Assembly optimisations
This commit is contained in:
parent
189dc9b102
commit
0f486d6804
133
src/tilemap.S
133
src/tilemap.S
|
|
@ -148,7 +148,7 @@ _samplePixel: # (r4: xPos, r5: yPos) -> r0
|
|||
.type _draw3DLine, @function
|
||||
|
||||
_draw3DLine: # (r4: x, r5: y, r6: dx, r7: dy) -> r0
|
||||
# vramLine is stored in a global because I don't want to deal with the stack
|
||||
# vramLine is stored in a global because I don't want to deal with loading it from the stack
|
||||
# Save registers
|
||||
mov.l r8,@-r15
|
||||
mov.l r9,@-r15
|
||||
|
|
@ -165,122 +165,117 @@ _draw3DLine: # (r4: x, r5: y, r6: dx, r7: dy) -> r0
|
|||
# Load vramLine into r8
|
||||
mov.l .vramLine, r8
|
||||
mov.l @r8, r8
|
||||
|
||||
# Load xOffset into r12
|
||||
mov.l .xOffset, r12
|
||||
mov.w @r12, r12
|
||||
|
||||
# Load yOffset into r2
|
||||
mov.l .yOffset, r2
|
||||
mov.w @r2, r2
|
||||
|
||||
# Use r9 as the loop counter
|
||||
mov #0, r9
|
||||
# Load 198 into it and go backwards
|
||||
# Counting down is better because we only have to load the value of 198 once
|
||||
mov.w .halfWidth, r9
|
||||
.loop:
|
||||
# TODO: Avoid the mov by making r10/r11 the shifted values, and modify the inlined samplePixel to use r10/r11 instead of r4/r5?
|
||||
# Set r4 to x >> 16
|
||||
mov r4, r10
|
||||
# shlr16 r4
|
||||
swap.w r4, r4
|
||||
exts.w r4, r4
|
||||
# Set r5 to y >> 16
|
||||
mov r5, r11
|
||||
# shlr16 r5
|
||||
swap.w r5, r5
|
||||
exts.w r5, r5
|
||||
# Set r10 to x >> 16
|
||||
swap.w r4, r10
|
||||
exts.w r10, r10
|
||||
# Set r11 to y >> 16
|
||||
swap.w r5, r11
|
||||
exts.w r11, r11
|
||||
# Call samplePixel
|
||||
|
||||
|
||||
# TODO: When inlining this into the loop, we can make sure to only do these loads once if we have the registers available
|
||||
# START: INLINED VERSION OF samplePixel
|
||||
# (though I made some changes to it to optimize it)
|
||||
# add xOffset to xPos
|
||||
mov.l .xOffset, r1
|
||||
mov.w @r1, r1
|
||||
add r1, r4
|
||||
add r12, r10
|
||||
# add yOffset to yPos
|
||||
mov.l .yOffset, r1
|
||||
mov.w @r1, r1
|
||||
add r1, r5
|
||||
add r2, r11
|
||||
# divide by 4
|
||||
shlr2 r4
|
||||
shlr2 r5
|
||||
shlr2 r10
|
||||
mov #0b111, r0
|
||||
shlr2 r11
|
||||
# get the position of the pixel in the tile
|
||||
# copy them into other registers so we can use the original ones for the tileID
|
||||
mov r4, r6
|
||||
mov #0b111, r0
|
||||
mov r10, r6
|
||||
and r0, r6
|
||||
mov r5, r7
|
||||
mov r11, r7
|
||||
and r0, r7
|
||||
# get the colour of the pixel in the tile
|
||||
# get the tile ID by calling getTileID
|
||||
# Inlined version of getTileID
|
||||
mov r4, r0
|
||||
or r5, r0
|
||||
|
||||
# START: INLINED VERSION OF getTileID
|
||||
# (also with some changes to optimize it)
|
||||
mov r10, r0
|
