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match lowering: Hide Candidate from outside the lowering algorithm #127159

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merged 5 commits into from
Aug 1, 2024
Merged

match lowering: Hide Candidate from outside the lowering algorithm #127159

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9e05fb6
Small simplification
Nadrieril Jun 23, 2024
e2fd9aa
Set up false edges in `lower_match_tree`
Nadrieril Jun 23, 2024
cbdacec
Abstract out the candidate manipulation not in the main algorithm
Nadrieril Jun 23, 2024
c747166
Visiting bindings is straightforward now
Nadrieril Jun 23, 2024
08bcc01
Entirely hide `Candidate`s from outside `lower_match_tree`
Nadrieril Jun 30, 2024
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460 changes: 279 additions & 181 deletions compiler/rustc_mir_build/src/build/matches/mod.rs
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78 changes: 14 additions & 64 deletions compiler/rustc_mir_build/src/build/matches/util.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,3 @@
use std::marker::PhantomData;

use rustc_data_structures::fx::FxIndexMap;
use rustc_middle::mir::*;
use rustc_middle::ty::Ty;
Expand All @@ -18,18 +16,17 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
&mut self,
from_block: BasicBlock,
real_target: BasicBlock,
imaginary_target: Option<BasicBlock>,
imaginary_target: BasicBlock,
source_info: SourceInfo,
) {
match imaginary_target {
Some(target) if target != real_target => {
self.cfg.terminate(
from_block,
source_info,
TerminatorKind::FalseEdge { real_target, imaginary_target: target },
);
}
_ => self.cfg.goto(from_block, source_info, real_target),
if imaginary_target != real_target {
self.cfg.terminate(
from_block,
source_info,
TerminatorKind::FalseEdge { real_target, imaginary_target },
);
} else {
self.cfg.goto(from_block, source_info, real_target)
}
}
}
Expand Down Expand Up @@ -71,10 +68,14 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
/// a MIR pass run after borrow checking.
pub(super) fn collect_fake_borrows<'tcx>(
cx: &mut Builder<'_, 'tcx>,
candidates: &[&mut Candidate<'_, 'tcx>],
candidates: &[Candidate<'_, 'tcx>],
temp_span: Span,
scrutinee_base: PlaceBase,
) -> Vec<(Place<'tcx>, Local, FakeBorrowKind)> {
if candidates.iter().all(|candidate| !candidate.has_guard) {
// Fake borrows are only used when there is a guard.
return Vec::new();
}
let mut collector =
FakeBorrowCollector { cx, scrutinee_base, fake_borrows: FxIndexMap::default() };
for candidate in candidates.iter() {
Expand Down Expand Up @@ -222,57 +223,6 @@ impl<'a, 'b, 'tcx> FakeBorrowCollector<'a, 'b, 'tcx> {
}
}

/// Visit all the bindings of these candidates. Because or-alternatives bind the same variables, we
/// only explore the first one of each or-pattern.
pub(super) fn visit_bindings<'tcx>(
candidates: &[&mut Candidate<'_, 'tcx>],
f: impl FnMut(&Binding<'tcx>),
) {
let mut visitor = BindingsVisitor { f, phantom: PhantomData };
for candidate in candidates.iter() {
visitor.visit_candidate(candidate);
}
}

pub(super) struct BindingsVisitor<'tcx, F> {
f: F,
phantom: PhantomData<&'tcx ()>,
}

impl<'tcx, F> BindingsVisitor<'tcx, F>
where
F: FnMut(&Binding<'tcx>),
{
fn visit_candidate(&mut self, candidate: &Candidate<'_, 'tcx>) {
for binding in &candidate.extra_data.bindings {
(self.f)(binding)
}
for match_pair in &candidate.match_pairs {
self.visit_match_pair(match_pair);
}
}

fn visit_flat_pat(&mut self, flat_pat: &FlatPat<'_, 'tcx>) {
for binding in &flat_pat.extra_data.bindings {
(self.f)(binding)
}
for match_pair in &flat_pat.match_pairs {
self.visit_match_pair(match_pair);
}
}

fn visit_match_pair(&mut self, match_pair: &MatchPairTree<'_, 'tcx>) {
if let TestCase::Or { pats, .. } = &match_pair.test_case {
// All the or-alternatives should bind the same locals, so we only visit the first one.
self.visit_flat_pat(&pats[0])
} else {
for subpair in &match_pair.subpairs {
self.visit_match_pair(subpair);
}
}
}
}

