re PR target/52828 (powerpc -m32 -Os writes register saves below stack)

	PR target/52828
	* config/rs6000/rs6000.c (rs6000_emit_stack_tie): Rewrite with
	tie regs on destination of sets.  Delete forward declaration.
	(rs6000_emit_stack_reset): Update rs6000_emit_stack_tie calls.
	(rs6000_emit_prologue): Likewise.
	(rs6000_emit_epilogue): Likewise.  Use in place of gen_frame_tie
	and gen_stack_tie.
	(is_mem_ref): Use tie_operand to recognise stack ties.
	* config/rs6000/predicates.md (tie_operand): New.
	* config/rs6000/rs6000.md (restore_stack_block): Generate new
	stack tie rtl.
	(restore_stack_nonlocal): Likewise.
	(stack_tie): Update.
	(frame_tie): Delete.

From-SVN: r186397

4 files changed, 73 insertions, 41 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a0b7aa7..3c0bb61 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,20 @@
+2012-04-13  Alan Modra  <amodra@gmail.com>
+
+	PR target/52828
+	* config/rs6000/rs6000.c (rs6000_emit_stack_tie): Rewrite with
+	tie regs on destination of sets.  Delete forward declaration.
+	(rs6000_emit_stack_reset): Update rs6000_emit_stack_tie calls.
+	(rs6000_emit_prologue): Likewise.
+	(rs6000_emit_epilogue): Likewise.  Use in place of gen_frame_tie
+	and gen_stack_tie.
+	(is_mem_ref): Use tie_operand to recognise stack ties.
+	* config/rs6000/predicates.md (tie_operand): New.
+	* config/rs6000/rs6000.md (restore_stack_block): Generate new
+	stack tie rtl.
+	(restore_stack_nonlocal): Likewise.
+	(stack_tie): Update.
+	(frame_tie): Delete.
+
 2012-04-12  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>
 
 	* tree-ssa-reassoc.c (attempt_builtin_powi_stats): Change %ld to
diff --git a/gcc/config/rs6000/predicates.md b/gcc/config/rs6000/predicates.md
index 29dd18d..232773d 100644
--- a/gcc/config/rs6000/predicates.md
+++ b/gcc/config/rs6000/predicates.md
@@ -1451,3 +1451,13 @@
 
   return 1;
 })
+
+;; Return 1 if OP is a stack tie operand.
+(define_predicate "tie_operand"
+  (match_code "parallel")
+{
+  return (GET_CODE (XVECEXP (op, 0, 0)) == SET
+	  && GET_CODE (XEXP (XVECEXP (op, 0, 0), 0)) == MEM
+	  && GET_MODE (XEXP (XVECEXP (op, 0, 0), 0)) == BLKmode
+	  && XEXP (XVECEXP (op, 0, 0), 1) == const0_rtx);
+})
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index d053931..ceb6448 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -925,7 +925,6 @@ static const char *rs6000_invalid_within_doloop (const_rtx);
 static bool rs6000_legitimate_address_p (enum machine_mode, rtx, bool);
 static bool rs6000_debug_legitimate_address_p (enum machine_mode, rtx, bool);
 static rtx rs6000_generate_compare (rtx, enum machine_mode);
-static void rs6000_emit_stack_tie (void);
 static bool spe_func_has_64bit_regs_p (void);
 static rtx gen_frame_mem_offset (enum machine_mode, rtx, int);
 static unsigned rs6000_hash_constant (rtx);
@@ -18505,12 +18504,29 @@ rs6000_aix_asm_output_dwarf_table_ref (char * frame_table_label)
    and the change to the stack pointer.  */
 
 static void
-rs6000_emit_stack_tie (void)
+rs6000_emit_stack_tie (rtx fp, bool hard_frame_needed)
 {
-  rtx mem = gen_frame_mem (BLKmode,
-			   gen_rtx_REG (Pmode, STACK_POINTER_REGNUM));
+  rtvec p;
+  int i;
+  rtx regs[3];
+
+  i = 0;
+  regs[i++] = gen_rtx_REG (Pmode, STACK_POINTER_REGNUM);
+  if (hard_frame_needed)
+    regs[i++] = gen_rtx_REG (Pmode, HARD_FRAME_POINTER_REGNUM);
+  if (!(REGNO (fp) == STACK_POINTER_REGNUM
+	|| (hard_frame_needed
+	    && REGNO (fp) == HARD_FRAME_POINTER_REGNUM)))
+    regs[i++] = fp;
 
-  emit_insn (gen_stack_tie (mem));
+  p = rtvec_alloc (i);
+  while (--i >= 0)
+    {
+      rtx mem = gen_frame_mem (BLKmode, regs[i]);
+      RTVEC_ELT (p, i) = gen_rtx_SET (VOIDmode, mem, const0_rtx);
+    }
+
+  emit_insn (gen_stack_tie (gen_rtx_PARALLEL (VOIDmode, p)));
 }
 
 /* Emit the correct code for allocating stack space, as insns.
@@ -19130,7 +19146,7 @@ rs6000_emit_stack_reset (rs6000_stack_t *info,
       || (TARGET_SPE_ABI
 	  && info->spe_64bit_regs_used != 0
 	  && info->first_gp_reg_save != 32))
-    rs6000_emit_stack_tie ();
+    rs6000_emit_stack_tie (frame_reg_rtx, frame_pointer_needed);
   
   if (frame_reg_rtx != sp_reg_rtx)
     {
@@ -19350,7 +19366,7 @@ rs6000_emit_prologue (void)
 	}
       rs6000_emit_allocate_stack (info->total_size, copy_reg);
       if (frame_reg_rtx != sp_reg_rtx)
-	rs6000_emit_stack_tie ();
+	rs6000_emit_stack_tie (frame_reg_rtx, false);
     }
 
