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90 lines
6.2 KiB
ReStructuredText
90 lines
6.2 KiB
ReStructuredText
TODO
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====
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- IR: reduce the number of branch instructions such as BEQ, BEQR, etc (gradually), replace with CMP(I) + status branch instruction
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- IR: reduce amount of CMP/CMPI after instructions that set the status bits correctly (LOADs? INC? etc), but only after setting the status bits is verified!
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...
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Need help with
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^^^^^^^^^^^^^^
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- getting the IR in shape for code generation
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- atari target: more details details about the machine, fixing library routines. I have no clue whatsoever.
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- see the :ref:`portingguide` for details on what information is needed.
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Future Things and Ideas
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^^^^^^^^^^^^^^^^^^^^^^^
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Compiler:
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- [much work:] more support for (64tass) SEGMENTS ?
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- (What, how, isn't current BSS support enough?)
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- Add a mechanism to allocate variables into golden ram (or segments really) (see GoldenRam class)
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- maybe treat block "golden" in a special way: can only contain vars, every var will be allocated in the Golden ram area?
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- maybe or may not needed: the variables can NOT have initialization values, they will all be set to zero on startup (simple memset)
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just initialize them yourself in start() if you need a non-zero value .
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- OR.... do all this automatically if 'golden' is enabled as a compiler option? So compiler allocates in ZP first, then Golden Ram, then regular ram
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- OR.... make all this more generic and use some %segment option to create real segments for 64tass?
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- (need separate step in codegen and IR to write the "golden" variables)
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- ir: idea: (but LLVM IR simply keeps the variables, so not a good idea then?...): replace all scalar variables by an allocated register. Keep a table of the variable to register mapping (including the datatype)
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global initialization values are simply a list of LOAD instructions.
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Variables replaced include all subroutine parameters! So the only variables that remain as variables are arrays and strings.
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- ir: add more optimizations in IRPeepholeOptimizer
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- ir: the @split arrays are currently also split in _lsb/_msb arrays in the IR, and operations take multiple (byte) instructions that may lead to verbose and slow operation and machine code generation down the line.
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- ir: for expressions with array indexes that occur multiple times, can we avoid loading them into new virtualregs everytime and just reuse a single virtualreg as indexer? (simple form of common subexpression elimination)
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- PtAst/IR: more complex common subexpression eliminations
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- can we get rid of pieces of asmgen.AssignmentAsmGen by just reusing the AugmentableAssignment ? generated code should not suffer
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- [problematic due to using 64tass:] better support for building library programs, where unused .proc shouldn't be deleted from the assembly?
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Perhaps replace all uses of .proc/.pend/.endproc by .block/.bend will fix that with a compiler flag?
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But all library code written in asm uses .proc already..... (textual search/replace when writing the actual asm?)
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Once new codegen is written that is based on the IR, this point is mostly moot anyway as that will have its own dead code removal on the IR level.
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- Zig-like try-based error handling where the V flag could indicate error condition? and/or BRK to jump into monitor on failure? (has to set BRK vector for that) But the V flag is also set on certain normal instructions
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- generate WASM to eventually run prog8 on a browser canvas? Use binaryen toolkit or my binaryen kotlin library?
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Libraries:
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- fix the problems in atari target, and flesh out its libraries.
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- c128 target: make syslib more complete (missing kernal routines)?
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- c64: make the graphics.BITMAP_ADDRESS configurable (VIC banking)
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- optimize several inner loops in gfx2 even further?
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- actually implement modes 3 and perhaps even 2 to gfx2 (lores 16 color and 4 color)
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Expressions:
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- Once the evalstack-free expression codegen is in place, the Eval Stack can be removed from the compiler.
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Machinedefinition, .p8 and .asm library files, all routines operationg on estack, and everything saving/restoring the X register related to this stack.
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- Or rewrite expression tree evaluation such that it doesn't use an eval stack but flatten the tree into linear code
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that, for instance, uses a fixed number of predetermined value 'variables'?
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The VM IL solves this already (by using unlimited registers) but that still lacks a translation to 6502.
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- this removes the need for the BinExprSplitter? (which is problematic and very limited now)
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and perhaps the assignment splitting in BeforeAsmAstChanger too
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Optimizations:
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- VariableAllocator: can we think of a smarter strategy for allocating variables into zeropage, rather than first-come-first-served?
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for instance, vars used inside loops first, then loopvars, then uwords used as pointers, then the rest
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- various optimizers skip stuff if compTarget.name==VMTarget.NAME. Once 6502-codegen is done from IR code,
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those checks should probably be removed, or be made permanent
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STRUCTS again?
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--------------
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What if we were to re-introduce Structs in prog8? Some thoughts:
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- can contain only numeric types (byte,word,float) - no nested structs, no reference types (strings, arrays) inside structs
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- is just some syntactic sugar for a scoped set of variables -> ast transform to do exactly this before codegen. Codegen doesn't know about struct.
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- no arrays of struct -- because too slow on 6502 to access those, rather use struct of arrays instead.
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can we make this a compiler/codegen only issue? i.e. syntax is just as if it was an array of structs?
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or make it explicit in the syntax so that it is clear what the memory layout of it is.
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- ability to assign struct variable to another? this is slow but can be quite handy sometimes.
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however how to handle this in a function that gets the struct passed as reference? Don't allow it there? (there's no pointer dereferencing concept in prog8)
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- ability to be passed as argument to a function (by reference)?
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however there is no typed pointer in prog8 at the moment so this can't be implemented in a meaningful way yet,
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because there is no way to reference it as the struct type again. (current ast gets the by-reference parameter
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type replaced by uword)
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So-- maybe don't replace the parameter type in the ast? Should fix that for str and array types as well then
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