re PR middle-end/19405 (18_support/numeric_limits.cc fails on ppc-darwin (long doubles))

	PR middle-end/19405
	* real.h (REAL_MODE_FORMAT_COMPOSITE_P): New macro.
	* fold-const.c (const_binop): Avoid constant folding floating
	point operations in modes that use composite representations.
	* simplify-rtx.c (simplify_binary_operation): Likewise.

From-SVN: r94653

gcc/ChangeLog

+2005-02-02  Roger Sayle  <roger@eyesopen.com>
+
+	PR middle-end/19405
+	* real.h (REAL_MODE_FORMAT_COMPOSITE_P): New macro.
+	* fold-const.c (const_binop): Avoid constant folding floating
+	point operations in modes that use composite representations.
+	* simplify-rtx.c (simplify_binary_operation): Likewise.
+
 2005-02-02  Geoffrey Keating  <geoffk@apple.com>
 
 	* config/rs6000/altivec.md (altivec_dst): Make the first operand

gcc/fold-const.c

@@ -1517,9 +1517,12 @@ const_binop (enum tree_code code, tree arg1, tree arg2, int notrunc)
 
       /* Don't constant fold this floating point operation if the
 	 result may dependent upon the run-time rounding mode and
-	 flag_rounding_math is set.  */
+	 flag_rounding_math is set, or if GCC's software emulation
+	 is unable to accurately represent the result.  */
       
-      if (flag_rounding_math
+      if ((flag_rounding_math
+	   || (REAL_MODE_FORMAT_COMPOSITE_P (mode)
+	       && !flag_unsafe_math_optimizations))
 	  && (inexact || !real_identical (&result, &value)))
 	return NULL_TREE;
 

gcc/real.h

@@ -157,6 +157,12 @@ extern const struct real_format *
 
 #define REAL_MODE_FORMAT(MODE) (real_format_for_mode[(MODE) - MIN_MODE_FLOAT])
 
+/* The following macro determines whether the floating point format is
+   composite, i.e. may contain non-consecutive mantissa bits, in which
+   case compile-time FP overflow may not model run-time overflow.  */
+#define REAL_MODE_FORMAT_COMPOSITE_P(MODE) \
+	((REAL_MODE_FORMAT(MODE))->pnan < (REAL_MODE_FORMAT (MODE))->p)
+
 /* Declare functions in real.c.  */
 
 /* Binary or unary arithmetic on tree_code.  */

gcc/simplify-rtx.c

@@ -1346,8 +1346,12 @@ simplify_binary_operation (enum rtx_code code, enum machine_mode mode,
 
 	  /* Don't constant fold this floating point operation if the
 	     result may dependent upon the run-time rounding mode and
-	     flag_rounding_math is set.  */
-	  if (flag_rounding_math
+	     flag_rounding_math is set, or if GCC's software emulation
+	     is unable to accurately represent the result.  */
+
+	  if ((flag_rounding_math
+	       || (REAL_MODE_FORMAT_COMPOSITE_P (mode)
+		   && !flag_unsafe_math_optimizations))
 	      && (inexact || !real_identical (&result, &value)))
 	    return NULL_RTX;