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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 | /*---------------------------------------------------------------------------+ | reg_mul.c | | | | Multiply one FPU_REG by another, put the result in a destination FPU_REG. | | | | Copyright (C) 1992,1993 | | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, | | Australia. E-mail billm@vaxc.cc.monash.edu.au | | | | | +---------------------------------------------------------------------------*/ /*---------------------------------------------------------------------------+ | The destination may be any FPU_REG, including one of the source FPU_REGs. | +---------------------------------------------------------------------------*/ #include "exception.h" #include "reg_constant.h" #include "fpu_emu.h" #include "fpu_system.h" /* This routine must be called with non-empty source registers */ int reg_mul(FPU_REG const *a, FPU_REG const *b, FPU_REG *dest, unsigned int control_w) { char saved_sign = dest->sign; char sign = (a->sign ^ b->sign); if (!(a->tag | b->tag)) { /* Both regs Valid, this should be the most common case. */ dest->sign = sign; if ( reg_u_mul(a, b, dest, control_w) ) { dest->sign = saved_sign; return 1; } return 0; } else if ((a->tag <= TW_Zero) && (b->tag <= TW_Zero)) { #ifdef DENORM_OPERAND if ( ((b->tag == TW_Valid) && (b->exp <= EXP_UNDER)) || ((a->tag == TW_Valid) && (a->exp <= EXP_UNDER)) ) { if ( denormal_operand() ) return 1; } #endif DENORM_OPERAND /* Must have either both arguments == zero, or one valid and the other zero. The result is therefore zero. */ reg_move(&CONST_Z, dest); /* The 80486 book says that the answer is +0, but a real 80486 behaves this way. IEEE-754 apparently says it should be this way. */ dest->sign = sign; return 0; } else { /* Must have infinities, NaNs, etc */ if ( (a->tag == TW_NaN) || (b->tag == TW_NaN) ) { return real_2op_NaN(a, b, dest); } else if (a->tag == TW_Infinity) { if (b->tag == TW_Zero) { return arith_invalid(dest); } /* Zero*Infinity is invalid */ else { #ifdef DENORM_OPERAND if ( (b->tag == TW_Valid) && (b->exp <= EXP_UNDER) && denormal_operand() ) return 1; #endif DENORM_OPERAND reg_move(a, dest); dest->sign = sign; } return 0; } else if (b->tag == TW_Infinity) { if (a->tag == TW_Zero) { return arith_invalid(dest); } /* Zero*Infinity is invalid */ else { #ifdef DENORM_OPERAND if ( (a->tag == TW_Valid) && (a->exp <= EXP_UNDER) && denormal_operand() ) return 1; #endif DENORM_OPERAND reg_move(b, dest); dest->sign = sign; } return 0; } #ifdef PARANOID else { EXCEPTION(EX_INTERNAL|0x102); return 1; } #endif PARANOID } } |