Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /*---------------------------------------------------------------------------+ |
| 2 | | reg_divide.c | |
| 3 | | | |
| 4 | | Divide one FPU_REG by another and put the result in a destination FPU_REG.| |
| 5 | | | |
| 6 | | Copyright (C) 1996 | |
| 7 | | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia | |
| 8 | | E-mail billm@jacobi.maths.monash.edu.au | |
| 9 | | | |
| 10 | | Return value is the tag of the answer, or-ed with FPU_Exception if | |
| 11 | | one was raised, or -1 on internal error. | |
| 12 | | | |
| 13 | +---------------------------------------------------------------------------*/ |
| 14 | |
| 15 | /*---------------------------------------------------------------------------+ |
| 16 | | The destination may be any FPU_REG, including one of the source FPU_REGs. | |
| 17 | +---------------------------------------------------------------------------*/ |
| 18 | |
| 19 | #include "exception.h" |
| 20 | #include "reg_constant.h" |
| 21 | #include "fpu_emu.h" |
| 22 | #include "fpu_system.h" |
| 23 | |
| 24 | /* |
| 25 | Divide one register by another and put the result into a third register. |
| 26 | */ |
| 27 | int FPU_div(int flags, int rm, int control_w) |
| 28 | { |
| 29 | FPU_REG x, y; |
| 30 | FPU_REG const *a, *b, *st0_ptr, *st_ptr; |
| 31 | FPU_REG *dest; |
| 32 | u_char taga, tagb, signa, signb, sign, saved_sign; |
| 33 | int tag, deststnr; |
| 34 | |
| 35 | if ( flags & DEST_RM ) |
| 36 | deststnr = rm; |
| 37 | else |
| 38 | deststnr = 0; |
| 39 | |
| 40 | if ( flags & REV ) |
| 41 | { |
| 42 | b = &st(0); |
| 43 | st0_ptr = b; |
| 44 | tagb = FPU_gettag0(); |
| 45 | if ( flags & LOADED ) |
| 46 | { |
| 47 | a = (FPU_REG *)rm; |
| 48 | taga = flags & 0x0f; |
| 49 | } |
| 50 | else |
| 51 | { |
| 52 | a = &st(rm); |
| 53 | st_ptr = a; |
| 54 | taga = FPU_gettagi(rm); |
| 55 | } |
| 56 | } |
| 57 | else |
| 58 | { |
| 59 | a = &st(0); |
| 60 | st0_ptr = a; |
| 61 | taga = FPU_gettag0(); |
| 62 | if ( flags & LOADED ) |
| 63 | { |
| 64 | b = (FPU_REG *)rm; |
| 65 | tagb = flags & 0x0f; |
| 66 | } |
| 67 | else |
| 68 | { |
| 69 | b = &st(rm); |
| 70 | st_ptr = b; |
| 71 | tagb = FPU_gettagi(rm); |
| 72 | } |
| 73 | } |
| 74 | |
| 75 | signa = getsign(a); |
| 76 | signb = getsign(b); |
| 77 | |
| 78 | sign = signa ^ signb; |
| 79 | |
| 80 | dest = &st(deststnr); |
| 81 | saved_sign = getsign(dest); |
| 82 | |
| 83 | if ( !(taga | tagb) ) |
| 84 | { |
| 85 | /* Both regs Valid, this should be the most common case. */ |
| 86 | reg_copy(a, &x); |
| 87 | reg_copy(b, &y); |
| 88 | setpositive(&x); |
| 89 | setpositive(&y); |
| 90 | tag = FPU_u_div(&x, &y, dest, control_w, sign); |
| 91 | |
| 92 | if ( tag < 0 ) |
| 93 | return tag; |
| 94 | |
| 95 | FPU_settagi(deststnr, tag); |
| 96 | return tag; |
| 97 | } |
| 98 | |
| 99 | if ( taga == TAG_Special ) |
| 100 | taga = FPU_Special(a); |
| 101 | if ( tagb == TAG_Special ) |
| 102 | tagb = FPU_Special(b); |
| 103 | |
| 104 | if ( ((taga == TAG_Valid) && (tagb == TW_Denormal)) |
| 105 | || ((taga == TW_Denormal) && (tagb == TAG_Valid)) |
