私はアセンブリを学んでおり、Digital-Mars C++ コンパイラ (intel sytanx の方が読みやすい) 内で SSE および MMX レジスタの実験を開始しました。var_1 を値として取り、それを var_2 数値システムに変換するプログラムを完成させました (これは今のところ 8 ビットです。後で 32 64 128 に拡張します)。プログラムは、次の 2 つの方法でこれを行います。
__asmインライン化%(modulo) 演算子の通常の C++ の方法。
質問: xmm0-7 および mm0-7 レジスターを使用するより効率的な方法と、それらの正確なバイトを al,ah... 8 ビット レジスターと交換する方法を教えてください。
C++ の通常の %(modulo) 演算子は、私のコンピューター (pentium-m centrino 2.0GHz) の __asm と比較して非常に遅いです。__asmmで除算命令をなくす方法を教えていただけるとさらに早くなります。
プログラムを実行すると、次のようになります。
(for the values: var_1=17,var_2=2,all loops are 200M times)
17 is 10001 in number system 2
__asm(clock)...........: 7250 <------too bad. it is 8-bit calc.
C++(clock).............: 12250 <------not very slow(var_2 is a power of 2)
(for the values: var_1=33,var_2=7,all loops are 200M times)
33 is 45 in number system 7
__asm(clock)..........: 2875 <-------not good. it is 8-bit calc.
C++(clock)............: 6328 <----------------really slow(var_2 is not a power of 2)
2 番目の C++ コード (% 演算子を含むもの): /////////////////////////////////// ///////////////////
t1=clock();//reference time
for(int i=0;i<200000000;i++)
{
y=x;
counter=0;
while(y>g)
{
var_3[counter]=y%g;
y/=g;
counter++;
}
var_3[counter]=y%g;
}
t2=clock();//final time
_asm コード://///////////////////////////////////////// /////////////////////////////////////////////// ///////////
__asm // i love assembly in some parts of C++
{
pushf //here does register backup
push eax
push ebx
push ecx
push edx
push edi
mov eax,0h //this will be outer loop counter init to zero
//init of medium-big registers to zero
movd xmm0,eax //cannot set to immediate constant: xmm0=outer loop counter
shufps xmm0,xmm0,0h //this makes all bits zero
movd xmm1,eax
movd xmm2,eax
shufps xmm1,xmm1,0h
shufps xmm2,xmm2,0h
movd xmm2,eax
shufps xmm3,xmm3,0h//could have made pxor xmm3,xmm3(single instruction)
//init complete(xmm0,xmm1,xmm2,xmm3 are zero)
movd xmm1,[var_1] //storing variable_1 to register
movd xmm2,[var_2] //storing var_2 to register
lea ebx,var_3 //calculate var_3 address
movd xmm3,ebx //storing var_3's address to register
for_loop:
mov eax,0h
//this line is index-init to zero(digit array index)
movd edx,xmm2
mov cl,dl //this is the var_1 stored in cl
movd edx,xmm1
mov al,dl //this is the var_2 stored in al
mov edx,0h
dng:
mov ah,00h //preparation for a 8-bit division
div cl //divide
movd ebx,xmm3 //get var_3 address
add ebx,edx //i couldnt find a way to multiply with 4
add ebx,edx //so i added 4 times ^^
add ebx,edx //add
add ebx,edx //last adding
//below, mov [ebx],ah is the only memory accessing instruction
mov [ebx],ah //(8 bit)this line is equivalent to var_3[i]=remainder
inc edx //i++;
cmp al,00h //is division zero?
jne dng //if no, loop again
//here edi register has the number of digits
movd eax,xmm0 //get the outer loop counter from medium-big register
add eax,01h //j++;
movd xmm0,eax //store the new counter to medium-big register
cmp eax,0BEBC200h //is j<(200,000,000) ?
jb for_loop //if yes, go loop again
mov [var_3_size],edx //now we have number of digits too!
