re PR tree-optimization/24964 (Does not optimise abs(x)**2 to x**2)

	PR tree-optimization/24964
	* simplify-rtx.c (simplify_binary_operation_1): Add function comment.
	<MULT>: Minor clean-up.  Don't convert x*-1.0 into -x if we honor
	signaling NaNs.  Optimize -x*-x as x*x for all float modes, and
	abs(x)*abs(x) as x*x for scalar floating point modes.

	* gcc.target/i386/387-10.c: New test case.

From-SVN: r114206

4 files changed, 62 insertions, 7 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index dc310f6..97ec80cd 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2006-05-29  Roger Sayle  <roger@eyesopen.com>
+
+	PR tree-optimization/24964
+	* simplify-rtx.c (simplify_binary_operation_1): Add function comment.
+	<MULT>: Minor clean-up.  Don't convert x*-1.0 into -x if we honor
+	signaling NaNs.  Optimize -x*-x as x*x for all float modes, and
+	abs(x)*abs(x) as x*x for scalar floating point modes.
+
 2006-05-29  Sebastian Pop  <pop@cri.ensmp.fr>
 
 	PR middle-end/27745
diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index 7199316..c51ca9e 100644
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -1472,6 +1472,11 @@ simplify_binary_operation (enum rtx_code code, enum machine_mode mode,
   return simplify_binary_operation_1 (code, mode, op0, op1, trueop0, trueop1);
 }
 
+/* Subroutine of simplify_binary_operation.  Simplify a binary operation
+   CODE with result mode MODE, operating on OP0 and OP1.  If OP0 and/or
+   OP1 are constant pool references, TRUEOP0 and TRUEOP1 represent the
+   actual constants.  */
+
 static rtx
 simplify_binary_operation_1 (enum rtx_code code, enum machine_mode mode,
 			     rtx op0, rtx op1, rtx trueop0, rtx trueop1)
@@ -1907,12 +1912,12 @@ simplify_binary_operation_1 (enum rtx_code code, enum machine_mode mode,
 	return simplify_gen_binary (ASHIFT, mode, op0, GEN_INT (val));
 
       /* Likewise for multipliers wider than a word.  */
-      else if (GET_CODE (trueop1) == CONST_DOUBLE
-	       && (GET_MODE (trueop1) == VOIDmode
-		   || GET_MODE_CLASS (GET_MODE (trueop1)) == MODE_INT)
-	       && GET_MODE (op0) == mode
-	       && CONST_DOUBLE_LOW (trueop1) == 0
-	       && (val = exact_log2 (CONST_DOUBLE_HIGH (trueop1))) >= 0)
+      if (GET_CODE (trueop1) == CONST_DOUBLE
+	  && (GET_MODE (trueop1) == VOIDmode
+	      || GET_MODE_CLASS (GET_MODE (trueop1)) == MODE_INT)
+	  && GET_MODE (op0) == mode
+	  && CONST_DOUBLE_LOW (trueop1) == 0
+	  && (val = exact_log2 (CONST_DOUBLE_HIGH (trueop1))) >= 0)
 	return simplify_gen_binary (ASHIFT, mode, op0,
 				    GEN_INT (val + HOST_BITS_PER_WIDE_INT));
 
@@ -1927,10 +1932,27 @@ simplify_binary_operation_1 (enum rtx_code code, enum machine_mode mode,
 	  if (REAL_VALUES_EQUAL (d, dconst2))
 	    return simplify_gen_binary (PLUS, mode, op0, copy_rtx (op0));
 
-	  if (REAL_VALUES_EQUAL (d, dconstm1))
+	  if (!HONOR_SNANS (mode)
+	      && REAL_VALUES_EQUAL (d, dconstm1))
 	    return simplify_gen_unary (NEG, mode, op0, mode);
 	}
 
+      /* Optimize -x * -x as x * x.  */
+      if (FLOAT_MODE_P (mode)
+	  && GET_CODE (op0) == NEG
+	  && GET_CODE (op1) == NEG
+	  && rtx_equal_p (XEXP (op0, 0), XEXP (op1, 0))
+	  && !side_effects_p (XEXP (op0, 0)))
+	return simplify_gen_binary (MULT, mode, XEXP (op0, 0), XEXP (op1, 0));
+
+      /* Likewise, optimize abs(x) * abs(x) as x * x.  */
+      if (SCALAR_FLOAT_MODE_P (mode)
+	  && GET_CODE (op0) == ABS
+	  && GET_CODE (op1) == ABS
+	  && rtx_equal_p (XEXP (op0, 0), XEXP (op1, 0))
+	  && !side_effects_p (XEXP (op0, 0)))
+	return simplify_gen_binary (MULT, mode, XEXP (op0, 0), XEXP (op1, 0));
+
       /* Reassociate multiplication, but for floating point MULTs
 	 only when the user specifies unsafe math optimizations.  */
       if (! FLOAT_MODE_P (mode)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 96c5729..8778352 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2006-05-29  Roger Sayle  <roger@eyesopen.com>
+
+	PR tree-optimization/24964
+	* gcc.target/i386/387-10.c: New test case.
+
 2006-05-28  Thomas Koenig  <Thomas.Koenig@online.de>
 
 	* intrinsics/string_intrinsics.c (compare_string):
diff --git a/gcc/testsuite/gcc.target/i386/387-10.c b/gcc/testsuite/gcc.target/i386/387-10.c
new file mode 100644
index 0000000..150515b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/387-10.c
@@ -0,0 +1,20 @@
+/* PR tree-optimization/24964 */
+/* { dg-do compile { target i?86-*-* x86_64-*-* } } */
+/* { dg-options "-O2 -mfpmath=387" } */
+
+double fabs(double x);
+
+double test1(double x)
+{
+  double t = fabs(x);
+  return t*t;
+}
+
+double test2(double x)
+{
+  double t = -x;
+  return t*t;
+}
+
+/* { dg-final { scan-assembler-not "fchs" } } */
+/* { dg-final { scan-assembler-not "fabs" } } */