* config/i386/i386.c (ix86_emit_restore_reg_using_pop): Prototype.

            (ix86_adjust_stack_and_probe_stack_clash): Use a push/pop sequence

            to probe at the start of a noreturn function.

            * gcc.target/i386/stack-check-12.c: New test

diff -Nrup a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c

--- a/gcc/config/i386/i386.c	2017-11-03 13:35:17.641528205 -0600

+++ b/gcc/config/i386/i386.c	2017-11-03 13:37:39.489361692 -0600

@@ -64,6 +64,7 @@ along with GCC; see the file COPYING3.

 #include "tree-flow.h"

 static rtx legitimize_dllimport_symbol (rtx, bool);

+static void ix86_emit_restore_reg_using_pop (rtx);

 #ifndef CHECK_STACK_LIMIT

 #define CHECK_STACK_LIMIT (-1)

@@ -9884,8 +9885,14 @@ ix86_adjust_stack_and_probe_stack_clash

      we just probe when we cross PROBE_INTERVAL.  */

   if (TREE_THIS_VOLATILE (cfun->decl))

     {

-      emit_stack_probe (plus_constant (Pmode, stack_pointer_rtx,

-				       -GET_MODE_SIZE (word_mode)));

+      /* We can safely use any register here since we're just going to push

+	 its value and immediately pop it back.  But we do try and avoid

+	 argument passing registers so as not to introduce dependencies in

+	 the pipeline.  For 32 bit we use %esi and for 64 bit we use %rax.  */

+      rtx dummy_reg = gen_rtx_REG (word_mode, TARGET_64BIT ? AX_REG : SI_REG);

+      rtx insn = emit_insn (gen_push (dummy_reg));

+      RTX_FRAME_RELATED_P (insn) = 1;

+      ix86_emit_restore_reg_using_pop (dummy_reg);

       emit_insn (gen_blockage ());

     }

diff -Nrup a/gcc/testsuite/gcc.target/i386/stack-check-12.c b/gcc/testsuite/gcc.target/i386/stack-check-12.c

--- a/gcc/testsuite/gcc.target/i386/stack-check-12.c	1969-12-31 17:00:00.000000000 -0700

+++ b/gcc/testsuite/gcc.target/i386/stack-check-12.c	2017-11-03 13:36:15.104055651 -0600

@@ -0,0 +1,19 @@

+/* { dg-do compile } */

+/* { dg-options "-O2 -fstack-clash-protection -mtune=generic -fomit-frame-pointer" } */

+/* { dg-require-effective-target supports_stack_clash_protection } */

+

+__attribute__ ((noreturn)) void exit (int);

+

+__attribute__ ((noreturn)) void

+f (void)

+{

+  asm volatile ("nop" ::: "edi");

+  exit (1);

+}

+

+/* { dg-final { scan-assembler-not "or\[ql\]" } } */

+/* { dg-final { scan-assembler "pushl	%esi" { target ia32 } } } */

+/* { dg-final { scan-assembler "popl	%esi" { target ia32 } } }*/

+/* { dg-final { scan-assembler "pushq	%rax" { target { ! ia32 } } } } */

+/* { dg-final { scan-assembler "popq	%rax" { target { ! ia32 } } } }*/

+