[PATCH] Fix folding of logb (-Inf) (PR tree-optimization/57066)

[Marek Polacek]

On Thu, Apr 25, 2013 at 05:31:29PM +0200, Jakub Jelinek wrote:
> > +	    /* For logb(-Inf) we have to return +Inf.  */
> > +	    if (value->cl == rvc_inf && !tree_expr_nonnegative_p (arg))
> 
> Why not
> 	if (value->cl == rvc_inf && value->sign)
> or
> 	if (real_isinf (value) && real_isneg (value))
> instead?

That's better, yeah.
I was searching for something that tells me whether *tree* is
negative, and not REAL_VALUE_TYPE.  I like the second variant more.
Thanks.

Ok for trunk/4.8/4.7?

2013-04-25  Marek Polacek  <polacek@redhat.com>
 
        * builtins.c (fold_builtin_logb): Return +Inf for -Inf.
 
        * gcc.dg/torture/builtin-logb-1.c: Adjust testcase.

--- gcc/builtins.c.mp	2013-04-25 12:52:37.463451032 +0200
+++ gcc/builtins.c	2013-04-25 17:37:50.846784390 +0200
@@ -9698,7 +9698,16 @@ fold_builtin_logb (location_t loc, tree
       case rvc_inf:
 	/* If arg is Inf or NaN and we're logb, return it.  */
 	if (TREE_CODE (rettype) == REAL_TYPE)
-	  return fold_convert_loc (loc, rettype, arg);
+	  {
+	    /* For logb(-Inf) we have to return +Inf.  */
+	    if (real_isinf (value) && real_isneg (value))
+	      {
+		REAL_VALUE_TYPE tem;
+		real_inf (&tem);
+		return build_real (rettype, tem);
+	      }
+	    return fold_convert_loc (loc, rettype, arg);
+	  }
 	/* Fall through... */
       case rvc_zero:
 	/* Zero may set errno and/or raise an exception for logb, also
--- gcc/testsuite/gcc.dg/torture/builtin-logb-1.c.mp	2013-04-25 13:23:18.408224450 +0200
+++ gcc/testsuite/gcc.dg/torture/builtin-logb-1.c	2013-04-25 17:22:42.459765203 +0200
@@ -48,25 +48,25 @@ extern void link_error(int);
 /* Test if FUNCRES(FUNC(NEG FUNCARG(ARGARG))) is false.  Check the
    sign as well.  */
 #ifndef __SPU__
-#define TESTIT3(FUNC,NEG,FUNCARG,ARGARG,FUNCRES) do { \
+#define TESTIT3(FUNC,NEG,FUNCARG,ARGARG,FUNCRES,NEG2) do { \
   if (!__builtin_##FUNCRES##f(__builtin_##FUNC(NEG __builtin_##FUNCARG##f(ARGARG))) \
-      || CKSGN_F(__builtin_##FUNC##f(NEG __builtin_##FUNCARG##f(ARGARG)), NEG __builtin_##FUNCARG##f(ARGARG))) \
+      || CKSGN_F(__builtin_##FUNC##f(NEG __builtin_##FUNCARG##f(ARGARG)), NEG2 __builtin_##FUNCARG##f(ARGARG))) \
     link_error(__LINE__); \
   if (!__builtin_##FUNCRES(__builtin_##FUNC(NEG __builtin_##FUNCARG(ARGARG))) \
-      || CKSGN(__builtin_##FUNC(NEG __builtin_##FUNCARG(ARGARG)), NEG __builtin_##FUNCARG(ARGARG))) \
+      || CKSGN(__builtin_##FUNC(NEG __builtin_##FUNCARG(ARGARG)), NEG2 __builtin_##FUNCARG(ARGARG))) \
     link_error(__LINE__); \
   if (!__builtin_##FUNCRES##l(__builtin_##FUNC##l(NEG __builtin_##FUNCARG##l(ARGARG))) \
-      || CKSGN_L(__builtin_##FUNC##l(NEG __builtin_##FUNCARG##l(ARGARG)), NEG __builtin_##FUNCARG##l(ARGARG))) \
+      || CKSGN_L(__builtin_##FUNC##l(NEG __builtin_##FUNCARG##l(ARGARG)), NEG2 __builtin_##FUNCARG##l(ARGARG))) \
     link_error(__LINE__); \
   } while (0)
 #else
-#define TESTIT3(FUNC,NEG,FUNCARG,ARGARG,FUNCRES) do { \
+#define TESTIT3(FUNC,NEG,FUNCARG,ARGARG,FUNCRES,NEG2) do { \
   /* SPU single-precision floating point format does not support Inf or Nan.  */ \
   if (!__builtin_##FUNCRES(__builtin_##FUNC(NEG __builtin_##FUNCARG(ARGARG))) \
-      || CKSGN(__builtin_##FUNC(NEG __builtin_##FUNCARG(ARGARG)), NEG __builtin_##FUNCARG(ARGARG))) \
+      || CKSGN(__builtin_##FUNC(NEG __builtin_##FUNCARG(ARGARG)), NEG2 __builtin_##FUNCARG(ARGARG))) \
     link_error(__LINE__); \
   if (!__builtin_##FUNCRES##l(__builtin_##FUNC##l(NEG __builtin_##FUNCARG##l(ARGARG))) \
-      || CKSGN_L(__builtin_##FUNC##l(NEG __builtin_##FUNCARG##l(ARGARG)), NEG __builtin_##FUNCARG##l(ARGARG))) \
+      || CKSGN_L(__builtin_##FUNC##l(NEG __builtin_##FUNCARG##l(ARGARG)), NEG2 __builtin_##FUNCARG##l(ARGARG))) \
     link_error(__LINE__); \
   } while (0)
 #endif
@@ -173,15 +173,15 @@ foo(void)
 
   /* Test for f(+-Inf) -> +-Inf and f(+-NaN) -> +-NaN, regardless of
      the radix.  */
-  TESTIT3 (logb, ,inf, , isinf);
-  TESTIT3 (logb, - ,inf, , isinf);
-  TESTIT3 (logb,  ,nan, "", isnan);
-  TESTIT3 (logb, - ,nan, "", isnan);
-
-  TESTIT3 (significand, ,inf, , isinf);
-  TESTIT3 (significand, - ,inf, , isinf);
-  TESTIT3 (significand,  ,nan, "", isnan);
-  TESTIT3 (significand, - ,nan, "", isnan);
+  TESTIT3 (logb, ,inf, , isinf, );
+  TESTIT3 (logb, - ,inf, , isinf, );
+  TESTIT3 (logb,  ,nan, "", isnan, );
+  TESTIT3 (logb, - ,nan, "", isnan, -);
+
+  TESTIT3 (significand, ,inf, , isinf, );
+  TESTIT3 (significand, - ,inf, , isinf, -);
+  TESTIT3 (significand,  ,nan, "", isnan, );
+  TESTIT3 (significand, - ,nan, "", isnan, -);
 }
 
 int main()

	Marek