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authorJoseph Myers <joseph@codesourcery.com>2014-05-14 12:38:56 +0000
committerJoseph Myers <joseph@codesourcery.com>2014-05-14 12:38:56 +0000
commit1a84c3d6d4bc43c92b6531b09d732e2e9c750dea (patch)
treef58a4fd81f814868dad8426ca0da232b618e0ac2 /sysdeps/ieee754
parent01dbacd22a8d5e0053f8d0cf13a80286b6cfe79b (diff)
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Fix log1pl (LDBL_MAX) in FE_UPWARD mode (bug 16564).
Bug 16564 is spurious overflow of log1pl (LDBL_MAX) in FE_UPWARD mode,
resulting from log1pl adding 1 to its argument (for arguments not
close to 0), which overflows in that mode.  This patch fixes this by
avoiding adding 1 to large arguments (precisely what counts as large
depends on the floating-point format).

Tested x86_64 and x86, and spot-checked log1pl tests on mips64 and
powerpc64.

	[BZ #16564]
	* sysdeps/i386/fpu/s_log1pl.S (__log1pl): Do not add 1 to positive
	arguments with exponent 65 or above.
	* sysdeps/ieee754/ldbl-128/s_log1pl.c (__log1pl): Do not add 1 to
	arguments 0x1p113L or above.
	* sysdeps/ieee754/ldbl-128ibm/s_log1pl.c (__log1pl): Do not add 1
	to arguments 0x1p107L or above.
	* sysdeps/x86_64/fpu/s_log1pl.S (__log1pl): Do not add 1 to
	positive arguments with exponent 65 or above.
	* math/auto-libm-test-in: Add more tests of log1p.
	* math/auto-libm-test-out: Regenerated.
Diffstat (limited to 'sysdeps/ieee754')
-rw-r--r--sysdeps/ieee754/ldbl-128/s_log1pl.c5
-rw-r--r--sysdeps/ieee754/ldbl-128ibm/s_log1pl.c5
2 files changed, 8 insertions, 2 deletions
diff --git a/sysdeps/ieee754/ldbl-128/s_log1pl.c b/sysdeps/ieee754/ldbl-128/s_log1pl.c
index d8d89f0a8c..4a30af62fa 100644
--- a/sysdeps/ieee754/ldbl-128/s_log1pl.c
+++ b/sysdeps/ieee754/ldbl-128/s_log1pl.c
@@ -144,7 +144,10 @@ __log1pl (long double xm1)
 	return xm1;
     }
 
-  x = xm1 + 1.0L;
+  if (xm1 >= 0x1p113L)
+    x = xm1;
+  else
+    x = xm1 + 1.0L;
 
   /* log1p(-1) = -inf */
   if (x <= 0.0L)
diff --git a/sysdeps/ieee754/ldbl-128ibm/s_log1pl.c b/sysdeps/ieee754/ldbl-128ibm/s_log1pl.c
index a346383052..e4bb6e8d9b 100644
--- a/sysdeps/ieee754/ldbl-128ibm/s_log1pl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/s_log1pl.c
@@ -140,7 +140,10 @@ __log1pl (long double xm1)
   if (((hx & 0x7fffffff) | lx) == 0)
     return xm1;
 
-  x = xm1 + 1.0L;
+  if (xm1 >= 0x1p107L)
+    x = xm1;
+  else
+    x = xm1 + 1.0L;
 
   /* log1p(-1) = -inf */
   if (x <= 0.0L)