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Add a pointee_metadata_ty_or_projection helper

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Scott McMurray 2024-06-22 12:11:14 -07:00
parent 9140c9ad5b
commit a76e1d9b09
8 changed files with 102 additions and 67 deletions
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19
compiler/rustc_mir_transform/src/gvn.rs
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@ -987,23 +987,14 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
// `*const [T]` -> `*const T` which remove metadata.
// We run on potentially-generic MIR, though, so unlike codegen
// we can't always know exactly what the metadata are.
// Thankfully, equality on `ptr_metadata_ty_or_tail` gives us
// what we need: `Ok(meta_ty)` if the metadata is known, or
// `Err(tail_ty)` if not. Matching metadata is ok, but if
// that's not known, then matching tail types is also ok,
// allowing things like `*mut (?A, ?T)` <-> `*mut (?B, ?T)`.
// To allow things like `*mut (?A, ?T)` <-> `*mut (?B, ?T)`,
// it's fine to get a projection as the type.
// FIXME: Would it be worth trying to normalize, rather than
// passing the identity closure? Or are the types in the
// just accepting the projection? Or are the types in the
// Cast realistically about as normalized as we can get anyway?
Value::Cast { kind: CastKind::PtrToPtr, value: inner, from, to }
if from
.builtin_deref(true)
.unwrap()
.ptr_metadata_ty_or_tail(self.tcx, |t| t)
== to
.builtin_deref(true)
.unwrap()
.ptr_metadata_ty_or_tail(self.tcx, |t| t) =>
if from.pointee_metadata_ty_or_projection(self.tcx)
== to.pointee_metadata_ty_or_projection(self.tcx) =>
{
arg_index = *inner;
was_updated = true;