time to rewrite some C function to ASM 68K in NEOPHOENIX for speed up the game
I'm a total newbie in asm 68K so forgive me for any stupid questions, here's the first one:
//C code:
unsigned short code,A;
int x,y,yBg,k;
yBg=(A&0x1F)+k
*VRAM_OFFSET = 0x0800 + (x<<6) + (yBg<<1);
*VRAM_VIDEO = 512+code;
*VRAM_VIDEO = ((code >> 5)| 0x00 ) << 3;
//ASM code:
__asm__(
"move.w #0x0800, %%d1 \n" //
"movw %0, %%d0 \n" // load x from C
"lsl.w #0x6, %%d0 \n" //-- x<<6
"add.w %%d0, %%d1 \n" // 0x0800+(x<<6)
"movw %1, %%d0 \n" // load y=A & 0x1F from C
"andi.w #0x001f, %%d0 \n" // y=(A&0x1F)
"movw %2, %%d2 \n" //-- Load k from C in d2
"add.w %%d2, %%d0 \n" // yBg=y+k
"lsl.w #0x1, %%d0 \n" // yBg<<1
"add.w %%d0, %%d1 \n" // 0x0800+(x<<6)+(yBg<<1)
"move.w %%d1, (0x3C0000) \n" // write data to VRAM_OFFSET
"move.w %3, %%d0 \n" // load code from C
"move.w %%d0, %%d1 \n" // Backup code into d1
"add.w #0x200, %%d0 \n" // 512+code
"move.w %%d0, (0x3C0002) \n" // VRAM_VIDEO in a0 *VRAM_VIDEO = 512+code
"and.w #0xffe0, %%d1 \n"
"lsl.w #0x3, %%d1 \n"
"move.w %%d1, (0x3C0002) \n" // *VRAM_VIDEO VRAM_VIDEO in a0 ((code >> 5) | 0x00 ) << 8
:
:"a"(x), "a"(A), "a"(k), "a" (code)
:"d0" ,"d1", "d2"
);
This code work fine.
The question is: How can I optimize the ASM code? It's possible?
Thanks
Ciao
BEY