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Merged
merged 4 commits into from
Oct 1, 2020
Merged

Implement multiple return terminator optimization #74839

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f54bfac
Implement multiple return terminators optimization
alarsyo Oct 1, 2020
f0d407e
Bless mir-opt tests with new opt
alarsyo Oct 1, 2020
268f786
Add test for multiple terminator optimization
alarsyo Oct 1, 2020
46c0bd3
Bless mir-opt tests for 32 bit
alarsyo Oct 1, 2020
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3 changes: 3 additions & 0 deletions compiler/rustc_mir/src/transform/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@ pub mod inline;
pub mod instcombine;
pub mod instrument_coverage;
pub mod match_branches;
pub mod multiple_return_terminators;
pub mod no_landing_pads;
pub mod nrvo;
pub mod promote_consts;
Expand Down Expand Up @@ -464,6 +465,7 @@ fn run_optimization_passes<'tcx>(
&remove_unneeded_drops::RemoveUnneededDrops,
&match_branches::MatchBranchSimplification,
// inst combine is after MatchBranchSimplification to clean up Ne(_1, false)
&multiple_return_terminators::MultipleReturnTerminators,
&instcombine::InstCombine,
&const_prop::ConstProp,
&simplify_branches::SimplifyBranches::new("after-const-prop"),
Expand All @@ -478,6 +480,7 @@ fn run_optimization_passes<'tcx>(
&simplify::SimplifyCfg::new("final"),
&nrvo::RenameReturnPlace,
&simplify::SimplifyLocals,
&multiple_return_terminators::MultipleReturnTerminators,
];

// Optimizations to run even if mir optimizations have been disabled.
Expand Down
38 changes: 38 additions & 0 deletions compiler/rustc_mir/src/transform/multiple_return_terminators.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,38 @@
//! This pass removes jumps to basic blocks containing only a return, and replaces them with a
//! return instead.

use crate::transform::{simplify, MirPass, MirSource};
use rustc_index::bit_set::BitSet;
use rustc_middle::mir::*;
use rustc_middle::ty::TyCtxt;

pub struct MultipleReturnTerminators;

impl<'tcx> MirPass<'tcx> for MultipleReturnTerminators {
fn run_pass(&self, tcx: TyCtxt<'tcx>, _: MirSource<'tcx>, body: &mut Body<'tcx>) {
if tcx.sess.opts.debugging_opts.mir_opt_level < 3 {
return;
}

// find basic blocks with no statement and a return terminator
let mut bbs_simple_returns = BitSet::new_empty(body.basic_blocks().len());
let bbs = body.basic_blocks_mut();
for idx in bbs.indices() {
if bbs[idx].statements.is_empty()
&& bbs[idx].terminator().kind == TerminatorKind::Return
{
bbs_simple_returns.insert(idx);
}
}

for bb in bbs {
if let TerminatorKind::Goto { target } = bb.terminator().kind {
if bbs_simple_returns.contains(target) {
bb.terminator_mut().kind = TerminatorKind::Return;
}
}
}

simplify::remove_dead_blocks(body)
}
}
42 changes: 18 additions & 24 deletions ...nch_68867.try_sum.EarlyOtherwiseBranch.before-SimplifyBranches-after-copy-prop.after.diff
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Original file line number Diff line number Diff line change
Expand Up @@ -91,7 +91,7 @@
+ StorageLive(_35); // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:11: 23:18
+ _35 = Ne(_34, _11); // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:11: 23:18
+ StorageDead(_34); // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:11: 23:18
+ switchInt(move _35) -> [false: bb8, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:11: 23:18
+ switchInt(move _35) -> [false: bb7, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:11: 23:18
}

bb1: {
Expand All @@ -107,10 +107,9 @@
StorageDead(_33); // scope 0 at $DIR/early_otherwise_branch_68867.rs:27:27: 27:28
- StorageDead(_3); // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:6: 28:7
- StorageDead(_4); // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:1: 29:2
- goto -> bb10; // scope 0 at $DIR/early_otherwise_branch_68867.rs:27:14: 27:28
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:6: 28:7
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:1: 29:2
+ goto -> bb6; // scope 0 at $DIR/early_otherwise_branch_68867.rs:27:14: 27:28
return; // scope 0 at $DIR/early_otherwise_branch_68867.rs:27:14: 27:28
}