#[must_use]
pub(crate) fn ref_pat_borrow_kind(ref_mutability: Mutability) -> BorrowKind {
match ref_mutability {
Expand Down
56 changes: 30 additions & 26 deletions tests/mir-opt/building/match/match_false_edges.full_tested_match.built.after.mir
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Original file line number Diff line number Diff line change
Expand Up @@ -37,11 +37,11 @@ fn full_tested_match() -> () {
}

bb2: {
falseEdge -> [real: bb7, imaginary: bb3];
falseEdge -> [real: bb8, imaginary: bb3];
}

bb3: {
falseEdge -> [real: bb12, imaginary: bb5];
falseEdge -> [real: bb7, imaginary: bb5];
}

bb4: {
Expand All @@ -50,26 +50,41 @@ fn full_tested_match() -> () {

bb5: {
_1 = (const 3_i32, const 3_i32);
goto -> bb13;
goto -> bb14;
}

bb6: {
goto -> bb1;
}

bb7: {
StorageLive(_9);
_9 = ((_2 as Some).0: i32);
StorageLive(_10);
_10 = _9;
_1 = (const 2_i32, move _10);
StorageDead(_10);
StorageDead(_9);
goto -> bb14;
}

bb8: {
StorageLive(_6);
_6 = &((_2 as Some).0: i32);
_3 = &fake shallow _2;
StorageLive(_7);
_7 = guard() -> [return: bb8, unwind: bb15];
_7 = guard() -> [return: bb10, unwind: bb16];
}

bb8: {
switchInt(move _7) -> [0: bb10, otherwise: bb9];
bb9: {
goto -> bb3;
}

bb9: {
bb10: {
switchInt(move _7) -> [0: bb12, otherwise: bb11];
}

bb11: {
StorageDead(_7);
FakeRead(ForMatchGuard, _3);
FakeRead(ForGuardBinding, _6);
Expand All @@ -81,44 +96,33 @@ fn full_tested_match() -> () {
StorageDead(_8);
StorageDead(_5);
StorageDead(_6);
goto -> bb13;
goto -> bb14;
}

bb10: {
goto -> bb11;
bb12: {
goto -> bb13;
}

bb11: {
bb13: {
StorageDead(_7);
StorageDead(_6);
goto -> bb3;
}

bb12: {
StorageLive(_9);
_9 = ((_2 as Some).0: i32);
StorageLive(_10);
_10 = _9;
_1 = (const 2_i32, move _10);
StorageDead(_10);
StorageDead(_9);
goto -> bb13;
goto -> bb9;
}

bb13: {
bb14: {
PlaceMention(_1);
StorageDead(_2);
StorageDead(_1);
_0 = const ();
return;
}

bb14: {
bb15: {
FakeRead(ForMatchedPlace(None), _1);
unreachable;
}

bb15 (cleanup): {
bb16 (cleanup): {
resume;
}
}
44 changes: 24 additions & 20 deletions tests/mir-opt/building/match/match_false_edges.full_tested_match2.built.after.mir
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Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,7 @@ fn full_tested_match2() -> () {
}

bb2: {
falseEdge -> [real: bb7, imaginary: bb5];
falseEdge -> [real: bb8, imaginary: bb5];
}

bb3: {
Expand All @@ -48,34 +48,43 @@ fn full_tested_match2() -> () {
_1 = (const 2_i32, move _10);
StorageDead(_10);
StorageDead(_9);
goto -> bb13;
goto -> bb14;
}

bb4: {
goto -> bb1;
}

bb5: {
falseEdge -> [real: bb12, imaginary: bb3];
falseEdge -> [real: bb7, imaginary: bb3];
}

bb6: {
goto -> bb1;
}

bb7: {
_1 = (const 3_i32, const 3_i32);
goto -> bb14;
}

bb8: {
StorageLive(_6);
_6 = &((_2 as Some).0: i32);
_3 = &fake shallow _2;
StorageLive(_7);
_7 = guard() -> [return: bb8, unwind: bb15];
_7 = guard() -> [return: bb10, unwind: bb16];
}

bb8: {
switchInt(move _7) -> [0: bb10, otherwise: bb9];
bb9: {
falseEdge -> [real: bb3, imaginary: bb5];
}

bb9: {
bb10: {
switchInt(move _7) -> [0: bb12, otherwise: bb11];
}

bb11: {
StorageDead(_7);
FakeRead(ForMatchGuard, _3);
FakeRead(ForGuardBinding, _6);
Expand All @@ -87,38 +96,33 @@ fn full_tested_match2() -> () {
StorageDead(_8);
StorageDead(_5);
StorageDead(_6);
goto -> bb13;
goto -> bb14;
}

bb10: {
goto -> bb11;
bb12: {
goto -> bb13;
}

bb11: {
bb13: {
StorageDead(_7);
StorageDead(_6);
falseEdge -> [real: bb3, imaginary: bb5];
}

bb12: {
_1 = (const 3_i32, const 3_i32);
goto -> bb13;
goto -> bb9;
}

bb13: {
bb14: {
PlaceMention(_1);
StorageDead(_2);
StorageDead(_1);
_0 = const ();
return;
}

bb14: {
bb15: {
FakeRead(ForMatchedPlace(None), _1);
unreachable;
}

bb15 (cleanup): {
bb16 (cleanup): {
resume;
}
}
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