mirror of
https://github.com/lscharen/iigs-game-engine.git
synced 2024-06-08 03:29:32 +00:00
463 lines
16 KiB
ArmAsm
463 lines
16 KiB
ArmAsm
; Template and equates for GTE blitter
|
|
|
|
mx %00
|
|
|
|
DP_ADDR equ entry_1-base+1
|
|
BG1_ADDR equ entry_2-base+1
|
|
STK_ADDR equ entry_3-base+1
|
|
|
|
CODE_ENTRY equ entry_jmp-base+1 ; low byte of the page-aligned jump address
|
|
CODE_TOP equ loop-base
|
|
CODE_LEN equ top-base
|
|
CODE_EXIT equ even_exit-base
|
|
|
|
; Locations that need the page offset added
|
|
PagePatches da {long_0-base+2}
|
|
da {long_1-base+2}
|
|
da {long_2-base+2}
|
|
da {long_3-base+2}
|
|
da {long_4-base+2}
|
|
da {long_5-base+2}
|
|
da {long_6-base+2}
|
|
da {odd_entry-base+2}
|
|
da {loop_exit_1-base+2}
|
|
da {loop_exit_2-base+2}
|
|
da {loop_back-base+2}
|
|
da {loop_exit_3-base+2}
|
|
da {even_exit-base+2}
|
|
PagePatchNum equ *-PagePatches
|
|
|
|
BankPatches da {long_0-base+3}
|
|
da {long_1-base+3}
|
|
da {long_2-base+3}
|
|
da {long_3-base+3}
|
|
da {long_4-base+3}
|
|
da {long_5-base+3}
|
|
da {long_6-base+3}
|
|
BankPatchNum equ *-BankPatches
|
|
|
|
; Patch out the final JMP to jump to the long JML return code
|
|
;
|
|
; Y = starting line * $1000
|
|
SetReturn lda #$0280 ; BRA *+4
|
|
sta CODE_EXIT,y
|
|
rts
|
|
|
|
ResetReturn lda #$004C ; JMP $XX00
|
|
sta CODE_EXIT,y
|
|
rts
|
|
|
|
; Fill in the even_exit JMP instruction to jump to the next line (all but last line)
|
|
SetNextLine lda #$F000+{entry_3-base}
|
|
ldy #CODE_EXIT+1
|
|
ldx #15*2
|
|
jmp SetAbsAddrs
|
|
|
|
; Patch an 8-bit or 16-bit value into the bank. These are a set up unrolled loops to
|
|
; quickly patch in a constanct value, or a value from an array into a given set of
|
|
; templates.
|
|
;
|
|
; Because we have structured everything as parallel code blocks, most updates to the blitter
|
|
; reduce to storing a constant value and have an amortized cost of just a single store.
|
|
;
|
|
; The utility of these routines is that they also handle setting just a range of lines.
|
|
;
|
|
; X = number of lines * 2, 0 to 32
|
|
; Y = starting line * $1000
|
|
; A = value
|
|
;
|
|
; Set M to 0 or 1
|
|
SetConst jmp (:tbl,x)
|
|
:tbl da :bottom-00,:bottom-03,:bottom-06,:bottom-09
|
|
da :bottom-12,:bottom-15,:bottom-18,:bottom-21
|
|
da :bottom-24,:bottom-27,:bottom-30,:bottom-33
|
|
da :bottom-36,:bottom-39,:bottom-42,:bottom-45
|
|
da :bottom-48
|
|
:top sta $F000,y
|
|
sta $E000,y
|
|
sta $D000,y
|
|
sta $C000,y
|
|
sta $B000,y
|
|
sta $A000,y
|
|
sta $9000,y
|
|
sta $8000,y
|
|
sta $7000,y
|
|
sta $6000,y
|
|
sta $5000,y
|
|
sta $4000,y
|
|