+ bb2: {
Expand All @@ -131,7 +130,7 @@
+ nop; // scope 1 at $DIR/early_otherwise_branch_68867.rs:23:49: 23:50
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:49: 23:50
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:49: 23:50
+ goto -> bb7; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
+ goto -> bb6; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
+ }
+
bb3: {
Expand All @@ -154,7 +153,7 @@
+ nop; // scope 2 at $DIR/early_otherwise_branch_68867.rs:24:49: 24:50
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:24:49: 24:50
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:24:49: 24:50
+ goto -> bb7; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
+ goto -> bb6; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
}

bb4: {
Expand All @@ -177,7 +176,7 @@
+ nop; // scope 3 at $DIR/early_otherwise_branch_68867.rs:25:55: 25:56
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:25:55: 25:56
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:25:55: 25:56
+ goto -> bb7; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
+ goto -> bb6; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
}

bb5: {
Expand All @@ -200,7 +199,7 @@
+ nop; // scope 4 at $DIR/early_otherwise_branch_68867.rs:26:55: 26:56
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:26:55: 26:56
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:26:55: 26:56
+ goto -> bb7; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
+ goto -> bb6; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
}

bb6: {
Expand All @@ -221,7 +220,11 @@
- StorageDead(_14); // scope 1 at $DIR/early_otherwise_branch_68867.rs:23:49: 23:50
- StorageDead(_13); // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:49: 23:50
- StorageDead(_12); // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:49: 23:50
- goto -> bb11; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
- goto -> bb10; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:5: 28:7
+ discriminant(_0) = 0; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:5: 28:7
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:6: 28:7
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:1: 29:2
+ return; // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:2: 29:2
}

Expand All @@ -243,15 +246,10 @@
- StorageDead(_19); // scope 2 at $DIR/early_otherwise_branch_68867.rs:24:49: 24:50
- StorageDead(_18); // scope 0 at $DIR/early_otherwise_branch_68867.rs:24:49: 24:50
- StorageDead(_17); // scope 0 at $DIR/early_otherwise_branch_68867.rs:24:49: 24:50
- goto -> bb11; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:5: 28:7
+ discriminant(_0) = 0; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:5: 28:7
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:6: 28:7
+ nop; // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:1: 29:2
+ goto -> bb6; // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:2: 29:2
}

bb8: {
- goto -> bb10; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
- }
-
- bb8: {
- StorageLive(_22); // scope 0 at $DIR/early_otherwise_branch_68867.rs:25:16: 25:19
- _22 = (((*(_4.0: &ViewportPercentageLength)) as Vmin).0: f32); // scope 0 at $DIR/early_otherwise_branch_68867.rs:25:16: 25:19
- StorageLive(_23); // scope 0 at $DIR/early_otherwise_branch_68867.rs:25:28: 25:33
Expand All @@ -269,7 +267,7 @@
- StorageDead(_24); // scope 3 at $DIR/early_otherwise_branch_68867.rs:25:55: 25:56
- StorageDead(_23); // scope 0 at $DIR/early_otherwise_branch_68867.rs:25:55: 25:56
- StorageDead(_22); // scope 0 at $DIR/early_otherwise_branch_68867.rs:25:55: 25:56
- goto -> bb11; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
- goto -> bb10; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
- }
-
- bb9: {
Expand All @@ -290,19 +288,15 @@
- StorageDead(_29); // scope 4 at $DIR/early_otherwise_branch_68867.rs:26:55: 26:56
- StorageDead(_28); // scope 0 at $DIR/early_otherwise_branch_68867.rs:26:55: 26:56
- StorageDead(_27); // scope 0 at $DIR/early_otherwise_branch_68867.rs:26:55: 26:56
- goto -> bb11; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
- goto -> bb10; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
- }
-
- bb10: {
- return; // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:2: 29:2
- }
-
- bb11: {
- ((_0 as Ok).0: ViewportPercentageLength) = move _3; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:5: 28:7
- discriminant(_0) = 0; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:5: 28:7
- StorageDead(_3); // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:6: 28:7
- StorageDead(_4); // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:1: 29:2
- goto -> bb10; // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:2: 29:2
- return; // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:2: 29:2
+ StorageDead(_35); // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:21: 23:30
+ switchInt(_11) -> [0_isize: bb2, 1_isize: bb3, 2_isize: bb4, 3_isize: bb5, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:21: 23:30
}
Expand Down
31 changes: 12 additions & 19 deletions src/test/mir-opt/early_otherwise_branch_68867.try_sum.EarlyOtherwiseBranch.diff
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Expand Up @@ -73,7 +73,7 @@
+ StorageLive(_35); // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:11: 23:18
+ _35 = Ne(_34, _11); // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:11: 23:18
+ StorageDead(_34); // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:11: 23:18
+ switchInt(move _35) -> [false: bb8, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:11: 23:18
+ switchInt(move _35) -> [false: bb7, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:11: 23:18
}

