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| author | Joseph Myers <joseph@codesourcery.com> | 2012-04-09 22:32:45 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2012-04-09 22:32:45 +0000 |
| commit | 8f9a2faee0619ed5fad7b9c54b64f866b0264bde (patch) | |
| tree | c5545fa72a99dcee226d2c4ffc3adca24e1a2124 /sysdeps/i386/fpu | |
| parent | bcc8d6617ba029c288fff9680a02b9a3b1caa9c0 (diff) | |
| download | glibc-8f9a2faee0619ed5fad7b9c54b64f866b0264bde.tar.gz glibc-8f9a2faee0619ed5fad7b9c54b64f866b0264bde.tar.xz glibc-8f9a2faee0619ed5fad7b9c54b64f866b0264bde.zip | |
Fix spurious overflow exceptions from x86/x86_64 powl (bug 13872).
Diffstat (limited to 'sysdeps/i386/fpu')
| -rw-r--r-- | sysdeps/i386/fpu/e_powl.S | 31 |
1 files changed, 19 insertions, 12 deletions
diff --git a/sysdeps/i386/fpu/e_powl.S b/sysdeps/i386/fpu/e_powl.S index 0e7c05bb82..5b166eab4b 100644 --- a/sysdeps/i386/fpu/e_powl.S +++ b/sysdeps/i386/fpu/e_powl.S @@ -35,6 +35,9 @@ p63: .byte 0, 0, 0, 0, 0, 0, 0xe0, 0x43 ASM_TYPE_DIRECTIVE(p64,@object) p64: .byte 0, 0, 0, 0, 0, 0, 0xf0, 0x43 ASM_SIZE_DIRECTIVE(p64) + ASM_TYPE_DIRECTIVE(p78,@object) +p78: .byte 0, 0, 0, 0, 0, 0, 0xd0, 0x44 + ASM_SIZE_DIRECTIVE(p78) .section .rodata.cst16,"aM",@progbits,16 @@ -166,6 +169,21 @@ ENTRY(__ieee754_powl) fxch // x : y fabs // |x| : y fxch // y : |x| + // If y has absolute value at least 1L<<78, then any finite + // nonzero x will result in 0 (underflow), 1 or infinity (overflow). + // Saturate y to those bounds to avoid overflow in the calculation + // of y*log2(x). + fld %st // y : y : |x| + fabs // |y| : y : |x| + fcompl MO(p78) // y : |x| + fnstsw + sahf + jc 3f + fstp %st(0) // pop y + fldl MO(p78) // 1L<<78 : |x| + testb $2, %dl + jz 3f // y > 0 + fchs // -(1L<<78) : |x| .align ALIGNARG(4) 3: /* y is a real number. */ fxch // x : y @@ -185,11 +203,6 @@ ENTRY(__ieee754_powl) 7: fyl2x // log2(x) : y 8: fmul %st(1) // y*log2(x) : y - fxam - fnstsw - andb $0x45, %ah - cmpb $0x05, %ah // is y*log2(x) == ħinf ? - je 28f fst %st(1) // y*log2(x) : y*log2(x) frndint // int(y*log2(x)) : y*log2(x) fsubr %st, %st(1) // int(y*log2(x)) : fract(y*log2(x)) @@ -198,13 +211,7 @@ ENTRY(__ieee754_powl) faddl MO(one) // 2^fract(y*log2(x)) : int(y*log2(x)) fscale // 2^fract(y*log2(x))*2^int(y*log2(x)) : int(y*log2(x)) fstp %st(1) // 2^fract(y*log2(x))*2^int(y*log2(x)) - jmp 29f - -28: fstp %st(1) // y*log2(x) - fldl MO(one) // 1 : y*log2(x) - fscale // 2^(y*log2(x)) : y*log2(x) - fstp %st(1) // 2^(y*log2(x)) -29: testb $2, %dh + testb $2, %dh jz 292f // x is negative. If y is an odd integer, negate the result. fldt 24(%esp) // y : abs(result) |