Fix ldbl-128/ldbl-128ibm lgamma spurious "invalid", incorrect signgam (bug 18952).

The ldbl-128 / ldbl-128ibm implementation of lgammal converts (the
floor of minus) non-integer negative arguments to int to determine the
value of signgam.  When those values are outside the range of int,
this produces spurious "invalid" exceptions and incorrect values of
signgam.  This patch fixes this by instead determining signgam through
comparing half the integer in question to floor of half the integer.

Tested for mips64, x86_64 and x86.

	[BZ #18952]
	* sysdeps/ieee754/ldbl-128/e_lgammal_r.c (__ieee754_lgammal_r): Do
	not convert non-integer negative arguments to int to determine the
	value of signgam.
	* math/auto-libm-test-in: Add more tests of lgamma.
	* math/auto-libm-test-out: Regenerated.

diff --git a/ChangeLog b/ChangeLog
index 61a4b539fe1255ada66e3ce11f0c66b6a729ee0d..9e23da11b42531f3e88a345eb0c6b840b13c5d23 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 2015-09-11  Joseph Myers  <joseph@codesourcery.com>
 
+       [BZ #18952]
+       * sysdeps/ieee754/ldbl-128/e_lgammal_r.c (__ieee754_lgammal_r): Do
+       not convert non-integer negative arguments to int to determine the
+       value of signgam.
+       * math/auto-libm-test-in: Add more tests of lgamma.
+       * math/auto-libm-test-out: Regenerated.
+
        * math/auto-libm-test-in: Add more tests of acosh, atanh, cbrt,
        cosh, csqrt, erfc, expm1 and lgamma.
        * math/auto-libm-test-out: Regenerated.

diff --git a/NEWS b/NEWS
index 3e78630caf69f9563d0040f94b5f5ee6bef1f504..65e706c9da4d48e5544c2a7918683f8e7c1b529b 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -13,7 +13,7 @@ Version 2.23
   16973, 17787, 17905, 18084, 18086, 18240, 18265, 18370, 18421, 18480,
   18525, 18610, 18618, 18647, 18661, 18674, 18675, 18681, 18757, 18778,
   18781, 18787, 18789, 18790, 18795, 18796, 18820, 18823, 18824, 18863,
-  18870, 18873, 18887, 18921.
+  18870, 18873, 18887, 18921, 18952.
 
 * The obsolete header <regexp.h> has been removed.  Programs that require
   this header must be updated to use <regex.h> instead.

diff --git a/math/auto-libm-test-in b/math/auto-libm-test-in
index 84b3df0beeebf1b143f735ccff986b90694a6791..83eb4cf8c3ca50138780598846d2af23e2cfb85f 100644 (file)
--- a/math/auto-libm-test-in
+++ b/math/auto-libm-test-in
@@ -2047,6 +2047,9 @@ lgamma -0xffffffffffffffffp-1
 lgamma -0x3ffffffffffffffffffffffffffp-1
 lgamma -0x1ffffffffffffffffffffffffffffp-1
 
+lgamma -0x100000000.8p0
+lgamma -0x100000001.8p0
+
 lgamma -0.25
 lgamma -0.5
 lgamma -0.75

