| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame^] | 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 | } |