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| author | Joseph Myers <joseph@codesourcery.com> | 2016-06-03 21:30:12 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2016-06-03 21:30:12 +0000 |
| commit | 8cbd1453ec1c59e54652edcd88256f4023ff77b9 (patch) | |
| tree | fd75adff737c0b9172a5e59d2307d36e5190afe8 | |
| parent | cfac4de69cc70fbd6364e58cf77891a7a30f2e09 (diff) | |
| download | glibc-8cbd1453ec1c59e54652edcd88256f4023ff77b9.zip glibc-8cbd1453ec1c59e54652edcd88256f4023ff77b9.tar.gz glibc-8cbd1453ec1c59e54652edcd88256f4023ff77b9.tar.bz2 | |
Fix x86/x86_64 nextafterl incrementing negative subnormals (bug 20205).
The x86 / x86_64 implementation of nextafterl (also used for
nexttowardl) produces incorrect results (NaNs) when negative
subnormals, the low 32 bits of whose mantissa are zero, are
incremented towards zero. This patch fixes this by disabling the
logic to decrement the exponent in that case.
Tested for x86_64 and x86.
[BZ #20205]
* sysdeps/i386/fpu/s_nextafterl.c (__nextafterl): Do not adjust
exponent when incrementing negative subnormal with low mantissa
word zero.
* math/libm-test.inc (nextafter_test_data) [TEST_COND_intel96]:
Add another test.
| -rw-r--r-- | ChangeLog | 9 | ||||
| -rw-r--r-- | math/libm-test.inc | 4 | ||||
| -rw-r--r-- | sysdeps/i386/fpu/s_nextafterl.c | 2 |
3 files changed, 14 insertions, 1 deletions
@@ -1,3 +1,12 @@ +2016-06-03 Joseph Myers <joseph@codesourcery.com> + + [BZ #20205] + * sysdeps/i386/fpu/s_nextafterl.c (__nextafterl): Do not adjust + exponent when incrementing negative subnormal with low mantissa + word zero. + * math/libm-test.inc (nextafter_test_data) [TEST_COND_intel96]: + Add another test. + 2016-06-03 Florian Weimer <fweimer@redhat.com> * libio/wstrops.c (_IO_wstr_overflow, enlarge_userbuf): Use diff --git a/math/libm-test.inc b/math/libm-test.inc index 8c64c8e..aaa0148 100644 --- a/math/libm-test.inc +++ b/math/libm-test.inc @@ -9965,6 +9965,10 @@ static const struct test_ff_f_data nextafter_test_data[] = TEST_ff_f (nextafter, -min_subnorm_value, 0, minus_zero, INEXACT_EXCEPTION|UNDERFLOW_EXCEPTION|ERRNO_ERANGE), TEST_ff_f (nextafter, -min_subnorm_value, minus_zero, minus_zero, INEXACT_EXCEPTION|UNDERFLOW_EXCEPTION|ERRNO_ERANGE), +#if TEST_COND_intel96 + TEST_ff_f (nextafter, -0x0.fffffffep-16382L, 0.0L, -0x0.fffffffdfffffffep-16382L, INEXACT_EXCEPTION|UNDERFLOW_EXCEPTION|ERRNO_ERANGE), +#endif + #if MANT_DIG >= 64 // XXX Enable once gcc is fixed. //TEST_ff_f (nextafter, 0x0.00000040000000000000p-16385L, -0.1L, 0x0.0000003ffffffff00000p-16385L), diff --git a/sysdeps/i386/fpu/s_nextafterl.c b/sysdeps/i386/fpu/s_nextafterl.c index 188dc21..600ad7a 100644 --- a/sysdeps/i386/fpu/s_nextafterl.c +++ b/sysdeps/i386/fpu/s_nextafterl.c @@ -86,7 +86,7 @@ long double __nextafterl(long double x, long double y) if(esy>=0||(esx>esy||((esx==esy)&&(hx>hy||((hx==hy)&&(lx>ly)))))){ /* x < y, x -= ulp */ if(lx==0) { - if (hx <= 0x80000000) { + if (hx <= 0x80000000 && esx != 0xffff8000) { esx -= 1; hx = hx - 1; if ((esx&0x7fff) > 0) |