1 // SPDX-License-Identifier: GPL-2.0 2 /*---------------------------------------------------------------------------+ 3 | reg_mul.c | 4 | | 5 | Multiply one FPU_REG by another, put the result in a destination FPU_REG. | 6 | | 7 | Copyright (C) 1992,1993,1997 | 8 | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia | 9 | E-mail billm@suburbia.net | 10 | | 11 | Returns the tag of the result if no exceptions or errors occurred. | 12 | | 13 +---------------------------------------------------------------------------*/ 14 15 /*---------------------------------------------------------------------------+ 16 | The destination may be any FPU_REG, including one of the source FPU_REGs. | 17 +---------------------------------------------------------------------------*/ 18 19 #include "fpu_emu.h" 20 #include "exception.h" 21 #include "reg_constant.h" 22 #include "fpu_system.h" 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 if (!(taga | tagb)) { 40 /* Both regs Valid, this should be the most common case. */ 41 42 tag = 43 FPU_u_mul(a, b, dest, control_w, sign, 44 exponent(a) + exponent(b)); 45 if (tag < 0) { 46 setsign(dest, saved_sign); 47 return tag; 48 } 49 FPU_settagi(deststnr, tag); 50 return tag; 51 } 52 53 if (taga == TAG_Special) 54 taga = FPU_Special(a); 55 if (tagb == TAG_Special) 56 tagb = FPU_Special(b); 57 58 if (((taga == TAG_Valid) && (tagb == TW_Denormal)) 59 || ((taga == TW_Denormal) && (tagb == TAG_Valid)) 60 || ((taga == TW_Denormal) && (tagb == TW_Denormal))) { 61 FPU_REG x, y; 62 if (denormal_operand() < 0) 63 return FPU_Exception; 64 65 FPU_to_exp16(a, &x); 66 FPU_to_exp16(b, &y); 67 tag = FPU_u_mul(&x, &y, dest, control_w, sign, 68 exponent16(&x) + exponent16(&y)); 69 if (tag < 0) { 70 setsign(dest, saved_sign); 71 return tag; 72 } 73 FPU_settagi(deststnr, tag); 74 return tag; 75 } else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) { 76 if (((tagb == TW_Denormal) || (taga == TW_Denormal)) 77 && (denormal_operand() < 0)) 78 return FPU_Exception; 79 80 /* Must have either both arguments == zero, or 81 one valid and the other zero. 82 The result is therefore zero. */ 83 FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr); 84 /* The 80486 book says that the answer is +0, but a real 85 80486 behaves this way. 86 IEEE-754 apparently says it should be this way. */ 87 setsign(dest, sign); 88 return TAG_Zero; 89 } 90 /* Must have infinities, NaNs, etc */ 91 else if ((taga == TW_NaN) || (tagb == TW_NaN)) { 92 return real_2op_NaN(b, tagb, deststnr, &st(0)); 93 } else if (((taga == TW_Infinity) && (tagb == TAG_Zero)) 94 || ((tagb == TW_Infinity) && (taga == TAG_Zero))) { 95 return arith_invalid(deststnr); /* Zero*Infinity is invalid */ 96 } else if (((taga == TW_Denormal) || (tagb == TW_Denormal)) 97 && (denormal_operand() < 0)) { 98 return FPU_Exception; 99 } else if (taga == TW_Infinity) { 100 FPU_copy_to_regi(a, TAG_Special, deststnr); 101 setsign(dest, sign); 102 return TAG_Special; 103 } else if (tagb == TW_Infinity) { 104 FPU_copy_to_regi(b, TAG_Special, deststnr); 105 setsign(dest, sign); 106 return TAG_Special; 107 } 108 #ifdef PARANOID 109 else { 110 EXCEPTION(EX_INTERNAL | 0x102); 111 return FPU_Exception; 112 } 113 #endif /* PARANOID */ 114 115 return 0; 116 } 117