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* config/i386/i386.c (ix86_emit_restore_reg_using_pop): Prototype.
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(ix86_adjust_stack_and_probe_stack_clash): Use a push/pop sequence
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to probe at the start of a noreturn function.
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* gcc.target/i386/stack-check-12.c: New test
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diff -Nrup a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
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--- a/gcc/config/i386/i386.c 2017-11-03 13:35:17.641528205 -0600
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+++ b/gcc/config/i386/i386.c 2017-11-03 13:37:39.489361692 -0600
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@@ -64,6 +64,7 @@ along with GCC; see the file COPYING3.
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#include "tree-flow.h"
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static rtx legitimize_dllimport_symbol (rtx, bool);
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+static void ix86_emit_restore_reg_using_pop (rtx);
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#ifndef CHECK_STACK_LIMIT
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#define CHECK_STACK_LIMIT (-1)
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@@ -9884,8 +9885,14 @@ ix86_adjust_stack_and_probe_stack_clash
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we just probe when we cross PROBE_INTERVAL. */
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if (TREE_THIS_VOLATILE (cfun->decl))
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{
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- emit_stack_probe (plus_constant (Pmode, stack_pointer_rtx,
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- -GET_MODE_SIZE (word_mode)));
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+ /* We can safely use any register here since we're just going to push
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+ its value and immediately pop it back. But we do try and avoid
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+ argument passing registers so as not to introduce dependencies in
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+ the pipeline. For 32 bit we use %esi and for 64 bit we use %rax. */
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+ rtx dummy_reg = gen_rtx_REG (word_mode, TARGET_64BIT ? AX_REG : SI_REG);
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+ rtx insn = emit_insn (gen_push (dummy_reg));
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+ RTX_FRAME_RELATED_P (insn) = 1;
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+ ix86_emit_restore_reg_using_pop (dummy_reg);
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emit_insn (gen_blockage ());
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}
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diff -Nrup a/gcc/testsuite/gcc.target/i386/stack-check-12.c b/gcc/testsuite/gcc.target/i386/stack-check-12.c
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--- a/gcc/testsuite/gcc.target/i386/stack-check-12.c 1969-12-31 17:00:00.000000000 -0700
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+++ b/gcc/testsuite/gcc.target/i386/stack-check-12.c 2017-11-03 13:36:15.104055651 -0600
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@@ -0,0 +1,19 @@
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+/* { dg-do compile } */
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+/* { dg-options "-O2 -fstack-clash-protection -mtune=generic -fomit-frame-pointer" } */
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+/* { dg-require-effective-target supports_stack_clash_protection } */
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+
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+__attribute__ ((noreturn)) void exit (int);
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+
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+__attribute__ ((noreturn)) void
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+f (void)
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+{
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+ asm volatile ("nop" ::: "edi");
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+ exit (1);
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+}
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+
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+/* { dg-final { scan-assembler-not "or\[ql\]" } } */
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+/* { dg-final { scan-assembler "pushl %esi" { target ia32 } } } */
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+/* { dg-final { scan-assembler "popl %esi" { target ia32 } } }*/
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+/* { dg-final { scan-assembler "pushq %rax" { target { ! ia32 } } } } */
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+/* { dg-final { scan-assembler "popq %rax" { target { ! ia32 } } } }*/
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+
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