- rtx_code_label *loop_label, *pause_label;
+ rtx_code_label *loop_label, *pause_label, *done_label;
machine_mode mode = GET_MODE (target);
old_reg = gen_reg_rtx (mode);
new_reg = old_reg;
loop_label = gen_label_rtx ();
pause_label = gen_label_rtx ();
+ done_label = gen_label_rtx ();
old_mem = copy_to_reg (mem);
emit_label (loop_label);
emit_move_insn (old_reg, old_mem);
@@ -23207,11 +23208,15 @@ void ix86_expand_atomic_fetch_op_loop (rtx target, rtx mem, rtx val,
GET_MODE (success), 1, loop_label,
profile_probability::guessed_never ());
+ emit_jump_insn (gen_jump (done_label));
+ emit_barrier ();
+
/* If mem is not expected, pause and loop back. */
emit_label (pause_label);
emit_insn (gen_pause ());
emit_jump_insn (gen_jump (loop_label));
emit_barrier ();
+ emit_label (done_label);
}
#include "gt-i386-expand.h"
diff --git a/gcc/testsuite/gcc.target/i386/pr103069-2.c b/gcc/testsuite/gcc.target/i386/pr103069-2.c
index 8ac824cc8e8..b3f2235fd55 100644
--- a/gcc/testsuite/gcc.target/i386/pr103069-2.c
+++ b/gcc/testsuite/gcc.target/i386/pr103069-2.c
@@ -1,5 +1,5 @@
-/* PR target/103068 */
-/* { dg-do compile } */
+/* PR target/103069 */
+/* { dg-do run } */
/* { dg-additional-options "-O2 -march=x86-64 -mtune=generic" } */
#include <stdlib.h>
@@ -37,13 +37,14 @@ FUNC_ATOMIC_RELAX (char, xor)
#define TEST_ATOMIC_FETCH_LOGIC(TYPE, OP) \
{ \
TYPE a = 11, b = 101, res, exp; \
+ TYPE c = 11, d = 101; \
res = relax_##TYPE##_##OP##_fetch (&a, b); \
- exp = f_##TYPE##_##OP##_fetch (&a, b); \
+ exp = f_##TYPE##_##OP##_fetch (&c, d); \
if (res != exp) \
abort (); \
- a = 21, b = 92; \
+ a = c = 21, b = d = 92; \
res = relax_##TYPE##_fetch_##OP (&a, b); \
- exp = f_##TYPE##_fetch_##OP (&a, b); \
+ exp = f_##TYPE##_fetch_##OP (&c, d); \
if (res != exp) \
abort (); \
}
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