| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /*---------------------------------------------------------------------------+ |
| 2 | | polynomial_Xsig.S | |
| 3 | | | |
| 4 | | Fixed point arithmetic polynomial evaluation. | |
| 5 | | | |
| 6 | | Copyright (C) 1992,1993,1994,1995 | |
| 7 | | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, | |
| 8 | | Australia. E-mail billm@jacobi.maths.monash.edu.au | |
| 9 | | | |
| 10 | | Call from C as: | |
| 11 | | void polynomial_Xsig(Xsig *accum, unsigned long long x, | |
| 12 | | unsigned long long terms[], int n) | |
| 13 | | | |
| 14 | | Computes: | |
| 15 | | terms[0] + (terms[1] + (terms[2] + ... + (terms[n-1]*x)*x)*x)*x) ... )*x | |
| 16 | | and adds the result to the 12 byte Xsig. | |
| 17 | | The terms[] are each 8 bytes, but all computation is performed to 12 byte | |
| 18 | | precision. | |
| 19 | | | |
| 20 | | This function must be used carefully: most overflow of intermediate | |
| 21 | | results is controlled, but overflow of the result is not. | |
| 22 | | | |
| 23 | +---------------------------------------------------------------------------*/ |
| 24 | .file "polynomial_Xsig.S" |
| 25 | |
| 26 | #include "fpu_emu.h" |
| 27 | |
| 28 | |
| 29 | #define TERM_SIZE $8 |
| 30 | #define SUM_MS -20(%ebp) /* sum ms long */ |
| 31 | #define SUM_MIDDLE -24(%ebp) /* sum middle long */ |
| 32 | #define SUM_LS -28(%ebp) /* sum ls long */ |
| 33 | #define ACCUM_MS -4(%ebp) /* accum ms long */ |
| 34 | #define ACCUM_MIDDLE -8(%ebp) /* accum middle long */ |
| 35 | #define ACCUM_LS -12(%ebp) /* accum ls long */ |
| 36 | #define OVERFLOWED -16(%ebp) /* addition overflow flag */ |
| 37 | |
| 38 | .text |
| 39 | ENTRY(polynomial_Xsig) |
| 40 | pushl %ebp |
| 41 | movl %esp,%ebp |
| 42 | subl $32,%esp |
| 43 | pushl %esi |
| 44 | pushl %edi |
| 45 | pushl %ebx |
| 46 | |
| 47 | movl PARAM2,%esi /* x */ |
| 48 | movl PARAM3,%edi /* terms */ |
| 49 | |
| 50 | movl TERM_SIZE,%eax |
| 51 | mull PARAM4 /* n */ |
| 52 | addl %eax,%edi |
| 53 | |
| 54 | movl 4(%edi),%edx /* terms[n] */ |
| 55 | movl %edx,SUM_MS |
| 56 | movl (%edi),%edx /* terms[n] */ |
| 57 | movl %edx,SUM_MIDDLE |
| 58 | xor %eax,%eax |
| 59 | movl %eax,SUM_LS |
| 60 | movb %al,OVERFLOWED |
| 61 | |
| 62 | subl TERM_SIZE,%edi |
| 63 | decl PARAM4 |
| 64 | js L_accum_done |
| 65 | |
| 66 | L_accum_loop: |
| 67 | xor %eax,%eax |
| 68 | movl %eax,ACCUM_MS |
| 69 | movl %eax,ACCUM_MIDDLE |
| 70 | |
| 71 | movl SUM_MIDDLE,%eax |
| 72 | mull (%esi) /* x ls long */ |
| 73 | movl %edx,ACCUM_LS |
| 74 | |
| 75 | movl SUM_MIDDLE,%eax |
| 76 | mull 4(%esi) /* x ms long */ |
| 77 | addl %eax,ACCUM_LS |
| 78 | adcl %edx,ACCUM_MIDDLE |
| 79 | adcl $0,ACCUM_MS |
| 80 | |
| 81 | movl SUM_MS,%eax |
| 82 | mull (%esi) /* x ls long */ |
| 83 | addl %eax,ACCUM_LS |
| 84 | adcl %edx,ACCUM_MIDDLE |
| 85 | adcl $0,ACCUM_MS |
| 86 | |
| 87 | movl SUM_MS,%eax |
| 88 | mull 4(%esi) /* x ms long */ |
| 89 | addl %eax,ACCUM_MIDDLE |
| 90 | adcl %edx,ACCUM_MS |
| 91 | |
| 92 | testb $0xff,OVERFLOWED |
| 93 | jz L_no_overflow |
| 94 | |
| 95 | movl (%esi),%eax |
| 96 | addl %eax,ACCUM_MIDDLE |
| 97 | movl 4(%esi),%eax |
| 98 | adcl %eax,ACCUM_MS /* This could overflow too */ |
| 99 | |
| 100 | L_no_overflow: |
| 101 | |
| 102 | /* |
| 103 | * Now put the sum of next term and the accumulator |
| 104 | * into the sum register |
| 105 | */ |
| 106 | movl ACCUM_LS,%eax |
| 107 | addl (%edi),%eax /* term ls long */ |
| 108 | movl %eax,SUM_LS |
| 109 | movl ACCUM_MIDDLE,%eax |
| 110 | adcl (%edi),%eax /* term ls long */ |
| 111 | movl %eax,SUM_MIDDLE |
| 112 | movl ACCUM_MS,%eax |
| 113 | adcl 4(%edi),%eax /* term ms long */ |
| 114 | movl %eax,SUM_MS |
| 115 | sbbb %al,%al |
| 116 | movb %al,OVERFLOWED /* Used in the next iteration */ |
| 117 | |
| 118 | subl TERM_SIZE,%edi |
| 119 | decl PARAM4 |
| 120 | jns L_accum_loop |
| 121 | |
| 122 | L_accum_done: |
| 123 | movl PARAM1,%edi /* accum */ |
| 124 | movl SUM_LS,%eax |
| 125 | addl %eax,(%edi) |
| 126 | movl SUM_MIDDLE,%eax |
| 127 | adcl %eax,4(%edi) |
| 128 | movl SUM_MS,%eax |
| 129 | adcl %eax,8(%edi) |
| 130 | |
| 131 | popl %ebx |
| 132 | popl %edi |
| 133 | popl %esi |
| 134 | leave |
| 135 | ret |