Eliminate redundent register loads
This commit is contained in:
Lucas Scharenbroich
parent
f5a27362a7
commit
0f920acd03
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@ -33,8 +33,8 @@ _RestoreBG0Opcodes
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lda LastPatchOffset ; If zero, there are no saved opcodes
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sta :exit_offset
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:loop
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ldx :virt_line_x2
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:loop
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ldal BTableLow,x ; Get the address of the first code field line
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tay
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@ -47,8 +47,7 @@ _RestoreBG0Opcodes
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txa ; lda :virt_line_x2
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and #$001E
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eor #$FFFF
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inc
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clc
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sec
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adc #32
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min :lines_left_x2
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sta :draw_count_x2 ; Do half of this many lines
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@ -60,12 +59,13 @@ _RestoreBG0Opcodes
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clc
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adc :exit_offset ; Add some offsets to get the base address in the code field line
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jsr RestoreOpcode
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jsr (RestoreOpcode,x)
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lda :virt_line_x2 ; advance to the virtual line after the segment we just
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clc ; filled in
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adc :draw_count_x2
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sta :virt_line_x2
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tax
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lda :lines_left_x2 ; subtract the number of lines we just completed
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sec
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@ -113,16 +113,16 @@ _ApplyBG0XPosPre
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_ApplyBG0XPos
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:virt_line equ tmp1
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:lines_left equ tmp2
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:draw_count equ tmp3
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:stk_save equ tmp0
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:virt_line_x2 equ tmp1
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:lines_left_x2 equ tmp2
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:draw_count_x2 equ tmp3
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:exit_offset equ tmp4
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:entry_offset equ tmp5
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:exit_bra equ tmp6
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:exit_address equ tmp7
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:base_address equ tmp8
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:draw_count_x2 equ tmp9
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:opcode equ tmp0
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:opcode equ tmp9
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:odd_entry_offset equ tmp10
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; If there are saved opcodes that have not been restored, do not run this routine
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@ -133,10 +133,12 @@ _ApplyBG0XPos
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; This code is fairly succinct. See the corresponding code in Vert.s for more detailed comments.
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:ok
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lda StartYMod208 ; This is the base line of the virtual screen
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sta :virt_line ; Keep track of it
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asl
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sta :virt_line_x2 ; Keep track of it
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lda ScreenHeight
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sta :lines_left
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asl
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sta :lines_left_x2
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; Calculate the exit and entry offsets into the code fields. This is a bit tricky, because odd-aligned
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; rendering causes the left and right edges to move in a staggered fashion.
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@ -280,32 +282,30 @@ _ApplyBG0XPos
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; 3. Writes the JMP entry point to enter the code field
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phb ; Save the existing bank
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tsc
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sta :stk_save
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:loop
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lda :virt_line
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asl ; This will clear the carry bit
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tax
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ldx :virt_line_x2
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ldal BTableLow,x ; Get the address of the first code field line
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tay ; Save it to use as the base address
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clc
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adc :exit_offset ; Add some offsets to get the base address in the code field line
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sta :exit_address
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sty :base_address
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sep #$20
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ldal BTableHigh,x
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pha
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plb ; This is the bank that will receive the updates
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rep #$20
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plb
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lda :virt_line
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and #$000F
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txa
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and #$001E
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eor #$FFFF
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inc
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clc
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adc #16
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min :lines_left
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sec
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adc #32
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min :lines_left_x2
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sta :draw_count ; Do this many lines
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asl
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sta :draw_count_x2
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; First step is to set the BRA instruction to exit the code field at the proper location. There
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@ -317,64 +317,63 @@ _ApplyBG0XPos
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; screen
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; y is already set to :base_address
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tax ; :draw_count_x2
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lda :exit_address ; Save from this location
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jsr SaveOpcode
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clc ; advance to the virtual line after the segment we just
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adc :virt_line_x2 ; filled in
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sta :virt_line_x2
