bjoernager/rust
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PR feedback: better comments and debug asserts

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This commit is contained in:
Scott McMurray 2023-05-21 10:58:32 -07:00
parent 977ac5b4dd
commit 05bf42bfa9
1 changed files with 19 additions and 3 deletions
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22
compiler/rustc_mir_transform/src/prettify.rs
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@ -11,6 +11,10 @@ use rustc_middle::mir::*;
use rustc_middle::ty::TyCtxt; use rustc_middle::ty::TyCtxt;
use rustc_session::Session; use rustc_session::Session;
/// Rearranges the basic blocks into a *reverse post-order*.
///
/// Thus after this pass, all the successors of a block are later than it in the
/// `IndexVec`, unless that successor is a back-edge (such as from a loop).
pub struct ReorderBasicBlocks; pub struct ReorderBasicBlocks;
impl<'tcx> MirPass<'tcx> for ReorderBasicBlocks { impl<'tcx> MirPass<'tcx> for ReorderBasicBlocks {
@ -33,6 +37,12 @@ impl<'tcx> MirPass<'tcx> for ReorderBasicBlocks {
} }
} }
/// Rearranges the locals into *use* order.
///
/// Thus after this pass, a local with a smaller [`Location`] where it was first
/// assigned or referenced will have a smaller number.
///
/// (Does not reorder arguments nor the [`RETURN_PLACE`].)
pub struct ReorderLocals; pub struct ReorderLocals;
impl<'tcx> MirPass<'tcx> for ReorderLocals { impl<'tcx> MirPass<'tcx> for ReorderLocals {
@ -45,8 +55,8 @@ impl<'tcx> MirPass<'tcx> for ReorderLocals {
LocalFinder { map: IndexVec::new(), seen: BitSet::new_empty(body.local_decls.len()) }; LocalFinder { map: IndexVec::new(), seen: BitSet::new_empty(body.local_decls.len()) };
// We can't reorder the return place or the arguments // We can't reorder the return place or the arguments
for i in 0..=body.arg_count { for local in (0..=body.arg_count).map(Local::from_usize) {
finder.track(Local::from_usize(i)); finder.track(local);
} }
for (bb, bbd) in body.basic_blocks.iter_enumerated() { for (bb, bbd) in body.basic_blocks.iter_enumerated() {
@ -64,7 +74,11 @@ impl<'tcx> MirPass<'tcx> for ReorderLocals {
} }
let mut updater = LocalUpdater { map: finder.map.invert_bijective_mapping(), tcx }; let mut updater = LocalUpdater { map: finder.map.invert_bijective_mapping(), tcx };
debug_assert_eq!(updater.map[RETURN_PLACE], RETURN_PLACE);
for local in (0..=body.arg_count).map(Local::from_usize) {
debug_assert_eq!(updater.map[local], local);
}
updater.visit_body_preserves_cfg(body); updater.visit_body_preserves_cfg(body);
permute(&mut body.local_decls, &updater.map); permute(&mut body.local_decls, &updater.map);
@ -112,6 +126,8 @@ impl LocalFinder {
impl<'tcx> Visitor<'tcx> for LocalFinder { impl<'tcx> Visitor<'tcx> for LocalFinder {
fn visit_local(&mut self, l: Local, context: PlaceContext, _location: Location) { fn visit_local(&mut self, l: Local, context: PlaceContext, _location: Location) {
// Exclude non-uses to keep `StorageLive` from controlling where we put
// a `Local`, since it might not actually be assigned until much later.
if context.is_use() { if context.is_use() {
self.track(l); self.track(l);
} }