9af6fee87d
Support tail calls in mir via `TerminatorKind::TailCall`
This is one of the interesting bits in tail call implementation — MIR support.
This adds a new `TerminatorKind` which represents a tail call:
```rust
TailCall {
func: Operand<'tcx>,
args: Vec<Operand<'tcx>>,
fn_span: Span,
},
```
*Structurally* this is very similar to a normal `Call` but is missing a few fields:
- `destination` — tail calls don't write to destination, instead they pass caller's destination to the callee (such that eventual `return` will write to the caller of the function that used tail call)
- `target` — similarly to `destination` tail calls pass the caller's return address to the callee, so there is nothing to do
- `unwind` — I _think_ this is applicable too, although it's a bit confusing
- `call_source` — `become` forbids operators and is not created as a lowering of something else; tail calls always come from HIR (at least for now)
It might be helpful to read the interpreter implementation to understand what `TailCall` means exactly, although I've tried documenting it too.
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There are a few `FIXME`-questions still left, ideally we'd be able to answer them during review ':)
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r? `@oli-obk`
cc `@scottmcm` `@DrMeepster` `@JakobDegen`
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| .. | ||
| abi | ||
| debuginfo | ||
| driver | ||
| intrinsics | ||
| optimize | ||
| allocator.rs | ||
| analyze.rs | ||
| archive.rs | ||
| base.rs | ||
| cast.rs | ||
| codegen_i128.rs | ||
| common.rs | ||
| compiler_builtins.rs | ||
| concurrency_limiter.rs | ||
| config.rs | ||
| constant.rs | ||
| discriminant.rs | ||
| global_asm.rs | ||
| inline_asm.rs | ||
| lib.rs | ||
| linkage.rs | ||
| main_shim.rs | ||
| num.rs | ||
| pointer.rs | ||
| pretty_clif.rs | ||
| toolchain.rs | ||
| trap.rs | ||
| unsize.rs | ||
| unwind_module.rs | ||
| value_and_place.rs | ||
| vtable.rs | ||