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Subject: Re: BitScan with reset - not so impressive with 3DNow!

Author: Gerd Isenberg

Date: 17:27:39 12/02/02

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Ahh.. i see,

a special kind of popcount for consecutive trailing "ones".
I love this interactive programming lessions.

Gerd

Btw.: Impressive assembler listing:

00401003 8B 4C 24 0C          mov         ecx,dword ptr [esp+0Ch]
00401007 8B 31                mov         esi,dword ptr [ecx]
00401009 8B 79 04             mov         edi,dword ptr [ecx+4]
0040100C 8B D6                mov         edx,esi
0040100E 8B C7                mov         eax,edi
00401010 83 C2 FF             add         edx,0FFFFFFFFh
00401013 83 D0 FF             adc         eax,0FFFFFFFFh
00401016 23 F2                and         esi,edx
00401018 23 F8                and         edi,eax
0040101A 89 31                mov         dword ptr [ecx],esi
0040101C 89 79 04             mov         dword ptr [ecx+4],edi
0040101F 8B CF                mov         ecx,edi
00401021 33 D6                xor         edx,esi
00401023 33 C1                xor         eax,ecx
00401025 33 C2                xor         eax,edx
00401027 5F                   pop         edi
00401028 35 81 FC C5 01       xor         eax,1C5FC81h
0040102D 5E                   pop         esi
0040102E 8B D0                mov         edx,eax
00401030 C1 EA 10             shr         edx,10h
00401033 03 C2                add         eax,edx
00401035 33 D2                xor         edx,edx
00401037 8B C8                mov         ecx,eax
00401039 C1 E9 08             shr         ecx,8
0040103C 2A C1                sub         al,cl
0040103E 25 FF 00 00 00       and         eax,0FFh
00401043 8A 90 D5 62 40 00    mov         dl,byte ptr [eax+4062D5h]
00401049 8B C2                mov         eax,edx
0040104B C3                   ret



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