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lda :exit_address ; Save from this location
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jsr (SaveOpcode,x) ; X = :exit_address on return
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txy ; ldy :exit_address -- starting at this address
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ldx :draw_count_x2 ; Do this many lines
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lda :exit_bra ; Copy this value into all of the lines
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ldy :exit_address ; starting at this address
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jsr SetConst
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jsr (SetConst,x) ; All registers are preserved
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; Next, patch in the CODE_ENTRY value, which is the low byte of a JMP instruction. This is an
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; 8-bit operation and, since the PEA code is bank aligned, we use the entry_offset value directly
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sep #$20
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ldx :draw_count_x2
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; ldx :draw_count_x2
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lda :entry_offset
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ldy :base_address
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jsr SetCodeEntry
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jsr (SetCodeEntry,x) ; All registers are preserved
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; Now, patch in the opcode
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ldx :draw_count_x2
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; ldx :draw_count_x2
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lda :opcode
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ldy :base_address ; Y-register is preserved, this can be removed
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jsr SetCodeEntryOpcode
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jsr (SetCodeEntryOpcode,x) ; All registers are preserved
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; If this is an odd entry, also set the odd_entry low byte and save the operand high byte
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lda :odd_entry_offset
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beq :not_odd
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ldx :draw_count_x2
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ldy :base_address ; Y-register is preserved, this can be removed
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jsr SetOddCodeEntry
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; NOTE: SetOddCodeEntry and SaveHighOperand can probably be combined to eliminate call/return overhead
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ldx :draw_count_x2
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ldy :base_address ; Y-register is preserved, this can be removed
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pei :exit_address
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jmp :SaveHighOperand ; Only used once, so "inline" it
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; ldx :draw_count_x2
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jsr (SetOddCodeEntry,x) ; All registers are preserved
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; ldx :draw_count_x2
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jmp (:SaveHighOperand,x) ; Only used once, so "inline" it
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:save_high_op_rtn
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:not_odd
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rep #$20
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rep #$21 ; clear the carry
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; Do the end of the loop -- update the virtual line counter and reduce the number
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; of lines left to render
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lda :virt_line ; advance to the virtual line after the segment we just
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clc ; filled in
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adc :draw_count
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sta :virt_line
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lda :lines_left ; subtract the number of lines we just completed
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lda :lines_left_x2 ; subtract the number of lines we just completed
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sec
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sbc :draw_count
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sta :lines_left
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sbc :draw_count_x2
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sta :lines_left_x2
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jne :loop
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lda :stk_save
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tcs
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plb
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rts
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@ -387,45 +386,43 @@ _ApplyBG0XPos
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; Y = starting line * $1000
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; A = code field location * $1000
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:SaveHighOperand
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jmp (:tbl,x)
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:tbl da :bottom
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da :bottom
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da :do01,:do02,:do03,:do04
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da :do05,:do06,:do07,:do08
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da :do09,:do10,:do11,:do12
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da :do13,:do14,:do15,:do16
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:do15 plx
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:do15 ldx :exit_address ; accumulator is in 8-bit mode, so can't use TAX
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bra :x15
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:do14 plx
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:do14 ldx :exit_address
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bra :x14
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:do13 plx
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:do13 ldx :exit_address
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bra :x13
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:do12 plx
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:do12 ldx :exit_address
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bra :x12
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:do11 plx
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:do11 ldx :exit_address
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bra :x11
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:do10 plx
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:do10 ldx :exit_address
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bra :x10
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:do09 plx
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:do09 ldx :exit_address
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bra :x09
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:do08 plx
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:do08 ldx :exit_address
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bra :x08
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:do07 plx
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:do07 ldx :exit_address
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bra :x07
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:do06 plx
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:do06 ldx :exit_address
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bra :x06
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:do05 plx
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:do05 ldx :exit_address
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bra :x05
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:do04 plx
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:do04 ldx :exit_address
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bra :x04
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:do03 plx
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:do03 ldx :exit_address
