re PR rtl-optimization/576 (gcc performs invalid optimization with float operations when different rounding mode.)

	PR rtl-optimization/576
	* real.c (real_arithmetic): Change return type from void to bool
	to return an indication that the result may be inexact.
	* real.h (real_arithmeric): Update prototype.
	* fold-const.c (const_binop):  Don't constant fold floating
	point expressions when the user specifies -frounding-math and
	the result may depend upon the run-time rounding mode.
	(fold_convert_const_real_from_real): Clean-up.
	(fold_initializer): Ignore flag_rounding_math for initializers.
	* simplify-rtx.c (simplify_binary_operation): Likewise, don't
	constant fold FP operations with flag_rounding_math if the
	result may depend upon the run-time rounding mode.

From-SVN: r94020

1 files changed, 8 insertions, 10 deletions

diff --git a/gcc/real.c b/gcc/real.c
index 5871d1e..a748b87 100644
--- a/gcc/real.c
+++ b/gcc/real.c
@@ -972,9 +972,10 @@ do_fix_trunc (REAL_VALUE_TYPE *r, const REAL_VALUE_TYPE *a)
 }
 
 /* Perform the binary or unary operation described by CODE.
-   For a unary operation, leave OP1 NULL.  */
+   For a unary operation, leave OP1 NULL.  This function returns
+   true if the result may be inexact due to loss of precision.  */
 
-void
+bool
 real_arithmetic (REAL_VALUE_TYPE *r, int icode, const REAL_VALUE_TYPE *op0,
 		 const REAL_VALUE_TYPE *op1)
 {
@@ -983,20 +984,16 @@ real_arithmetic (REAL_VALUE_TYPE *r, int icode, const REAL_VALUE_TYPE *op0,
   switch (code)
     {
     case PLUS_EXPR:
-      do_add (r, op0, op1, 0);
-      break;
+      return do_add (r, op0, op1, 0);
 
     case MINUS_EXPR:
-      do_add (r, op0, op1, 1);
-      break;
+      return do_add (r, op0, op1, 1);
 
     case MULT_EXPR:
-      do_multiply (r, op0, op1);
-      break;
+      return do_multiply (r, op0, op1);
 
     case RDIV_EXPR:
-      do_divide (r, op0, op1);
-      break;
+      return do_divide (r, op0, op1);
 
     case MIN_EXPR:
       if (op1->cl == rvc_nan)
@@ -1033,6 +1030,7 @@ real_arithmetic (REAL_VALUE_TYPE *r, int icode, const REAL_VALUE_TYPE *op0,
     default:
       gcc_unreachable ();
     }
+  return false;
 }
 
 /* Legacy.  Similar, but return the result directly.  */