sta $3000,y
|
|
sta $2000,y
|
|
sta $1000,y
|
|
sta $0000,y
|
|
:bottom rts
|
|
|
|
; SetScreenAddrs
|
|
;
|
|
; A = initial screen location (largest)
|
|
; Y = starting line * $1000
|
|
; X = number of lines
|
|
;
|
|
; Automatically decrements address by 160 bytes each line
|
|
SetScreenAddrs sec
|
|
jmp (:tbl,x)
|
|
:tbl da :bottom-00,:bottom-03,:bottom-09,:bottom-15
|
|
da :bottom-21,:bottom-27,:bottom-33,:bottom-39
|
|
da :bottom-45,:bottom-51,:bottom-57,:bottom-63
|
|
da :bottom-69,:bottom-75,:bottom-81,:bottom-87
|
|
da :bottom-93
|
|
:top sta STK_ADDR+$F000,y
|
|
sbc #160
|
|
sta STK_ADDR+$E000,y
|
|
sbc #160
|
|
sta STK_ADDR+$D000,y
|
|
sbc #160
|
|
sta STK_ADDR+$C000,y
|
|
sbc #160
|
|
sta STK_ADDR+$B000,y
|
|
sbc #160
|
|
sta STK_ADDR+$A000,y
|
|
sbc #160
|
|
sta STK_ADDR+$9000,y
|
|
sbc #160
|
|
sta STK_ADDR+$8000,y
|
|
sbc #160
|
|
sta STK_ADDR+$7000,y
|
|
sbc #160
|
|
sta STK_ADDR+$6000,y
|
|
sbc #160
|
|
sta STK_ADDR+$5000,y
|
|
sbc #160
|
|
sta STK_ADDR+$4000,y
|
|
sbc #160
|
|
sta STK_ADDR+$3000,y
|
|
sbc #160
|
|
sta STK_ADDR+$2000,y
|
|
sbc #160
|
|
sta STK_ADDR+$1000,y
|
|
sbc #160
|
|
sta STK_ADDR+$0000,y
|
|
:bottom rts
|
|
|
|
; SetAbsAddres
|
|
;
|
|
; A = absolute address (largest)
|
|
; Y = offset
|
|
; X = number of lines
|
|
;
|
|
; Stores a value and decrements by $1000 for each line
|
|
SetAbsAddrs sec
|
|
jmp (:tbl,x)
|
|
:tbl da :bottom-00,:bottom-03,:bottom-09,:bottom-15
|
|
da :bottom-21,:bottom-27,:bottom-33,:bottom-39
|
|
da :bottom-45,:bottom-51,:bottom-57,:bottom-63
|
|
da :bottom-69,:bottom-75,:bottom-81,:bottom-87
|
|
da :bottom-93
|
|
:top sta $F000,y
|
|
sbc #$1000
|
|
sta $E000,y
|
|
sbc #$1000
|
|
sta $D000,y
|
|
sbc #$1000
|
|
sta $C000,y
|
|
sbc #$1000
|
|
sta $B000,y
|
|
sbc #$1000
|
|
sta $A000,y
|
|
sbc #$1000
|
|
sta $9000,y
|
|
sbc #$1000
|
|
sta $8000,y
|
|
sbc #$1000
|
|
sta $7000,y
|
|
sbc #$1000
|
|
sta $6000,y
|
|
sbc #$1000
|
|
sta $5000,y
|
|
sbc #$1000
|
|
sta $4000,y
|
|
sbc #$1000
|
|
sta $3000,y
|
|
sbc #$1000
|
|
sta $2000,y
|
|
sbc #$1000
|
|
sta $1000,y
|
|
sbc #$1000
|
|
sta $0000,y
|
|
:bottom rts
|
|
|
|
; Full up a full bank with blitter templates. Currently we can fit 16 lines per bank, so need
|
|
; a total of 13 banks to hold the 208 lines to full-screen support
|
|
|
|
target equ 0
|
|
BuildBank
|
|
stz target
|
|
sta target+2
|
|
:next
|
|
jsr BuildLine2
|
|
lda target
|
|
clc
|
|
adc #$1000
|
|
sta target
|
|
bcc :next
|
|
|
|
rts
|
|
|
|
; this is a relocation subroutine, it is responsible for copying the template to a
|
|
; memory location and patching up the necessary instructions.
