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| author | Joseph Myers <joseph@codesourcery.com> | 2015-09-15 16:50:02 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2015-09-15 16:50:02 +0000 |
| commit | 828bf6828b048b1482e95f84ca92e5fe0edcdc0c (patch) | |
| tree | eb047446bae21ae21674f282ec3970a75dbb9362 /sysdeps/i386/fpu/e_exp10.S | |
| parent | 333ceaa54bc27de48fc6eecc7b0a3e75a0c5ce50 (diff) | |
| download | glibc-828bf6828b048b1482e95f84ca92e5fe0edcdc0c.tar.gz glibc-828bf6828b048b1482e95f84ca92e5fe0edcdc0c.tar.xz glibc-828bf6828b048b1482e95f84ca92e5fe0edcdc0c.zip | |
Fix i386 exp10 missing underflows (bug 18966).
On i386, the double version of exp10 can miss underflow exceptions if the result is in the subnormal range for double but the last 11 bits of the 64-bit extended-precision mantissa happen to be zero. This patch forces the exception in a similar way to previous fixes. As with the exp2 and exp fixes, the exp10f changes may in fact not be needed to ensure underflow exceptions, but are included for consistency and to fix the exp10 part of bug 18875 by ensuring that excess range and precision is removed from underflowing return values. Tested for x86_64 and x86. [BZ #18875] [BZ #18966] * sysdeps/i386/fpu/e_exp10.S (dbl_min): New object. (MO): New macro. (__ieee754_exp10): For small results, force underflow exception and remove excess range and precision from return value. * sysdeps/i386/fpu/e_exp10f.S (flt_min): New object. (MO): New macro. (__ieee754_exp10f): For small results, force underflow exception and remove excess range and precision from return value. * math/auto-libm-test-in: Add more tests of exp10. * math/auto-libm-test-out: Regenerated.
Diffstat (limited to 'sysdeps/i386/fpu/e_exp10.S')
| -rw-r--r-- | sysdeps/i386/fpu/e_exp10.S | 34 |
1 files changed, 33 insertions, 1 deletions
diff --git a/sysdeps/i386/fpu/e_exp10.S b/sysdeps/i386/fpu/e_exp10.S index 1e32b07848..fa54732e2a 100644 --- a/sysdeps/i386/fpu/e_exp10.S +++ b/sysdeps/i386/fpu/e_exp10.S @@ -4,8 +4,25 @@ #include <machine/asm.h> + .section .rodata.cst8,"aM",@progbits,8 + + .p2align 3 + .type dbl_min,@object +dbl_min: .byte 0, 0, 0, 0, 0, 0, 0x10, 0 + ASM_SIZE_DIRECTIVE(dbl_min) + +#ifdef PIC +# define MO(op) op##@GOTOFF(%ecx) +#else +# define MO(op) op +#endif + + .text /* 10^x = 2^(x * log2(10)) */ ENTRY(__ieee754_exp10) +#ifdef PIC + LOAD_PIC_REG (cx) +#endif fldl 4(%esp) /* I added the following ugly construct because exp(+-Inf) resulted in NaN. The ugliness results from the bright minds at Intel. @@ -28,7 +45,22 @@ ENTRY(__ieee754_exp10) faddp /* 2^(fract(x * log2(10))) */ fscale /* e^x */ fstp %st(1) - ret + fldl MO(dbl_min) + fld %st(1) + fucompp + fnstsw + sahf + jnc 3f + subl $8, %esp + cfi_adjust_cfa_offset (8) + fld %st(0) + fmul %st(0) + fstpl (%esp) + fstpl (%esp) + fldl (%esp) + addl $8, %esp + cfi_adjust_cfa_offset (-8) +3: ret 1: testl $0x200, %eax /* Test sign. */ jz 2f /* If positive, jump. */ |