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While the SysV ABI is not that complicated, LLVM does not allow us
direct access to enforce it. By mimicking the IR generated by clang,
we can trick LLVM into doing the right thing. This involves two main
additions:
1. `AGG` ABI class
This is not part of the spec, but since we have to track class per
eightbyte and not per struct, the current enum is not enough. I
considered adding multiple classes like: `INTEGER_INTEGER`,
`INTEGER_SSE`, `SSE_INTEGER`. However, all of those cases would trigger
the same code path so it's simpler to collapse into one. This class is
only used on SysV.
2. LLVM C ABI type
Clang uses different types in C ABI function signatures than the
original structs passed in, and does conversion. For example, this
struct: `{ i8, i8, float }` would use `{ i16, float }` at ABI boundaries.
When passed as an argument, it is instead split into two arguments `i16`
and `float`. Therefore, for every struct that passes ABI boundaries we
need to keep track of its corresponding ABI type. Here are some more
examples:
```
| Struct | ABI equivalent |
| { i8, i8, i8, i8 } | i32 |
| { float, float } | double |
| { float, i32, i8 } | { float, i64 } |
```
Then, we must update function calls, returns, parameter lists and inits
to properly convert back and forth as needed.
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* 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
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