|
|
;
|
|
; X = low word of address (must be a multiple of $1000)
|
|
; A = high word of address (bank)
|
|
BuildLine
|
|
stx target
|
|
sta target+2
|
|
|
|
BuildLine2
|
|
lda #CODE_LEN ; round up to an even number of bytes
|
|
inc
|
|
and #$FFFE
|
|
beq :nocopy
|
|
dec
|
|
dec
|
|
tay
|
|
:loop lda base,y
|
|
sta [target],y
|
|
|
|
dey
|
|
dey
|
|
bpl :loop
|
|
|
|
:nocopy lda #0 ; copy is complete, now patch up the addresses
|
|
sep #$20
|
|
|
|
ldx #0
|
|
lda target+2 ; patch in the bank for the absolute long addressing mode
|
|
:dobank ldy BankPatches,x
|
|
sta [target],y
|
|
inx
|
|
inx
|
|
cpx #BankPatchNum
|
|
bcc :dobank
|
|
|
|
ldx #0
|
|
:dopage ldy PagePatches,x ; patch the page addresses by adding the page offset to each
|
|
lda [target],y
|
|
clc
|
|
adc target+1
|
|
sta [target],y
|
|
inx
|
|
inx
|
|
cpx #PagePatchNum
|
|
bcc :dopage
|
|
|
|
:out
|
|
rep #$20
|
|
rts
|
|
|
|
; start of the template code
|
|
base
|
|
entry_1 ldx #0000
|
|
entry_2 ldy #0000
|
|
entry_3 lda #0000
|
|
tcs
|
|
|
|
long_0
|
|
entry_jmp jmp $0100
|
|
dfb $00 ; if the screen is odd-aligned, then the opcode is set to
|
|
; ; $AF to convert to a LDA long instruction. This puts the
|
|
; ; first two bytes of the instruction field in the accumulator
|
|
; ; and falls through to the next instruction.
|
|
;
|
|
; ; We structure the line so that the entry point only needs to
|
|
; ; update the low-byte of the address, the means it takes only
|
|
; ; an amortized 4-cycles per line to set the entry pointbra
|
|
|
|
right_odd bit #$000B ; Check the bottom nibble to quickly identify a PEA instruction
|
|
beq r_is_pea ; This costs 6 cycles in the fast-path
|
|
|
|
bit #$0040 ; Check bit 6 to distinguish between JMP and all of the LDA variants
|
|
bne r_is_jmp
|
|
|
|
long_1 stal *+4-base
|
|
dfb $00,$00 ; this here to avoid needing a BRA instruction back. So the fast-path
|
|
; ; gets a 1-cycle penalty, but we save 3 cycles here.
|
|
|
|
r_is_pea xba ; fast code for PEA
|
|
sep #$30
|
|
pha
|
|
rep #$30
|
|
odd_entry jmp $0100 ; unconditionally jump into the "next" instruction in the
|
|
; ; code field. This is OK, even if the entry point was the
|
|
; ; last instruction, because there is a JMP at the end of
|
|
; ; the code field, so the code will simply jump to that
|
|
; ; instruction directly.
|
|
; ;
|
|
; ; As with the original entry point, because all of the
|
|
; ; code field is page-aligned, only the low byte needs to
|
|
; ; be updated when the scroll position changes
|
|
|
|
r_is_jmp sep #$41 ; Set the C and V flags which tells a snippet to push only the low byte
|
|
long_2 ldal entry_jmp+1-base
|
|
long_3 stal *+5-base
|
|
dfb $4C,$00,$00 ; Jump back to address in entry_jmp (this takes 16 cycles, is there a better way?)
|
|
|
|
; This is the spot that needs to be page-aligned. In addition to simplifying the entry address
|
|
; and only needing to update a byte instad of a word, because the code breaks out of the
|
|
; code field with a BRA instruction, we keep everything within a page to avoid the 1-cycle
|
|
; page-crossing penalty of the branch.
|
|
ds 204
|
|
loop_exit_1 jmp odd_exit-base ; +0 Alternate exit point depending on whether the left edge is
|
|
loop_exit_2 jmp even_exit-base ; +3 odd-aligned
|
|
|
|
loop lup 82 ; +6 Set up 82 PEA instructions, which is 328 pixels and consumes 246 bytes
|
|
pea $0000 ; This is 41 8x8 tiles in width. Need to have N+1 tiles for screen overlap
|
|
--^
|
|
loop_back jmp loop-base ; +252 Ensure execution continues to loop around
|
|
loop_exit_3 jmp even_exit-base ; +255
|
|
|
|
odd_exit lda #0000 ; This operand field is *always* used to hold the original 2 bytes of the code field
|
|
; ; that are replaced by the needed BRA instruction to exit the code field. When the
|
|
; ; left edge is odd-aligned, we are able to immediately load the value and perform
|
|
; ; similar logic to the right_odd code path above
|
|
|
|
left_odd bit #$000B
|
|
beq l_is_pea
|
|
|
|
bit #$0040
|
|
bne l_is_jmp
|
|
|
|
long_4 stal *+4-base
|
|
dfb $00,$00
|
|
l_is_pea xba
|
|
sep #$30
|
|
pha
|
|
rep #$30
|
|
bra even_exit
|
|
l_is_jmp sep #$01 ; Set the C flag (V is always cleared at this point) which tells a snippet to push only the high byte
|
|
long_5 ldal entry_jmp+1-base
|
|
long_6 stal *+5-base
|
|
dfb $4C,$00,$00 ; Jump back to address in entry_jmp (this takes 13 cycles, is there a better way?)
