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Chris Pressey 2018-09-07 17:47:59 +01:00
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TODO.md
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@ -1,20 +1,16 @@
TODO for SixtyPical
===================
### `low` and `high` address operators
### 16-bit `cmp`
To turn `word` type into `byte`.
This is because we don't actually want `low` and `high` address operators
that turn `word` type into `byte`.
Trying to remember if we have a compelling case for this or now. The best I can think
of is for implementing 16-bit `cmp` in an efficient way. Maybe we should see if we
can get by with 16-bit `cmp` instead though.
This is because this immediately makes things harder (that is, effectively
impossible) to analyze.
The problem is that once a byte is extracted, putting it back into a word is awkward.
The address operators have to modify a destination in a special way. That is, when
you say `st a, >word`, you are updating `word` to be `word & $ff | a << 8`, somelike.
Is that consistent with `st`? Well, probably it is, but we have to explain it.
It might make more sense, then, for it to be "part of the operation" instead of "part of
the reference"; something like `st.hi x, word`; `st.lo y, word`. Dunno.
16-bit `cmp` also benefits from some special differences between `cmp`
and `sub` on 6502, so it would be nice to capture them.
### Save values to other-than-the-stack
@ -32,7 +28,7 @@ would be a good candidate for such.
Check that the buffer being read or written to through pointer, appears in appropriate
inputs or outputs set.
In the analysis, when we obtain a pointer, we need to record, in contect, what buffer
In the analysis, when we obtain a pointer, we need to record, in context, what buffer
that pointer came from.
When we write through that pointer, we need to set that buffer as written.
@ -73,8 +69,8 @@ error.
More generally, define a block as having zero or one `goto`s at the end. (and `goto`s cannot
appear elsewhere.)
If a block ends in a `call` can that be converted to end in a `goto`? Why not? I think it can.
The constraints should iron out the same both ways.
If a block ends in a `call` can that be converted to end in a `goto`? Why not? I think it can,
if the block is in tail position. The constraints should iron out the same both ways.
And - once we have this - why do we need `goto` to be in tail position, strictly?
As long as the routine has consistent type context every place it exits, that should be fine.
@ -86,3 +82,8 @@ Search a searchlist of include paths. And use them to make libraries of routine
One such library routine might be an `interrupt routine` type for various architectures.
Since "the supervisor" has stored values on the stack, we should be able to trash them
with impunity, in such a routine.
### Line numbers in analysis error messages
For analysis errors, there is a line number, but it's the line of the routine
after the routine in which the analysis error occurred. Fix this.