[backport gcc-4.9/trunk r198308 <mikpe@it.uu.se>]

gcc/

2013-04-25  Marek Polacek  <polacek@redhat.com>

	PR tree-optimization/57066
        * builtins.c (fold_builtin_logb): Return +Inf for -Inf.

gcc/testsuite/

2013-04-25  Marek Polacek  <polacek@redhat.com>

	PR tree-optimization/57066
        * gcc.dg/torture/builtin-logb-1.c: Adjust testcase.

--- gcc-4.8.0/gcc/builtins.c.~1~	2013-01-10 21:38:27.000000000 +0100
+++ gcc-4.8.0/gcc/builtins.c	2013-04-27 14:14:27.123424443 +0200
@@ -9694,7 +9694,16 @@ 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-4.8.0/gcc/testsuite/gcc.dg/torture/builtin-logb-1.c.~1~	2012-03-14 17:33:37.000000000 +0100
+++ gcc-4.8.0/gcc/testsuite/gcc.dg/torture/builtin-logb-1.c	2013-04-27 14:14:27.133424428 +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()