How to optimize C code for NGPC?

[winteriscoming]

a bit of asm in your c code ?

Personally, I use asm for hblank code, sometimes using also bank register switch (incf, decf or ldf)

Do you know ldir(w) and lddr(w) ? (check asm doc: e_900h_chap3_cpu_4.pdf) 

something like:

void moveRam(void*dst,void*src,u32 count)
{
__ASM(" ld xbc,(xsp+12) ");
__ASM(" ld xhl,(xsp+8) ");
__ASM(" ld xde,(xsp+4) ");
__ASM(" ldirw (xde+),(xhl+) ");
}


can be improved without using a function and direct access to global var to init dst & src (maybe you can use DMA for async mem transfert)

Most of the time, -O3 is better than my own asm "optimizations", that's why I often add a -S to check how it's compiled.

It appears my makefile has always had -O3.  I can barely stumble my way through ASM, but I am attempting to learn.

In my case, everything needed by hblank is known during vblank.

Here is my hblank code that references some global variables.  I added notes where the pain point is for performance.

Code:

void __interrupt myHBL()
{
   u8 y = RAS_Y;
   
   myHBCounter++;
   
    if(y==8){
        
    
     if(showHUD){
         SCR1_Y=plane1.planeY;
         SCR1_X=plane1.planeX;
         SPR_Y=0;
         if(currentLevel.isBossRoom)SCR2_Y=plane2.planeY;
     }
    
    
    
    }
    //everything above works fine
    //everything below kills performance
    
    //performance suffers is screenSplit is true
    else if (screenSplit){
        if(y==60)   SCR2_X=split1;
        else if(y==100)  SCR2_X=split2;
    }
}

What is the best way to shift this to ASM?