mirror of https://github.com/safiire/n65.git
Fixed an issue with referencing outer scoped symbols
This commit is contained in:
Safiire
parent
411e8b9873
commit
a48d10474e
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@ -1,55 +0,0 @@
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; Create an iNES header
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.ines {"prog": 1, "char": 1, "mapper": 0, "mirror": 1}
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; Main code segment
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.org $C000
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start:
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SEI ; disable IRQs
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CLD ; disable decimal mode
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LDX #$40
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STX $4017 ; disable APU frame IRQ
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LDX #$FF
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TXS ; Set up stack
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INX ; now X = 0
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STX $2000 ; disable NMI
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STX $2001 ; disable rendering
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STX $4010 ; disable DMC IRQs
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vblankwait1: ; First wait for vblank to make sure PPU is ready
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BIT $2002
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BPL vblankwait1
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clrmem:
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LDA #$00
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STA $0000, X
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STA $0100, X
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STA $0200, X
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STA $0400, X
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STA $0500, X
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STA $0600, X
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STA $0700, X
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LDA #$FE
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STA $0300, X
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INX
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BNE clrmem
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vblankwait2: ; Second wait for vblank, PPU is ready after this
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BIT $2002
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BPL vblankwait2
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LDA #$60 ;intensify blues
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STA $2001
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forever:
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JMP forever ;jump back to Forever, infinite loop
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nmi:
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RTI
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.org $FFFA ;first of the three vectors starts here
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.dw nmi ;when an NMI happens (once per frame if enabled) the processor will jump to the label NMI:
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.dw start ;when the processor first turns on or is reset, it will jump to the label RESET:
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.dw $0 ;external interrupt IRQ is not used in this tutorial
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@ -1,9 +1,9 @@
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; Create an iNES header
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.ines {"prog": 1, "char": 0, "mapper": 0, "mirror": 1}
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; Create an iNES header
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.ines {"prog": 1, "char": 0, "mapper": 0, "mirror": 1}
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; Here is the start of our code
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.org $C000
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start:
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.org $C000
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.scope main
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LDA #$01 ; square 1
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STA $4015
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LDA #$F8 ; period low
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@ -12,13 +12,13 @@ start:
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STA $4003
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LDA #$BF ; volume
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STA $4000
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forever:
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JMP forever
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forever:
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JMP forever
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nmi:
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nothing:
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RTI
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.org $FFFA ; Here are the three interrupt vectors
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.dw nmi ; VBlank non-maskable interrupt
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.dw start ; When the processor is reset or powers on
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.dw $0 ; External interrupt IRQ
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.dw nothing ; VBlank non-maskable interrupt
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.dw main ; When the processor is reset or powers on
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.dw nothing ; External interrupt IRQ
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@ -239,7 +239,7 @@
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;;;;
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; Update the sprite, I don't exactly understand the DMA call yet.
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update_sprite:
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.scope update_sprite
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lda #>sprite
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sta nes.sprite.dma ; Jam page $200-$2FF into SPR-RAM, how do we get these numbers?
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lda sprite.x
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@ -262,11 +262,12 @@ update_sprite:
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adc dx zp
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sta sprite.x
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rts
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.
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;;;;
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; Read the first controller, and handle input
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react_to_input:
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.scope react_to_input
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lda #$01 ; strobe joypad
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sta nes.controller1
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lda #$00
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@ -306,11 +307,12 @@ react_to_input:
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stx sprite.y
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not_dn:
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rts ; Ignore left and right
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.
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;;;;
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; XORing with $ff toggles between 0x1 and 0xfe (-1)
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reverse_dx:
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.scope reverse_dx
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lda #$FF
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eor dx zp
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clc
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@ -318,30 +320,32 @@ reverse_dx:
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sta dx zp
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jsr low_c ; Play the reverse low C note
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rts
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.
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;;;;
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; Scroll the screen if we have to
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scroll_screen:
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.scope scroll_screen
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ldx #$00 ; Reset VRAM Address to $0000
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stx nes.vram.address
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stx nes.vram.address
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ldx scroll zp ; Do we need to scroll at all?
