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Allow StorageDead(s) of the target block could be copied to the branching block #93987

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Allow StorageDead(s) of the target block could be copied to the branching block #93987

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22 changes: 16 additions & 6 deletions compiler/rustc_mir_transform/src/const_goto.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,13 @@ impl<'tcx> MirPass<'tcx> for ConstGoto {
let new_goto = TerminatorKind::Goto { target: opt.target_to_use_in_goto };
debug!("SUCCESS: replacing `{:?}` with `{:?}`", terminator.kind, new_goto);
terminator.kind = new_goto;

let bridge_bb_statement = &body.basic_blocks()[opt.bridge_bb].statements;
if !bridge_bb_statement.is_empty() {
let storagedeads = bridge_bb_statement.clone();
body.basic_blocks_mut()[opt.bb_with_goto].statements.extend(storagedeads);
Comment on lines +47 to +50
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let bridge_bb_statement = &body.basic_blocks()[opt.bridge_bb].statements;
if !bridge_bb_statement.is_empty() {
let storagedeads = bridge_bb_statement.clone();
body.basic_blocks_mut()[opt.bb_with_goto].statements.extend(storagedeads);
let bridge_bb_statements = &body.basic_blocks()[opt.bridge_bb].statements;
if !bridge_bb_statements.is_empty() {
let storagedeads = bridge_bb_statements.into_iter().cloned();
body.basic_blocks_mut()[opt.bb_with_goto].statements.extend(storagedeads);

debug!("SUCCESS: extending terminator's basic block with briding basic block.");
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debug!("SUCCESS: extending terminator's basic block with briding basic block.");
debug!("SUCCESS: extending terminator's basic block with bridging basic block.");

}
}

// if we applied optimizations, we potentially have some cfg to cleanup to
Expand All @@ -67,12 +74,13 @@ impl<'tcx> Visitor<'tcx> for ConstGotoOptimizationFinder<'_, 'tcx> {
// We found a constant being assigned to `place`.
// Now check that the target of this Goto switches on this place.
let target_bb = &self.body.basic_blocks()[target];

// FIXME(simonvandel): We are conservative here when we don't allow
// any statements in the target basic block.
// This could probably be relaxed to allow `StorageDead`s which could be
// copied to the predecessor of this block.
if !target_bb.statements.is_empty() {
let target_bb_statements = &target_bb.statements;
if !target_bb_statements.is_empty()
&& !target_bb_statements.iter().all(|statement| match statement.kind {
StatementKind::StorageDead(_) => true,
_ => false,
})
{
None?
}

Expand All @@ -86,6 +94,7 @@ impl<'tcx> Visitor<'tcx> for ConstGotoOptimizationFinder<'_, 'tcx> {
let target_to_use_in_goto = targets.target_for_value(const_value);
self.optimizations.push(OptimizationToApply {
bb_with_goto: location.block,
bridge_bb: target,
target_to_use_in_goto,
});
}
Expand All @@ -99,6 +108,7 @@ impl<'tcx> Visitor<'tcx> for ConstGotoOptimizationFinder<'_, 'tcx> {

struct OptimizationToApply {
bb_with_goto: BasicBlock,
bridge_bb: BasicBlock,
target_to_use_in_goto: BasicBlock,
}

Expand Down
42 changes: 42 additions & 0 deletions src/test/mir-opt/const_goto.match_nested_if.MatchBranchSimplification.diff
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@@ -0,0 +1,42 @@
- // MIR for `match_nested_if` before MatchBranchSimplification
+ // MIR for `match_nested_if` after MatchBranchSimplification

fn match_nested_if() -> bool {
let mut _0: bool; // return place in scope 0 at $DIR/const_goto.rs:16:25: 16:29
let _1: bool; // in scope 0 at $DIR/const_goto.rs:17:9: 17:12
let mut _2: bool; // in scope 0 at $DIR/const_goto.rs:18:24: 18:28
+ let mut _3: bool; // in scope 0 at $DIR/const_goto.rs:18:24: 18:28
scope 1 {
debug val => _1; // in scope 1 at $DIR/const_goto.rs:17:9: 17:12
}

