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42 lines
963 B
ArmAsm
42 lines
963 B
ArmAsm
/*
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* Written by J.T. Conklin <jtc@netbsd.org>.
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* Public domain.
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*/
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#include <machine/asm.h>
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RCSID("$NetBSD: e_exp.S,v 1.7 1996/07/03 17:31:28 jtc Exp $")
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/* e^x = 2^(x * log2(e)) */
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ENTRY(__ieee754_exp)
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fldl 4(%esp)
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/* I added the following ugly construct because exp(+-Inf) resulted
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in NaN. The ugliness results from the bright minds at Intel.
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For the i686 the code can be written better.
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-- drepper@cygnus.com. */
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fxam /* Is NaN or +-Inf? */
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fstsw %ax
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movb $0x45, %dh
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andb %ah, %dh
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cmpb $0x05, %dh
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je 1f /* Is +-Inf, jump. */
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fldl2e
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fmulp /* x * log2(e) */
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fld %st
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frndint /* int(x * log2(e)) */
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fsubr %st,%st(1) /* fract(x * log2(e)) */
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fxch
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f2xm1 /* 2^(fract(x * log2(e))) - 1 */
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fld1
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faddp /* 2^(fract(x * log2(e))) */
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fscale /* e^x */
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fstp %st(1)
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ret
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1: testl $0x200, %eax /* Test sign. */
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jz 2f /* If positive, jump. */
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fstp %st
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fldz /* Set result to 0. */
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2: ret
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END (__ieee754_exp)
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