mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-14 17:11:06 +00:00
4ba7a00fe3
This patch fixes __ieee754_logl (-LDBL_MAX) on x86_64 and x86 not to subtract 1 from its argument and so cause spurious overflow in FE_DOWNWARD mode. (For any argument strictly less than -1, it doesn't matter whether or not 1 is subtracted before computing log1p, as long as the result doesn't overflow to -Inf.) Tested x86_64 and x86. (This particular case lacks test coverage, since the testsuite doesn't cover -lieee, but it will be covered by tests after the following patch to test pow in all rounding modes, which was the context in which this bug was found.) [BZ #17022] * sysdeps/i386/fpu/e_logl.S (__ieee754_logl): Do not subtract 1 from arguments -2 or below. * sysdeps/i386/i686/fpu/e_logl.S (__ieee754_logl): Likewise. * sysdeps/x86_64/fpu/e_logl.S (__ieee754_logl): Likewise.
88 lines
1.8 KiB
ArmAsm
88 lines
1.8 KiB
ArmAsm
/*
|
|
* Written by J.T. Conklin <jtc@netbsd.org>.
|
|
* Public domain.
|
|
*
|
|
* Adapted for `long double' by Ulrich Drepper <drepper@cygnus.com>.
|
|
* Adapted for x86-64 by Andreas Jaeger <aj@suse.de>.
|
|
*/
|
|
|
|
#include <machine/asm.h>
|
|
|
|
|
|
.section .rodata.cst8,"aM",@progbits,8
|
|
|
|
.p2align 3
|
|
.type one,@object
|
|
one: .double 1.0
|
|
ASM_SIZE_DIRECTIVE(one)
|
|
/* It is not important that this constant is precise. It is only
|
|
a value which is known to be on the safe side for using the
|
|
fyl2xp1 instruction. */
|
|
.type limit,@object
|
|
limit: .double 0.29
|
|
ASM_SIZE_DIRECTIVE(limit)
|
|
|
|
|
|
#ifdef PIC
|
|
# define MO(op) op##(%rip)
|
|
#else
|
|
# define MO(op) op
|
|
#endif
|
|
|
|
.text
|
|
ENTRY(__ieee754_logl)
|
|
fldln2 // log(2)
|
|
fldt 8(%rsp) // x : log(2)
|
|
fxam
|
|
fnstsw
|
|
fld %st // x : x : log(2)
|
|
testb $1, %ah
|
|
jnz 3f // in case x is NaN or +-Inf
|
|
movzwl 8+8(%rsp), %eax
|
|
cmpl $0xc000, %eax
|
|
jae 6f // x <= -2, avoid overflow from -LDBL_MAX - 1.
|
|
4: fsubl MO(one) // x-1 : x : log(2)
|
|
6: fld %st // x-1 : x-1 : x : log(2)
|
|
fabs // |x-1| : x-1 : x : log(2)
|
|
fcompl MO(limit) // x-1 : x : log(2)
|
|
fnstsw // x-1 : x : log(2)
|
|
andb $0x45, %ah
|
|
jz 2f
|
|
fxam
|
|
fnstsw
|
|
andb $0x45, %ah
|
|
cmpb $0x40, %ah
|
|
jne 5f
|
|
fabs // log(1) is +0 in all rounding modes.
|
|
5: fstp %st(1) // x-1 : log(2)
|
|
fyl2xp1 // log(x)
|
|
ret
|
|
|
|
2: fstp %st(0) // x : log(2)
|
|
fyl2x // log(x)
|
|
ret
|
|
|
|
3: testb $4, %ah
|
|
jnz 4b // in case x is +-Inf
|
|
fstp %st(1)
|
|
fstp %st(1)
|
|
ret
|
|
END (__ieee754_logl)
|
|
|
|
|
|
ENTRY(__logl_finite)
|
|
fldln2 // log(2)
|
|
fldt 8(%rsp) // x : log(2)
|
|
fld %st // x : x : log(2)
|
|
fsubl MO(one) // x-1 : x : log(2)
|
|
fld %st // x-1 : x-1 : x : log(2)
|
|
fabs // |x-1| : x-1 : x : log(2)
|
|
fcompl MO(limit) // x-1 : x : log(2)
|
|
fnstsw // x-1 : x : log(2)
|
|
andb $0x45, %ah
|
|
jz 2b
|
|
fstp %st(1) // x-1 : log(2)
|
|
fyl2xp1 // log(x)
|
|
ret
|
|
END (__logl_finite)
|