|
|
|
|
; JMP opcode = $4C, JML opcode = $5C
|
|
even_exit jmp $1000 ; Jump to the next line.
|
|
ds 1 ; space so that the last line in a bank can be patched into a JML
|
|
full_return jml blt_return ; Full exit
|
|
|
|
; Special epilogue: skip a number of bytes and jump back into the code field. This is useful for
|
|
; large, floating panels in the attract mode of a game, or to overlay solid
|
|
; dialog.
|
|
|
|
epilogue_1 tsc
|
|
sec
|
|
sbc #0
|
|
tcs
|
|
jmp $0000 ; This jumps back into the code field
|
|
:out jmp $0000 ; This jumps to the next epilogue chain element
|
|
ds 1
|
|
|
|
; Special epilogue: re-enable interrupts. Used every 8 or 16 lines to allow music to continue playing
|
|
epilogue_2 ldal STATE_REG ; Read Bank 0 / Write Bank 0
|
|
and #$FFCF
|
|
stal STATE_REG
|
|
ldal stk_save ; restore the stack
|
|
tcs
|
|
cli
|
|
nop ; Give a couple of cycles
|
|
sei
|
|
ldal STATE_REG
|
|
ora #$0010 ; Read Bank 0 / Write Bank 1
|
|
stal STATE_REG
|
|
jmp $0000
|
|
ds 1
|
|
|
|
; These are the special code snippets -- there is a 1:1 relationship between each snippet space
|
|
; and a 3-byte entry in the code field. Thus, each snippet has a hard-coded JMP to return to
|
|
; the next code field location
|
|
;
|
|
; The snippet is required to handle the odd-alignment in-line; there is no facility for
|
|
; patching or intercepting these values due to their complexity. The only requirements
|
|
; are:
|
|
;
|
|
; 1. Carry Clear -> 16-bit write and return to the next code field operand
|
|
; 2. Carry Set
|
|
; a. Overflow set -> Low 8-bit write and return to the next code field operand
|
|
; b. Overflow clear -> High 8-bit write and exit the line
|
|
; c. Always clear the Carry flags. It's actually OK to leave the overflow bit in
|
|
; its passed state, because having the carry bit clear prevent evaluation of
|
|
; the V bit.
|
|
;
|
|
; Snippet Samples:
|
|
;
|
|
; Standard Two-level Mix (27 bytes)
|
|
;
|
|
; Optimal = 18 cycles (LDA/AND/ORA/PHA)
|
|
; 16-bit write = 23 cycles
|
|
; 8-bit low = 35 cycles
|
|
; 8-bit high = 36 cycles
|
|
;
|
|
; start lda (00),y
|
|
; and #MASK
|
|
; ora #DATA ; 14 cycles to load the data
|
|
; bcs 8_bit
|
|
; pha
|
|
; out jmp next ; Fast-path completes in 9 additional cycles
|
|
|
|
; 8_bit sep #$30 ; Switch to 8 bit mode
|
|
; bvs r_edge ; Need to switch if doing the left edge
|
|
; xba
|
|
; r_edge pha ; push the value
|
|
; rep #$31 ; put back into 16-bit mode and clear the carry bit, as required
|
|
; bvs out ; jmp out and continue if this is the right edge
|
|
; jmp even_exit ; exit the line otherwise
|
|
; ;
|
|
; ; The slow paths have 21 and 22 cycles for the right and left
|
|
; ; odd-aligned cases respectively.
|
|
|
|
; snippets ds 32*82
|
|
top
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|