1 /*---------------------------------------------------------------------------+ 2 | reg_mul.c | 3 | | 4 | Multiply one FPU_REG by another, put the result in a destination FPU_REG. | 5 | | 6 | Copyright (C) 1992,1993,1997 | 7 | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia | 8 | E-mail billm@suburbia.net | 9 | | 10 | Returns the tag of the result if no exceptions or errors occurred. | 11 | | 12 +---------------------------------------------------------------------------*/ 13 14 /*---------------------------------------------------------------------------+ 15 | The destination may be any FPU_REG, including one of the source FPU_REGs. | 16 +---------------------------------------------------------------------------*/ 17 18 #include "fpu_emu.h" 19 #include "exception.h" 20 #include "reg_constant.h" 21 #include "fpu_system.h" 22 23 /* 24 Multiply two registers to give a register result. 25 The sources are st(deststnr) and (b,tagb,signb). 26 The destination is st(deststnr). 27 */ 28 /* This routine must be called with non-empty source registers */ 29 int FPU_mul(FPU_REG const *b, u_char tagb, int deststnr, int control_w) 30 { 31 FPU_REG *a = &st(deststnr); 32 FPU_REG *dest = a; 33 u_char taga = FPU_gettagi(deststnr); 34 u_char saved_sign = getsign(dest); 35 u_char sign = (getsign(a) ^ getsign(b)); 36 int tag; 37 38 if (!(taga | tagb)) { 39 /* Both regs Valid, this should be the most common case. */ 40 41 tag = 42 FPU_u_mul(a, b, dest, control_w, sign, 43 exponent(a) + exponent(b)); 44 if (tag < 0) { 45 setsign(dest, saved_sign); 46 return tag; 47 } 48 FPU_settagi(deststnr, tag); 49 return tag; 50 } 51 52 if (taga == TAG_Special) 53 taga = FPU_Special(a); 54 if (tagb == TAG_Special) 55 tagb = FPU_Special(b); 56 57 if (((taga == TAG_Valid) && (tagb == TW_Denormal)) 58 || ((taga == TW_Denormal) && (tagb == TAG_Valid)) 59 || ((taga == TW_Denormal) && (tagb == TW_Denormal))) { 60 FPU_REG x, y; 61 if (denormal_operand() < 0) 62 return FPU_Exception; 63 64 FPU_to_exp16(a, &x); 65 FPU_to_exp16(b, &y); 66 tag = FPU_u_mul(&x, &y, dest, control_w, sign, 67 exponent16(&x) + exponent16(&y)); 68 if (tag < 0) { 69 setsign(dest, saved_sign); 70 return tag; 71 } 72 FPU_settagi(deststnr, tag); 73 return tag; 74 } else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) { 75 if (((tagb == TW_Denormal) || (taga == TW_Denormal)) 76 && (denormal_operand() < 0)) 77 return FPU_Exception; 78 79 /* Must have either both arguments == zero, or 80 one valid and the other zero. 81 The result is therefore zero. */ 82 FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr); 83 /* The 80486 book says that the answer is +0, but a real 84 80486 behaves this way. 85 IEEE-754 apparently says it should be this way. */ 86 setsign(dest, sign); 87 return TAG_Zero; 88 } 89 /* Must have infinities, NaNs, etc */ 90 else if ((taga == TW_NaN) || (tagb == TW_NaN)) { 91 return real_2op_NaN(b, tagb, deststnr, &st(0)); 92 } else if (((taga == TW_Infinity) && (tagb == TAG_Zero)) 93 || ((tagb == TW_Infinity) && (taga == TAG_Zero))) { 94 return arith_invalid(deststnr); /* Zero*Infinity is invalid */ 95 } else if (((taga == TW_Denormal) || (tagb == TW_Denormal)) 96 && (denormal_operand() < 0)) { 97 return FPU_Exception; 98 } else if (taga == TW_Infinity) { 99 FPU_copy_to_regi(a, TAG_Special, deststnr); 100 setsign(dest, sign); 101 return TAG_Special; 102 } else if (tagb == TW_Infinity) { 103 FPU_copy_to_regi(b, TAG_Special, deststnr); 104 setsign(dest, sign); 105 return TAG_Special; 106 } 107 #ifdef PARANOID 108 else { 109 EXCEPTION(EX_INTERNAL | 0x102); 110 return FPU_Exception; 111 } 112 #endif /* PARANOID */ 113 114 return 0; 115 } 116