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[WIP] Re-enable the early otherwise branch optimization #121397

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[WIP] Re-enable the early otherwise branch optimization #121397

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0533c43
Add test case for #119014
DianQK Feb 21, 2024
c340ced
Resolve unsound hoisting of discriminant in `EarlyOtherwiseBranch`
DianQK Feb 21, 2024
26afcef
Re-enable the early otherwise branch optimization
DianQK Feb 21, 2024
42926f6
Add FileCheck for `early_otherwise_branch*.rs`
DianQK Feb 22, 2024
9f14320
Apply `EarlyOtherwiseBranch` to scalar values
DianQK Feb 23, 2024
e73ae2f
Apply `EarlyOtherwiseBranch` for all targets with the same value
DianQK Feb 23, 2024
30b690b
Apply `EarlyOtherwiseBranch` even if the types are different when the…
DianQK Feb 23, 2024
8d0f254
Don't modify the otherwise of the switch
DianQK Feb 23, 2024
834683b
Remove the nonsense `may_hoist` check
DianQK Mar 3, 2024
73ef0c0
Move some cheaper checks earlier
DianQK Mar 3, 2024
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451 changes: 243 additions & 208 deletions compiler/rustc_mir_transform/src/early_otherwise_branch.rs
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25 changes: 25 additions & 0 deletions tests/codegen/enum/enum-early-otherwise-branch.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,25 @@
//@ compile-flags: -O

#![crate_type = "lib"]

pub enum Enum {
A(u32),
B(u32),
C(u32),
}

#[no_mangle]
pub fn foo(lhs: &Enum, rhs: &Enum) -> bool {
// CHECK-LABEL: define{{.*}}i1 @foo(
// CHECK-NOT: switch
// CHECK-NOT: br
// CHECK: [[SELECT:%.*]] = select
// CHECK-NEXT: ret i1 [[SELECT]]
// CHECK-NEXT: }
match (lhs, rhs) {
(Enum::A(lhs), Enum::A(rhs)) => lhs == rhs,
(Enum::B(lhs), Enum::B(rhs)) => lhs == rhs,
(Enum::C(lhs), Enum::C(rhs)) => lhs == rhs,
_ => false,
}
}
35 changes: 9 additions & 26 deletions tests/mir-opt/early_otherwise_branch.opt1.EarlyOtherwiseBranch.diff
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Original file line number Diff line number Diff line change
Expand Up @@ -12,8 +12,6 @@
let mut _7: isize;
let _8: u32;
let _9: u32;
+ let mut _10: isize;
+ let mut _11: bool;
scope 1 {
debug a => _8;
debug b => _9;
Expand All @@ -29,48 +27,33 @@
StorageDead(_5);
StorageDead(_4);
_7 = discriminant((_3.0: std::option::Option<u32>));
- switchInt(move _7) -> [1: bb2, otherwise: bb1];
+ StorageLive(_10);
+ _10 = discriminant((_3.1: std::option::Option<u32>));
+ StorageLive(_11);
+ _11 = Ne(_7, move _10);
+ StorageDead(_10);
+ switchInt(move _11) -> [0: bb4, otherwise: bb1];
switchInt(move _7) -> [1: bb2, otherwise: bb1];
}

bb1: {
+ StorageDead(_11);
_0 = const 1_u32;
- goto -> bb4;
+ goto -> bb3;
goto -> bb4;
}

bb2: {
- _6 = discriminant((_3.1: std::option::Option<u32>));
- switchInt(move _6) -> [1: bb3, otherwise: bb1];
- }
-
- bb3: {
_6 = discriminant((_3.1: std::option::Option<u32>));
switchInt(move _6) -> [1: bb3, otherwise: bb1];
}
bb3: {
StorageLive(_8);
_8 = (((_3.0: std::option::Option<u32>) as Some).0: u32);
StorageLive(_9);
_9 = (((_3.1: std::option::Option<u32>) as Some).0: u32);
_0 = const 0_u32;
StorageDead(_9);
StorageDead(_8);
- goto -> bb4;
+ goto -> bb3;
goto -> bb4;
}

