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authorJoseph Myers <joseph@codesourcery.com>2015-09-17 15:51:54 +0000
committerJoseph Myers <joseph@codesourcery.com>2015-09-17 15:51:54 +0000
commit46f74e1deee549b41160d353ce0c8f7db555d36c (patch)
tree19f07ad8fb51bb5e8de5106dc98654e7817eb04e /sysdeps/ieee754/ldbl-128
parente67dc1b57f1fc8407cb45bdb38ae1eaa0a5c6f78 (diff)
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Fix tgamma missing underflows (bug 18951).
Similar to various other bugs in this area, tgamma functions can fail
to raise the underflow exception when the result is tiny and inexact
but one or more low bits of the intermediate result that is scaled
down are zero.  This patch forces the exception in a similar way to
previous fixes.

Tested for x86_64, x86, mips64 and powerpc.

	[BZ #18951]
	* sysdeps/ieee754/dbl-64/e_gamma_r.c (__ieee754_gamma_r): Force
	underflow exception for small results.
	* sysdeps/ieee754/flt-32/e_gammaf_r.c (__ieee754_gammaf_r):
	Likewise.
	* sysdeps/ieee754/ldbl-128/e_gammal_r.c (__ieee754_gammal_r):
	Likewise.
	* sysdeps/ieee754/ldbl-128ibm/e_gammal_r.c (__ieee754_gammal_r):
	Likewise.
	* sysdeps/ieee754/ldbl-96/e_gammal_r.c (__ieee754_gammal_r):
	Likewise.
	* math/auto-libm-test-in: Add more tests of tgamma.
	* math/auto-libm-test-out: Regenerated.
Diffstat (limited to 'sysdeps/ieee754/ldbl-128')
-rw-r--r--sysdeps/ieee754/ldbl-128/e_gammal_r.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/sysdeps/ieee754/ldbl-128/e_gammal_r.c b/sysdeps/ieee754/ldbl-128/e_gammal_r.c
index c51b050e0e..c44f031745 100644
--- a/sysdeps/ieee754/ldbl-128/e_gammal_r.c
+++ b/sysdeps/ieee754/ldbl-128/e_gammal_r.c
@@ -194,6 +194,11 @@ __ieee754_gammal_r (long double x, int *signgamp)
 	      ret = M_PIl / (-x * sinpix
 			     * gammal_positive (-x, &exp2_adj));
 	      ret = __scalbnl (ret, -exp2_adj);
+	      if (ret < LDBL_MIN)
+		{
+		  long double force_underflow = ret * ret;
+		  math_force_eval (force_underflow);
+		}
 	    }
 	}
     }