re PR target/44199 (ppc64 glibc miscompilation)

	PR target/44199
	* config/rs6000/rs6000.c (rs6000_emit_epilogue): If cfun->calls_alloca
	or total_size is larger than red zone size for non-V4 ABI, emit a
	stack_tie resp. frame_tie insn before stack pointer restore.
	* config/rs6000/rs6000.md (frame_tie): New insn.

From-SVN: r159853

gcc/ChangeLog

+2010-05-26  Jakub Jelinek  <jakub@redhat.com>
+
+	PR target/44199
+	* config/rs6000/rs6000.c (rs6000_emit_epilogue): If cfun->calls_alloca
+	or total_size is larger than red zone size for non-V4 ABI, emit a
+	stack_tie resp. frame_tie insn before stack pointer restore.
+	* config/rs6000/rs6000.md (frame_tie): New insn.
+
 2010-05-25  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* function.h (struct function): Add can_throw_non_call_exceptions bit.

gcc/config/rs6000/rs6000.c

@@ -19796,6 +19796,16 @@ rs6000_emit_epilogue (int sibcall)
       frame_reg_rtx = sp_reg_rtx;
       if (DEFAULT_ABI == ABI_V4)
 	frame_reg_rtx = gen_rtx_REG (Pmode, 11);
+      /* Prevent reordering memory accesses against stack pointer restore.  */
+      else if (cfun->calls_alloca
+	       || offset_below_red_zone_p (-info->total_size))
+	{
+	  rtx mem1 = gen_rtx_MEM (BLKmode, hard_frame_pointer_rtx);
+	  rtx mem2 = gen_rtx_MEM (BLKmode, sp_reg_rtx);
+	  MEM_NOTRAP_P (mem1) = 1;
+	  MEM_NOTRAP_P (mem2) = 1;
+	  emit_insn (gen_frame_tie (mem1, mem2));
+	}
 
       insn = emit_insn (gen_add3_insn (frame_reg_rtx, hard_frame_pointer_rtx,
 				       GEN_INT (info->total_size)));
@@ -19805,6 +19815,14 @@ rs6000_emit_epilogue (int sibcall)
 	   && DEFAULT_ABI != ABI_V4
 	   && !crtl->calls_eh_return)
     {
+      /* Prevent reordering memory accesses against stack pointer restore.  */
+      if (cfun->calls_alloca
+	  || offset_below_red_zone_p (-info->total_size))
+	{
+	  rtx mem = gen_rtx_MEM (BLKmode, sp_reg_rtx);
+	  MEM_NOTRAP_P (mem) = 1;
+	  emit_insn (gen_stack_tie (mem));
+	}
       insn = emit_insn (gen_add3_insn (sp_reg_rtx, sp_reg_rtx,
 				       GEN_INT (info->total_size)));
       sp_offset = 0;

gcc/config/rs6000/rs6000.md

@@ -15286,6 +15286,15 @@
   ""
   [(set_attr "length" "0")])
 
+; Like stack_tie, but depend on both fp and sp based memory.
+(define_insn "frame_tie"
+  [(set (match_operand:BLK 0 "memory_operand" "+m")
+	(unspec:BLK [(match_dup 0)
+		     (match_operand:BLK 1 "memory_operand" "m")] UNSPEC_TIE))]
+  ""
+  ""
+  [(set_attr "length" "0")])
+
 
 (define_expand "epilogue"
   [(use (const_int 0))]