/*---------------------------------------------------------------------------+ | reg_mul.c | | | | Multiply one FPU_REG by another, put the result in a destination FPU_REG. | | | | Copyright (C) 1992,1993,1997 | | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia | | E-mail billm@suburbia.net | | | | Returns the tag of the result if no exceptions or errors occurred. | | | +---------------------------------------------------------------------------*/ /*---------------------------------------------------------------------------+ | The destination may be any FPU_REG, including one of the source FPU_REGs. | +---------------------------------------------------------------------------*/ #include "fpu_emu.h" #include "exception.h" #include "reg_constant.h" #include "fpu_system.h" /* Multiply two registers to give a register result. The sources are st(deststnr) and (b,tagb,signb). The destination is st(deststnr). */ /* This routine must be called with non-empty source registers */ int FPU_mul(FPU_REG const *b, u_char tagb, int deststnr, int control_w) { FPU_REG *a = &st(deststnr); FPU_REG *dest = a; u_char taga = FPU_gettagi(deststnr); u_char saved_sign = getsign(dest); u_char sign = (getsign(a) ^ getsign(b)); int tag; if ( !(taga | tagb) ) { /* Both regs Valid, this should be the most common case. */ tag = FPU_u_mul(a, b, dest, control_w, sign, exponent(a) + exponent(b)); if ( tag < 0 ) { setsign(dest, saved_sign); return tag; } FPU_settagi(deststnr, tag); return tag; } if ( taga == TAG_Special ) taga = FPU_Special(a); if ( tagb == TAG_Special ) tagb = FPU_Special(b); if ( ((taga == TAG_Valid) && (tagb == TW_Denormal)) || ((taga == TW_Denormal) && (tagb == TAG_Valid)) || ((taga == TW_Denormal) && (tagb == TW_Denormal)) ) { FPU_REG x, y; if ( denormal_operand() < 0 ) return FPU_Exception; FPU_to_exp16(a, &x); FPU_to_exp16(b, &y); tag = FPU_u_mul(&x, &y, dest, control_w, sign, exponent16(&x) + exponent16(&y)); if ( tag < 0 ) { setsign(dest, saved_sign); return tag; } FPU_settagi(deststnr, tag); return tag; } else if ( (taga <= TW_Denormal) && (tagb <= TW_Denormal) ) { if ( ((tagb == TW_Denormal) || (taga == TW_Denormal)) && (denormal_operand() < 0) ) return FPU_Exception; /* Must have either both arguments == zero, or one valid and the other zero. The result is therefore zero. */ FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr); /* 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. */ setsign(dest, sign); return TAG_Zero; } /* Must have infinities, NaNs, etc */ else if ( (taga == TW_NaN) || (tagb == TW_NaN) ) { return real_2op_NaN(b, tagb, deststnr, &st(0)); } else if ( ((taga == TW_Infinity) && (tagb == TAG_Zero)) || ((tagb == TW_Infinity) && (taga == TAG_Zero)) ) { return arith_invalid(deststnr); /* Zero*Infinity is invalid */ } else if ( ((taga == TW_Denormal) || (tagb == TW_Denormal)) && (denormal_operand() < 0) ) { return FPU_Exception; } else if (taga == TW_Infinity) { FPU_copy_to_regi(a, TAG_Special, deststnr); setsign(dest, sign); return TAG_Special; } else if (tagb == TW_Infinity) { FPU_copy_to_regi(b, TAG_Special, deststnr); setsign(dest, sign); return TAG_Special; } #ifdef PARANOID else { EXCEPTION(EX_INTERNAL|0x102); return FPU_Exception; } #endif /* PARANOID */ }