mirror of https://github.com/bochs-emu/Bochs
141 lines
3.6 KiB
C
141 lines
3.6 KiB
C
/*---------------------------------------------------------------------------+
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| reg_u_add.c |
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| Add two valid (TAG_Valid) FPU_REG numbers, of the same sign, and put the |
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| result in a destination FPU_REG. |
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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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| Return value is the tag of the answer, or-ed with FPU_Exception if |
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| one was raised, or -1 on internal error. |
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+---------------------------------------------------------------------------*/
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/*
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| Kernel addition routine FPU_u_add(reg *arg1, reg *arg2, reg *answ).
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| Takes two valid reg f.p. numbers (TAG_Valid), which are
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| treated as unsigned numbers,
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| and returns their sum as a TAG_Valid or TAG_Special f.p. number.
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| The returned number is normalized.
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| Basic checks are performed if PARANOID is defined.
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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_add(const FPU_REG *arg1, const FPU_REG *arg2, FPU_REG *answ,
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u16 control_w, u_char sign, s32 expa, s32 expb)
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{
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const FPU_REG *rtmp;
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FPU_REG shifted;
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u32 extent = 0;
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int ediff = expa - expb, ed2, eflag, ovfl, carry;
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if ( ediff < 0 )
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{
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ediff = -ediff;
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rtmp = arg1;
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arg1 = arg2;
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arg2 = rtmp;
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expa = expb;
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}
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/* Now we have exponent of arg1 >= exponent of arg2 */
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answ->exp = expa;
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#ifdef PARANOID
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if ( !(arg1->sigh & 0x80000000) || !(arg2->sigh & 0x80000000) )
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{
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EXCEPTION(EX_INTERNAL|0x201);
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return -1;
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}
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#endif
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if ( ediff == 0 )
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{
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extent = 0;
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shifted.sigl = arg2->sigl;
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shifted.sigh = arg2->sigh;
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}
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else if ( ediff < 32 )
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{
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ed2 = 32 - ediff;
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extent = arg2->sigl << ed2;
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shifted.sigl = arg2->sigl >> ediff;
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shifted.sigl |= (arg2->sigh << ed2);
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shifted.sigh = arg2->sigh >> ediff;
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}
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else if ( ediff < 64 )
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{
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ediff -= 32;
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if ( ! ediff )
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{
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eflag = 0;
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extent = arg2->sigl;
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shifted.sigl = arg2->sigh;
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}
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else
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{
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ed2 = 32 - ediff;
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eflag = arg2->sigl;
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if ( eflag )
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extent |= 1;
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extent = arg2->sigl >> ediff;
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extent |= (arg2->sigh << ed2);
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shifted.sigl = arg2->sigh >> ediff;
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}
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shifted.sigh = 0;
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}
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else
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{
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ediff -= 64;
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if ( ! ediff )
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{
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eflag = arg2->sigl;
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extent = arg2->sigh;
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}
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else
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{
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ed2 = 64 - ediff;
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eflag = arg2->sigl | arg2->sigh;
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extent = arg2->sigh >> ediff;
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}
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shifted.sigl = 0;
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shifted.sigh = 0;
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if ( eflag )
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extent |= 1;
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}
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answ->sigh = arg1->sigh + shifted.sigh;
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ovfl = shifted.sigh > answ->sigh;
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answ->sigl = arg1->sigl + shifted.sigl;
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if ( shifted.sigl > answ->sigl )
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{
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answ->sigh ++;
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if ( answ->sigh == 0 )
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ovfl = 1;
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}
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if ( ovfl )
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{
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carry = extent & 1;
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extent >>= 1;
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extent |= carry;
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if ( answ->sigl & 1 )
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extent |= 0x80000000;
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answ->sigl >>= 1;
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if ( answ->sigh & 1 )
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answ->sigl |= 0x80000000;
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answ->sigh >>= 1;
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answ->sigh |= 0x80000000;
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answ->exp ++;
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}
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return FPU_round(answ, extent, 0, control_w, sign);
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}
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