82 lines
1.5 KiB
NASM
82 lines
1.5 KiB
NASM
mov r1, 0
|
|
qcall clz
|
|
add zr, zr, zr
|
|
mov r1, 0x1
|
|
qcall clz
|
|
add zr, zr, zr
|
|
add r1, zr, 0xAAAA
|
|
lsl r1, r1, 6
|
|
qcall popc
|
|
|
|
pub rotate_left:
|
|
; (r1 >> r2) | (r1 << (32 - r2))
|
|
sub r3, zr, r2
|
|
add r3, r3, 32
|
|
lsr r3, r1, r3
|
|
lsl r1, r1, r2
|
|
or r1, r1, r3
|
|
|
|
jmp r13
|
|
|
|
pub rotate_right:
|
|
; (r1 << r2) | (r1 >> (32 - r2))
|
|
sub r3, zr, r2
|
|
add r3, r3, 32
|
|
lsl r3, r1, r3
|
|
lsr r1, r1, r2
|
|
or r1, r1, r3
|
|
|
|
jmp r13
|
|
|
|
pub clz:
|
|
; special case
|
|
mov r4, 0
|
|
; since we start the loop by shifting r2 load twice the value we need
|
|
mov r2, 32
|
|
mov r3, r1
|
|
; divide and conquer algorithm
|
|
clz_loop:
|
|
; next finer step
|
|
lsr r2, r2, 1
|
|
; abort if there is no finer step
|
|
cmp r2, 0
|
|
je clz_end
|
|
; see if there are still some 1 bits left with this additional shift
|
|
lsr r3, r3, r2
|
|
add r4, r4, r2
|
|
cmp r3, 0
|
|
jne clz_loop
|
|
; undo shift if it resulted in zero
|
|
sub r4, r4, r2
|
|
lsr r3, r1, r4
|
|
jmp clz_loop
|
|
clz_end:
|
|
; we calculated the position of the last 1 from the least significant side
|
|
; inverse is what we want (position of last 0 from most significant side)
|
|
mov r1, 31
|
|
sub r1, r1, r4
|
|
jmp r13
|
|
|
|
pub popc:
|
|
mov r2, 0x0101 ; load mask of 0x01010101
|
|
lsl r2, r2, 16
|
|
or r2, r2, 0x0101
|
|
|
|
mov r3, 8 ; bits in byte
|
|
mov r4, 0 ; pop count of each byte
|
|
popc_loop:
|
|
and r5, r1, r2 ; extract least significant bit of byte
|
|
add r4, r4, r5
|
|
|
|
lsr r1, r1, 1 ; cycle through bits
|
|
sub r3, r3, 1
|
|
cmp r3, 0
|
|
jg popc_loop
|
|
|
|
; sum up bytes
|
|
lsr r2, r4, 8
|
|
add r4, r4, r2
|
|
lsr r2, r4, 16
|
|
add r4, r4, r2
|
|
and r1, r4, 0xFF ; mask out end result in lowest byte
|
|
jmp r13 |