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| author | Joseph Myers <joseph@codesourcery.com> | 2014-06-23 20:12:33 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2014-06-23 20:12:33 +0000 |
| commit | 4da6db51880289f0bf41b39e05cf9bb1c4769c47 (patch) | |
| tree | 9f57512f4561f512366c93cf7430d5b75d4852fd /sysdeps/i386/fpu/e_powf.S | |
| parent | 5686b236cccdc8c72788b7996537ed92ac3a3c8c (diff) | |
| download | glibc-4da6db51880289f0bf41b39e05cf9bb1c4769c47.tar glibc-4da6db51880289f0bf41b39e05cf9bb1c4769c47.tar.gz glibc-4da6db51880289f0bf41b39e05cf9bb1c4769c47.tar.bz2 glibc-4da6db51880289f0bf41b39e05cf9bb1c4769c47.zip | |
Fix pow overflow in non-default rounding modes (bug 16315).
This patch fixes bug 16315, bad pow handling of overflow/underflow in
non-default rounding modes. Tests of pow are duly converted to
ALL_RM_TEST to run all tests in all rounding modes.
There are two main issues here. First, various implementations
compute a negative result by negating a positive result, but this
yields inappropriate overflow / underflow values for directed
rounding, so either overflow / underflow results need recomputing in
the correct sign, or the relevant overflowing / underflowing operation
needs to be made to have a result of the correct sign. Second, the
dbl-64 implementation sets FE_TONEAREST internally; in the overflow /
underflow case, the result needs recomputing in the original rounding
mode.
Tested x86_64 and x86 and ulps updated accordingly.
[BZ #16315]
* sysdeps/i386/fpu/e_pow.S (__ieee754_pow): Ensure possibly
overflowing or underflowing operations take place with sign of
result.
* sysdeps/i386/fpu/e_powf.S (__ieee754_powf): Likewise.
* sysdeps/i386/fpu/e_powl.S (__ieee754_powl): Likewise.
* sysdeps/ieee754/dbl-64/e_pow.c: Include <math.h>.
(__ieee754_pow): Recompute overflowing and underflowing results in
original rounding mode.
* sysdeps/x86/fpu/powl_helper.c: Include <stdbool.h>.
(__powl_helper): Allow negative argument X and scale negated value
as needed. Avoid passing value outside [-1, 1] to f2xm1.
* sysdeps/x86_64/fpu/e_powl.S (__ieee754_powl): Ensure possibly
overflowing or underflowing operations take place with sign of
result.
* sysdeps/x86_64/fpu/multiarch/e_pow.c [HAVE_FMA4_SUPPORT]:
Include <math.h>.
* math/auto-libm-test-in: Add more tests of pow.
* math/auto-libm-test-out: Regenerated.
* math/libm-test.inc (pow_test): Use ALL_RM_TEST.
(pow_tonearest_test_data): Remove.
(pow_test_tonearest): Likewise.
(pow_towardzero_test_data): Likewise.
(pow_test_towardzero): Likewise.
(pow_downward_test_data): Likewise.
(pow_test_downward): Likewise.
(pow_upward_test_data): Likewise.
(pow_test_upward): Likewise.
(main): Don't call removed functions.
* sysdeps/i386/fpu/libm-test-ulps: Update.
* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.
Diffstat (limited to 'sysdeps/i386/fpu/e_powf.S')
| -rw-r--r-- | sysdeps/i386/fpu/e_powf.S | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/sysdeps/i386/fpu/e_powf.S b/sysdeps/i386/fpu/e_powf.S index 89d30d8187..3735654a4e 100644 --- a/sysdeps/i386/fpu/e_powf.S +++ b/sysdeps/i386/fpu/e_powf.S @@ -129,12 +129,22 @@ ENTRY(__ieee754_powf) 4: fldl MO(one) // 1 : x fxch + /* If y is even, take the absolute value of x. Otherwise, + ensure all intermediate values that might overflow have the + sign of x. */ + testb $1, %dl + jnz 6f + fabs + 6: shrl $1, %edx jnc 5f fxch + fabs fmul %st(1) // x : ST*x fxch -5: fmul %st(0), %st // x*x : ST*x +5: fld %st // x : x : ST*x + fabs // |x| : x : ST*x + fmulp // |x|*x : ST*x testl %edx, %edx jnz 6b fstp %st(0) // ST*x |