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NetBSD/lib/libm/arch/i387/e_exp.S

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ArmAsm
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FPU specific math code.
1994-02-11 21:20:17 +03:00
/*
Winning Strategies has placed this code into the Public Domain
1995-04-29 02:43:31 +04:00
* Written by J.T. Conklin <jtc@netbsd.org>.
* Public domain.
FPU specific math code.
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*/
#include <machine/asm.h>
It's necessary to use 64 bit precision to avoid errors in the least significant bit(s) (for some operands).
1996-07-03 21:27:34 +04:00
RCSID("$NetBSD: e_exp.S,v 1.6 1996/07/03 17:27:34 jtc Exp $")
Added RCS ID's. ID's use new RCSID macro from <machine/asm.h>.
1994-03-12 04:30:22 +03:00
FPU specific math code.
1994-02-11 21:20:17 +03:00
/* e^x = 2^(x * log2(e)) */
ENTRY(__ieee754_exp)
It's necessary to use 64 bit precision to avoid errors in the least significant bit(s) (for some operands).
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pushl %ebp
movl %esp,%ebp
subl $8,%esp
fstcw -12(%ebp) /* store fpu control word */
movw -12(%ebp),%dx
orw $0x0180,%dx
movw %dx,-16(%ebp)
fldcw -16(%ebp) /* load modfied control word */
fldl 8(%ebp)
FPU specific math code.
1994-02-11 21:20:17 +03:00
fldl2e
fmulp /* x * log2(e) */
fstl %st(1)
frndint /* int(x * log2(e)) */
fstl %st(2)
fsubrp /* fract(x * log2(e)) */
f2xm1 /* 2^(fract(x * log2(e))) - 1 */
fld1
faddp /* 2^(fract(x * log2(e))) */
fscale /* e^x */
Fix from Bruce Evans. Commited to FreeBSD earlier this month, but was never forwarded to me :-(. > Clean up the FP stack before returning. The i387 exp() leaked an FP > register on its first call. Subsequent calls reused the register so > the leak didn't accumulate.
1996-06-25 06:07:09 +04:00
fstpl %st(1)
It's necessary to use 64 bit precision to avoid errors in the least significant bit(s) (for some operands).
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fldcw -12(%ebp) /* restore original control word */
leave
FPU specific math code.
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ret