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beq no_scroll
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beq return
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dex
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stx scroll zp
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lda #$00
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sta nes.ppu.scroll ; Write 0 for Horiz. Scroll value
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stx nes.ppu.scroll ; Write the value of 'scroll' for Vert. Scroll value
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no_scroll:
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return:
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rts
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.
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;;;;
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; Play a low C note on square 1
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low_c:
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.scope low_c
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pha
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lda #$84
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sta nes.apu.pulse1.control
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@ -351,11 +355,12 @@ low_c:
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sta nes.apu.pulse1.ct
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pla
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rts
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.
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;;;;
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; Play a high C note on square 1
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high_c:
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.scope high_c
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pha
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lda #$86
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sta nes.apu.pulse1.control
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@ -365,15 +370,17 @@ high_c:
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sta nes.apu.pulse1.ct
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pla
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rts
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.
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;;;;
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; Update everything on every vblank
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vblank:
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.scope vblank
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jsr scroll_screen
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jsr update_sprite
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jsr react_to_input
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rti
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.
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;;;;
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@ -9,13 +9,6 @@
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; Create an iNES header
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.ines {"prog": 1, "char": 0, "mapper": 0, "mirror": 0}
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;;;;
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; Here is a good spot to associate zero page memory addresses
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; with quick access variables in the program.
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.org $0200
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sprite:
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;;;;
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; Setup the interrupt vectors
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@ -28,7 +21,7 @@ sprite:
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.org $C000
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;;;;
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; Here is our code entry point, which we'll call main.
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main:
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.scope main
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; Disable interrupts and decimal flag
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sei
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cld
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@ -85,15 +78,16 @@ main:
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cli
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forever:
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jmp forever
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.
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;;;;
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; Update everything on every vblank
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vblank:
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vblank:
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rti
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;;;;
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; Don't do anything on IRQ
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irq:
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irq:
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rti
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@ -1,30 +0,0 @@
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;;;;
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; Create an iNES header
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.ines {"prog": 1, "char": 0, "mapper": 0, "mirror": 0}
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;;;;
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;; Start a prog segment number 0
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.segment prog 0
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.org $8000
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.scope main
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sei
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cld
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loop:
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ldx $00
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inx
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stx $00
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jmp loop
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.
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vblank:
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irq:
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rti
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;;;;
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;; Vector table
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.org $FFFA
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.dw vblank
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.dw main
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.dw irq
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@ -67,6 +67,23 @@ module Assembler6502
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end
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####
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## Return an object that contains the assembler's current state
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def get_current_state
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saved_program_counter, saved_segment, saved_bank = @program_counter, @current_segment, @current_bank
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saved_scope = symbol_table.scope_stack.dup
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OpenStruct.new(program_counter: saved_program_counter, segment: saved_segment, bank: saved_bank, scope: saved_scope)
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end
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####
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## Set the current state from an OpenStruct
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def set_current_state(struct)
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@program_counter, @current_segment, @current_bank = struct.program_counter, struct.segment, struct.bank
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symbol_table.scope_stack = struct.scope.dup
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end
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####
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## This is the main assemble method, it parses one line into an object
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## which when given a reference to this assembler, controls the assembler
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@ -95,6 +112,23 @@ module Assembler6502
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end
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####
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## This rewinds the state of the assembler, so a promise can be
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## executed with a previous state, for example if we can't resolve
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## a symbol right now, and want to try during the second pass
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def with_saved_state(&block)
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## Save the current state of the assembler
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old_state = get_current_state
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lambda do
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## Set the assembler state back to the old state and run the block like that
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set_current_state(old_state)
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block.call(self)
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end
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end
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####
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## Write to memory space. Typically, we are going to want to write
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## to the location of the current PC, current segment, and current bank.
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@ -43,18 +43,13 @@ module Assembler6502
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## This is a little complicated, I admit.
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def exec(assembler)
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## Save these current values into the closure
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pc = assembler.program_counter
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segment = assembler.current_segment
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bank = assembler.current_bank
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## Create a promise, if this symbol is not defined yet.
