/ bisubmbw.s (emx+gcc) -- Copyright (c) 1996 by Eberhard Mattes #include .globl __bi_sub_mul_bw #define n 0 #define v 4 / int _bi_sub_mul_bw (_bi_bigint *dst, const _bi_bigint *src, _bi_word factor) #define dst 8(%ebp) #define src 12(%ebp) #define factor 16(%ebp) #define dst_n_extra -4(%ebp) .text __bi_sub_mul_bw: pushl %ebp movl %esp, %ebp PROFILE_FRAME subl $4, %esp pushl %ebx pushl %esi pushl %edi cmpl $0, factor je Lnothing movl src, %esi movl n(%esi), %ecx testl %ecx, %ecx jz Lnothing movl dst, %edi movl n(%edi), %eax subl %ecx, %eax jb Lret_one movl %eax, dst_n_extra movl v(%edi), %edi movl v(%esi), %esi xorl %ebx, %ebx /* EBX = mul_carry + sub_borrow */ /* This loops processes all the words of src. */ ALIGN L1: movl (%esi), %eax mull factor leal 4(%esi), %esi addl %ebx, %eax adcl $0, %edx movl %edx, %ebx subl %eax, (%edi) adcl $0, %ebx leal 4(%edi), %edi dec %ecx jnz L1 movl dst_n_extra, %ecx /* Process carry from the multiplication. This needs to be done only once, no loop. */ testl %ebx, %ebx jz Lno_mul_carry testl %ecx, %ecx jz Lrestore /* Overflow */ subl %ebx, (%edi) leal 4(%edi), %edi sbbl %ebx, %ebx /* EBX non-zero iff borrow */ dec %ecx ALIGN Lno_mul_carry: /* Process borrow for the remaining words of dst. */ testl %ebx, %ebx jz Lno_borrow testl %ecx, %ecx jz Lrestore ALIGN L2: subl $1, (%edi) decl %ecx leal 4(%edi), %edi jnc Lno_borrow jnz L2 jmp Lrestore ALIGN Lno_borrow: /* Normalize. */ movl dst, %ebx movl n(%ebx), %ecx ALIGN L3: cmpl $0, -4(%edi) jnz Ldone subl $4, %edi dec %ecx jnz L3 ALIGN Ldone: movl %ecx, n(%ebx) xorl %eax, %eax ALIGN Lreturn: popl %edi popl %esi popl %ebx leave EPILOGUE(_bi_sub_mul_bw) /* The result would be negative. Restore the original DST. */ ALIGN Lrestore: movl src, %esi movl dst, %edi movl n(%esi), %ecx movl v(%edi), %edi movl v(%esi), %esi xorl %ebx, %ebx ALIGN L4: movl (%esi), %eax mull factor leal 4(%esi), %esi addl %ebx, %eax adcl $0, %edx movl %edx, %ebx addl %eax, (%edi) adcl $0, %ebx leal 4(%edi), %edi dec %ecx jnz L4 cmpl $0, dst_n_extra je Lrestore_done addl %ebx, (%edi) ALIGN Lrestore_done: movl $1, %eax jmp Lreturn ALIGN Lnothing: xorl %eax, %eax jmp Lreturn ALIGN Lret_one: movl $1, %eax jmp Lreturn