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 /* 25 Multiply two registers to give a register result. 26 The sources are st(deststnr) and (b,tagb,signb). 27 The destination is st(deststnr). 28 */ 29 /* This routine must be called with non-empty source registers */ 30 int FPU_mul(FPU_REG const *b, u_char tagb, int deststnr, int control_w) 31 { 32 FPU_REG *a = &st(deststnr); 33 FPU_REG *dest = a; 34 u_char taga = FPU_gettagi(deststnr); 35 u_char saved_sign = getsign(dest); 36 u_char sign = (getsign(a) ^ getsign(b)); 37 int tag; 38 39 40 if ( !(taga | tagb) ) 41 { 42 /* Both regs Valid, this should be the most common case. */ 43 44 tag = FPU_u_mul(a, b, dest, control_w, sign, exponent(a) + exponent(b)); 45 if ( tag < 0 ) 46 { 47 setsign(dest, saved_sign); 48 return tag; 49 } 50 FPU_settagi(deststnr, tag); 51 return tag; 52 } 53 54 if ( taga == TAG_Special ) 55 taga = FPU_Special(a); 56 if ( tagb == TAG_Special ) 57 tagb = FPU_Special(b); 58 59 if ( ((taga == TAG_Valid) && (tagb == TW_Denormal)) 60 || ((taga == TW_Denormal) && (tagb == TAG_Valid)) 61 || ((taga == TW_Denormal) && (tagb == TW_Denormal)) ) 62 { 63 FPU_REG x, y; 64 if ( denormal_operand() < 0 ) 65 return FPU_Exception; 66 67 FPU_to_exp16(a, &x); 68 FPU_to_exp16(b, &y); 69 tag = FPU_u_mul(&x, &y, dest, control_w, sign, 70 exponent16(&x) + exponent16(&y)); 71 if ( tag < 0 ) 72 { 73 setsign(dest, saved_sign); 74 return tag; 75 } 76 FPU_settagi(deststnr, tag); 77 return tag; 78 } 79 else if ( (taga <= TW_Denormal) && (tagb <= TW_Denormal) ) 80 { 81 if ( ((tagb == TW_Denormal) || (taga == TW_Denormal)) 82 && (denormal_operand() < 0) ) 83 return FPU_Exception; 84 85 /* Must have either both arguments == zero, or 86 one valid and the other zero. 87 The result is therefore zero. */ 88 FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr); 89 /* The 80486 book says that the answer is +0, but a real 90 80486 behaves this way. 91 IEEE-754 apparently says it should be this way. */ 92 setsign(dest, sign); 93 return TAG_Zero; 94 } 95 /* Must have infinities, NaNs, etc */ 96 else if ( (taga == TW_NaN) || (tagb == TW_NaN) ) 97 { 98 return real_2op_NaN(b, tagb, deststnr, &st(0)); 99 } 100 else if ( ((taga == TW_Infinity) && (tagb == TAG_Zero)) 101 || ((tagb == TW_Infinity) && (taga == TAG_Zero)) ) 102 { 103 return arith_invalid(deststnr); /* Zero*Infinity is invalid */ 104 } 105 else if ( ((taga == TW_Denormal) || (tagb == TW_Denormal)) 106 && (denormal_operand() < 0) ) 107 { 108 return FPU_Exception; 109 } 110 else if (taga == TW_Infinity) 111 { 112 FPU_copy_to_regi(a, TAG_Special, deststnr); 113 setsign(dest, sign); 114 return TAG_Special; 115 } 116 else if (tagb == TW_Infinity) 117 { 118 FPU_copy_to_regi(b, TAG_Special, deststnr); 119 setsign(dest, sign); 120 return TAG_Special; 121 } 122 123 #ifdef PARANOID 124 else 125 { 126 EXCEPTION(EX_INTERNAL|0x102); 127 return FPU_Exception; 128 } 129 #endif /* PARANOID */ 130 131 return 0; 132 } 133