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| author | Joseph Myers <joseph@codesourcery.com> | 2015-09-24 23:43:57 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2015-09-24 23:43:57 +0000 |
| commit | f6987f5aa4c2ef7270bcb0a828808bd3db53520b (patch) | |
| tree | 47bb4bea42d9cf529c14ee3b16d8fc8c6ac02388 /sysdeps/i386/fpu | |
| parent | 2fd9177c92328e5c861c60ec9d0c4588cf0d9376 (diff) | |
| download | glibc-f6987f5aa4c2ef7270bcb0a828808bd3db53520b.tar.gz glibc-f6987f5aa4c2ef7270bcb0a828808bd3db53520b.tar.xz glibc-f6987f5aa4c2ef7270bcb0a828808bd3db53520b.zip | |
Fix hypot missing underflows (bug 18803).
Similar to various other bugs in this area, hypot functions can fail to raise the underflow exception when the result is tiny and inexact but one or more low bits of the intermediate result that is scaled down (or, in the i386 case, converted from a wider evaluation format) are zero. This patch forces the exception in a similar way to previous fixes. Note that this issue cannot arise for implementations of hypotf using double (or wider) for intermediate evaluation (if hypotf should underflow, that means the double square root is being computed of some number of the form N*2^-298, for 0 < N < 2^46, which is exactly represented as a double, and whatever the rounding mode such a square root cannot have a mantissa with all zeroes after the initial 23 bits). Thus no changes are made to hypotf implementations in this patch, only to hypot and hypotl. Tested for x86_64, x86, mips64 and powerpc. [BZ #18803] * sysdeps/i386/fpu/e_hypot.S: Use DEFINE_DBL_MIN. (MO): New macro. (__ieee754_hypot) [PIC]: Load PIC register. (__ieee754_hypot): Use DBL_NARROW_EVAL_UFLOW_NONNEG instead of DBL_NARROW_EVAL. * sysdeps/ieee754/dbl-64/e_hypot.c (__ieee754_hypot): Use math_check_force_underflow_nonneg in case where result might be tiny. * sysdeps/ieee754/ldbl-128/e_hypotl.c (__ieee754_hypotl): Likewise. * sysdeps/ieee754/ldbl-128ibm/e_hypotl.c (__ieee754_hypotl): Likewise. * sysdeps/ieee754/ldbl-96/e_hypotl.c (__ieee754_hypotl): Likewise. * sysdeps/powerpc/fpu/e_hypot.c (__ieee754_hypot): Likewise. * math/auto-libm-test-in: Add more tests of hypot. * math/auto-libm-test-out: Regenerated.
Diffstat (limited to 'sysdeps/i386/fpu')
| -rw-r--r-- | sysdeps/i386/fpu/e_hypot.S | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/sysdeps/i386/fpu/e_hypot.S b/sysdeps/i386/fpu/e_hypot.S index 5323fde01e..e69ea096ab 100644 --- a/sysdeps/i386/fpu/e_hypot.S +++ b/sysdeps/i386/fpu/e_hypot.S @@ -20,8 +20,19 @@ #include <sysdep.h> #include <i386-math-asm.h> +DEFINE_DBL_MIN + +#ifdef PIC +# define MO(op) op##@GOTOFF(%edx) +#else +# define MO(op) op +#endif + .text ENTRY(__ieee754_hypot) +#ifdef PIC + LOAD_PIC_REG (dx) +#endif fldl 4(%esp) // x fxam fnstsw @@ -38,7 +49,7 @@ ENTRY(__ieee754_hypot) fmul %st(0) // x * x : y * y faddp // x * x + y * y fsqrt - DBL_NARROW_EVAL + DBL_NARROW_EVAL_UFLOW_NONNEG 2: ret // We have to test whether any of the parameters is Inf. |