| /* |
| * mpvecadd(mpdigit *a, int alen, mpdigit *b, int blen, mpdigit *sum) |
| * |
| * sum[0:alen] = a[0:alen-1] + b[0:blen-1] |
| * |
| * prereq: alen >= blen, sum has room for alen+1 digits |
| */ |
| |
| .text |
| |
| .p2align 2,0x90 |
| .globl mpvecadd |
| .type mpvecadd, @function |
| mpvecadd: |
| /* Prelude */ |
| pushl %ebp |
| movl %ebx, -4(%esp) /* save on stack */ |
| movl %esi, -8(%esp) |
| movl %edi, -12(%esp) |
| |
| movl 12(%esp), %edx /* alen */ |
| movl 20(%esp), %ecx /* blen */ |
| movl 8(%esp), %esi /* a */ |
| movl 16(%esp), %ebx /* b */ |
| subl %ecx, %edx |
| movl 24(%esp), %edi /* sum */ |
| xorl %ebp, %ebp /* this also sets carry to 0 */ |
| |
| /* skip addition if b is zero */ |
| testl %ecx,%ecx |
| je _add1 |
| |
| /* sum[0:blen-1],carry = a[0:blen-1] + b[0:blen-1] */ |
| _addloop1: |
| movl (%esi, %ebp, 4), %eax |
| adcl (%ebx, %ebp, 4), %eax |
| movl %eax, (%edi, %ebp, 4) |
| incl %ebp |
| loop _addloop1 |
| |
| _add1: |
| /* jump if alen > blen */ |
| incl %edx |
| movl %edx, %ecx |
| loop _addloop2 |
| |
| /* sum[alen] = carry */ |
| _addend: |
| jb _addcarry |
| movl $0, (%edi, %ebp, 4) |
| jmp done |
| |
| _addcarry: |
| movl $1, (%edi, %ebp, 4) |
| jmp done |
| |
| /* sum[blen:alen-1],carry = a[blen:alen-1] + 0 */ |
| _addloop2: |
| movl (%esi, %ebp, 4),%eax |
| adcl $0, %eax |
| movl %eax, (%edi, %ebp, 4) |
| incl %ebp |
| loop _addloop2 |
| jmp _addend |
| |
| done: |
| /* Postlude */ |
| movl -4(%esp), %ebx /* restore from stack */ |
| movl -8(%esp), %esi |
| movl -12(%esp), %edi |
| movl %esp, %ebp |
| leave |
| ret |
