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Improve generic CompareWord.

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This commit is contained in:
Rika Ichinose 2023-02-06 22:16:29 +03:00 committed by FPK
parent 15f29b8fa0
commit f0811e448d
1 changed files with 35 additions and 61 deletions
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96
rtl/inc/generic.inc
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@ -479,86 +479,60 @@ end;
{$ifndef FPC_SYSTEM_HAS_COMPAREWORD}
function CompareWord(Const buf1,buf2;len:SizeInt):SizeInt;
var
aligncount : sizeint;
psrc,pdest,pend : pword;
b : ptrint;
psrc,pdest,pend,pendpart : pword;
begin
b:=0;
psrc:=@buf1;
pdest:=@buf2;
if (len>4*sizeof(ptruint)-1)
pend:=psrc+len;
if (pend<psrc) or not ((len>=0) and (len<=High(PtrInt) div 2)) then
pend:=pword(high(ptruint)-2);
if (len>=2*sizeof(ptruint)) { len in words, so at least four pointers }
{$ifdef FPC_REQUIRES_PROPER_ALIGNMENT}
and ((PtrUInt(pdest) and (sizeof(PtrUInt)-1))=(PtrUInt(psrc) and (sizeof(PtrUInt)-1)))
and (((PtrUInt(pdest) and 1) or (PtrUInt(psrc) and 1))=0)
and ((PtrUInt(pdest) xor PtrUInt(psrc)) and (sizeof(PtrUInt)-1)=0)
and (PtrUInt(psrc) and 1=0)
{$endif FPC_REQUIRES_PROPER_ALIGNMENT}
then
begin
{ Align on native pointer size }
aligncount:=((sizeof(PtrUInt)-(PtrUInt(pdest) and (sizeof(PtrUInt)-1))) and (sizeof(PtrUInt)-1)) shr 1;
dec(len,aligncount);
pend:=psrc+aligncount;
while psrc<pend do
{ Align on native pointer size. Careful, these 'pendpart's are aligned even if 'psrc' is misaligned, so "psrc<>pendpart" must not be used. }
PtrUint(pendpart):=(PtrUint(psrc)+(sizeof(PtrUint)-1)) and PtrUint(not PtrUint(sizeof(PtrUint)-1));
while (psrc<pendpart) and (psrc^=pdest^) do
begin
b:=(ptrint(psrc^)-ptrint(pdest^));
if b<>0 then
begin
if b<0 then
exit(-1)
else
exit(1);
end;
inc(pdest);
inc(psrc);
end;
{ use sizeuint typecast to force shr optimization }
pptruint(pend):=pptruint(psrc)+(sizeuint(len)*2 div sizeof(ptruint));
len:=((len*2) and (sizeof(PtrUInt)-1)) shr 1;
while psrc<pend do
if psrc<pendpart then
exit(2*ord(psrc^>pdest^)-1);
PtrUint(pendpart):=PtrUint(pend) and PtrUint(not PtrUint(sizeof(PtrUint)-1));
while (psrc<pendpart) and (pptrint(psrc)^=pptrint(pdest)^) do
begin
b:=(pptrint(psrc)^-pptrint(pdest)^);
if b<>0 then
begin
len:=sizeof(ptruint) shr 1;
break;
end;
inc(pptruint(pdest));
inc(pptruint(psrc));
end;
if psrc<pendpart then
pointer(pend):=pointer(psrc)+sizeof(ptruint);
end;
if (psrc+len >= psrc) then
pend:=psrc+len
else
pend:=pword(high(ptruint)-2);
{$ifdef FPC_REQUIRES_PROPER_ALIGNMENT}
if ((PtrUInt(pdest) and 1) or (PtrUInt(psrc) and 1))<>0 then
while psrc<pend do
begin
b:=(ptrint(unaligned(psrc^))-ptrint(unaligned(pdest^)));
if b<>0 then
begin
if b<0 then
exit(-1)
else
exit(1);
end;
inc(pdest);
inc(psrc);
end
if (PtrUInt(pdest) or PtrUInt(psrc)) and 1<>0 then
begin
while (psrc<pend) and (unaligned(psrc^)=unaligned(pdest^)) do
begin
inc(pdest);
inc(psrc);
end;
if psrc<pend then
exit(2*ord(unaligned(psrc^)>unaligned(pdest^))-1);
end
else
{$endif FPC_REQUIRES_PROPER_ALIGNMENT}
while psrc<pend do
begin
b:=(ptrint(psrc^)-ptrint(pdest^));
if b<>0 then
begin
if b<0 then
exit(-1)
else
exit(1);
end;
inc(pdest);
inc(psrc);
end;
begin
while (psrc<pend) and (psrc^=pdest^) do
begin
inc(pdest);
inc(psrc);
end;
if psrc<pend then
exit(2*ord(psrc^>pdest^)-1);
end;
result:=0;
end;
{$endif not FPC_SYSTEM_HAS_COMPAREWORD}