106 lines
3.2 KiB
C
106 lines
3.2 KiB
C
/*---------------------------------------------------------------------------+
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| reg_mul.c |
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| Multiply one FPU_REG by another, put the result in a destination FPU_REG. |
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| Copyright (C) 1992,1993 |
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| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, |
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| Australia. E-mail billm@vaxc.cc.monash.edu.au |
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+---------------------------------------------------------------------------*/
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/*---------------------------------------------------------------------------+
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| The destination may be any FPU_REG, including one of the source FPU_REGs. |
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+---------------------------------------------------------------------------*/
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#include "exception.h"
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#include "reg_constant.h"
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#include "fpu_emu.h"
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#include "fpu_system.h"
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/* This routine must be called with non-empty source registers */
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int reg_mul(FPU_REG const *a, FPU_REG const *b,
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FPU_REG *dest, unsigned int control_w)
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{
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char saved_sign = dest->sign;
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char sign = (a->sign ^ b->sign);
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if (!(a->tag | b->tag))
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{
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/* Both regs Valid, this should be the most common case. */
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dest->sign = sign;
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if ( reg_u_mul(a, b, dest, control_w) )
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{
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dest->sign = saved_sign;
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return 1;
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}
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return 0;
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}
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else if ((a->tag <= TW_Zero) && (b->tag <= TW_Zero))
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{
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#ifdef DENORM_OPERAND
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if ( ((b->tag == TW_Valid) && (b->exp <= EXP_UNDER)) ||
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((a->tag == TW_Valid) && (a->exp <= EXP_UNDER)) )
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{
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if ( denormal_operand() ) return 1;
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}
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#endif DENORM_OPERAND
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/* Must have either both arguments == zero, or
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one valid and the other zero.
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The result is therefore zero. */
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reg_move(&CONST_Z, dest);
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#ifdef PECULIAR_486
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/* The 80486 book says that the answer is +0, but a real
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80486 appears to behave this way... */
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dest->sign = sign;
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#endif PECULIAR_486
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return 0;
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}
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else
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{
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/* Must have infinities, NaNs, etc */
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if ( (a->tag == TW_NaN) || (b->tag == TW_NaN) )
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{ return real_2op_NaN(a, b, dest); }
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else if (a->tag == TW_Infinity)
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{
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if (b->tag == TW_Zero)
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{ return arith_invalid(dest); } /* Zero*Infinity is invalid */
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else
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{
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#ifdef DENORM_OPERAND
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if ( (b->tag == TW_Valid) && (b->exp <= EXP_UNDER) &&
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denormal_operand() )
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return 1;
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#endif DENORM_OPERAND
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reg_move(a, dest);
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dest->sign = sign;
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}
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return 0;
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}
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else if (b->tag == TW_Infinity)
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{
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if (a->tag == TW_Zero)
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{ return arith_invalid(dest); } /* Zero*Infinity is invalid */
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else
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{
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#ifdef DENORM_OPERAND
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if ( (a->tag == TW_Valid) && (a->exp <= EXP_UNDER) &&
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denormal_operand() )
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return 1;
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#endif DENORM_OPERAND
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reg_move(b, dest);
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dest->sign = sign;
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}
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return 0;
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}
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#ifdef PARANOID
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else
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{
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EXCEPTION(EX_INTERNAL|0x102);
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return 1;
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}
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#endif PARANOID
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}
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}
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