re PR middle-end/15945 (Incorrect floating point optimization)

	PR middle-end/15945
	* simplify-rtx.c (simplify_binary_operation): Don't optimize out
	Inf + -Inf, Inf - Inf, Inf / Inf and 0 * Inf if flag_trapping_math.

From-SVN: r83121

gcc/ChangeLog

+2004-06-14  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/15945
+	* simplify-rtx.c (simplify_binary_operation): Don't optimize out
+	Inf + -Inf, Inf - Inf, Inf / Inf and 0 * Inf if flag_trapping_math.
+
 2004-06-14  Zdenek Dvorak  <rakdver@atrey.karlin.mff.cuni.cz>
 
 	* opts.sh (var_args): Fix regexp.

gcc/simplify-rtx.c

@@ -1277,6 +1277,41 @@ simplify_binary_operation (enum rtx_code code, enum machine_mode mode,
 	      && (flag_trapping_math || ! MODE_HAS_INFINITIES (mode)))
 	    return 0;
 
+	  if (MODE_HAS_INFINITIES (mode) && HONOR_NANS (mode)
+	      && flag_trapping_math
+	      && REAL_VALUE_ISINF (f0) && REAL_VALUE_ISINF (f1))
+	    {
+	      int s0 = REAL_VALUE_NEGATIVE (f0);
+	      int s1 = REAL_VALUE_NEGATIVE (f1);
+
+	      switch (code)
+		{
+		case PLUS:
+		  /* Inf + -Inf = NaN plus exception.  */
+		  if (s0 != s1)
+		    return 0;
+		  break;
+		case MINUS:
+		  /* Inf - Inf = NaN plus exception.  */
+		  if (s0 == s1)
+		    return 0;
+		  break;
+		case DIV:
+		  /* Inf / Inf = NaN plus exception.  */
+		  return 0;
+		default:
+		  break;
+		}
+	    }
+
+	  if (code == MULT && MODE_HAS_INFINITIES (mode) && HONOR_NANS (mode)
+	      && flag_trapping_math
+	      && ((REAL_VALUE_ISINF (f0) && REAL_VALUES_EQUAL (f1, dconst0))
+		  || (REAL_VALUE_ISINF (f1)
+		      && REAL_VALUES_EQUAL (f0, dconst0))))
+	    /* Inf * 0 = NaN plus exception.  */
+	    return 0;
+
 	  REAL_ARITHMETIC (value, rtx_to_tree_code (code), f0, f1);
 
 	  value = real_value_truncate (mode, value);