) Delphi large memory clearing quick algorithm (Application of Delphi MMX optimization algorithm 2)

Since the initial value of the dynamic array in Delphi is not always 0, setlength is used before each use of a one-dimensional array, and then fillchar is generally used for clearing, however, if the array is more than dozens of MB, the efficiency of fillchar is very low. For this reason, I specifically wrote some optimization code for clearing the array or memory.

 

1. Use the MMX command to optimize the zeroed Memory code:

Procedure zeromemorymmx (Destination: pointer; asize: DWORD );

// EdX, ECx, ESI, EDI, EBP

ASM

Pushad

MoV EDI, destination

MoV ECx, asize

SHR ECx, 3

Lea EDI, [EDI + ECx * 8]

Neg ECx

Pxor mm0, mm0

Pxor MM1, MM1

Pxor mm2, mm2

Pxor mm3, mm3

Pxor mm4, mm4

Pxor MM5, MM5

Pxor mm6, mm6

Pxor mm7, mm7

@ Writeloop:

Movntq qword [EDI + ECx * 8], mm0

Movntq qword [EDI + ECx * 8 + 8], MM1

Movntq qword [EDI + ECx * 8 + 16], mm2

Movntq qword [EDI + ECx * 8 + 24], mm3

Movntq qword [EDI + ECx * 8 + 32], mm4

Movntq qword [EDI + ECx * 8 + 40], MM5

Movntq qword [EDI + ECx * 8 + 48], mm6

Movntq qword [EDI + ECx * 8 + 56], mm7

Add ECx, 8

MoV eax, ECx

Neg eax

CMP eax, 8

Jle @ comm

Jnz @ writeloop

JMP @ end

@ COMM:

@ End:

Sfence

Emms

Popad

End;

2. Reset the Memory code optimized using the rep command:

Procedure zeromemoryrep (Destination: pointer; Length: DWORD); stdcall;

ASM

Pushad

XOR eax, eax // write data

MoV ECx, length // get the length

MoV EDI, destination // target pointer

Rep stosb

Popad

End;

 

The above two codes have been tested and found that the efficiency of using MMX on 50 m is higher than that of using rep. Rep is recommended for 50 m.