diff --git a/math/auto-libm-test-out b/math/auto-libm-test-out
index 14caa1d8424213979b3ec49d8000b1aa37c70bcf..747815b1c929e06ca51bec6e38e624623b3c56fd 100644 (file)
--- a/math/auto-libm-test-out
+++ b/math/auto-libm-test-out
@@ -153351,6 +153351,48 @@ lgamma -0x1ffffffffffffffffffffffffffffp-1
 = lgamma tonearest ldbl-128 -0xf.fffffffffffffffffffffffffff8p+108L : -0x4.ca1ea7c6bcac53b28539e9281ba4p+116L 1 : inexact-ok
 = lgamma towardzero ldbl-128 -0xf.fffffffffffffffffffffffffff8p+108L : -0x4.ca1ea7c6bcac53b28539e9281ba4p+116L 1 : inexact-ok
 = lgamma upward ldbl-128 -0xf.fffffffffffffffffffffffffff8p+108L : -0x4.ca1ea7c6bcac53b28539e9281ba4p+116L 1 : inexact-ok
+lgamma -0x100000000.8p0
+= lgamma downward dbl-64 -0x1.000000008p+32 : -0x1.52e42ff102e65p+36 -1 : inexact-ok
+= lgamma tonearest dbl-64 -0x1.000000008p+32 : -0x1.52e42ff102e65p+36 -1 : inexact-ok
+= lgamma towardzero dbl-64 -0x1.000000008p+32 : -0x1.52e42ff102e64p+36 -1 : inexact-ok
+= lgamma upward dbl-64 -0x1.000000008p+32 : -0x1.52e42ff102e64p+36 -1 : inexact-ok
+= lgamma downward ldbl-96-intel -0x1.000000008p+32L : -0x1.52e42ff102e64be4p+36L -1 : inexact-ok
+= lgamma tonearest ldbl-96-intel -0x1.000000008p+32L : -0x1.52e42ff102e64be2p+36L -1 : inexact-ok
+= lgamma towardzero ldbl-96-intel -0x1.000000008p+32L : -0x1.52e42ff102e64be2p+36L -1 : inexact-ok
+= lgamma upward ldbl-96-intel -0x1.000000008p+32L : -0x1.52e42ff102e64be2p+36L -1 : inexact-ok
+= lgamma downward ldbl-96-m68k -0x1.000000008p+32L : -0x1.52e42ff102e64be4p+36L -1 : inexact-ok
+= lgamma tonearest ldbl-96-m68k -0x1.000000008p+32L : -0x1.52e42ff102e64be2p+36L -1 : inexact-ok
+= lgamma towardzero ldbl-96-m68k -0x1.000000008p+32L : -0x1.52e42ff102e64be2p+36L -1 : inexact-ok
+= lgamma upward ldbl-96-m68k -0x1.000000008p+32L : -0x1.52e42ff102e64be2p+36L -1 : inexact-ok
+= lgamma downward ldbl-128 -0x1.000000008p+32L : -0x1.52e42ff102e64be289794d246256p+36L -1 : inexact-ok
+= lgamma tonearest ldbl-128 -0x1.000000008p+32L : -0x1.52e42ff102e64be289794d246255p+36L -1 : inexact-ok
+= lgamma towardzero ldbl-128 -0x1.000000008p+32L : -0x1.52e42ff102e64be289794d246255p+36L -1 : inexact-ok
+= lgamma upward ldbl-128 -0x1.000000008p+32L : -0x1.52e42ff102e64be289794d246255p+36L -1 : inexact-ok
+= lgamma downward ldbl-128ibm -0x1.000000008p+32L : -0x1.52e42ff102e64be289794d24628p+36L -1 : inexact-ok
+= lgamma tonearest ldbl-128ibm -0x1.000000008p+32L : -0x1.52e42ff102e64be289794d24628p+36L -1 : inexact-ok
+= lgamma towardzero ldbl-128ibm -0x1.000000008p+32L : -0x1.52e42ff102e64be289794d2462p+36L -1 : inexact-ok
+= lgamma upward ldbl-128ibm -0x1.000000008p+32L : -0x1.52e42ff102e64be289794d2462p+36L -1 : inexact-ok
+lgamma -0x100000001.8p0
