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Add failing test for remaining opcodes.
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@ -10,18 +10,72 @@ It is expected that a common use case for SixtyPical would be retroprogramming
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for the Commodore 64 and other 6502-based computers such as the VIC-20.
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Many SixtyPical instructions map precisely to 6502 opcodes. However, SixtyPical
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is not an assembly language. The programmer does not have total control over
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the layout of code and data in memory. The language has a type system which
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distinguishes addresses from non-addresses (16-bit values for which it does
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not make sense to treat them as addresses.) Some 6502 opcodes have no
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SixtyPical equivalent. Some SixtyPical instructions are named after 6502
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opcodes, but generate slightly different (safer, but intuitively related)
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sequences of opcodes. Et cetera.
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is not an assembly language: the programmer does not have total control over
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the layout of code and data in memory. Some 6502 opcodes have no SixtyPical
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equivalent, while some have an equivalent that acts in a slightly different
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(but intuitively related) way. And some commands are unique to SixtyPical.
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`sixtypical` is the reference implementation of SixtyPical. It is written in
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Haskell. It can currently parse and check a SixtyPical program, and can
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emit an Ophis assembler listing for it.
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This distribution will soon be placed under an open-source license.
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Quick Start
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-----------
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If you have `ghc`, Ophis, and VICE 2.4 installed, clone this repo, `cd` into it,
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and run
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./loadngo.sh eg/demo.60p
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The Big Idea(s)
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---------------
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### Typed Addresses ###
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SixtyPical distinguishes several kinds of addresses: those that hold a byte,
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those that hold a word (in low-byte-high-byte sequence), those that are the
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beginning of a table of bytes, and vectors (those that hold a word pointer to a
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machine-language routine.) It prevents the program from accessing them in
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certain ways. For example, these are illegal:
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reserve byte lives
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reserve word score
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routine do_it {
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lda score ; no! can't treat word as if it were a byte
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lda lives, x ; no! can't treat a byte as if it were a table
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}
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### Abstract Interpretation ###
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SixtyPical tries to prevent the program from using data that has no meaning.
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For example, the following is illegal:
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routine do_it {
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lda #0
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jsr update_score
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sta vic_border_colour ; uh... what do we know about reg A here?
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}
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...*unless* one of the following is true:
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* the A register is declared to be a meaningful output of `update_score`
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* `update_score` was determined to not change the value of the A registers
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The first must be done with an explicit declaration on `update_score` (NYI).
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The second will be done using abstract interpretation of the code of
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`update_score` (needs to be implemented again, now, and better).
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### Structured Programming ###
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You get an `if` and a `repeat` and instructions like `sei` work like `with`
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where they are followed by a block and the `cli` instruction is implicitly
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(and unavoidably) added at the end.
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For more information, see the docs (which are written in the form of a
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Falderal literate test suite.)
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Concepts
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--------
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@ -59,7 +113,7 @@ assembler, with the understanding that the value will be treated "like an
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address." This is generally an address into the operating system or hardware
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(e.g. kernal routine, I/O port, etc.)
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Not there yet:
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Not there. yet:
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> Inside a routine, an address may be declared with `temporary`. This is like
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> `static` in C, except the value at that address is not guaranteed to be
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@ -122,7 +176,7 @@ Unsupported Opcodes
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-------------------
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6502 opcodes with no language-level equivalent instructions in SixtyPical
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are `brk`, `cli`, `pla`, `plp`, `rti`, and `rts`. These may be
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are `brk`, `cli`, `pla`, `plp`, `rti`, `rts`, `tsx`, `txs`. These may be
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inserted into the output program as a SixtyPical → 6502 compiler sees fit,
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however.
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@ -255,12 +309,8 @@ In these, `absolute` must be a `reserve`d or `locate`d address.
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tay
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X tsx
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txa
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X txs
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tya
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TODO
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@ -271,3 +321,4 @@ TODO
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* Character tables ("strings" to everybody else)
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* Work out the analyses again and document them
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* Addressing modes; rename instructions to match
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* fix jmp (vector) syntax
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@ -6,6 +6,8 @@ Emitting Ophis from SixtyPical Programs
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-> Functionality "Emit ASM for SixtyPical program" is implemented by
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-> shell command "bin/sixtypical emit %(test-file)"
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Big test for parsing and emitting instructions.
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| reserve word vword
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| reserve byte vbyte
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| assign byte table table 1024
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@ -118,6 +120,42 @@ Emitting Ophis from SixtyPical Programs
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= vbyte: .byte 0
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= .alias table 1024
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| reserve word vword
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| reserve byte vbyte
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| assign byte table table 1024
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| routine main {
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| asl
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| asl vbyte
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| lsr
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| lsr vbyte
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| rol
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| rol vbyte
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| ror
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| ror vbyte
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| bit vbyte
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| eor #5
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| eor vbyte
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| }
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= main:
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= asl
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= asl vbyte
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= lsr
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= lsr vbyte
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= rol
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= rol vbyte
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= ror
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= ror vbyte
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= bit vbyte
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= eor #5
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= eor vbyte
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= rts
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=
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= vword: .word 0
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= vbyte: .byte 0
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= .alias table 1024
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Emitting an `if`.
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| assign byte screen $0400
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| routine main {
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| lda screen
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@ -143,6 +181,8 @@ Emitting Ophis from SixtyPical Programs
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=
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= .alias screen 1024
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Emitting a `repeat`.
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| assign byte screen 1024
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| reserve byte zero
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| routine main {
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