bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

Make the aggregate-then-transmute handling more general

Browse source
This commit is contained in:
Scott McMurray 2025-01-05 23:27:24 -08:00
parent 293f8e8941
commit b421a56364
4 changed files with 516 additions and 310 deletions
Download patch file Download diff file Expand all files Collapse all files

22
compiler/rustc_mir_transform/src/gvn.rs
View file

@ -1370,12 +1370,14 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
loop {
let mut was_updated_this_iteration = false;
// Transmuting `*const T` <=> `*mut T` is just a pointer cast,
// which we might be able to merge with other ones later.
// Transmuting between raw pointers is just a pointer cast so long as
// they have the same metadata type (like `*const i32` <=> `*mut u64`
// or `*mut [i32]` <=> `*const [u64]`), including the common special
// case of `*const T` <=> `*mut T`.
if let Transmute = kind
&& let ty::RawPtr(from_pointee, _) = from.kind()
&& let ty::RawPtr(to_pointee, _) = to.kind()
&& from_pointee == to_pointee
&& from.is_unsafe_ptr()
&& to.is_unsafe_ptr()
&& self.pointers_have_same_metadata(from, to)
{
*kind = PtrToPtr;
was_updated_this_iteration = true;
@ -1400,15 +1402,9 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
// Aggregate-then-Transmute can just transmute the original field value,
// so long as the bytes of a value from only from a single field.
if let Transmute = kind
&& let Value::Aggregate(
AggregateTy::Def(aggregate_did, aggregate_args),
variant_idx,
field_values,
) = self.get(value)
&& let aggregate_ty =
self.tcx.type_of(aggregate_did).instantiate(self.tcx, aggregate_args)
&& let Value::Aggregate(_aggregate_ty, variant_idx, field_values) = self.get(value)
&& let Some((field_idx, field_ty)) =
self.value_is_all_in_one_field(aggregate_ty, *variant_idx)
self.value_is_all_in_one_field(from, *variant_idx)
{
from = field_ty;
value = field_values[field_idx.as_usize()];