Fix acosf underflow (bug 14153).

diff --git a/ChangeLog b/ChangeLog
index c6c2cad..ceb3f5a 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2012-05-24  Joseph Myers  <joseph@codesourcery.com>
+
+       [BZ #14153]
+       * sysdeps/ieee754/flt-32/e_acosf.c (__ieee754_acosf): Return pi/2
+       for |x| <= 2**-26, not 2**-57.
+       * math/libm-test.inc (acos_test): Do not allow spurious underflow
+       exception.
+
 2012-05-24  Jeff Law  <law@redhat.com>
 
        * stdio-common/Makefile (tests): Add bug25.

diff --git a/NEWS b/NEWS
index 7ccfb90..932934d 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -28,7 +28,7 @@ Version 2.16
   13941, 13942, 13954, 13955, 13956, 13963, 13967, 13968, 13970, 13973,
   13979, 13983, 13986, 14012, 14027, 14033, 14034, 14036, 14040, 14043,
   14044, 14049, 14053, 14055, 14059, 14064, 14080, 14083, 14103, 14104,
-  14109, 14122, 14123
+  14109, 14122, 14123, 14153
 
 * ISO C11 support:
 

diff --git a/math/libm-test.inc b/math/libm-test.inc
index 5946ca8..ed13f53 100644 (file)
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -804,8 +804,7 @@ acos_test (void)
   TEST_f_f (acos, 0.5, M_PI_6l*2.0);
   TEST_f_f (acos, -0.5, M_PI_6l*4.0);
   TEST_f_f (acos, 0.75L, 0.722734247813415611178377352641333362L);
-  /* Bug 14153: spurious exception may occur.  */
-  TEST_f_f (acos, 2e-17L, 1.57079632679489659923132169163975144L, UNDERFLOW_EXCEPTION_OK_FLOAT);
+  TEST_f_f (acos, 2e-17L, 1.57079632679489659923132169163975144L);
   TEST_f_f (acos, 0.0625L, 1.50825556499840522843072005474337068L);
   TEST_f_f (acos, 0x0.ffffffp0L, 3.4526698471620358760324948263873649728491e-4L);
   TEST_f_f (acos, -0x0.ffffffp0L, 3.1412473866050770348750401337968641476999L);

diff --git a/sysdeps/ieee754/flt-32/e_acosf.c b/sysdeps/ieee754/flt-32/e_acosf.c
index c0f1d4e..6f792f6 100644 (file)
--- a/sysdeps/ieee754/flt-32/e_acosf.c
+++ b/sysdeps/ieee754/flt-32/e_acosf.c
@@ -46,7 +46,7 @@ __ieee754_acosf(float x)
            return (x-x)/(x-x);         /* acos(|x|>1) is NaN */
        }
        if(ix<0x3f000000) {     /* |x| < 0.5 */
-           if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/
+           if(ix<=0x32800000) return pio2_hi+pio2_lo;/*if|x|<=2**-26*/
            z = x*x;
            p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
            q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));