| Kyle Swenson | 8d8f654 | 2021-03-15 11:02:55 -0600 | [diff] [blame^] | 1 | /*---------------------------------------------------------------------------+ |
| 2 | | reg_norm.S | |
| 3 | | | |
| 4 | | Copyright (C) 1992,1993,1994,1995,1997 | |
| 5 | | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, | |
| 6 | | Australia. E-mail billm@suburbia.net | |
| 7 | | | |
| 8 | | Normalize the value in a FPU_REG. | |
| 9 | | | |
| 10 | | Call from C as: | |
| 11 | | int FPU_normalize(FPU_REG *n) | |
| 12 | | | |
| 13 | | int FPU_normalize_nuo(FPU_REG *n) | |
| 14 | | | |
| 15 | | Return value is the tag of the answer, or-ed with FPU_Exception if | |
| 16 | | one was raised, or -1 on internal error. | |
| 17 | | | |
| 18 | +---------------------------------------------------------------------------*/ |
| 19 | |
| 20 | #include "fpu_emu.h" |
| 21 | |
| 22 | |
| 23 | .text |
| 24 | ENTRY(FPU_normalize) |
| 25 | pushl %ebp |
| 26 | movl %esp,%ebp |
| 27 | pushl %ebx |
| 28 | |
| 29 | movl PARAM1,%ebx |
| 30 | |
| 31 | movl SIGH(%ebx),%edx |
| 32 | movl SIGL(%ebx),%eax |
| 33 | |
| 34 | orl %edx,%edx /* ms bits */ |
| 35 | js L_done /* Already normalized */ |
| 36 | jnz L_shift_1 /* Shift left 1 - 31 bits */ |
| 37 | |
| 38 | orl %eax,%eax |
| 39 | jz L_zero /* The contents are zero */ |
| 40 | |
| 41 | movl %eax,%edx |
| 42 | xorl %eax,%eax |
| 43 | subw $32,EXP(%ebx) /* This can cause an underflow */ |
| 44 | |
| 45 | /* We need to shift left by 1 - 31 bits */ |
| 46 | L_shift_1: |
| 47 | bsrl %edx,%ecx /* get the required shift in %ecx */ |
| 48 | subl $31,%ecx |
| 49 | negl %ecx |
| 50 | shld %cl,%eax,%edx |
| 51 | shl %cl,%eax |
| 52 | subw %cx,EXP(%ebx) /* This can cause an underflow */ |
| 53 | |
| 54 | movl %edx,SIGH(%ebx) |
| 55 | movl %eax,SIGL(%ebx) |
| 56 | |
| 57 | L_done: |
| 58 | cmpw EXP_OVER,EXP(%ebx) |
| 59 | jge L_overflow |
| 60 | |
| 61 | cmpw EXP_UNDER,EXP(%ebx) |
| 62 | jle L_underflow |
| 63 | |
| 64 | L_exit_valid: |
| 65 | movl TAG_Valid,%eax |
| 66 | |
| 67 | /* Convert the exponent to 80x87 form. */ |
| 68 | addw EXTENDED_Ebias,EXP(%ebx) |
| 69 | andw $0x7fff,EXP(%ebx) |
| 70 | |
| 71 | L_exit: |
| 72 | popl %ebx |
| 73 | leave |
| 74 | ret |
| 75 | |
| 76 | |
| 77 | L_zero: |
| 78 | movw $0,EXP(%ebx) |
| 79 | movl TAG_Zero,%eax |
| 80 | jmp L_exit |
| 81 | |
| 82 | L_underflow: |
| 83 | /* Convert the exponent to 80x87 form. */ |
| 84 | addw EXTENDED_Ebias,EXP(%ebx) |
| 85 | push %ebx |
| 86 | call arith_underflow |
| 87 | pop %ebx |
| 88 | jmp L_exit |
| 89 | |
| 90 | L_overflow: |
| 91 | /* Convert the exponent to 80x87 form. */ |
| 92 | addw EXTENDED_Ebias,EXP(%ebx) |
| 93 | push %ebx |
| 94 | call arith_overflow |
| 95 | pop %ebx |
| 96 | jmp L_exit |
| 97 | |
| 98 | |
| 99 | |
| 100 | /* Normalise without reporting underflow or overflow */ |
| 101 | ENTRY(FPU_normalize_nuo) |
| 102 | pushl %ebp |
| 103 | movl %esp,%ebp |
| 104 | pushl %ebx |
| 105 | |
| 106 | movl PARAM1,%ebx |
| 107 | |
| 108 | movl SIGH(%ebx),%edx |
| 109 | movl SIGL(%ebx),%eax |
| 110 | |
| 111 | orl %edx,%edx /* ms bits */ |
| 112 | js L_exit_nuo_valid /* Already normalized */ |
| 113 | jnz L_nuo_shift_1 /* Shift left 1 - 31 bits */ |
| 114 | |
| 115 | orl %eax,%eax |
| 116 | jz L_exit_nuo_zero /* The contents are zero */ |
| 117 | |
| 118 | movl %eax,%edx |
| 119 | xorl %eax,%eax |
| 120 | subw $32,EXP(%ebx) /* This can cause an underflow */ |
| 121 | |
| 122 | /* We need to shift left by 1 - 31 bits */ |
| 123 | L_nuo_shift_1: |
| 124 | bsrl %edx,%ecx /* get the required shift in %ecx */ |
| 125 | subl $31,%ecx |
| 126 | negl %ecx |
| 127 | shld %cl,%eax,%edx |
| 128 | shl %cl,%eax |
| 129 | subw %cx,EXP(%ebx) /* This can cause an underflow */ |
| 130 | |
| 131 | movl %edx,SIGH(%ebx) |
| 132 | movl %eax,SIGL(%ebx) |
| 133 | |
| 134 | L_exit_nuo_valid: |
| 135 | movl TAG_Valid,%eax |
| 136 | |
| 137 | popl %ebx |
| 138 | leave |
| 139 | ret |
| 140 | |
| 141 | L_exit_nuo_zero: |
| 142 | movl TAG_Zero,%eax |
| 143 | movw EXP_UNDER,EXP(%ebx) |
| 144 | |
| 145 | popl %ebx |
| 146 | leave |
| 147 | ret |