//here does registers revert back to old values
pop edi
pop edx
pop ecx
pop ebx
pop eax
popf
}
コード全体://///////////////////////////////////////// ////////////////////////////////////////
#include <iostream.h>
#include <cmath>
#include<stdlib.h>
#include<stdio.h>
#include<time.h>
int main()
{
srand(time(0));
clock_t t1=clock();
clock_t t2=clock();
int var_1=17; //number itself
int var_2=2; //number system
int var_3[100]; //digits to be showed(maximum 100 as seen )
int var_3_size=0;//asm block will decide what will the number of digits be
for(int i=0;i<100;i++)
{
var_3[i]=0; //here we initialize digits to zeroes
}
t1=clock();//reference time to take
__asm // i love assembly in some parts of C++
{
pushf //here does register backup
push eax
push ebx
push ecx
push edx
push edi
mov eax,0h //this will be outer loop counter init to zero
//init of medium-big registers to zero
movd xmm0,eax //cannot set to immediate constant: xmm0=outer loop counter
shufps xmm0,xmm0,0h //this makes all bits zero
movd xmm1,eax
movd xmm2,eax
shufps xmm1,xmm1,0h
shufps xmm2,xmm2,0h
movd xmm2,eax
shufps xmm3,xmm3,0h
//init complete(xmm0,xmm1,xmm2,xmm3 are zero)
movd xmm1,[var_1] //storing variable_1 to register
movd xmm2,[var_2] //storing var_2 to register
lea ebx,var_3 //calculate var_3 address
movd xmm3,ebx //storing var_3's address to register
for_loop:
mov eax,0h
//this line is index-init to zero(digit array index)
movd edx,xmm2
mov cl,dl //this is the var_1 stored in cl
movd edx,xmm1
mov al,dl //this is the var_2 stored in al
mov edx,0h
dng:
mov ah,00h //preparation for a 8-bit division
div cl //divide
movd ebx,xmm3 //get var_3 address
add ebx,edx //i couldnt find a way to multiply with 4
add ebx,edx //so i added 4 times ^^
add ebx,edx //add
add ebx,edx //last adding
//below, mov [ebx],ah is the only memory accessing instruction
mov [ebx],ah //(8 bit)this line is equivalent to var_3[i]=remainder
inc edx //i++;
cmp al,00h //is division zero?
jne dng //if no, loop again
//here edi register has the number of digits
movd eax,xmm0 //get the outer loop counter from medium-big register
add eax,01h //j++;
movd xmm0,eax //store the new counter to medium-big register
cmp eax,0BEBC200h //is j<(200,000,000) ?
jb for_loop //if yes, go loop again
mov [var_3_size],edx //now we have number of digits too!
//here does registers revert back to old values
pop edi
pop edx
pop ecx
pop ebx
pop eax
popf
}
t2=clock(); //finish time
printf("\n assembly_inline(clocks): %i for the 200 million calculations",(t2-t1));
printf("\n value %i(in decimal) is: ",var_1);
for(int i=var_3_size-1;i>=0;i--)
{
printf("%i",var_3[i]);
}
printf(" in the number system: %i \n",var_2);
//and: more readable form(end easier)
int counter=var_3_size;
int x=var_1;
int g=var_2;
int y=x;// backup
t1=clock();//reference time
for(int i=0;i<200000000;i++)
{
y=x;
counter=0;
while(y>g)
{
var_3[counter]=y%g;
y/=g;
counter++;
}
var_3[counter]=y%g;
}
t2=clock();//final time
printf("\n C++(clocks): %i for the 200 million calculations",(t2-t1));
printf("\n value %i(in decimal) is: ",x);
for(int i=var_3_size-1;i>=0;i--)
{
printf("%i",var_3[i]);
}
printf(" in the number system: %i \n",g);
return 0;
}
編集：これは32ビット版です
void get_digits_asm()
{
__asm
{
pushf //couldnt store this in other registers
movd xmm0,eax//storing in xmm registers instead of pushing
movd xmm1,ebx//
movd xmm2,ecx//
movd xmm3,edx//
movd xmm4,edi//end of push backups
mov eax,[variable_x]
mov ebx,[number_system]
mov ecx,0h
mov edi,0h
begin_loop:
mov edx,0h
div ebx
lea edi,digits
mov [edi+ecx*4],edx
add ecx,01h
cmp eax,ebx
ja begin_loop
mov edx,0
div ebx
lea edi,digits
mov [edi+ecx*4],edx
inc ecx
mov [digits_total],ecx
movd edi,xmm4//pop edi
movd edx,xmm3//pop edx
movd ecx,xmm2//pop ecx
movd ebx,xmm1//pop ebx
movd eax,xmm0//pop eax
popf
}
}