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Testing Inline ASM-VB
Strings
Math
General
Memory Search
Using inline ASM
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News
Files Visual Basic
Strings
Math
General
Properties
Memory
Methods Search
Testing Inline ASM-VB
Strings
Math
General
Memory Search
Using inline ASM
Submit!
Using MMX for alternative CopyMemoryWith our inline ASM we can use extra processor instructions that VB doesn't use. Simply use MMX or 3DNOW! instructions from your vb application.
This piece of code will provide an alternative CopyMemory call, which will copy memory using the MMX instructions. Check out the benchmarks :). Note that it was written by John Sagas.
User contributed notes:
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Public Function MemCopyMMX_PreFetch(ByVal Dest As Long, ByVal Source As Long, ByVal ln As Long) As Long ''MMX bits from SGI web site '#ASM_START '.MMX '.XMM ' push ebp ;save registers ' mov ebp, esp ' push ebx ' push esi ' push edi ' ' mov eax, [ebp+16] ; put byte count in eax ' mov esi, [ebp+12] ; copy source pointer into source index ' mov edi, [ebp+8] ; copy dest pointer into destination index ' cld ; copy bytes forward ' cmp eax, 64 ; if under 64 bytes long ' jl Under64PreFetch ; jump ' push eax ; place a copy of eax on the stack ' shr eax, 6 ; integer divide eax by 64 ' shl eax, 6 ; multiply eax by 64 to get dividend ' mov ecx, eax ; copy it into variable ' pop eax ; retrieve length in eax off the stack ' sub eax, ecx ; subtract dividend from length to get remainder ' mov ebx, eax ; copy remainder into variable ' shr ecx, 6 ; divide by 64 for DWORD data size ' ;shr ecx, 6 ;// 64 bytes per iteration ' 'loop1PreFetch: ' ' prefetchnta 64[ESI] ;// Prefetch next loop, non-temporal ' prefetchnta 96[ESI] ' movq mm1, 0[ESI] ;// Read in source data ' movq mm2, 8[ESI] ' movq mm3, 16[ESI] ' movq mm4, 24[ESI] ' movq mm5, 32[ESI] ' movq mm6, 40[ESI] ' movq mm7, 48[ESI] ' movq mm0, 56[ESI] ' ' movntq 0[EDI], mm1 ;// Non-temporal stores ' movntq 8[EDI], mm2 ' movntq 16[EDI], mm3 ' movntq 24[EDI], mm4 ' movntq 32[EDI], mm5 ' movntq 40[EDI], mm6 ' movntq 48[EDI], mm7 ' movntq 56[EDI], mm0 ' ' Add esi, 64 ' Add edi, 64 ' dec ecx ' jnz loop1PreFetch ' ' emms ' mov eax, ebx ; put remainder in ecx ' Under64PreFetch: ' push eax ; place a copy of eax on the stack ' shr eax, 2 ; integer divide eax by 4 ' shl eax, 2 ; multiply eax by 4 to get dividend ' mov ecx, eax ; copy it into variable ' pop eax ; retrieve length in eax off the stack ' sub eax, ecx ; subtract dividend from length to get remainder ' mov ebx, eax ; copy remainder into variable ' shr ecx, 2 ; divide by 4 for DWORD data size ' rep movsd ; repeat while not zero, move string DWORD ' mov ecx, ebx ; put remainder in ecx ' Under4PreFetch: ' rep movsb ; copy remaining BYTES from source to dest ' ' pop edi ' pop esi ' pop ebx ' mov esp, ebp ' pop ebp ' ret 12 ' '#ASM_END End Function |
| CopyMemAPI % faster than CopyMemMMX | CopyMemAPI (sec) | CopyMemMMX (sec) |
| 42.1% | 16.9461 | 11.9279 |
| 57.5% | 18.1806 | 11.5436 |
| 56.9% | 17.8849 | 11.3978 |
| 53.1% | 17.8775 | 11.6806 |
| 72.9% | 20.4509 | 11.8282 |
| CopyMemAPI % faster than CopyMemMMX | CopyMemAPI (sec) | CopyMemMMX (sec) |
| 61.4% | 36.7624 | 22.7733 |
| 59% | 35.6002 | 22.3967 |
| 60.7% | 36.5639 | 22.7487 |
| 46.7% | 34.0619 | 23.213 |
| 41.9% | 36.2374 | 25.5434 |
User contributed notes: