ARM Cortex Ax with NEON SIMD

ARM 除了 support Thumb SIMD之外,另一個針對大量Data傳輸所建立的指令集 NEON,可參考底下的 link 有詳細的說明. 其實說穿了就是 Hardware Parallel support.利用多個 operator 來同步執行..

Lect.10.arm soc.4 neon

View more presentations from sean chen.

底下就用 NEON 的概念來寫Parallel support,不過 compiler/Hardware 並沒有支援.所以還是只有自 High 而已...XD

#include <stdio.h>
#include <stdlib.h>
#include <inttypes.h>

#define BUF_SIZE 4

struct ABC {
 uint8_t A; 
 uint8_t B;
 uint8_t C;
 
} ABC_BUF[BUF_SIZE];

struct XYZ {
 uint8_t X;
 uint8_t Y;
 uint8_t Z;
} XYZ_BUF[BUF_SIZE]= {
 {       0,      0,      0},
 {      25,     25,     25},
 {       3,      5,      9},
 {       7,      5,      3},
};

void C_XYZ2ABC(){
int i;
     for(i=0; i<BUF_SIZE; i++){
 ABC_BUF[i].A = XYZ_BUF[i].X + XYZ_BUF[i].Y + XYZ_BUF[i].Z;
 ABC_BUF[i].B = XYZ_BUF[i].X + XYZ_BUF[i].Y - XYZ_BUF[i].Z;
 ABC_BUF[i].C = XYZ_BUF[i].X - XYZ_BUF[i].Y - XYZ_BUF[i].Z;
     }
}

void ASSEMBLY_XYZ2ABC(){
int i;
uint8_t tA,tB,tC;

   for( i=0; i<BUF_SIZE; i++ ){
                    tA = (XYZ_BUF[i].X + XYZ_BUF[i].Y);
          ABC_BUF[i].A = (tA           + XYZ_BUF[i].Z);

                    tB = (XYZ_BUF[i].X + XYZ_BUF[i].Y);
   ABC_BUF[i].B = (tB           - XYZ_BUF[i].Z);

                    tC = (XYZ_BUF[i].X - XYZ_BUF[i].Y);
          ABC_BUF[i].C = (tC           - XYZ_BUF[i].Z);
  }
}


uint32_t Exp4x8uint_8(uint8_t i24,uint8_t i16,uint8_t i8,uint8_t i0){
uint32_t r;
         r  = i24<<24;
         r += i16<<16;
         r += i8<<8;
         r += i0;
return r;
}

uint32_t Exe4x8uint_32(uint32_t a32,uint32_t b32,uint8_t op){
uint32_t r; 
uint8_t  ra24 = a32>>24;
uint8_t  ra16 = a32>>16;
uint8_t  ra8  = a32>>8;
uint8_t  ra0  = a32;

uint8_t  rb24 = b32>>24;
uint8_t  rb16 = b32>>16;
uint8_t  rb8  = b32>>8;
uint8_t  rb0  = b32;

switch(op){
   case 0: ra24 += rb24; ra16 += rb16; ra8 += rb8; ra0 += rb0; break; 
   case 1: ra24 -= rb24; ra16 -= rb16; ra8 -= rb8; ra0 -= rb0; break;
 }
 
 r  = ra24<<24;
 r += ra16<<16;
 r += ra8<<8;
 r += ra0;
 
 return r;
}

void NEON_XYZ2ABC(){
int i;
uint32_t X,Y,Z;
uint32_t A,B,C;

  for( i=0; i<BUF_SIZE; i=i+4 ){
 X = Exp4x8uint_8(XYZ_BUF[i+3].X, XYZ_BUF[i+2].X, XYZ_BUF[i+1].X, XYZ_BUF[i ].X);
 Y = Exp4x8uint_8(XYZ_BUF[i+3].Y, XYZ_BUF[i+2].Y, XYZ_BUF[i+1].Y, XYZ_BUF[i ].Y);
 Z = Exp4x8uint_8(XYZ_BUF[i+3].Z, XYZ_BUF[i+2].Z, XYZ_BUF[i+1].Z, XYZ_BUF[i ].Z);

        A  = Exe4x8uint_32(X,Y,0);
        A  = Exe4x8uint_32(A,Z,0);

        B  = Exe4x8uint_32(X,Y,0);
        B  = Exe4x8uint_32(B,Z,1);

        C  = Exe4x8uint_32(X,Y,1);
        C  = Exe4x8uint_32(C,Z,1);

        ABC_BUF[i+3].A = A>>24; ABC_BUF[i+2].A = A>>16;  ABC_BUF[i+1].A = A>>8; ABC_BUF[i].A = A; 
        ABC_BUF[i+3].B = B>>24; ABC_BUF[i+2].B = B>>16;  ABC_BUF[i+1].B = B>>8; ABC_BUF[i].B = B; 
        ABC_BUF[i+3].C = C>>24; ABC_BUF[i+2].C = C>>16;  ABC_BUF[i+1].C = C>>8; ABC_BUF[i].C = C; 
   }
}


void Display_ABC(){
int i; 
   for( i=0; i<BUF_SIZE; i++ ){
    printf("I     :: %3x,",i);
    printf("A[%2d]:: %3x,",i,ABC_BUF[i].A);
    printf("B[%2d]:: %3x,",i,ABC_BUF[i].B);
    printf("C[%2d]:: %3x,\n",i,ABC_BUF[i].C);
  }
  printf("\n");  
}

int main(int argc,char *argv[]){
 
 printf("C Code Result...\n");
 C_XYZ2ABC();
 Display_ABC();

 printf("NEON Result...\n");
 NEON_XYZ2ABC();
 Display_ABC();


return 0;
}

code download here Refs: RGB 2 YUV Optimizing Code for ARM Cortex-A8 with NEON SIMD