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promise = lambda do
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value = assembler.symbol_table.resolve_symbol(@value)
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promise = assembler.with_saved_state do |saved_assembler|
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value = saved_assembler.symbol_table.resolve_symbol(@value)
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bytes = [value & 0xFFFF].pack('S').bytes
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assembler.write_memory(bytes, pc, segment, bank)
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saved_assembler.write_memory(bytes)
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end
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## Try to execute it now, or setup the promise to return
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case @value
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when Fixnum
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@ -66,7 +61,7 @@ module Assembler6502
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rescue SymbolTable::UndefinedSymbol
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## Must still advance PC before returning promise, so we'll write
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## a place holder value of 0xDEAD
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assembler.write_memory([0xDE, 0xAD], pc, segment, bank)
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assembler.write_memory([0xDE, 0xAD])
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return promise
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end
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else
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@ -147,7 +147,6 @@ module Assembler6502
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if match_array.size == 4
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_, op, byte_selector, arg = match_array
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return Instruction.new(op, arg, mode, byte_selector.to_sym)
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puts "I found one with #{byte_selector} #{arg}"
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else
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_, op, arg = match_array
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return Instruction.new(op, arg, mode)
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@ -204,22 +203,16 @@ module Assembler6502
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## promise to resolve it later.
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def exec(assembler)
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## Save these current values into the closure/promise
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pc = assembler.program_counter
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segment = assembler.current_segment
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bank = assembler.current_bank
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## Create a promise if this symbol is not defined yet.
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promise = lambda do
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@arg = assembler.symbol_table.resolve_symbol(@arg)
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promise = assembler.with_saved_state do |saved_assembler|
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@arg = saved_assembler.symbol_table.resolve_symbol(@arg)
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## If the instruction uses a byte selector, we need to apply that.
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@arg = apply_byte_selector(@byte_selector, @arg)
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## If the instruction is relative we need to work out how far away it is
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@arg = @arg - pc - 2 if @mode == :relative
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@arg = @arg - saved_assembler.program_counter - 2 if @mode == :relative
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assembler.write_memory(emit_bytes, pc, segment, bank)
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saved_assembler.write_memory(emit_bytes)
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end
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case @arg
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@ -234,7 +227,7 @@ module Assembler6502
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placeholder = [@hex, 0xDE, 0xAD][0...@length]
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## I still have to write a placeholder instruction of the right
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## length. The promise will come back and resolve the address.
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assembler.write_memory(placeholder, pc, segment, bank)
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assembler.write_memory(placeholder)
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return promise
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end
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end
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@ -1,7 +1,9 @@
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require 'pry-byebug'
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module Assembler6502
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class SymbolTable
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attr_accessor :scope_stack
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##### Custom Exceptions
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class InvalidScope < StandardError; end
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@ -54,6 +56,7 @@ module Assembler6502
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end
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=begin
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####
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## Resolve symbol to a value, for example:
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## scope1.scope2.variable
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@ -61,7 +64,7 @@ module Assembler6502
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## You can just address anything by name in the current scope
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## To go backwards in scope you need to write the full path
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## like global.sprite.x or whatever
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def resolve_symbol(name)
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def resolve_symbol_old(name)
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value = if name.include?('.')
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path_ary = name.split('.').map(&:to_sym)
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@ -85,6 +88,57 @@ module Assembler6502
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end
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value
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end
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=end
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####
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##
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def resolve_symbol(name)
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method = name.include?('.') ? :resolve_symbol_dot_syntax : :resolve_symbol_scoped
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value = self.send(method, name)
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fail(UndefinedSymbol, name) if value.nil?
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value
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end
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####
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## Resolve symbol by working backwards through each
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## containing scope. Similarly named scopes shadow outer scopes
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def resolve_symbol_scoped(name)
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root = "-#{name}".to_sym
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stack = @scope_stack.dup
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loop do
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scope = retreive_scope(stack)
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## We see if there is a key either under this name, or root
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v = scope[name.to_sym] || scope[root]
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v = v.kind_of?(Hash) ? v[root] : v
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return v unless v.nil?
