From 524ae9ea2e3ae9f5bf5d655595fda827e9dc50a1 Mon Sep 17 00:00:00 2001 From: Joseph Myers Date: Thu, 26 Feb 2015 12:57:21 +0000 Subject: Fix ldbl-128ibm ilogbl near powers of 2 (bug 18029). The ldbl-128ibm implementation of ilogbl 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, ilogbl (0x1.ffffffffffffffp1L) returns 2 but should return 1. (This is similar to (fixed) bug 16740 for frexpl, and bug 18030 for logbl.) This patch adds checks for that case. Tested for powerpc. [BZ #18029] * sysdeps/ieee754/ldbl-128ibm/e_ilogbl.c (__ieee754_ilogbl): Adjust exponent of power of 2 down when low part has opposite sign. * math/libm-test.inc (ilogb_test_data): Add more tests. --- math/libm-test.inc | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'math') diff --git a/math/libm-test.inc b/math/libm-test.inc index b3396b6..6045764 100644 --- a/math/libm-test.inc +++ b/math/libm-test.inc @@ -7219,6 +7219,11 @@ static const struct test_f_i_data ilogb_test_data[] = TEST_f_i (ilogb, 1024, 10, NO_INEXACT_EXCEPTION), TEST_f_i (ilogb, -2000, 10, NO_INEXACT_EXCEPTION), +#if defined TEST_LDOUBLE && LDBL_MANT_DIG >= 57 + TEST_f_i (ilogb, 0x1.ffffffffffffffp1L, 1, NO_INEXACT_EXCEPTION), + TEST_f_i (ilogb, -0x1.ffffffffffffffp1L, 1, NO_INEXACT_EXCEPTION), +#endif + /* ilogb (0.0) == FP_ILOGB0 plus invalid exception */ TEST_f_i (ilogb, 0.0, FP_ILOGB0, NO_INEXACT_EXCEPTION|INVALID_EXCEPTION|ERRNO_EDOM), /* ilogb (qNaN) == FP_ILOGBNAN plus invalid exception */ -- cgit v1.1