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Fix fn_sig_for_fn_abi and the coroutine transform for generators

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There were three issues previously:
* The self argument was pinned, despite Iterator::next taking an
  unpinned mutable reference.
* A resume argument was passed, despite Iterator::next not having one.
* The return value was CoroutineState<Item, ()> rather than Option<Item>

While these things just so happened to work with the LLVM backend,
cg_clif does much stricter checks when trying to assign a value to a
place. In addition it can't handle the mismatch between the amount of
arguments specified by the FnAbi and the FnSig.
This commit is contained in:
bjorn3 2023-11-23 20:02:45 +00:00
parent 237339fda1
commit b7bc8d5cb7
7 changed files with 129 additions and 9 deletions
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32
compiler/rustc_mir_transform/src/coroutine.rs
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@ -617,6 +617,22 @@ fn replace_resume_ty_local<'tcx>(
}
}
/// Transforms the `body` of the coroutine applying the following transform:
///
/// - Remove the `resume` argument.
///
/// Ideally the async lowering would not add the `resume` argument.
///
/// The async lowering step and the type / lifetime inference / checking are
/// still using the `resume` argument for the time being. After this transform,
/// the coroutine body doesn't have the `resume` argument.
fn transform_gen_context<'tcx>(_tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
// This leaves the local representing the `resume` argument in place,
// but turns it into a regular local variable. This is cheaper than
// adjusting all local references in the body after removing it.
body.arg_count = 1;
}
struct LivenessInfo {
/// Which locals are live across any suspension point.
saved_locals: CoroutineSavedLocals,
@ -1337,7 +1353,15 @@ fn create_coroutine_resume_function<'tcx>(
insert_switch(body, cases, &transform, TerminatorKind::Unreachable);
make_coroutine_state_argument_indirect(tcx, body);
make_coroutine_state_argument_pinned(tcx, body);
match coroutine_kind {
// Iterator::next doesn't accept a pinned argument,
// unlike for all other coroutine kinds.
CoroutineKind::Gen(_) => {}
_ => {
make_coroutine_state_argument_pinned(tcx, body);
}
}
// Make sure we remove dead blocks to remove
// unrelated code from the drop part of the function
@ -1504,6 +1528,7 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
};
let is_async_kind = matches!(body.coroutine_kind(), Some(CoroutineKind::Async(_)));
let is_gen_kind = matches!(body.coroutine_kind(), Some(CoroutineKind::Gen(_)));
let (state_adt_ref, state_args) = match body.coroutine_kind().unwrap() {
CoroutineKind::Async(_) => {
// Compute Poll<return_ty>
@ -1609,6 +1634,11 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
body.arg_count = 2; // self, resume arg
body.spread_arg = None;
// Remove the context argument within generator bodies.
if is_gen_kind {
transform_gen_context(tcx, body);
}
// The original arguments to the function are no longer arguments, mark them as such.
// Otherwise they'll conflict with our new arguments, which although they don't have
// argument_index set, will get emitted as unnamed arguments.