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| author | Joseph Myers <joseph@codesourcery.com> | 2012-03-28 14:57:58 +0000 |
|---|---|---|
| committer | Joseph Myers <joseph@codesourcery.com> | 2012-03-28 14:57:58 +0000 |
| commit | d6270972f79fe89a96fa7a3909991dad2e317033 (patch) | |
| tree | 18ed157e89359cf8711d641916028dab73e37449 /sysdeps/x86_64/fpu | |
| parent | 414fca039edfece0dc9bfc266730e390124687de (diff) | |
| download | glibc-d6270972f79fe89a96fa7a3909991dad2e317033.tar.gz glibc-d6270972f79fe89a96fa7a3909991dad2e317033.tar.xz glibc-d6270972f79fe89a96fa7a3909991dad2e317033.zip | |
Fix pow of negative numbers to integer exponents (bugs 369, 2678, 3866).
Diffstat (limited to 'sysdeps/x86_64/fpu')
| -rw-r--r-- | sysdeps/x86_64/fpu/e_powl.S | 47 |
1 files changed, 43 insertions, 4 deletions
diff --git a/sysdeps/x86_64/fpu/e_powl.S b/sysdeps/x86_64/fpu/e_powl.S index 562791d302..0626ce4172 100644 --- a/sysdeps/x86_64/fpu/e_powl.S +++ b/sysdeps/x86_64/fpu/e_powl.S @@ -107,7 +107,7 @@ ENTRY(__ieee754_powl) fistpll -8(%rsp) // y : x fildll -8(%rsp) // int(y) : y : x fucomip %st(1),%st // y : x - jne 2f + jne 3f /* OK, we have an integer value for y. */ mov -8(%rsp),%eax @@ -145,7 +145,14 @@ ENTRY(__ieee754_powl) ret .align ALIGNARG(4) -2: /* y is a real number. */ +2: // y is a large integer (absolute value at least 1L<<63), but + // may be odd unless at least 1L<<64. So it may be necessary + // to adjust the sign of a negative result afterwards. + fxch // x : y + fabs // |x| : y + fxch // y : |x| + .align ALIGNARG(4) +3: /* y is a real number. */ fxch // x : y fldl MO(one) // 1.0 : x : y fldl MO(limit) // 0.29 : 1.0 : x : y @@ -176,13 +183,45 @@ 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)) - ret + 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)) - ret +29: testb $2, %dh + jz 292f + // x is negative. If y is an odd integer, negate the result. + fldt 24(%rsp) // y : abs(result) + fldl MO(p64) // 1L<<64 : y : abs(result) + fld %st(1) // y : 1L<<64 : y : abs(result) + fabs // |y| : 1L<<64 : y : abs(result) + fcomip %st(1), %st // 1L<<64 : y : abs(result) + fstp %st(0) // y : abs(result) + jnc 291f + fldl MO(p63) // p63 : y : abs(result) + fxch // y : p63 : abs(result) + fprem // y%p63 : p63 : abs(result) + fstp %st(1) // y%p63 : abs(result) + + // We must find out whether y is an odd integer. + fld %st // y : y : abs(result) + fistpll -8(%rsp) // y : abs(result) + fildll -8(%rsp) // int(y) : y : abs(result) + fucomip %st(1),%st // y : abs(result) + ffreep %st // abs(result) + jne 292f + + // OK, the value is an integer, but is it odd? + mov -8(%rsp), %eax + mov -4(%rsp), %edx + andb $1, %al + jz 290f // jump if not odd + // It's an odd integer. + fchs +290: ret +291: fstp %st(0) // abs(result) +292: ret // pow(x,±0) = 1 .align ALIGNARG(4) |