+= lgamma downward dbl-64 -0x1.000000018p+32 : -0x1.52e42ff265ca8p+36 1 : inexact-ok
+= lgamma tonearest dbl-64 -0x1.000000018p+32 : -0x1.52e42ff265ca8p+36 1 : inexact-ok
+= lgamma towardzero dbl-64 -0x1.000000018p+32 : -0x1.52e42ff265ca7p+36 1 : inexact-ok
+= lgamma upward dbl-64 -0x1.000000018p+32 : -0x1.52e42ff265ca7p+36 1 : inexact-ok
+= lgamma downward ldbl-96-intel -0x1.000000018p+32L : -0x1.52e42ff265ca7bd4p+36L 1 : inexact-ok
+= lgamma tonearest ldbl-96-intel -0x1.000000018p+32L : -0x1.52e42ff265ca7bd2p+36L 1 : inexact-ok
+= lgamma towardzero ldbl-96-intel -0x1.000000018p+32L : -0x1.52e42ff265ca7bd2p+36L 1 : inexact-ok
+= lgamma upward ldbl-96-intel -0x1.000000018p+32L : -0x1.52e42ff265ca7bd2p+36L 1 : inexact-ok
+= lgamma downward ldbl-96-m68k -0x1.000000018p+32L : -0x1.52e42ff265ca7bd4p+36L 1 : inexact-ok
+= lgamma tonearest ldbl-96-m68k -0x1.000000018p+32L : -0x1.52e42ff265ca7bd2p+36L 1 : inexact-ok
+= lgamma towardzero ldbl-96-m68k -0x1.000000018p+32L : -0x1.52e42ff265ca7bd2p+36L 1 : inexact-ok
+= lgamma upward ldbl-96-m68k -0x1.000000018p+32L : -0x1.52e42ff265ca7bd2p+36L 1 : inexact-ok
+= lgamma downward ldbl-128 -0x1.000000018p+32L : -0x1.52e42ff265ca7bd24518407be41dp+36L 1 : inexact-ok
+= lgamma tonearest ldbl-128 -0x1.000000018p+32L : -0x1.52e42ff265ca7bd24518407be41dp+36L 1 : inexact-ok
+= lgamma towardzero ldbl-128 -0x1.000000018p+32L : -0x1.52e42ff265ca7bd24518407be41cp+36L 1 : inexact-ok
+= lgamma upward ldbl-128 -0x1.000000018p+32L : -0x1.52e42ff265ca7bd24518407be41cp+36L 1 : inexact-ok
+= lgamma downward ldbl-128ibm -0x1.000000018p+32L : -0x1.52e42ff265ca7bd24518407be48p+36L 1 : inexact-ok
+= lgamma tonearest ldbl-128ibm -0x1.000000018p+32L : -0x1.52e42ff265ca7bd24518407be4p+36L 1 : inexact-ok
+= lgamma towardzero ldbl-128ibm -0x1.000000018p+32L : -0x1.52e42ff265ca7bd24518407be4p+36L 1 : inexact-ok
+= lgamma upward ldbl-128ibm -0x1.000000018p+32L : -0x1.52e42ff265ca7bd24518407be4p+36L 1 : inexact-ok
 lgamma -0.25
 = lgamma downward flt-32 -0x4p-4f : 0x1.96ee68p+0f -1 : inexact-ok
 = lgamma tonearest flt-32 -0x4p-4f : 0x1.96ee68p+0f -1 : inexact-ok

diff --git a/sysdeps/ieee754/ldbl-128/e_lgammal_r.c b/sysdeps/ieee754/ldbl-128/e_lgammal_r.c
index abf0f15995e2220628f078292153ce2e5cd11155..500aacc9c476980dc154e7354c127b1191c5bf64 100644 (file)
--- a/sysdeps/ieee754/ldbl-128/e_lgammal_r.c
+++ b/sysdeps/ieee754/ldbl-128/e_lgammal_r.c
@@ -787,8 +787,8 @@ __ieee754_lgammal_r (long double x, int *signgamp)
       p = __floorl (q);
       if (p == q)
        return (one / (p - p));
-      i = p;
-      if ((i & 1) == 0)
+      long double halfp = p * 0.5L;
+      if (halfp == __floorl (halfp))
        *signgamp = -1;
       else
        *signgamp = 1;