re PR tree-optimization/17892 (gcc-4.0 should not reassociate floating point add or multiplication)

Fix for PR tree-optimization/17892.
OKed by Roger Sayle.

From-SVN: r90395

gcc/ChangeLog

+2004-11-10  Fariborz Jahanian <fjahanian@apple.com>
+
+	PR tree-optimization/17892
+    	* tree-ssa-dom.c (unsafe_associative_fp_binop): Add test for
+	MINUS_EXPR operator.
+
 2004-11-10  James A. Morrison  <phython@gcc.gnu.org>
 
 	PR target/18230

gcc/testsuite/ChangeLog

+2004-11-10  Fariborz Jahanian <fjahanian@apple.com>
+
+        * gcc.c-torture/execute/ieee/unsafe-fp-assoc-1.c: 
+	New test for PR tree-optimization/17892.
+
 2004-11-09  Mark Mitchell  <mark@codesourcery.com>
 
 	PR c++/18369

gcc/tree-ssa-dom.c

@@ -1644,7 +1644,8 @@ unsafe_associative_fp_binop (tree exp)
 {
   enum tree_code code = TREE_CODE (exp);
   return !(!flag_unsafe_math_optimizations
-           && (code == MULT_EXPR || code == PLUS_EXPR)
+           && (code == MULT_EXPR || code == PLUS_EXPR
+	       || code == MINUS_EXPR)
            && FLOAT_TYPE_P (TREE_TYPE (exp)));
 }