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[PATCH] Fix PR16356


This fixes PR 16356, a regression caused by floatdisf2_internal2
manipulating its input register rather than copying to a new output reg.
While I was poking at this problem, I noticed we can get rid of one of
the branches in this expander by using the following trick:

  if (x & 2047)
    {
      x &= ~2047;
      x |= 2048;
    }

can be implemented as

  tmp = x & 2047;
  tmp += 2047;
  x |= tmp;
  x &= ~2047;

Removing the branch allows floatdisf2_internal2 to be used when
TARGET_POWERPC64, because the old branch condition was the only reason
that this insn needed to be TARGET_64BIT.

	PR rtl-optimization/16356
	* config/rs6000/rs6000.md (floatdisf2_internal2): Rewrite with
	separate output register and one less jump.  Enable for powerpc64.
	(floatdisf2): Adjust for above.

Bootstrapped and regression tested powerpc64-linux.  Also tested that
a few G random long values convert to exactly the same floats as older
compilers give.  OK to apply?  3.4 too?

--- gcc-virgin/gcc/config/rs6000/rs6000.md	2004-11-15 17:05:37.000000000 +1030
+++ gcc-current/gcc/config/rs6000/rs6000.md	2004-11-26 08:48:09.671759913 +1030
@@ -5402,16 +5402,18 @@
 (define_expand "floatdisf2"
   [(set (match_operand:SF 0 "gpc_reg_operand" "")
         (float:SF (match_operand:DI 1 "gpc_reg_operand" "")))]
-  "TARGET_64BIT && TARGET_HARD_FLOAT && TARGET_FPRS"
+  "TARGET_POWERPC64 && TARGET_HARD_FLOAT && TARGET_FPRS"
   "
 {
+  rtx val = operands[1];
   if (!flag_unsafe_math_optimizations)
     {
       rtx label = gen_label_rtx ();
-      emit_insn (gen_floatdisf2_internal2 (operands[1], label));
+      val = gen_reg_rtx (DImode);
+      emit_insn (gen_floatdisf2_internal2 (val, operands[1], label));
       emit_label (label);
     }
-  emit_insn (gen_floatdisf2_internal1 (operands[0], operands[1]));
+  emit_insn (gen_floatdisf2_internal1 (operands[0], val));
   DONE;
 }")
 
@@ -5436,30 +5438,31 @@
 ;; by a bit that won't be lost at that stage, but is below the SFmode
 ;; rounding position.
 (define_expand "floatdisf2_internal2"
-  [(parallel [(set (match_dup 4)
-		   (compare:CC (and:DI (match_operand:DI 0 "" "")
-				       (const_int 2047))
-			       (const_int 0)))
-	      (set (match_dup 2) (and:DI (match_dup 0) (const_int 2047)))
-	      (clobber (match_scratch:CC 7 ""))])
-   (set (match_dup 3) (ashiftrt:DI (match_dup 0) (const_int 53)))
-   (set (match_dup 3) (plus:DI (match_dup 3) (const_int 1)))
-   (set (pc) (if_then_else (eq (match_dup 4) (const_int 0))
-			   (label_ref (match_operand:DI 1 "" ""))
-			   (pc)))
-   (set (match_dup 5) (compare:CCUNS (match_dup 3) (const_int 2)))
-   (set (pc) (if_then_else (ltu (match_dup 5) (const_int 0))
-			   (label_ref (match_dup 1))
+  [(set (match_dup 3) (ashiftrt:DI (match_operand:DI 1 "" "")
+				   (const_int 53)))
+   (parallel [(set (match_operand:DI 0 "" "") (and:DI (match_dup 1)
+						      (const_int 2047)))
+	      (clobber (scratch:CC))])
+   (set (match_dup 3) (plus:DI (match_dup 3)
+			       (const_int 1)))
+   (set (match_dup 0) (plus:DI (match_dup 0)
+			       (const_int 2047)))
+   (set (match_dup 4) (compare:CCUNS (match_dup 3)
+				     (const_int 3)))
+   (set (match_dup 0) (ior:DI (match_dup 0)
+			      (match_dup 1)))
+   (parallel [(set (match_dup 0) (and:DI (match_dup 0)
+					 (const_int -2048)))
+	      (clobber (scratch:CC))])
+   (set (pc) (if_then_else (geu (match_dup 4) (const_int 0))
+			   (label_ref (match_operand:DI 2 "" ""))
 			   (pc)))
-   (set (match_dup 0) (xor:DI (match_dup 0) (match_dup 2)))
-   (set (match_dup 0) (ior:DI (match_dup 0) (const_int 2048)))]
-  "TARGET_64BIT && TARGET_HARD_FLOAT && TARGET_FPRS"
+   (set (match_dup 0) (match_dup 1))]
+  "TARGET_POWERPC64 && TARGET_HARD_FLOAT && TARGET_FPRS"
   "
 {
-  operands[2] = gen_reg_rtx (DImode);
   operands[3] = gen_reg_rtx (DImode);
-  operands[4] = gen_reg_rtx (CCmode);
-  operands[5] = gen_reg_rtx (CCUNSmode);
+  operands[4] = gen_reg_rtx (CCUNSmode);
 }")
 
 ;; Define the DImode operations that can be done in a small number

-- 
Alan Modra
IBM OzLabs - Linux Technology Centre


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