mirror of
https://github.com/Zeal-Operating-System/ZealOS.git
synced 2024-12-26 23:36:32 +00:00
69 lines
1.4 KiB
HolyC
Executable file
69 lines
1.4 KiB
HolyC
Executable file
/*When I was a kid with a Commodore 64,
|
||
the 6502 chip had no multiply inst
|
||
and this is how we had to do it, except,
|
||
I used more regs in this example.
|
||
*/
|
||
asm {
|
||
//Opcodes are slightly different to make writing my x86_64 assembler easier.
|
||
//See $LK,"::/Compiler/OpCodes.DD"$.
|
||
|
||
//You can clobber RAX,RBX,RCX,RDX,R8,R9. The compiler expects that.
|
||
|
||
MUL_BY_HAND_U8_U8_TO_U16: //This is only for fun.
|
||
//8bit * 8bit-->16bit
|
||
//AL*BL-->AX
|
||
MOV CL,8
|
||
SHL AX,8
|
||
@@05: SHL1 AX
|
||
JNC @@10
|
||
ADD AL,BL
|
||
@@10: DEC CL
|
||
JNZ @@05
|
||
RET
|
||
|
||
_MUL_BY_HAND_U8_U8_TO_U16:: //C callable
|
||
PUSH RBP
|
||
MOV RBP,RSP
|
||
MOV AL,U8 SF_ARG1[RBP] //$LK,"SF_ARG1",A="FF:::/Kernel/KernelA.HH,SF_ARG1"$
|
||
MOV BL,U8 SF_ARG2[RBP]
|
||
CALL MUL_BY_HAND_U8_U8_TO_U16
|
||
MOVZX RAX,AX
|
||
POP RBP
|
||
RET1 16
|
||
|
||
_MUL_U64_U64_TO_U128::
|
||
//64bit * 64bit-->128bit
|
||
PUSH RBP
|
||
MOV RBP,RSP
|
||
MOV RBX,U64 SF_ARG3[RBP]
|
||
MOV RAX,U64 SF_ARG1[RBP] //$LK,"SF_ARG1",A="FF:::/Kernel/KernelA.HH,SF_ARG1"$
|
||
MUL U64 SF_ARG2[RBP] //Res RDX:RAX 128bit
|
||
MOV U64 [RBX],RAX
|
||
MOV U64 8[RBX],RDX
|
||
POP RBP
|
||
RET1 24
|
||
};
|
||
|
||
//My convention is to put an underscore
|
||
//on C callable asm routines.
|
||
_extern _MUL_BY_HAND_U8_U8_TO_U16 U16 MulU8(U8 n1,U8 n2);
|
||
|
||
class U128
|
||
{
|
||
U64 lo,hi;
|
||
};
|
||
|
||
_extern _MUL_U64_U64_TO_U128 U0 MulU64(I64 n1,I64 n2,U128 *_prod);
|
||
|
||
U0 MulByHand()
|
||
{
|
||
U128 p;
|
||
"2*7 =0x%X\n",MulU8(2,7);
|
||
"100*10=0x%X\n",MulU8(100,10);
|
||
|
||
MulU64(0x0123456789ABCDEF,0x1000001,&p);
|
||
"0x0123466789ABCDEF*0x1000001=0x%016X%016X\n",p.hi,p.lo;
|
||
}
|
||
|
||
MulByHand;
|
||
|