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bra :x03
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:do02 plx
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:do02 ldx :exit_address
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bra :x02
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:do01 plx
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:do01 ldx :exit_address
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bra :x01
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:do16 plx
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:do16 ldx :exit_address
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:x16 lda $F002,x
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sta OPCODE_HIGH_SAVE+$F000,y
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:x15 lda $E002,x
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@ -469,9 +466,7 @@ _ApplyBG0XPos
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; Y = starting line * $1000
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; A = code field location * $1000
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SaveOpcode
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jmp (:tbl,x)
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:tbl da :bottom
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da :bottom
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da :do01,:do02,:do03,:do04
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da :do05,:do06,:do07,:do08
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da :do09,:do10,:do11,:do12
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@ -550,9 +545,7 @@ SaveOpcode
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; Y = starting line * $1000
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; A = code field location * $1000
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RestoreOpcode
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jmp (:tbl,x)
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:tbl da :bottom
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da :bottom
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da :do01,:do02,:do03,:do04
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da :do05,:do06,:do07,:do08
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da :do09,:do10,:do11,:do12
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@ -631,8 +624,7 @@ RestoreOpcode
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; Y = starting line * $1000
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; A = address low byte
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SetCodeEntry
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jmp (:tbl,x)
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:tbl da :bottom-00,:bottom-03,:bottom-06,:bottom-09
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da :bottom-00,:bottom-03,:bottom-06,:bottom-09
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da :bottom-12,:bottom-15,:bottom-18,:bottom-21
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da :bottom-24,:bottom-27,:bottom-30,:bottom-33
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da :bottom-36,:bottom-39,:bottom-42,:bottom-45
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@ -663,8 +655,7 @@ SetCodeEntry
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; Y = starting line * $1000
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; A = address low byte
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SetOddCodeEntry
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jmp (:tbl,x)
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:tbl da :bottom-00,:bottom-03,:bottom-06,:bottom-09
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da :bottom-00,:bottom-03,:bottom-06,:bottom-09
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da :bottom-12,:bottom-15,:bottom-18,:bottom-21
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da :bottom-24,:bottom-27,:bottom-30,:bottom-33
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da :bottom-36,:bottom-39,:bottom-42,:bottom-45
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@ -695,8 +686,7 @@ SetOddCodeEntry
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; Y = starting line * $1000
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; A = opcode value
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SetCodeEntryOpcode
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jmp (:tbl,x)
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:tbl da :bottom-00,:bottom-03,:bottom-06,:bottom-09
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da :bottom-00,:bottom-03,:bottom-06,:bottom-09
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da :bottom-12,:bottom-15,:bottom-18,:bottom-21
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da :bottom-24,:bottom-27,:bottom-30,:bottom-33
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da :bottom-36,:bottom-39,:bottom-42,:bottom-45
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@ -87,9 +87,8 @@ Counter equ tmp3
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; A = value
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;
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; Set M to 0 or 1
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SetConst ; Need a blank line here, otherwise the :tbl local variable resolveds backwards
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jmp (:tbl,x)
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:tbl da :bottom-00,:bottom-03,:bottom-06,:bottom-09
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SetConst
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da :bottom-00,:bottom-03,:bottom-06,:bottom-09
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da :bottom-12,:bottom-15,:bottom-18,:bottom-21
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da :bottom-24,:bottom-27,:bottom-30,:bottom-33
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da :bottom-36,:bottom-39,:bottom-42,:bottom-45
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@ -7,29 +7,36 @@
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; lines in the correct order
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_ApplyBG0YPos
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:rtbl_idx equ tmp0
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:virt_line equ tmp1
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:lines_left equ tmp2
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:draw_count equ tmp3
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:rtbl_idx_x2 equ tmp0
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:virt_line_x2 equ tmp1
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:lines_left_x2 equ tmp2
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:draw_count_x2 equ tmp3
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:stk_save equ tmp4
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; First task is to fill in the STK_ADDR values by copying them from the RTable array. We
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; copy from RTable[i] into BlitField[StartY+i]. As with all of this code, the difficult part
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; is decomposing the update across banks
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stz :rtbl_idx ; Start copying from the first entry in the table
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stz :rtbl_idx_x2 ; Start copying from the first entry in the table
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lda StartY ; This is the base line of the virtual screen
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jsr Mod208
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sta StartYMod208
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sta :virt_line ; Keep track of it
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asl
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sta :virt_line_x2 ; Keep track of it
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phb ; Save the current bank
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tsc ; we intentionally leak one byte of stack in each loop
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sta :stk_save ; iteration, so save the stack to repair at the end
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; copy a range of address from the table into the destination bank. If we restrict ourselves to
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; rectangular playfields, this can be optimized to just subtracting a constant value. See the
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; Templates::SetScreenAddrs subroutine.
