sparc.md (UNSPEC_FRAME_BLOCKAGE): New constant.

	* config/sparc/sparc.md (UNSPEC_FRAME_BLOCKAGE): New constant.
	(frame_blockage): New expander.
	(frame_blockage<P:mode>): New instruction.
	* config/sparc/sparc.c (sparc_expand_prologue): When the sequence of
	instructions establishing the frame isn't atomic, emit frame blockage.

From-SVN: r182420

gcc/ChangeLog

+2011-12-16  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* config/sparc/sparc.md (UNSPEC_FRAME_BLOCKAGE): New constant.
+	(frame_blockage): New expander.
+	(frame_blockage<P:mode>): New instruction.
+	* config/sparc/sparc.c (sparc_expand_prologue): When the sequence of
+	instructions establishing the frame isn't atomic, emit frame blockage.
+
 2011-12-16  Tristan Gingold  <gingold@adacore.com>
 
 	* config/alpha/vms.h (USE_TM_CLONE_REGISTRY): Define.

gcc/config/sparc/sparc.c

@@ -4972,8 +4972,9 @@ sparc_expand_prologue (void)
       else if (size <= 8192)
 	{
 	  insn = emit_insn (gen_stack_pointer_inc (GEN_INT (-4096)));
-	  /* %sp is still the CFA register.  */
 	  RTX_FRAME_RELATED_P (insn) = 1;
+
+	  /* %sp is still the CFA register.  */
 	  insn = emit_insn (gen_stack_pointer_inc (GEN_INT (4096 - size)));
 	}
       else
@@ -4996,8 +4997,18 @@ sparc_expand_prologue (void)
       else if (size <= 8192)
 	{
 	  emit_window_save (GEN_INT (-4096));
+
 	  /* %sp is not the CFA register anymore.  */
 	  emit_insn (gen_stack_pointer_inc (GEN_INT (4096 - size)));
+
+	  /* Make sure no %fp-based store is issued until after the frame is
+	     established.  The offset between the frame pointer and the stack
+	     pointer is calculated relative to the value of the stack pointer
+	     at the end of the function prologue, and moving instructions that
+	     access the stack via the frame pointer between the instructions
+	     that decrement the stack pointer could result in accessing the
+	     register window save area, which is volatile.  */
+	  emit_insn (gen_frame_blockage ());
 	}
       else
 	{

gcc/config/sparc/sparc.md

@@ -28,6 +28,7 @@
   [(UNSPEC_MOVE_PIC		0)
    (UNSPEC_UPDATE_RETURN	1)
    (UNSPEC_LOAD_PCREL_SYM	2)
+   (UNSPEC_FRAME_BLOCKAGE      3)
    (UNSPEC_MOVE_PIC_LABEL	5)
    (UNSPEC_SETH44		6)
    (UNSPEC_SETM44		7)
@@ -6375,6 +6376,25 @@
   ""
   [(set_attr "length" "0")])
 
+;; Do not schedule instructions accessing memory before this point.
+
+(define_expand "frame_blockage"
+  [(set (match_dup 0)
+	(unspec:BLK [(match_dup 1)] UNSPEC_FRAME_BLOCKAGE))]
+  ""
+{
+  operands[0] = gen_rtx_MEM (BLKmode, gen_rtx_SCRATCH (Pmode));
+  MEM_VOLATILE_P (operands[0]) = 1;
+  operands[1] = stack_pointer_rtx;
+})
+
+(define_insn "*frame_blockage<P:mode>"
+  [(set (match_operand:BLK 0 "" "")
+	(unspec:BLK [(match_operand:P 1 "" "")] UNSPEC_FRAME_BLOCKAGE))]
+  ""
+  ""
+  [(set_attr "length" "0")])
+
 (define_expand "probe_stack"
   [(set (match_operand 0 "memory_operand" "") (const_int 0))]
   ""