| 106 | || ((taga == TW_Denormal) && (tagb == TW_Denormal)) ) |
| 107 | { |
| 108 | if ( denormal_operand() < 0 ) |
| 109 | return FPU_Exception; |
| 110 | |
| 111 | FPU_to_exp16(a, &x); |
| 112 | FPU_to_exp16(b, &y); |
| 113 | tag = FPU_u_div(&x, &y, dest, control_w, sign); |
| 114 | if ( tag < 0 ) |
| 115 | return tag; |
| 116 | |
| 117 | FPU_settagi(deststnr, tag); |
| 118 | return tag; |
| 119 | } |
| 120 | else if ( (taga <= TW_Denormal) && (tagb <= TW_Denormal) ) |
| 121 | { |
| 122 | if ( tagb != TAG_Zero ) |
| 123 | { |
| 124 | /* Want to find Zero/Valid */ |
| 125 | if ( tagb == TW_Denormal ) |
| 126 | { |
| 127 | if ( denormal_operand() < 0 ) |
| 128 | return FPU_Exception; |
| 129 | } |
| 130 | |
| 131 | /* The result is zero. */ |
| 132 | FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr); |
| 133 | setsign(dest, sign); |
| 134 | return TAG_Zero; |
| 135 | } |
| 136 | /* We have an exception condition, either 0/0 or Valid/Zero. */ |
| 137 | if ( taga == TAG_Zero ) |
| 138 | { |
| 139 | /* 0/0 */ |
| 140 | return arith_invalid(deststnr); |
| 141 | } |
| 142 | /* Valid/Zero */ |
| 143 | return FPU_divide_by_zero(deststnr, sign); |
| 144 | } |
| 145 | /* Must have infinities, NaNs, etc */ |
| 146 | else if ( (taga == TW_NaN) || (tagb == TW_NaN) ) |
| 147 | { |
| 148 | if ( flags & LOADED ) |
| 149 | return real_2op_NaN((FPU_REG *)rm, flags & 0x0f, 0, st0_ptr); |
| 150 | |
| 151 | if ( flags & DEST_RM ) |
| 152 | { |
| 153 | int tag; |
| 154 | tag = FPU_gettag0(); |
| 155 | if ( tag == TAG_Special ) |
| 156 | tag = FPU_Special(st0_ptr); |
| 157 | return real_2op_NaN(st0_ptr, tag, rm, (flags & REV) ? st0_ptr : &st(rm)); |
| 158 | } |
| 159 | else |
| 160 | { |
| 161 | int tag; |
| 162 | tag = FPU_gettagi(rm); |
| 163 | if ( tag == TAG_Special ) |
| 164 | tag = FPU_Special(&st(rm)); |
| 165 | return real_2op_NaN(&st(rm), tag, 0, (flags & REV) ? st0_ptr : &st(rm)); |
| 166 | } |
| 167 | } |
| 168 | else if (taga == TW_Infinity) |
| 169 | { |
| 170 | if (tagb == TW_Infinity) |
| 171 | { |
| 172 | /* infinity/infinity */ |
| 173 | return arith_invalid(deststnr); |
| 174 | } |
| 175 | else |
| 176 | { |
| 177 | /* tagb must be Valid or Zero */ |
| 178 | if ( (tagb == TW_Denormal) && (denormal_operand() < 0) ) |
| 179 | return FPU_Exception; |
| 180 | |
| 181 | /* Infinity divided by Zero or Valid does |
| 182 | not raise and exception, but returns Infinity */ |
| 183 | FPU_copy_to_regi(a, TAG_Special, deststnr); |
| 184 | setsign(dest, sign); |
| 185 | return taga; |
| 186 | } |
| 187 | } |
| 188 | else if (tagb == TW_Infinity) |
| 189 | { |
| 190 | if ( (taga == TW_Denormal) && (denormal_operand() < 0) ) |
| 191 | return FPU_Exception; |
| 192 | |
| 193 | /* The result is zero. */ |
| 194 | FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr); |
| 195 | setsign(dest, sign); |
| 196 | return TAG_Zero; |
| 197 | } |
| 198 | #ifdef PARANOID |
| 199 | else |
| 200 | { |
| 201 | EXCEPTION(EX_INTERNAL|0x102); |
| 202 | return FPU_Exception; |
| 203 | } |
| 204 | #endif /* PARANOID */ |
| 205 | |
| 206 | return 0; |
| 207 | } |