bb0: {
StorageLive(_1); // scope 0 at $DIR/const_goto.rs:17:9: 17:12
StorageLive(_2); // scope 0 at $DIR/const_goto.rs:18:24: 18:28
_2 = const true; // scope 0 at $DIR/const_goto.rs:18:24: 18:28
- switchInt(move _2) -> [false: bb2, otherwise: bb1]; // scope 0 at $DIR/const_goto.rs:18:24: 18:28
- }
-
- bb1: {
+ StorageLive(_3); // scope 0 at $DIR/const_goto.rs:18:24: 18:28
+ _3 = move _2; // scope 0 at $DIR/const_goto.rs:18:24: 18:28
StorageDead(_2); // scope 0 at $DIR/const_goto.rs:18:51: 18:52
- _1 = const true; // scope 0 at $DIR/const_goto.rs:24:13: 24:17
- goto -> bb3; // scope 0 at $DIR/const_goto.rs:24:13: 24:17
- }
-
- bb2: {
- StorageDead(_2); // scope 0 at $DIR/const_goto.rs:18:51: 18:52
- _1 = const false; // scope 0 at $DIR/const_goto.rs:26:14: 26:19
- goto -> bb3; // scope 0 at $DIR/const_goto.rs:26:14: 26:19
- }
-
- bb3: {
+ _1 = Ne(_3, const false); // scope 0 at $DIR/const_goto.rs:26:14: 26:19
+ StorageDead(_3); // scope 0 at $DIR/const_goto.rs:18:24: 18:28
_0 = _1; // scope 1 at $DIR/const_goto.rs:28:5: 28:8
StorageDead(_1); // scope 0 at $DIR/const_goto.rs:29:1: 29:2
return; // scope 0 at $DIR/const_goto.rs:29:2: 29:2
}
}

18 changes: 18 additions & 0 deletions src/test/mir-opt/const_goto.rs
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Expand Up @@ -11,6 +11,24 @@ pub enum Foo {
fn issue_77355_opt(num: Foo) -> u64 {
if matches!(num, Foo::B | Foo::C) { 23 } else { 42 }
}

// EMIT_MIR const_goto.match_nested_if.MatchBranchSimplification.diff
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// EMIT_MIR const_goto.match_nested_if.MatchBranchSimplification.diff
// EMIT_MIR const_goto.match_nested_if.MatchBranchSimplification.diff
// EMIT_MIR const_goto.match_nested_if.ConstGoto.diff

fn match_nested_if() -> bool {
let val = match () {
() if if if if true { true } else { false } { true } else { false } {
true
} else {
false
} =>
{
true
}
_ => false,
};
val
}

fn main() {
issue_77355_opt(Foo::A);
let _ = match_nested_if();
}
167 changes: 98 additions & 69 deletions ...test/mir-opt/matches_reduce_branches.match_nested_if.MatchBranchSimplification.32bit.diff
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Original file line number Diff line number Diff line change
@@ -1,85 +1,114 @@
- // MIR for `match_nested_if` before MatchBranchSimplification
+ // MIR for `match_nested_if` after MatchBranchSimplification

fn match_nested_if() -> bool {
let mut _0: bool; // return place in scope 0 at $DIR/matches_reduce_branches.rs:39:25: 39:29
let _1: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:40:9: 40:12
let mut _2: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
let mut _3: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
let mut _4: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
+ let mut _5: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
+ let mut _6: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
+ let mut _7: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
fn match_nested_if(_1: bool, _2: bool) -> bool {
debug flag0 => _1; // in scope 0 at $DIR/matches_reduce_branches.rs:39:20: 39:25
debug flag1 => _2; // in scope 0 at $DIR/matches_reduce_branches.rs:39:33: 39:38
let mut _0: bool; // return place in scope 0 at $DIR/matches_reduce_branches.rs:39:49: 39:53
let _3: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:40:9: 40:12
let mut _4: (); // in scope 0 at $DIR/matches_reduce_branches.rs:40:21: 40:23
let mut _5: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:41:15: 45:10
let mut _6: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:78
let mut _7: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:53
let mut _8: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
let mut _9: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:42:13: 42:18
let mut _10: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:42:21: 42:26
let mut _11: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:44:13: 44:18
let mut _12: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:44:21: 44:26
+ let mut _13: bool; // in scope 0 at $DIR/matches_reduce_branches.rs:41:15: 45:10
scope 1 {
debug val => _1; // in scope 1 at $DIR/matches_reduce_branches.rs:40:9: 40:12
debug val => _3; // in scope 1 at $DIR/matches_reduce_branches.rs:40:9: 40:12
}

bb0: {
StorageLive(_1); // scope 0 at $DIR/matches_reduce_branches.rs:40:9: 40:12
StorageLive(_2); // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
StorageLive(_3); // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
StorageLive(_4); // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
_4 = const true; // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
- switchInt(move _4) -> [false: bb2, otherwise: bb1]; // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
- }
-
- bb1: {
- _3 = const true; // scope 0 at $DIR/matches_reduce_branches.rs:41:31: 41:35
- goto -> bb3; // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
- }
-
- bb2: {
- _3 = const false; // scope 0 at $DIR/matches_reduce_branches.rs:41:45: 41:50
- goto -> bb3; // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
- }
-
- bb3: {
+ StorageLive(_5); // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
+ _5 = move _4; // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
+ _3 = Ne(_5, const false); // scope 0 at $DIR/matches_reduce_branches.rs:41:45: 41:50
+ StorageDead(_5); // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
StorageDead(_4); // scope 0 at $DIR/matches_reduce_branches.rs:41:51: 41:52
- switchInt(move _3) -> [false: bb5, otherwise: bb4]; // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
- }
-
- bb4: {
- _2 = const true; // scope 0 at $DIR/matches_reduce_branches.rs:41:55: 41:59
- goto -> bb6; // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
- }
-
- bb5: {
- _2 = const false; // scope 0 at $DIR/matches_reduce_branches.rs:41:69: 41:74
- goto -> bb6; // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
- }
-
- bb6: {
+ StorageLive(_6); // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
+ _6 = move _3; // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
+ _2 = Ne(_6, const false); // scope 0 at $DIR/matches_reduce_branches.rs:41:69: 41:74
+ StorageDead(_6); // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:52
StorageDead(_3); // scope 0 at $DIR/matches_reduce_branches.rs:41:75: 41:76
- switchInt(move _2) -> [false: bb8, otherwise: bb7]; // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
StorageLive(_3); // scope 0 at $DIR/matches_reduce_branches.rs:40:9: 40:12
StorageLive(_4); // scope 0 at $DIR/matches_reduce_branches.rs:40:21: 40:23
StorageLive(_5); // scope 0 at $DIR/matches_reduce_branches.rs:41:15: 45:10
StorageLive(_6); // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:78
StorageLive(_7); // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:53
StorageLive(_8); // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
_8 = const true; // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
switchInt(move _8) -> [false: bb2, otherwise: bb1]; // scope 0 at $DIR/matches_reduce_branches.rs:41:24: 41:28
}

bb1: {
_7 = _1; // scope 0 at $DIR/matches_reduce_branches.rs:41:31: 41:36
goto -> bb3; // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:53
}

bb2: {
_7 = _2; // scope 0 at $DIR/matches_reduce_branches.rs:41:46: 41:51
goto -> bb3; // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:53
}

bb3: {
StorageDead(_8); // scope 0 at $DIR/matches_reduce_branches.rs:41:52: 41:53
switchInt(move _7) -> [false: bb5, otherwise: bb4]; // scope 0 at $DIR/matches_reduce_branches.rs:41:21: 41:53
}

bb4: {
_6 = _2; // scope 0 at $DIR/matches_reduce_branches.rs:41:56: 41:61
goto -> bb6; // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:78
}

bb5: {
_6 = _1; // scope 0 at $DIR/matches_reduce_branches.rs:41:71: 41:76
goto -> bb6; // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:78
}

bb6: {
StorageDead(_7); // scope 0 at $DIR/matches_reduce_branches.rs:41:77: 41:78
switchInt(move _6) -> [false: bb8, otherwise: bb7]; // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:78
}

bb7: {
StorageLive(_9); // scope 0 at $DIR/matches_reduce_branches.rs:42:13: 42:18
_9 = _1; // scope 0 at $DIR/matches_reduce_branches.rs:42:13: 42:18
StorageLive(_10); // scope 0 at $DIR/matches_reduce_branches.rs:42:21: 42:26
_10 = _2; // scope 0 at $DIR/matches_reduce_branches.rs:42:21: 42:26
_5 = BitAnd(move _9, move _10); // scope 0 at $DIR/matches_reduce_branches.rs:42:13: 42:26
StorageDead(_10); // scope 0 at $DIR/matches_reduce_branches.rs:42:25: 42:26
StorageDead(_9); // scope 0 at $DIR/matches_reduce_branches.rs:42:25: 42:26
goto -> bb9; // scope 0 at $DIR/matches_reduce_branches.rs:41:15: 45:10
}

bb8: {
StorageLive(_11); // scope 0 at $DIR/matches_reduce_branches.rs:44:13: 44:18
_11 = _1; // scope 0 at $DIR/matches_reduce_branches.rs:44:13: 44:18
StorageLive(_12); // scope 0 at $DIR/matches_reduce_branches.rs:44:21: 44:26
_12 = _2; // scope 0 at $DIR/matches_reduce_branches.rs:44:21: 44:26
_5 = BitOr(move _11, move _12); // scope 0 at $DIR/matches_reduce_branches.rs:44:13: 44:26
StorageDead(_12); // scope 0 at $DIR/matches_reduce_branches.rs:44:25: 44:26
StorageDead(_11); // scope 0 at $DIR/matches_reduce_branches.rs:44:25: 44:26
goto -> bb9; // scope 0 at $DIR/matches_reduce_branches.rs:41:15: 45:10
}

bb9: {
- switchInt(move _5) -> [false: bb11, otherwise: bb10]; // scope 0 at $DIR/matches_reduce_branches.rs:41:15: 45:10
- }
-
- bb7: {
+ StorageLive(_7); // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
+ _7 = move _2; // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
StorageDead(_2); // scope 0 at $DIR/matches_reduce_branches.rs:45:9: 45:10
- _1 = const true; // scope 0 at $DIR/matches_reduce_branches.rs:47:13: 47:17
- goto -> bb9; // scope 0 at $DIR/matches_reduce_branches.rs:47:13: 47:17
- bb10: {
+ StorageLive(_13); // scope 0 at $DIR/matches_reduce_branches.rs:41:15: 45:10
+ _13 = move _5; // scope 0 at $DIR/matches_reduce_branches.rs:41:15: 45:10
StorageDead(_6); // scope 0 at $DIR/matches_reduce_branches.rs:45:9: 45:10
StorageDead(_5); // scope 0 at $DIR/matches_reduce_branches.rs:45:9: 45:10
- _3 = const true; // scope 0 at $DIR/matches_reduce_branches.rs:47:13: 47:17
- goto -> bb12; // scope 0 at $DIR/matches_reduce_branches.rs:47:13: 47:17
- }
-
- bb8: {
- StorageDead(_2); // scope 0 at $DIR/matches_reduce_branches.rs:45:9: 45:10
- _1 = const false; // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
- goto -> bb9; // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
- bb11: {
- StorageDead(_6); // scope 0 at $DIR/matches_reduce_branches.rs:45:9: 45:10
- StorageDead(_5); // scope 0 at $DIR/matches_reduce_branches.rs:45:9: 45:10
- _3 = const false; // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
- goto -> bb12; // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
- }
-
- bb9: {
+ _1 = Ne(_7, const false); // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
+ StorageDead(_7); // scope 0 at $DIR/matches_reduce_branches.rs:41:18: 41:76
_0 = _1; // scope 1 at $DIR/matches_reduce_branches.rs:51:5: 51:8
StorageDead(_1); // scope 0 at $DIR/matches_reduce_branches.rs:52:1: 52:2
- bb12: {
+ _3 = Ne(_13, const false); // scope 0 at $DIR/matches_reduce_branches.rs:49:14: 49:19
+ StorageDead(_13); // scope 0 at $DIR/matches_reduce_branches.rs:41:15: 45:10
StorageDead(_4); // scope 0 at $DIR/matches_reduce_branches.rs:50:6: 50:7
_0 = _3; // scope 1 at $DIR/matches_reduce_branches.rs:51:5: 51:8
StorageDead(_3); // scope 0 at $DIR/matches_reduce_branches.rs:52:1: 52:2
return; // scope 0 at $DIR/matches_reduce_branches.rs:52:2: 52:2
}
}
Expand Down
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