- bb4: {
+ bb3: {
bb4: {
StorageDead(_3);
return;
+ }
+
+ bb4: {
+ StorageDead(_11);
+ switchInt(_7) -> [1: bb2, otherwise: bb1];
}
}

90 changes: 90 additions & 0 deletions tests/mir-opt/early_otherwise_branch.opt10.EarlyOtherwiseBranch.diff
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Original file line number Diff line number Diff line change
@@ -0,0 +1,90 @@
- // MIR for `opt10` before EarlyOtherwiseBranch
+ // MIR for `opt10` after EarlyOtherwiseBranch

fn opt10(_1: E8, _2: E16) -> u32 {
debug x => _1;
debug y => _2;
let mut _0: u32;
let mut _3: (E8, E16);
let mut _4: E8;
let mut _5: E16;
let mut _6: u16;
let mut _7: u16;
let mut _8: u16;
let mut _9: u8;
+ let mut _10: u16;

bb0: {
StorageLive(_3);
StorageLive(_4);
_4 = move _1;
StorageLive(_5);
_5 = move _2;
_3 = (move _4, move _5);
StorageDead(_5);
StorageDead(_4);
_9 = discriminant((_3.0: E8));
- switchInt(move _9) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb9];
+ StorageLive(_10);
+ _10 = discriminant((_3.1: E16));
+ switchInt(move _10) -> [0: bb7, otherwise: bb1];
}

bb1: {
+ StorageDead(_10);
_0 = const 0_u32;
- goto -> bb8;
+ goto -> bb5;
}

bb2: {
- _6 = discriminant((_3.1: E16));
- switchInt(move _6) -> [0: bb5, otherwise: bb1];
+ _0 = const 1_u32;
+ goto -> bb5;
}

bb3: {
- _7 = discriminant((_3.1: E16));
- switchInt(move _7) -> [0: bb6, otherwise: bb1];
+ _0 = const 2_u32;
+ goto -> bb5;
}

bb4: {
- _8 = discriminant((_3.1: E16));
- switchInt(move _8) -> [0: bb7, otherwise: bb1];
+ _0 = const 3_u32;
+ goto -> bb5;
}

bb5: {
- _0 = const 1_u32;
- goto -> bb8;
+ StorageDead(_3);
+ return;
}

bb6: {
- _0 = const 2_u32;
- goto -> bb8;
+ unreachable;
}

bb7: {
- _0 = const 3_u32;
- goto -> bb8;
- }
-
- bb8: {
- StorageDead(_3);
- return;
- }
-
- bb9: {
- unreachable;
+ StorageDead(_10);
+ switchInt(_9) -> [0: bb2, 1: bb3, 2: bb4, otherwise: bb6];
}
}

15 changes: 10 additions & 5 deletions tests/mir-opt/early_otherwise_branch.opt2.EarlyOtherwiseBranch.diff
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Original file line number Diff line number Diff line change
Expand Up @@ -30,13 +30,13 @@
StorageDead(_5);
StorageDead(_4);
_8 = discriminant((_3.0: std::option::Option<u32>));
- switchInt(move _8) -> [0: bb2, 1: bb3, otherwise: bb1];
- switchInt(move _8) -> [0: bb2, 1: bb3, otherwise: bb7];
+ StorageLive(_11);
+ _11 = discriminant((_3.1: std::option::Option<u32>));
+ StorageLive(_12);
+ _12 = Ne(_8, move _11);
+ StorageDead(_11);
+ switchInt(move _12) -> [0: bb5, otherwise: bb1];
+ switchInt(move _12) -> [0: bb6, otherwise: bb1];
}

bb1: {
Expand Down Expand Up @@ -70,7 +70,7 @@

- bb5: {
+ bb3: {
_0 = const 0_u32;
_0 = const 2_u32;
- goto -> bb6;
+ goto -> bb4;
}
Expand All @@ -79,11 +79,16 @@
+ bb4: {
StorageDead(_3);
return;
}

