Index: i386.md
===================================================================
--- i386.md	(revision 235620)
+++ i386.md	(working copy)
@@ -88,6 +88,7 @@
   UNSPEC_SET_GOT_OFFSET
   UNSPEC_MEMORY_BLOCKAGE
   UNSPEC_STACK_CHECK
+  UNSPEC_PROBE_STACK
 
   ;; TLS support
   UNSPEC_TP
@@ -17552,6 +17553,30 @@
   DONE;
 })
 
+(define_expand "probe_stack"
+  [(match_operand 0 "memory_operand")]
+  ""
+{
+  rtx (*insn) (rtx, rtx)
+    = (GET_MODE (operands[0]) == DImode
+       ? gen_probe_stack_di : gen_probe_stack_si);
+
+  emit_insn (insn (operands[0], const0_rtx));
+  DONE;
+})
+
+;; Use OR for stack probes, this is shorter.
+(define_insn "probe_stack_<mode>"
+  [(set (match_operand:W 0 "memory_operand" "=m")
+	(unspec:W [(match_operand:W 1 "const0_operand")]
+		  UNSPEC_PROBE_STACK))
+   (clobber (reg:CC FLAGS_REG))]
+  ""
+  "or{<imodesuffix>}\t{%1, %0|%0, %1}"
+  [(set_attr "type" "alu1")
+   (set_attr "mode" "<MODE>")
+   (set_attr "length_immediate" "1")])
+  
 (define_insn "adjust_stack_and_probe<mode>"
   [(set (match_operand:P 0 "register_operand" "=r")
 	(unspec_volatile:P [(match_operand:P 1 "register_operand" "0")]