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90 lines
3.4 KiB
Markdown
90 lines
3.4 KiB
Markdown
SixtyPical
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==========
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_Version 0.11. Work-in-progress, everything is subject to change._
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SixtyPical is a very low-level programming language, similar to 6502 assembly,
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with static analysis through abstract interpretation.
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In practice, this means it catches things like
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* you forgot to clear carry before adding something to the accumulator
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* a subroutine that you call trashes a register you thought was preserved
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* you tried to write the address of something that was not a routine, to
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a jump vector
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and suchlike. It also provides some convenient operations and abstractions
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based on common machine-language programming idioms, such as
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* copying values from one register to another (via a third register when
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there are no underlying instructions that directly support it)
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* explicit tail calls
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* indirect subroutine calls
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The reference implementation can analyze and compile SixtyPical programs to
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6502 machine code.
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Documentation
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-------------
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* [Design Goals](doc/Design%20Goals.md)
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* [SixtyPical specification](doc/SixtyPical.md)
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* [SixtyPical revision history](HISTORY.md)
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* [Literate test suite for SixtyPical syntax](tests/SixtyPical%20Syntax.md)
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* [Literate test suite for SixtyPical execution](tests/SixtyPical%20Execution.md)
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* [Literate test suite for SixtyPical analysis](tests/SixtyPical%20Analysis.md)
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* [Literate test suite for SixtyPical compilation](tests/SixtyPical%20Compilation.md)
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* [6502 Opcodes used/not used in SixtyPical](doc/6502%20Opcodes.md)
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TODO
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----
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### Demo game
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Finish the little demo "game" where you can move a block around the screen with
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the joystick (i.e. bring it up to par with the original demo game that was written
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for SixtyPical)
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### `low` and `high` address operators
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To turn `word` type into `byte`.
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### Save registers on stack
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This preserves them, so that, semantically, they can be used later even though they
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are trashed inside the block.
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### Range checking in the abstract interpretation
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If you copy the address of a buffer (say it is size N) to a pointer, it is valid.
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If you add a value from 0 to N-1 to the pointer, it is still valid.
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But if you add a value ≥ N to it, it becomes invalid.
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This should be tracked in the abstract interpretation.
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(If only because abstract interpretation is the major point of this project!)
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### Routine-local static memory locations
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These would not need to appear in the inputs/outputs/trashes sets of the routines
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that call this routine.
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These might be forced to specify an initial value so that they can always be
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assumed to be meaningful.
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### More modes for `copy`
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* don't allow `copy foo, a` probably. insist on `ld a, foo` for this.
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* have `copy` instruction able to copy a byte to a user-def mem loc, etc.
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* `copy x, [ptr] + y`
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* Maybe even `copy [ptra] + y, [ptrb] + y`, which can be compiled to indirect LDA then indirect STA!
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### And at some point...
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* Check that the buffer being read or written to through pointer, appears in approporiate inputs or outputs set.
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* always analyze before executing or compiling, unless told not to
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* `interrupt` routines -- to indicate that "the supervisor" has stored values on the stack, so we can trash them.
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* error messages that include the line number of the source code
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* add absolute addressing in shl/shr, absolute-indexed for add, sub, etc.
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* check and disallow recursion.
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* automatic tail-call optimization (could be tricky, w/constraints?)
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* re-order routines and optimize tail-calls to fallthroughs
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