- bb7: {
+ bb5: {
unreachable;
+ }
+
+ bb5: {
+ bb6: {
+ StorageDead(_12);
+ switchInt(_8) -> [0: bb3, 1: bb2, otherwise: bb1];
+ switchInt(_8) -> [0: bb3, 1: bb2, otherwise: bb5];
}
}

72 changes: 45 additions & 27 deletions tests/mir-opt/early_otherwise_branch.opt3.EarlyOtherwiseBranch.diff
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Original file line number Diff line number Diff line change
Expand Up @@ -10,13 +10,14 @@
let mut _5: std::option::Option<bool>;
let mut _6: isize;
let mut _7: isize;
let _8: u32;
let _9: bool;
+ let mut _10: isize;
+ let mut _11: bool;
let mut _8: isize;
let _9: u32;
let _10: bool;
+ let mut _11: isize;
+ let mut _12: bool;
scope 1 {
debug a => _8;
debug b => _9;
debug a => _9;
debug b => _10;
}

bb0: {
Expand All @@ -28,49 +29,66 @@
_3 = (move _4, move _5);
StorageDead(_5);
StorageDead(_4);
_7 = discriminant((_3.0: std::option::Option<u32>));
- switchInt(move _7) -> [1: bb2, otherwise: bb1];
+ StorageLive(_10);
+ _10 = discriminant((_3.1: std::option::Option<bool>));
_8 = discriminant((_3.0: std::option::Option<u32>));
- switchInt(move _8) -> [0: bb2, 1: bb3, otherwise: bb7];
+ StorageLive(_11);
+ _11 = Ne(_7, move _10);
+ StorageDead(_10);
+ switchInt(move _11) -> [0: bb4, otherwise: bb1];
+ _11 = discriminant((_3.1: std::option::Option<bool>));
+ StorageLive(_12);
+ _12 = Ne(_8, move _11);
+ StorageDead(_11);
+ switchInt(move _12) -> [0: bb6, otherwise: bb1];
}

bb1: {
+ StorageDead(_11);
+ StorageDead(_12);
_0 = const 1_u32;
- goto -> bb4;
+ goto -> bb3;
- goto -> bb6;
+ goto -> bb4;
}

bb2: {
- _6 = discriminant((_3.1: std::option::Option<bool>));
- switchInt(move _6) -> [1: bb3, otherwise: bb1];
- switchInt(move _6) -> [0: bb5, otherwise: bb1];
- }
-
- bb3: {
StorageLive(_8);
_8 = (((_3.0: std::option::Option<u32>) as Some).0: u32);
- _7 = discriminant((_3.1: std::option::Option<bool>));
- switchInt(move _7) -> [1: bb4, otherwise: bb1];
- }
-
- bb4: {
StorageLive(_9);
_9 = (((_3.1: std::option::Option<bool>) as Some).0: bool);
_9 = (((_3.0: std::option::Option<u32>) as Some).0: u32);
StorageLive(_10);
_10 = (((_3.1: std::option::Option<bool>) as Some).0: bool);
_0 = const 0_u32;
StorageDead(_10);
StorageDead(_9);
StorageDead(_8);
- goto -> bb4;
+ goto -> bb3;
- goto -> bb6;
+ goto -> bb4;
}

- bb4: {
- bb5: {
+ bb3: {
_0 = const 2_u32;
- goto -> bb6;
+ goto -> bb4;
}

- bb6: {
+ bb4: {
StorageDead(_3);
return;
}

- bb7: {
+ bb5: {
unreachable;
+ }
+
+ bb4: {
+ StorageDead(_11);
+ switchInt(_7) -> [1: bb2, otherwise: bb1];
+ bb6: {
+ StorageDead(_12);
+ switchInt(_8) -> [0: bb3, 1: bb2, otherwise: bb5];
}
}

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