This commit intentions to have no functional changes. The only purpose
is to delete the struct IrInst, which is the common base struct that
both IrInstSrc (ZIR) and IrInstGen (AIR) instructions embed.
This untangles stage1 ZIR and AIR memory layout, paving the way for a
following commit to reduce memory usage.
One more step towards lowering the memory footprint of stage1. This flag
was hiding in padding but now that it is gone we can re-arrange the
memory layout more easily.
* AstGen: implement "unreachable code" error for blocks. This works at
the statement level.
* stage1: remove the "unreachable code" error implementation, which
means removing the `is_gen` field from IrInstSrc. This is one small
step towards a smaller memory footprint for stage1. The benefits
won't be realized until a future commit because this flag took
advantage of padding.
There may be a regression here with "union has no associated enum"
error, and there is a regression with the following code:
```zig
const a = noreturn;
```
A future commit will address these regressions.
Currently, stage1 runs astgen for every comptime function call,
resulting in identifier strings being allocated multiple times,
wasting memory. As a workaround until the code is adjusted to
make astgen run only once per source node, we memoize the
result into the AST.
* Rename `ir_gen_*` to `astgen_*`
- Oops, meant to do this in a separate commit. My bad.
* tokenizer: avoid using designated initializer syntax.
MSVC does not support it.
This is progress towards making Stage1Zir immutable, so that we can
avoid generating it for every comptime function call.
Also rename IrExecutableGen to Stage1Air.
* Extracts AstGen logic from ir.cpp into astgen.cpp. Reduces the
largest file of stage1 from 33,551 lines to 25,510.
* tokenizer: rework it completely to match the stage2 tokenizer logic.
They can now be maintained together; when one is changed, the other
can be changed in the same way.
- Each token now takes up 13 bytes instead of 64 bytes. The tokenizer
does not parse char literals, string literals, integer literals,
etc into meaningful data. Instead, that happens during parsing or
astgen.
- no longer store line offsets. Error messages scan source
files to find the line/column as needed (same as stage2).
- main loop: instead of checking the loop, handle a null byte
explicitly in the switch statements. This is a nice improvement
that we may want to backport to stage2.
- delete some dead tokens, artifacts of past syntax that no longer
exists.
* Parser: fix a TODO by parsing builtin functions as tokens rather than
`@` as a separate token. This is how stage2 does it.
* Remove some debugging infrastructure. These will need to be redone,
if at all, as the code migrates to match stage2.
- remove the ast_render code.
- remove the IR debugging stuff
- remove teh token printing code
