97 lines
2.5 KiB
C
97 lines
2.5 KiB
C
/*---------------------------------------------------------------------------+
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| reg_u_mul.c |
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| $Id: reg_u_mul.c,v 1.3 2001-10-06 03:53:46 bdenney Exp $
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| Core multiplication routine |
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| Copyright (C) 1992,1993,1995,1997,1999 |
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| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
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| E-mail billm@melbpc.org.au |
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+---------------------------------------------------------------------------*/
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/*---------------------------------------------------------------------------+
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| Basic multiplication routine. |
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| Does not check the resulting exponent for overflow/underflow |
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| Internal working is at approx 128 bits. |
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| Result is rounded to nearest 53 or 64 bits, using "nearest or even". |
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+---------------------------------------------------------------------------*/
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#include "exception.h"
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#include "fpu_emu.h"
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#include "control_w.h"
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int FPU_u_mul(const FPU_REG *a, const FPU_REG *b, FPU_REG *c, u16 cw,
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u_char sign, int expon)
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{
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u64 mu, ml, mi;
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u32 lh, ll, th, tl;
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#ifdef PARANOID
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if ( ! (a->sigh & 0x80000000) || ! (b->sigh & 0x80000000) )
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{
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EXCEPTION(EX_INTERNAL|0x205);
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}
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#endif
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ml = a->sigl;
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ml *= b->sigl;
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ll = ml;
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lh = ml >> 32;
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mu = a->sigh;
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mu *= b->sigh;
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mi = a->sigh;
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mi *= b->sigl;
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tl = mi;
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th = mi >> 32;
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lh += tl;
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if ( tl > lh )
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mu ++;
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mu += th;
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mi = a->sigl;
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mi *= b->sigh;
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tl = mi;
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th = mi >> 32;
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lh += tl;
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if ( tl > lh )
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mu ++;
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mu += th;
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ml = lh;
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ml <<= 32;
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ml += ll;
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expon -= EXP_BIAS-1;
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if ( expon <= EXP_WAY_UNDER )
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expon = EXP_WAY_UNDER;
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c->exp = expon;
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if ( ! (mu & BX_CONST64(0x8000000000000000)) )
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{
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mu <<= 1;
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if ( ml & BX_CONST64(0x8000000000000000) )
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mu |= 1;
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ml <<= 1;
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c->exp --;
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}
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ll = ml;
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lh = ml >> 32;
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if ( ll )
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lh |= 1;
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c->sigl = mu;
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c->sigh = mu >> 32;
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return FPU_round(c, lh, 0, cw, sign);
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}
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