Am 02.06.2011 18:45, schrieb José Mejuto:
> Hello FPC,
>
> PlainCompare CompareByte XCompareByte
> ------------ ----------- ------------
> Equal arrays 1000 elements 16250 ms 625 ms 656 ms
> Diff. arrays 1000 elements 62 ms 640 ms 656 ms
>
> Equal arrays 32 elements 547 ms 625 ms 547 ms
> Diff. arrays 32 elements 62 ms 640 ms 62 ms
>
I improved the original CompareByte, please tell me how it works for you.
function CompareByte(Const buf1,buf2;len:SizeInt):SizeInt; assembler;
var
saveesi,saveedi : longint;
savebl : byte;
asm
{$ifdef REGCALL}
cmpl $57,%ecx
jg .LCmpbyteFull
movb %bl,savebl
.LCmpbyteLoop:
movb (%eax),%bl
cmpb (%edx),%bl
leal 1(%eax),%eax
leal 1(%edx),%edx
jne .LCmpbyteExitFast
decl %ecx
jne .LCmpbyteLoop
.LCmpbyteExitFast:
seteb %al
movb savebl,%bl
leave
ret
.LCmpbyteFull:
movl %edi,saveedi
movl %esi,saveesi
cld
movl %eax,%edi
movl %edx,%esi
movl %ecx,%eax
{$else}
movl %edi,saveedi
movl %esi,saveesi
cld
movl buf2,%esi { Load params}
movl buf1,%edi
movl len,%eax
{$endif}
testl %eax,%eax {We address -1(%esi), so we have to deal with
len=0}
je .LCmpbyteExit
cmpl $10,%eax {<7 not worth aligning and go through all
trouble}
jl .LCmpbyte2
movl %edi,%ecx { Align on 32bits }
negl %ecx { calc bytes to align (%edi and 3) xor 3=
-%edi and 3}
andl $3,%ecx
subl %ecx,%eax { Subtract from number of bytes to go}
orl %ecx,%ecx
rep
cmpsb {The actual 32-bit Aligning}
jne .LCmpbyte3
movl %eax,%ecx {bytes to do, divide by 4}
andl $3,%eax {remainder}
shrl $2,%ecx {The actual division}
orl %ecx,%ecx {Sets zero flag if ecx=0 -> no cmp}
rep
cmpsl
je .LCmpbyte2 { All equal? then to the left over bytes}
movl $4,%eax { Not equal. Rescan the last 4 bytes bytewise}
subl %eax,%esi
subl %eax,%edi
.LCmpbyte2:
movl %eax,%ecx {bytes still to (re)scan}
orl %eax,%eax {prevent disaster in case %eax=0}
.balign 4
rep
cmpsb
.LCmpbyte3:
movzbl -1(%esi),%ecx
movzbl -1(%edi),%eax // Compare failing (or equal) position
subl %ecx,%eax
.LCmpbyteExit:
movl saveedi,%edi
movl saveesi,%esi
end;
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