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104 lines
7.4 KiB
ReStructuredText
104 lines
7.4 KiB
ReStructuredText
TODO
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====
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For next release
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^^^^^^^^^^^^^^^^
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- bug: 2 repeats in same subroutine -> duplicate label error? see repeat_bug.p8
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- bug: f_read() can't deal with running out of banked ram? maybe only cx16diskio.f_read()?
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- add McCarthy evaluation to shortcircuit and/or expressions. Both conditional expressions and assignments!
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- add some more optimizations in vmPeepholeOptimizer
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- vm Instruction needs to know what the read-registers/memory are, and what the write-register/memory is.
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this info is needed for more advanced optimizations and later code generation steps.
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Need help with
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^^^^^^^^^^^^^^
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- c128 target: various machine specific things (free zp locations, how banking works, getting the floating point routines working, ...)
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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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- vm: implement remaining sin/cos functions in math.p8
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- vm: somehow deal with asmsubs otherwise the vm IR can't fully encode all of prog8
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- vm: don't store symbol names in instructions to make optimizing the IR easier? but what about jumps to labels. And it's no longer readable by humans.
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- vm: how to remove all unused subroutines? (in the 6502 assembly codegen, we let 64tass solve this for us)
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- vm: rather than being able to jump to any 'address' (IPTR), use 'blocks' that have entry and exit points -> even better dead code elimination possible too
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- when the vm is stable and *if* its language can get promoted to prog8 IL, the variable allocation should be changed.
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It's now done before the vm code generation, but the IL should probably not depend on the allocations already performed.
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So the CodeGen doesn't do VariableAlloc *before* the codegen, but as a last step.
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- generate WASM from the new ast (or from vm code?) to run prog8 on a browser canvas?
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- createAssemblyAndAssemble(): make it possible to actually get rid of the VarDecl nodes by fixing the rest of the code mentioned there.
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but probably better to rewrite the 6502 codegen on top of the new Ast.
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- simplifyConditionalExpression() should not split expression if it still results in stack-based evaluation, but how does it know?
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- simplifyConditionalExpression() sometimes introduces needless assignment to r9 tempvar (what scenarios?)
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- make it possible to use cpu opcodes such as 'nop' as variable names by prefixing all asm vars with something such as ``p8v_``? Or not worth it (most 3 letter opcodes as variables are nonsensical anyway)
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then we can get rid of the instruction lists in the machinedefinitions as well?
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- [problematic due to using 64tass:] add a compiler option to not remove unused subroutines. this allows for building library programs. But this won't work with 64tass's .proc ...
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Perhaps replace all uses of .proc/.pend by .block/.bend will fix that?
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(but we lose the optimizing aspect of the assembler where it strips out unused code.
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There's not really a dynamic switch possible as all assembly lib code is static and uses one or the other)
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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)
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- add special (u)word array type (or modifier?) that puts the array into memory as 2 separate byte-arrays 1 for LSB 1 for MSB -> allows for word arrays of length 256 and faster indexing
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- ast: don't rewrite by-reference parameter type to uword, but keep the original type (str, array)
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BUT that makes the handling of these types different between the scope they are defined in, and the
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scope they get passed in by reference... unless we make str and array types by-reference ALWAYS? BUT that
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makes simple code accessing them in the declared scope very slow because that then has to always go through
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the pointer rather than directly referencing the variable symbol in the generated asm....
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Libraries:
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- fix the problems in c128 target, and flesh out its libraries.
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- fix the problems in atari target, and flesh out its libraries.
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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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- add modes 2 and 3 to gfx2 (lowres 4 color and 16 color)?
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- add a flood fill routine to gfx2?
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Expressions:
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- rethink the whole "isAugmentable" business. Because the way this is determined, should always also be exactly mirrorred in the AugmentableAssignmentAsmGen or you'll get a crash at code gen time.
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note: the new Ast doesn't need this any more so maybe we can get rid of it altogether in the old AST - but it's still used for something in the UnusedCodeRemover.
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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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- rewrite expression tree evaluation such that it doesn't use an eval stack but flatten the tree into linear code that uses a fixed number of predetermined value 'variables'?
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"Three address code" was mentioned. https://en.wikipedia.org/wiki/Three-address_code
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these variables have to be unique for each subroutine because they could otherwise be interfered with from irq routines etc.
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The VM IL solves this already (by using unlimited registers) but 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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- various optimizers skip stuff if compTarget.name==VMTarget.NAME. Once (if?) 6502-codegen is no longer done from
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the old CompilerAst, those checks should probably be removed, or be made permanent
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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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- AssignmentAsmGen.assignExpression() -> improve code gen for assigning boolean comparison expressions
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Check what the vm target does here, maybe just do this as part of the vm -> 6502 codegen.
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- when a for loop's loopvariable isn't referenced in the body, and the iterations are known, replace the loop by a repeatloop
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but we have no efficient way right now to see if the body references a variable.
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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
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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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