Fix missing exp2 overflow exception (bug 13871)

["Joseph S. Myers" <joseph at codesourcery dot com>]

This patch fixes bug 13871, missing overflow exception from exp2.  The
exp2 wrapper checks the range of the input and calls __kernel_standard
if appropriate to handle errors, but __kernel_standard does not deal
with exceptions.  This patch changes the exp2 wrappers to follow the
same approach as the exp10 wrappers: call the actual __ieee754_exp2*
implementation first (which will generate any required exceptions) and
only then test for error cases.

Tested x86 and x86_64.

2012-03-21  Joseph Myers  <joseph@codesourcery.com>

	[BZ #13871]
	* math/w_exp2.c: Do not include <float.h>.
	(o_threshold, u_threshold): Remove.
	(__exp2): Calculate result before checking finiteness and calling
	__kernel_standard.
	* math/w_exp2f.c: Likewise.
	* math/w_exp2l.c: Likewise.
	* math/libm-test.inc (exp2_test): Require overflow exception for
	1e6 input.

diff --git a/math/libm-test.inc b/math/libm-test.inc
index af3d645..ff14299 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -3108,8 +3108,7 @@ exp2_test (void)
 
   TEST_f_f (exp2, 10, 1024);
   TEST_f_f (exp2, -1, 0.5);
-  /* Bug 13871: OVERFLOW exception may be missing.  */
-  TEST_f_f (exp2, 1e6, plus_infty, OVERFLOW_EXCEPTION_OK);
+  TEST_f_f (exp2, 1e6, plus_infty, OVERFLOW_EXCEPTION);
   TEST_f_f (exp2, -1e6, 0);
   TEST_f_f (exp2, 0.75L, 1.68179283050742908606225095246642979L);
 
diff --git a/math/w_exp2.c b/math/w_exp2.c
index 7a3b0af..b5d8e25 100644
--- a/math/w_exp2.c
+++ b/math/w_exp2.c
@@ -2,23 +2,19 @@
  * wrapper exp2(x)
  */
 
-#include <float.h>
 #include <math.h>
 #include <math_private.h>
 
-static const double o_threshold = (double) DBL_MAX_EXP;
-static const double u_threshold = (double) (DBL_MIN_EXP - DBL_MANT_DIG - 1);
-
 double
 __exp2 (double x)
 {
-  if (__builtin_expect (islessequal (x, u_threshold)
-			|| isgreater (x, o_threshold), 0)
-      && _LIB_VERSION != _IEEE_ && __finite (x))
+  double z = __ieee754_exp2 (x);
+  if (__builtin_expect (!__finite (z), 0)
+      && __finite (x) && _LIB_VERSION != _IEEE_)
     /* exp2 overflow: 44, exp2 underflow: 45 */
-    return __kernel_standard (x, x, 44 + (x <= o_threshold));
+    return __kernel_standard (x, x, 44 + !!__signbit (x));
 
-  return __ieee754_exp2 (x);
+  return z;
 }
 weak_alias (__exp2, exp2)
 #ifdef NO_LONG_DOUBLE
diff --git a/math/w_exp2f.c b/math/w_exp2f.c
index c4e9e94..7c277ef 100644
--- a/math/w_exp2f.c
+++ b/math/w_exp2f.c
@@ -2,22 +2,18 @@
  * wrapper exp2f(x)
  */
 
-#include <float.h>
 #include <math.h>
 #include <math_private.h>
 
-static const float o_threshold = (float) FLT_MAX_EXP;
-static const float u_threshold = (float) (FLT_MIN_EXP - FLT_MANT_DIG - 1);
-
 float
 __exp2f (float x)
 {
-  if (__builtin_expect (islessequal (x, u_threshold)
-			|| isgreater (x, o_threshold), 0)
-      && _LIB_VERSION != _IEEE_ && __finitef (x))
+  float z = __ieee754_exp2f (x);
+  if (__builtin_expect (!__finitef (z), 0)
+      && __finitef (x) && _LIB_VERSION != _IEEE_)
     /* exp2 overflow: 144, exp2 underflow: 145 */
-    return __kernel_standard_f (x, x, 144 + (x <= o_threshold));
+    return __kernel_standard_f (x, x, 144 + !!__signbitf (x));
 
-  return __ieee754_exp2f (x);
+  return z;
 }
 weak_alias (__exp2f, exp2f)
diff --git a/math/w_exp2l.c b/math/w_exp2l.c
index 442a637..f05a8fe 100644
--- a/math/w_exp2l.c
+++ b/math/w_exp2l.c
@@ -2,23 +2,18 @@
  * wrapper exp2l(x)
  */
 
-#include <float.h>
 #include <math.h>
 #include <math_private.h>
 
-static const long double o_threshold = (long double) LDBL_MAX_EXP;
-static const long double u_threshold
-  = (long double) (LDBL_MIN_EXP - LDBL_MANT_DIG - 1);
-
 long double
 __exp2l (long double x)
 {
-  if (__builtin_expect (islessequal (x, u_threshold)
-			|| isgreater (x, o_threshold), 0)
-      && _LIB_VERSION != _IEEE_ && __finitel (x))
+  long double z = __ieee754_exp2l (x);
+  if (__builtin_expect (!__finitel (z), 0)
+      && __finitel (x) && _LIB_VERSION != _IEEE_)
     /* exp2 overflow: 244, exp2 underflow: 245 */
-    return __kernel_standard (x, x, 244 + (x <= o_threshold));
+    return __kernel_standard (x, x, 244 + !!__signbitl (x));
 
-  return __ieee754_exp2l (x);
+  return z;
 }
 weak_alias (__exp2l, exp2l)

-- 
Joseph S. Myers
joseph@codesourcery.com