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authorJoseph Myers <joseph@codesourcery.com>2015-02-26 15:13:22 +0000
committerJoseph Myers <joseph@codesourcery.com>2015-02-26 15:14:58 +0000
commit380bd0fd2418f8988217de950f8b8ff18af0cb2b (patch)
treeabb55a322fc5e1b829761d91a23510ecfc6bf1ee /math
parent4a28f4d55a6cc33474c0792fe93b5942d81bf185 (diff)
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Fix ldbl-128ibm logbl near powers of 2 (bug 18030).
The ldbl-128ibm implementation of logbl produces incorrect results
when the high part of the argument is a power of 2 and the low part a
nonzero number with the opposite sign (and so the returned exponent
should be 1 less than that of the high part).  For example, logbl
(0x1.ffffffffffffffp1L) returns 2 but should return 1.  (This is
similar to (fixed) bug 16740 for frexpl, and (fixed) bug 18029 for
ilogbl.)  This patch adds checks for that case.

Tested for powerpc.

	[BZ #18030]
	* sysdeps/ieee754/ldbl-128ibm/s_logbl.c (__logbl): Adjust exponent
	of power of 2 down when low part has opposite sign.
	* math/libm-test.inc (logb_test_data): Add more tests.
Diffstat (limited to 'math')
-rw-r--r--math/libm-test.inc5
1 files changed, 5 insertions, 0 deletions
diff --git a/math/libm-test.inc b/math/libm-test.inc
index 6045764fd3..7acd29bc13 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -7868,6 +7868,11 @@ static const struct test_f_f_data logb_test_data[] =
     TEST_f_f (logb, 0x1p-16400L, -16400, NO_INEXACT_EXCEPTION),
     TEST_f_f (logb, 0x.00000000001p-16382L, -16426, NO_INEXACT_EXCEPTION),
 #endif
+
+#if defined TEST_LDOUBLE && LDBL_MANT_DIG >= 57
+    TEST_f_f (logb, 0x1.ffffffffffffffp1L, 1, NO_INEXACT_EXCEPTION),
+    TEST_f_f (logb, -0x1.ffffffffffffffp1L, 1, NO_INEXACT_EXCEPTION),
+#endif
   };
 
 static void