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16-bit-compare

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TODO for SixtyPical

Save values to other-than-the-stack

Allow

save a to temp_a {
    ...
}

Which uses some other storage location instead of the stack. A local static would be a good candidate for such.

Associate each pointer with the buffer it points into

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 context, what buffer that pointer came from.

When we write through that pointer, we need to set that buffer as written.

When we read through the pointer, we need to check that the buffer is readable.

Table overlays

They are uninitialized, but the twist is, the address is a buffer that is an input to and/or output of the routine. So, they are defined (insofar as the buffer is defined.)

They are therefore a "view" of a section of a buffer.

This is slightly dangerous since it does permit aliases: the buffer and the table refer to the same memory.

Although, if they are static, you could say, in the routine in which they are static, as soon as you've established one, you can no longer use the buffer; and the ones you establish must be disjoint.

(That seems to be the most compelling case for restricting them to static.)

An alternative would be static pointers, which are currently not possible because pointers must be zero-page, thus @, thus uninitialized.

Question "consistent initialization"

Question the value of the "consistent initialization" principle for if statement analysis.

Part of this is the trashes at the end; I think what it should be is that the trashes after the if is the union of the trashes in each of the branches; this would obviate the need to trash values explicitly, but if you tried to access them afterwards, it would still error.

Tail-call optimization

More generally, define a block as having zero or one gotos at the end. (and gotos 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, 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.

"Include" directives

Search a searchlist of include paths. And use them to make libraries of routines.

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.