   /* Handle world saves specially here.  */
@@ -19854,7 +19870,7 @@ rs6000_emit_prologue (void)
 	sp_offset = info->total_size;
       rs6000_emit_allocate_stack (info->total_size, copy_reg);
       if (frame_reg_rtx != sp_reg_rtx)
-	rs6000_emit_stack_tie ();
+	rs6000_emit_stack_tie (frame_reg_rtx, false);
     }
 
   /* Set frame pointer, if needed.  */
@@ -20425,13 +20441,7 @@ rs6000_emit_epilogue (int sibcall)
       /* 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));
-	}
+	rs6000_emit_stack_tie (frame_reg_rtx, true);
 
       insn = emit_insn (gen_add3_insn (frame_reg_rtx, hard_frame_pointer_rtx,
 				       GEN_INT (info->total_size)));
@@ -20444,11 +20454,7 @@ rs6000_emit_epilogue (int sibcall)
       /* 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));
-	}
+	rs6000_emit_stack_tie (frame_reg_rtx, false);
       insn = emit_insn (gen_add3_insn (sp_reg_rtx, sp_reg_rtx,
 				       GEN_INT (info->total_size)));
       sp_offset = 0;
@@ -22835,8 +22841,7 @@ is_mem_ref (rtx pat)
   bool ret = false;
 
   /* stack_tie does not produce any real memory traffic.  */
-  if (GET_CODE (pat) == UNSPEC
-      && XINT (pat, 1) == UNSPEC_TIE)
+  if (tie_operand (pat, VOIDmode))
     return false;
 
   if (GET_CODE (pat) == MEM)
diff --git a/gcc/config/rs6000/rs6000.md b/gcc/config/rs6000/rs6000.md
index 1f5085d..3d27169 100644
--- a/gcc/config/rs6000/rs6000.md
+++ b/gcc/config/rs6000/rs6000.md
@@ -73,7 +73,6 @@
 (define_c_enum "unspec"
   [UNSPEC_FRSP			; frsp for POWER machines
    UNSPEC_PROBE_STACK		; probe stack memory reference
-   UNSPEC_TIE			; tie stack contents and stack pointer
    UNSPEC_TOCPTR		; address of a word pointing to the TOC
    UNSPEC_TOC			; address of the TOC (more-or-less)
    UNSPEC_MOVSI_GOT
@@ -11989,17 +11988,23 @@
 (define_expand "restore_stack_block"
   [(set (match_dup 2) (match_dup 3))
    (set (match_dup 4) (match_dup 2))
-   (set (match_dup 5) (unspec:BLK [(match_dup 5)] UNSPEC_TIE))
+   (match_dup 5)
    (set (match_operand 0 "register_operand" "")
 	(match_operand 1 "register_operand" ""))]
   ""
   "
 {
+  rtvec p;
+
   operands[1] = force_reg (Pmode, operands[1]);
   operands[2] = gen_reg_rtx (Pmode);
   operands[3] = gen_frame_mem (Pmode, operands[0]);
   operands[4] = gen_frame_mem (Pmode, operands[1]);
-  operands[5] = gen_frame_mem (BLKmode, operands[0]);
+  p = rtvec_alloc (1);
+  RTVEC_ELT (p, 0) = gen_rtx_SET (VOIDmode,
+				  gen_frame_mem (BLKmode, operands[0]),
+				  const0_rtx);
+  operands[5] = gen_rtx_PARALLEL (VOIDmode, p);
 }")
 
 (define_expand "save_stack_nonlocal"
@@ -12022,12 +12027,13 @@
   [(set (match_dup 2) (match_operand 1 "memory_operand" ""))
    (set (match_dup 3) (match_dup 4))
    (set (match_dup 5) (match_dup 2))
-   (set (match_dup 6) (unspec:BLK [(match_dup 6)] UNSPEC_TIE))
+   (match_dup 6)
    (set (match_operand 0 "register_operand" "") (match_dup 3))]
   ""
   "
 {
   int units_per_word = (TARGET_32BIT) ? 4 : 8;
+  rtvec p;
 
   /* Restore the backchain from the first word, sp from the second.  */
   operands[2] = gen_reg_rtx (Pmode);
@@ -12035,7 +12041,11 @@
   operands[1] = adjust_address_nv (operands[1], Pmode, 0);
   operands[4] = adjust_address_nv (operands[1], Pmode, units_per_word);
   operands[5] = gen_frame_mem (Pmode, operands[3]);
-  operands[6] = gen_frame_mem (BLKmode, operands[0]);
+  p = rtvec_alloc (1);
+  RTVEC_ELT (p, 0) = gen_rtx_SET (VOIDmode,
+				  gen_frame_mem (BLKmode, operands[0]),
+				  const0_rtx);
+  operands[6] = gen_rtx_PARALLEL (VOIDmode, p);
 }")
 
 ;; TOC register handling.
@@ -15899,25 +15909,15 @@
   [(set_attr "type" "branch")
    (set_attr "length" "4")])
 
-; These are to explain that changes to the stack pointer should
-; not be moved over stores to stack memory.
+; This is to explain that changes to the stack pointer should
+; not be moved over loads from or stores to stack memory.
 (define_insn "stack_tie"
-  [(set (match_operand:BLK 0 "memory_operand" "+m")
-        (unspec:BLK [(match_dup 0)] UNSPEC_TIE))]
-  ""
-  ""
-  [(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))]
+  [(match_parallel 0 "tie_operand"
+		   [(set (mem:BLK (reg 1)) (const_int 0))])]
   ""
   ""
   [(set_attr "length" "0")])
 
-
 (define_expand "epilogue"
   [(use (const_int 0))]
   ""