||||
or r11, r0
|
||||
shlr8 r0
|
||||
tst #0b11111000, r0
|
||||
# T is now 0 if we want to return 0
|
||||
bf .return0v3
|
||||
bf.s .endv2
|
||||
mov #0, r0
|
||||
# otherwise, continue
|
||||
mov #-3, r1
|
||||
shad r1, r4
|
||||
shad r1, r5
|
||||
# multiply r5 by 256
|
||||
shll8 r5
|
||||
add r5, r4
|
||||
# read from the tilemap
|
||||
mov.l .tilemap, r0
|
||||
shad r1, r10
|
||||
shad r1, r11
|
||||
# now r0 = _tilemap symbol = address of the variable, which is an array
|
||||
# shll2 r4
|
||||
mov.b @(r0, r4), r0
|
||||
mov.l .tilemap, r0
|
||||
# multiply r11 by 256
|
||||
shll8 r11
|
||||
add r11, r10
|
||||
# read from the tilemap
|
||||
# shll2 r10
|
||||
mov.b @(r0, r10), r0
|
||||
bra .endv2
|
||||
extu.b r0, r0
|
||||
.return0v3:
|
||||
# rts
|
||||
mov #0, r0
|
||||
.endv2:
|
||||
# END: INLINED VERSION OF getTileID
|
||||
|
||||
# r0 now contains the tile ID
|
||||
# multiply r7 by 8
|
||||
# Happens in branch delay slot
|
||||
shll2 r7
|
||||
add r7, r7
|
||||
mov #3, r1
|
||||
shad r1, r7
|
||||
# add r6 to r7
|
||||
add r6, r7
|
||||
# multiply r0 by 64
|
||||
shll8 r0
|
||||
shlr2 r0
|
||||
mov #6, r1
|
||||
shad r1, r0
|
||||
# add r0 to r7
|
||||
add r0, r7
|
||||
# read from the tileset
|
||||
mov.l .tileset, r0
|
||||
# now r0 = _tileset symbol = address of the variable, which is an array
|
||||
mov.b @(r0, r7), r0
|
||||
extu.b r0, r0
|
||||
# read from the palette
|
||||
mov.l .palette, r1
|
||||
extu.b r0, r0
|
||||
# now r1 = _palette symbol = address of the variable, which is an array
|
||||
# multiply r0 by 2
|
||||
add r0, r0
|
||||
# read from the palette
|
||||
mov.w @(r0, r1), r0
|
||||
extu.w r0, r0
|
||||
# End of samplePixel
|
||||
# END: INLINED VERSION OF samplePixel
|
||||
|
||||
|
||||
|
||||
|
||||
# Set r12 to the result
|
||||
mov r0, r12
|
||||
# Shift r12 left by 16
|
||||
shll16 r12
|
||||
# OR r12 with r0
|
||||
or r0, r12
|
||||
# Set r1 to the result
|
||||
mov r0, r1
|
||||
# Shift r1 left by 16
|
||||
shll16 r1
|
||||
# OR r1 with r0
|
||||
or r0, r1
|
||||
# Store r12 in vramLine
|
||||
mov.l r12, @r8
|
||||
mov.l r1, @r8
|
||||
# Decrement the loop counter and check if it's 0
|
||||
dt r9
|
||||
# Increment vramLine
|
||||
add #4, r8
|
||||
# Put the original values of r4 and r5 back
|
||||
mov r10, r4
|
||||
mov r11, r5
|
||||
# Increment x and y by dx and dy
|
||||
# Increment x by dx
|
||||
add r13, r4
|
||||
bf.s .loop
|
||||
# Increment y by dy (branch delay slot)
|
||||
add r14, r5
|
||||
# Increment the loop counter
|
||||
add #1, r9
|
||||
# Check if we're done
|
||||
# Load 198 from .halfWidth
|
||||
mov.w .halfWidth, r10
|
||||
cmp/eq r9, r10
|
||||
bf .loop
|
||||
|
||||
# Restore registers
|
||||
mov.l @r15+,r14
|
||||
|
|
|
|||
Loading…
Reference in New Issue