📄 div.s
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#.d3: cmpl $14,%esi jb .d3a pushl %edi movl a(%ebp,%esi),%edx # uj unshifed in dx (hiWord) movl a-4(%ebp,%esi),%eax # uj+1 unshifted movl a-8(%ebp,%esi),%ebx # uj+2 unshifted movl a-12(%ebp,%esi),%edi # uj+3 unshifted pushl %ecx movw d(%ebp),%cx.l12: cmpw $0,%cx je .l13 rcll $1,%edi rcll $1,%ebx rcll $1,%eax rcll $1,%edx decw %cx jmp .l12.l13: popl %ecx popl %edi jmp .qhat#.d3a: movl a(%ebp,%esi),%edx # uj unshifted movl a-4(%ebp,%esi),%eax # uj+1 unshifted movl a-8(%ebp,%esi),%ebx # uj+2 unshifted pushl %ecx movw d(%ebp),%cx.l14: cmpw $0,%cx je .l15 rcll $1,%ebx rcll $1,%eax rcll $1,%edx decw %cx jmp .l14.l15: popl %ecx##-----> Calculate and test qhat#.qhat: movl %eax,uj1(%ebp) # Store shifted uj+1 movl %ebx,uj2(%ebp) # Store shifted uj+2 movl v1(%ebp),%ebx # v1 in bx cmpl %edx,%ebx je .bm1 # If v1 = uj q = b - 1# divl %ebx # eax <- qhat# edx <- rhat: = uj*b + uj+1 -qhat*v1 = (uj*b + uj+1) mod v1 movl %eax,q1(%ebp) # Store qhat cmpl $0,%eax jne .l16 jmp .dml # If q = 0 process next digit#.bm1: movl $0x0ffffffff,%eax # eax <- qhat movl %eax,q1(%ebp) # Store qhat movl uj1(%ebp),%edx # edx <- uj+1 addl v1(%ebp),%edx # edx <- uj+1 + v1 =: rhat jc .d4 # rhat >= b => v2 * qhat < rhat * b#.l16: movl %edx,%ebx # ebx <- rhat mull v2(%ebp) # eax <- low(qhat * v2), edx <- high(qhat * v2) cmpl %ebx,%edx # rhat >= high(qhat * v2) ? jb .d4 # CF == 1? Then we're done ja .l17 # rhat < high(qhat * v2) => decrement qhat cmpl uj2(%ebp),%eax # uj+2 >= low(qhat * v2) ? jbe .d4 # CF == 1 OR ZF == 1? Then we're done#.l17: decl q1(%ebp) # Correct qhat-- addl v1(%ebp),%ebx # ebx <- rhat + v1 jc .d4 # rhat >= b => v2 * qhat < rhat * b subl v2(%ebp),%eax # (qhat * v2) - v2 sbb $0,%edx# cmpl %ebx,%edx # rhat >= high(qhat * v2) ? jb .d4 # CF == 1? Then we're done ja .l17 # rhat < high(qhat * v2) => decrement qhat cmpl uj2(%ebp),%eax # uj+2 >= low(qhat * v2) ? ja .l17 # CF==0 + ZF==0? => Repeat decrement of qhat#.d4: pushl %ecx # Store main counter pushl %esi # Store j + l(b) pushl %edi # Store j movw b(%ebp),%cx # Load counter with l(b) shrw $1,%cx jnc .d4a incw %cx.d4a: movl q1(%ebp),%ebx # q in bx movl $2,%esi movl $0,%edx # Dummy carry##-----> Multiplication and subtraction#.dms: push %edx movl %ebx,%eax # q in ax mull b(%ebp,%esi) # hi:dx lo:ax subl %eax,a(%ebp,%edi) adcl $0,%edx # Carry to next subtrahend popl %eax subl %eax,a(%ebp,%edi) adcl $0,%edx # Carry to next subtrahend incl %edi incl %edi incl %edi incl %edi incl %esi incl %esi incl %esi incl %esi loop .dms subl %edx,a(%ebp,%edi) jnc .dnc # No correction necessary if carry = 0##-----> Correction# popl %edi pushl %edi xorl %ecx,%ecx movw b(%ebp),%cx # Load counter with l(b) shrw $1,%cx jnc .d4b incw %cx.d4b: movl $2,%esi clc .d5: movl b(%ebp,%esi),%eax # b[i] adcl %eax,a(%ebp,%edi) # a[j+i] + b[i] incl %edi incl %edi incl %edi incl %edi incl %esi incl %esi incl %esi incl %esi loop .d5 # Outer loop jnc .d51 incl a(%ebp,%edi).d51: decl q1(%ebp) # q = q - 1##.dnc: popl %edi # Get pointers and counters popl %esi popl %ecx.dml: movl q1(%ebp),%eax # Get q movl %eax,q(%ebp,%edi) # q[j] = q subl $4,%edi subl $4,%esi decl %ecx # Inner loop jz .d6 jmp .d3#.d6: popl %edi # Load length l(a)-l(b)-1 in ULONGs addl $2,%edi # di points to loByte of last USHORT movl $0,%eax.l18: cmpw q(%ebp,%edi),%ax # q[l(a)-l(b)]=0 ? jne .d7 # If so ... decl %edi decl %edi # ... l(q) = l(a) - l(b) - 1 cmpl $0,%edi jne .l18.d7: movl %edi,%edx shrl $1,%edx # l(q) (#USHORTs) in dx movw %dx,q(%ebp) # Store l(q)##-----> Determine length of remainder# movl $0,%eax movw b(%ebp),%ax movl %eax,%ecx shlw $1,%ax movl %eax,%edi movl $0,%ebx incl %edi incl %edi.d8: decl %edi decl %edi # di points to loByte of a[l(b)] cmpw %bx,a(%ebp,%edi) loope .d8 jz .d9 # If a[bp][di]!= 0 ... incw %cx # ... l has to be incremented.d9: movw %cx,a(%ebp) # Store l(r)##-----> Store results#.dstore: movl %ebp,%esi movl %ebp,%ebx popl %ebp pushl %esi addl $q,%esi movl 16(%ebp),%edi # Offset of quotient movl $0,%ecx movw (%esi),%cx shrw $1,%cx jnc .l19 incw %cx.l19: cld cmpw $0,%cx je .qzero rep movsl .qzero: movsw ##-----> Store remainder# popl %esi.drs: movl 20(%ebp),%edi addl $a,%esi movl $0,%ecx movw (%esi),%cx shrw $1,%cx jnc .l20 incw %cx.l20: cld cmpw $0,%cx je .rzero rep movsl .rzero: movsw movl $0,%eax # Return-Value = 0: OK##*******************************************************************************# Security: Purge stackdivret: movl %ebx,%edi movl $(WORKSP-4)/4,%ecx cld rep stosl # Overwrite with 0 or -1#*******************************************************************************# popl %esi popl %edi popl %ebx movl %ebp,%esp popl %ebp ret ##.divz: movl $0,%eax # Return-Value = 0: Everything OK movl 20(%ebp),%edi # Destination Offset of remainder movl 16(%ebp),%esi # Destination offset of quotient movw %ax,(%edi) # Remainder = 0 movw %ax,(%esi) # Quotient = 0 jmp divret#.divbyz: movl $-1,%eax jmp divret # Return-Value = -1: Division by zero##-----> Case q = 0 and r = a#.dra: movl %ebp,%esi movl %ebp,%ebx popl %ebp movl 16(%ebp),%edi movw $0,(%edi) # q = 0 jmp .drs # Store remainder###>>>>>> Short Division##.dshort: movl $0,%ecx movw a(%ebp),%cx shrw $1,%cx jnc .dsh0 incw %cx.dsh0: movl %ecx,%edi shll $2,%edi subl $2,%edi movl $0,%edx movl b+2(%ebp),%ebx.dsh1: movl a(%ebp,%edi),%eax divl %ebx movl %eax,q(%ebp,%edi) subl $4,%edi loop .dsh1.dsh2: movl $0,%ecx movw a(%ebp),%cx movl %ecx,%esi shll $1,%esi.l21: movw q(%ebp,%esi),%bx cmpw $0,%bx jne .dsh3 decl %esi decl %esi decl %ecx cmpw $0,%cx jne .l21.dsh3: movw %cx,q(%ebp) movl %edx,a+2(%ebp) movw $2,a(%ebp) cmpw $0,a+4(%ebp) jne .dst movw $1,a(%ebp) cmpw $0,a+2(%ebp) jne .dst movw $0,a(%ebp).dst: jmp .dstore#⌨️ 快捷键说明
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