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## Pop the stack so we can decend to the parent scope, if any
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stack.pop
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return nil if stack.empty?
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end
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end
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####
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## Dot syntax means to check an absolute path to the symbol
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## :global is ignored if it is provided as part of the path
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def resolve_symbol_dot_syntax(name)
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path_ary = name.split('.').map(&:to_sym)
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symbol = path_ary.pop
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root = "-#{symbol}".to_sym
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path_ary.shift if path_ary.first == :global
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scope = retreive_scope(path_ary)
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## We see if there is a key either under this name, or root
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v = scope[symbol]
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v.kind_of?(Hash) ? v[root] : v
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end
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####
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@ -28,6 +28,34 @@ class TestSymbolTable < MiniTest::Test
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end
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####
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## Access something from an outer scope without dot syntax
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def test_outer_scope
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st = SymbolTable.new
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st.enter_scope('outer')
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st.define_symbol('dog', 'woof')
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st.enter_scope('inner')
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st.define_symbol('pig', 'oink')
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assert_equal('woof', st.resolve_symbol('dog'))
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end
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####
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## Access something from an outer scope without dot syntax
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def test_shadow
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st = SymbolTable.new
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st.enter_scope('outer')
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st.define_symbol('dog', 'woof')
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st.enter_scope('inner')
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st.define_symbol('dog', 'bark')
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assert_equal('bark', st.resolve_symbol('dog'))
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assert_equal('woof', st.resolve_symbol('outer.dog'))
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st.exit_scope
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st.exit_scope
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assert_equal('bark', st.resolve_symbol('outer.inner.dog'))
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end
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####
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## Test exiting a sub scope, and seeing that the variable is unavailable by simple name
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def test_exit_scope
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@ -153,5 +181,58 @@ class TestSymbolTable < MiniTest::Test
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assert_equal(0x8000, assembler.symbol_table.resolve_symbol('global.main'))
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end
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####
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## Fix a bug where we can't see a forward declared symbol in a scope
|
||||
def test_foward_declaration_in_scope
|
||||
program = <<-ASM
|
||||
;;;;
|
||||
; Create an iNES header
|
||||
.ines {"prog": 1, "char": 0, "mapper": 0, "mirror": 0}
|
||||
|
||||
;;;;
|
||||
; Try to expose a problem we have with scopes
|
||||
; We don't seem to be able to branch to a forward
|
||||
; declared symbol within a scope
|
||||
.org $8000
|
||||
.scope main
|
||||
sei
|
||||
cld
|
||||
lda #\$00
|
||||
bne forward_symbol
|
||||
nop
|
||||
nop
|
||||
nop
|
||||
forward_symbol:
|
||||
rts
|
||||
.
|
||||
ASM
|
||||
|
||||
#### There really should be an evaluate string method
|
||||
assembler = Assembler.new
|
||||
program.split(/\n/).each do |line|
|
||||
assembler.assemble_one_line(line)
|
||||
end
|
||||
puts YAML.dump(assembler.symbol_table)
|
||||
assembler.fulfill_promises
|
||||
|
||||
#### The forward symbol should have been resolved to +3, and the ROM should look like this:
|
||||
correct_rom = [0x4e, 0x45, 0x53, 0x1a, 0x1, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
|
||||
0x78, # SEI
|
||||
0xd8, # CLD
|
||||
0xa9, 0x0, # LDA immediate 0
|
||||
0xd0, 0x3, # BNE +3
|
||||
0xea, # NOP
|
||||
0xea, # NOP
|
||||
0xea, # NOP
|
||||
0x60 # RTS forward_symbol
|
||||
]
|
||||
|
||||
#### Grab the first 26 bytes of the rom and make sure they assemble to the above
|
||||
emitted_rom = assembler.emit_binary_rom.bytes[0...26]
|
||||
assert_equal(correct_rom, emitted_rom)
|
||||
#### Yup it is fixed now.
|
||||
end
|
||||
|
||||
end
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue