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match lowering: Clarify the main loop of the algorithm #127164

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merged 7 commits into from
Jul 12, 2024
Merged

match lowering: Clarify the main loop of the algorithm #127164

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5bf50e6
Move a function
Nadrieril Jun 30, 2024
bff4d21
Factor out the special handling of or-patterns
Nadrieril Jun 30, 2024
c5062f7
Move or-pattern expansion inside the main part of the algorithm
Nadrieril Jun 30, 2024
8a222ff
Don't try to save an extra block
Nadrieril Jun 30, 2024
fc40247
Factor out the "process remaining candidates" cases
Nadrieril Jun 30, 2024
3e030b3
Return the `otherwise_block` instead of passing it as argument
Nadrieril Jun 30, 2024
42772e9
Address review comments
Nadrieril Jul 5, 2024
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345 changes: 155 additions & 190 deletions compiler/rustc_mir_build/src/build/matches/mod.rs
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8 changes: 2 additions & 6 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 @@ -62,7 +62,7 @@ fn full_tested_match() -> () {
_6 = &((_2 as Some).0: i32);
_3 = &fake shallow _2;
StorageLive(_7);
_7 = guard() -> [return: bb8, unwind: bb16];
_7 = guard() -> [return: bb8, unwind: bb15];
}

bb8: {
Expand Down Expand Up @@ -118,11 +118,7 @@ fn full_tested_match() -> () {
unreachable;
}

bb15: {
goto -> bb14;
}

bb16 (cleanup): {
bb15 (cleanup): {
resume;
}
}
8 changes: 2 additions & 6 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 @@ -68,7 +68,7 @@ fn full_tested_match2() -> () {
_6 = &((_2 as Some).0: i32);
_3 = &fake shallow _2;
StorageLive(_7);
_7 = guard() -> [return: bb8, unwind: bb16];
_7 = guard() -> [return: bb8, unwind: bb15];
}

bb8: {
Expand Down Expand Up @@ -118,11 +118,7 @@ fn full_tested_match2() -> () {
unreachable;
}

bb15: {
goto -> bb14;
}

bb16 (cleanup): {
bb15 (cleanup): {
resume;
}
}
86 changes: 39 additions & 47 deletions tests/mir-opt/building/match/match_false_edges.main.built.after.mir
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Original file line number Diff line number Diff line change
Expand Up @@ -38,65 +38,61 @@ fn main() -> () {
StorageLive(_2);
_2 = Option::<i32>::Some(const 1_i32);
PlaceMention(_2);
_5 = discriminant(_2);
switchInt(move _5) -> [1: bb8, otherwise: bb2];
_4 = discriminant(_2);
switchInt(move _4) -> [1: bb2, otherwise: bb1];
}

bb1: {
FakeRead(ForMatchedPlace(None), _2);
unreachable;
falseEdge -> [real: bb14, imaginary: bb4];
}

bb2: {
falseEdge -> [real: bb15, imaginary: bb3];
falseEdge -> [real: bb9, imaginary: bb1];
}

bb3: {
_4 = discriminant(_2);
switchInt(move _4) -> [1: bb6, otherwise: bb4];
goto -> bb1;
}

bb4: {
_5 = discriminant(_2);
switchInt(move _5) -> [1: bb6, otherwise: bb5];
}

bb5: {
StorageLive(_14);
_14 = _2;
_1 = const 4_i32;
StorageDead(_14);
goto -> bb21;
}

bb5: {
goto -> bb1;
goto -> bb20;
}

bb6: {
falseEdge -> [real: bb16, imaginary: bb4];
falseEdge -> [real: bb15, imaginary: bb5];
}

bb7: {
goto -> bb4;
goto -> bb5;
}

bb8: {
falseEdge -> [real: bb10, imaginary: bb2];
FakeRead(ForMatchedPlace(None), _2);
unreachable;
}

bb9: {
goto -> bb2;
}

bb10: {
StorageLive(_7);
_7 = &((_2 as Some).0: i32);
_3 = &fake shallow _2;
StorageLive(_8);
_8 = guard() -> [return: bb11, unwind: bb24];
_8 = guard() -> [return: bb10, unwind: bb22];
}

bb11: {
switchInt(move _8) -> [0: bb13, otherwise: bb12];
bb10: {
switchInt(move _8) -> [0: bb12, otherwise: bb11];
}

bb12: {
bb11: {
StorageDead(_8);
FakeRead(ForMatchGuard, _3);
FakeRead(ForGuardBinding, _7);
Expand All @@ -105,42 +101,42 @@ fn main() -> () {
_1 = const 1_i32;
StorageDead(_6);
StorageDead(_7);
goto -> bb21;
goto -> bb20;
}

bb13: {
goto -> bb14;
bb12: {
goto -> bb13;
}

bb14: {
bb13: {
StorageDead(_8);
StorageDead(_7);
falseEdge -> [real: bb9, imaginary: bb2];
falseEdge -> [real: bb3, imaginary: bb1];
}

bb15: {
bb14: {
StorageLive(_9);
_9 = _2;
_1 = const 2_i32;
StorageDead(_9);
goto -> bb21;
goto -> bb20;
}

bb16: {
bb15: {
StorageLive(_11);
_11 = &((_2 as Some).0: i32);
_3 = &fake shallow _2;
StorageLive(_12);
StorageLive(_13);
_13 = (*_11);
_12 = guard2(move _13) -> [return: bb17, unwind: bb24];
_12 = guard2(move _13) -> [return: bb16, unwind: bb22];
}

bb17: {
switchInt(move _12) -> [0: bb19, otherwise: bb18];
bb16: {
switchInt(move _12) -> [0: bb18, otherwise: bb17];
}

bb18: {
bb17: {
StorageDead(_13);
StorageDead(_12);
FakeRead(ForMatchGuard, _3);
Expand All @@ -150,38 +146,34 @@ fn main() -> () {
_1 = const 3_i32;
StorageDead(_10);
StorageDead(_11);
goto -> bb21;
goto -> bb20;
}

bb19: {
goto -> bb20;
bb18: {
goto -> bb19;
}

bb20: {
bb19: {
StorageDead(_13);
StorageDead(_12);
StorageDead(_11);
falseEdge -> [real: bb7, imaginary: bb4];
falseEdge -> [real: bb7, imaginary: bb5];
}

bb21: {
bb20: {
PlaceMention(_1);
StorageDead(_2);
StorageDead(_1);
_0 = const ();
return;
}

bb22: {
bb21: {
FakeRead(ForMatchedPlace(None), _1);
unreachable;
}

bb23: {
goto -> bb22;
}

bb24 (cleanup): {
bb22 (cleanup): {
resume;
}
}
20 changes: 8 additions & 12 deletions tests/mir-opt/building/match/simple_match.match_bool.built.after.mir
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Original file line number Diff line number Diff line change
Expand Up @@ -6,37 +6,33 @@ fn match_bool(_1: bool) -> usize {

bb0: {
PlaceMention(_1);
switchInt(_1) -> [0: bb2, otherwise: bb4];
switchInt(_1) -> [0: bb1, otherwise: bb2];
}

bb1: {
FakeRead(ForMatchedPlace(None), _1);
unreachable;
_0 = const 20_usize;
goto -> bb6;
}

bb2: {
_0 = const 20_usize;
goto -> bb7;
falseEdge -> [real: bb5, imaginary: bb1];
}

bb3: {
goto -> bb1;
}

bb4: {
falseEdge -> [real: bb6, imaginary: bb2];
FakeRead(ForMatchedPlace(None), _1);
unreachable;
}

bb5: {
goto -> bb2;
}

bb6: {
_0 = const 10_usize;
goto -> bb7;
goto -> bb6;
}

bb7: {
bb6: {
return;
}
}
26 changes: 11 additions & 15 deletions tests/mir-opt/building/match/simple_match.match_enum.built.after.mir
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@ fn match_enum(_1: E1) -> bool {
bb0: {
PlaceMention(_1);
_2 = discriminant(_1);
switchInt(move _2) -> [0: bb3, 1: bb5, 2: bb7, otherwise: bb2];
switchInt(move _2) -> [0: bb2, 1: bb4, 2: bb6, otherwise: bb1];
}

bb1: {
Expand All @@ -17,44 +17,40 @@ fn match_enum(_1: E1) -> bool {
}

bb2: {
goto -> bb1;
goto -> bb8;
}

bb3: {
goto -> bb9;
goto -> bb1;
}

bb4: {
goto -> bb2;
goto -> bb8;
}

bb5: {
goto -> bb9;
goto -> bb1;
}

bb6: {
goto -> bb2;
_0 = const false;
goto -> bb10;
}

bb7: {
_0 = const false;
goto -> bb11;
goto -> bb1;
}

bb8: {
goto -> bb2;
falseEdge -> [real: bb9, imaginary: bb6];
}

bb9: {
falseEdge -> [real: bb10, imaginary: bb7];
}

bb10: {
_0 = const true;
goto -> bb11;
goto -> bb10;
}

bb11: {
bb10: {
return;
}
}
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