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lda ScreenHeight
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sta :lines_left
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asl
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sta :lines_left_x2
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; This is the verbose part -- figure out how many lines to draw. We don't want to artificially limit
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; the height of the visible screen (for example, doing an animated wipe while scrolling), so the screen
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@ -38,62 +45,47 @@ _ApplyBG0YPos
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; For larger values, we want to break things up on 16-line boundaries based on the virt_line value. So,
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;
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; draw_count = min(lines_left, (16 - (virt_line % 16))
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;
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; Note that almost everything in this loop can be done with 8-bit operations sincc the values are
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; all under 200. The one exception is the virt_line value which could exceed 256. This will be
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; a later optimization and might save around 10 cycles per iteration, or up to ~120 cycles per frame
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; and ~2,500 per secord. This is ~1% of our total CPU budget and is *just* enough cycles to be
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; interesting.... Another 8 cycles could be removed by doing all calculatinos pre-multiplied by 2
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; to avoid several 'asl' instructions
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phb
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:loop
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lda :virt_line
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asl
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tax
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ldx :virt_line_x2
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ldal BTableLow,x ; Get the address of the first code field line
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tay
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sep #$20
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ldal BTableHigh,x
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ldal BTableHigh,x ; Target bank in low byte, current bank in high
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pha
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plb ; This is the bank that will receive the updates
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rep #$20
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lda :virt_line
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and #$000F
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txa
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and #$001E
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eor #$FFFF
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inc
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clc
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adc #16
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min :lines_left
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sec
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adc #32
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min :lines_left_x2
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sta :draw_count ; Do this many lines
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asl
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sta :draw_count_x2 ; Do this many lines
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tax
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lda :rtbl_idx ; Read from this location in the RTable
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asl
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clc ; pre-advance virt_line_2 because we have the value
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adc :virt_line_x2
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sta :virt_line_x2
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jsr CopyRTableToStkAddr
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plb
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jsr (:CopyRTableToStkAddr,x) ; X = rtbl_idx_x2 on return
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lda :virt_line ; advance to the virtual line after the segment we just
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clc ; filled in
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adc :draw_count
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sta :virt_line
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txa ; carry flag is unchanged
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adc :draw_count_x2 ; advance the index into the RTable
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sta :rtbl_idx_x2
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lda :rtbl_idx ; advance the index into the RTable
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adc :draw_count
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sta :rtbl_idx
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lda :lines_left ; subtract the number of lines we just completed
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lda :lines_left_x2 ; subtract the number of lines we just completed
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sec
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sbc :draw_count
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sta :lines_left
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sbc :draw_count_x2
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sta :lines_left_x2
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jne :loop
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plb
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:out
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lda :stk_save
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tcs
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plb
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rts
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; Unrolled copy routine to move RTable intries into STK_ADDR position.
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@ -101,44 +93,43 @@ _ApplyBG0YPos
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; A = intect into the RTable array (x2)
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; Y = starting line * $1000
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; X = number of lines (x2)
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CopyRTableToStkAddr
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jmp (:tbl,x)
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:tbl da :none
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:CopyRTableToStkAddr
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da :none
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da :do01,:do02,:do03,:do04
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da :do05,:do06,:do07,:do08
|
||||
da :do09,:do10,:do11,:do12
|
||||
da :do13,:do14,:do15,:do16
|
||||
:do15 tax
|
||||
:do15 ldx :rtbl_idx_x2
|
||||
bra :x15
|
||||
:do14 tax
|
||||
:do14 ldx :rtbl_idx_x2
|
||||
bra :x14
|
||||
:do13 tax
|
||||
:do13 ldx :rtbl_idx_x2
|
||||
bra :x13
|
||||
:do12 tax
|
||||
:do12 ldx :rtbl_idx_x2
|
||||
bra :x12
|
||||
:do11 tax
|
||||
:do11 ldx :rtbl_idx_x2
|
||||
bra :x11
|
||||
:do10 tax
|
||||
:do10 ldx :rtbl_idx_x2
|
||||
bra :x10
|
||||
:do09 tax
|
||||
:do09 ldx :rtbl_idx_x2
|
||||
bra :x09
|
||||
:do08 tax
|
||||
:do08 ldx :rtbl_idx_x2
|
||||
bra :x08
|
||||
:do07 tax
|
||||
:do07 ldx :rtbl_idx_x2
|
||||
bra :x07
|
||||
:do06 tax
|
||||
:do06 ldx :rtbl_idx_x2
|
||||
bra :x06
|
||||
:do05 tax
|
||||
:do05 ldx :rtbl_idx_x2
|
||||
bra :x05
|
||||
:do04 tax
|
||||
:do04 ldx :rtbl_idx_x2
|
||||
bra :x04
|
||||
:do03 tax
|
||||
:do03 ldx :rtbl_idx_x2
|
||||
bra :x03
|
||||
:do02 tax
|
||||
:do02 ldx :rtbl_idx_x2
|
||||
bra :x02
|
||||
:do01 tax
|
||||
:do01 ldx :rtbl_idx_x2
|
||||
bra :x01
|
||||
:do16 tax
|
||||
:do16 ldx :rtbl_idx_x2
|
||||
ldal RTable+30,x
|
||||
sta STK_ADDR+$F000,y
|
||||
:x15 ldal RTable+28,x
|
||||
|
|
|
|||
Loading…
Reference in New Issue