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119 lines
4.4 KiB
Markdown
119 lines
4.4 KiB
Markdown
TODO for SixtyPical
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===================
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### Save values to other-than-the-stack
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Allow
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save a to temp_a {
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...
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}
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Which uses some other storage location instead of the stack. A local static
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would be a good candidate for such.
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### Analyze `call` within blocks?
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What happens if you call another routine from inside a `with interrupts off` block?
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What happens if you call another routine from inside a `save` block?
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What happens if you call another routine from inside a `point into` block?
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What happens if you call another routine from inside a `for` block?
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Remember that any of these may have a `goto` ... and they may have a second
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instance of the same block (e.g. `with interrupts off` nested within
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`with interrupts off` shouldn't be allowed to turn them back on after the
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inner block has finished -- even if there is no `call`.)
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These holes need to be plugged.
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### Reset pointer in `point into` blocks
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We have `point into` blocks, but maybe the action when entering such a
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block shouldn't always be to set the given pointer to the start of the given table.
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That is, sometimes we would like to start at some fixed offset. And
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sometimes we want to (re)set the pointer, without closing and starting a new block.
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### Pointers associated globally with a table
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We have `point into` blocks, but we would also like to sometimes pass a pointer
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around to different routines, and have them all "know" what table it operates on.
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We could associate every pointer variable with a specific table variable, in its
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declaration. This makes some things simple, and would allow us to know what table a
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pointer is supposed to point into, even if that pointer was passed into our routine.
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One drawback is that it would limit each pointer to be used only on one table. Since a
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pointer basically represents a zero-page location, and since those are a relatively scarce
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resource, we would prefer if a single pointer could be used to point into different tables
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at different times.
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These can co-exist with general, non-specific-table-linked `pointer` variables.
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### Local non-statics
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Somewhat related to the above, it should be possible to declare a local storage
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location which is not static.
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In this case, it would be considered uninitialized each time the routine was
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entered.
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So, you do not have a guarantee that it has a valid value. But you are guaranteed
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that no other routine can read or modify it.
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It also enables a trick: if there are two routines A and B, and A never calls B
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(even indirectly), and B never calls A (even indirectly), then their locals can
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be allocated at the same space.
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A local could also be given an explicit address. In this case, two locals in
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different routines could be given the same address, and as long as the condition
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in the above paragraph holds, that's okay. (If it doesn't, the analyzer should
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detect it.)
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This would permit local pointers, which would be one way of addressing the
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"same pointer to different tables" problem.
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### Copy byte to/from table
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Do we want a `copy bytevar, table + x` instruction? We don't currently have one.
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You have to `ld a`, `st a`. I think maybe we should have one.
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### Analyze memory usage
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If you define two variables that occupy the same address, an analysis error ought
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to be raised. (But there should also be a way to annotate this as intentional.
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Intentionally making two tables overlap could be valuable. However, the analysis
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will probably completely miss this fact.)
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### Character literals
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For goodness sake, let the programmer say `'A'` instead of `65`.
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### Character set mapping
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Not all computers think `'A'` should be `65`. Allow the character set to be
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mapped. Probably copy what Ophis does.
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### Tail-call optimization
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If a block ends in a `call` can that be converted to end in a `goto`? Why not? I think it can,
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if the block is in tail position. The constraints should iron out the same both ways.
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As long as the routine has consistent type context every place it exits, that should be fine.
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### "Include" directives
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Search a searchlist of include paths. And use them to make libraries of routines.
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One such library routine might be an `interrupt routine` type for various architectures.
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Since "the supervisor" has stored values on the stack, we should be able to trash them
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with impunity, in such a routine.
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### Line numbers in analysis error messages
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For analysis errors, there is a line number, but it's the line of the routine
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after the routine in which the analysis error occurred. Fix this.
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