bb1: {
Expand All @@ -89,8 +89,7 @@
StorageDead(_33); // scope 0 at $DIR/early_otherwise_branch_68867.rs:27:27: 27:28
StorageDead(_3); // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:6: 28:7
StorageDead(_4); // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:1: 29:2
- goto -> bb10; // scope 0 at $DIR/early_otherwise_branch_68867.rs:27:14: 27:28
+ goto -> bb6; // scope 0 at $DIR/early_otherwise_branch_68867.rs:27:14: 27:28
return; // scope 0 at $DIR/early_otherwise_branch_68867.rs:27:14: 27:28
}

- bb3: {
Expand Down Expand Up @@ -127,8 +126,8 @@
StorageDead(_14); // scope 1 at $DIR/early_otherwise_branch_68867.rs:23:49: 23:50
StorageDead(_13); // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:49: 23:50
StorageDead(_12); // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:49: 23:50
- goto -> bb11; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
+ goto -> bb7; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
- goto -> bb10; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
+ goto -> bb6; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
}

- bb7: {
Expand All @@ -150,8 +149,8 @@
StorageDead(_19); // scope 2 at $DIR/early_otherwise_branch_68867.rs:24:49: 24:50
StorageDead(_18); // scope 0 at $DIR/early_otherwise_branch_68867.rs:24:49: 24:50
StorageDead(_17); // scope 0 at $DIR/early_otherwise_branch_68867.rs:24:49: 24:50
- goto -> bb11; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
+ goto -> bb7; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
- goto -> bb10; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
+ goto -> bb6; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
}

- bb8: {
Expand All @@ -173,8 +172,8 @@
StorageDead(_24); // scope 3 at $DIR/early_otherwise_branch_68867.rs:25:55: 25:56
StorageDead(_23); // scope 0 at $DIR/early_otherwise_branch_68867.rs:25:55: 25:56
StorageDead(_22); // scope 0 at $DIR/early_otherwise_branch_68867.rs:25:55: 25:56
- goto -> bb11; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
+ goto -> bb7; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
- goto -> bb10; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
+ goto -> bb6; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
}

- bb9: {
Expand All @@ -196,26 +195,20 @@
StorageDead(_29); // scope 4 at $DIR/early_otherwise_branch_68867.rs:26:55: 26:56
StorageDead(_28); // scope 0 at $DIR/early_otherwise_branch_68867.rs:26:55: 26:56
StorageDead(_27); // scope 0 at $DIR/early_otherwise_branch_68867.rs:26:55: 26:56
- goto -> bb11; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
+ goto -> bb7; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
- goto -> bb10; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
+ goto -> bb6; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:8: 28:6
}

- bb10: {
+ bb6: {
return; // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:2: 29:2
}

- bb11: {
+ bb7: {
((_0 as Ok).0: ViewportPercentageLength) = move _3; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:5: 28:7
discriminant(_0) = 0; // scope 0 at $DIR/early_otherwise_branch_68867.rs:22:5: 28:7
StorageDead(_3); // scope 0 at $DIR/early_otherwise_branch_68867.rs:28:6: 28:7
StorageDead(_4); // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:1: 29:2
- goto -> bb10; // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:2: 29:2
+ goto -> bb6; // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:2: 29:2
return; // scope 0 at $DIR/early_otherwise_branch_68867.rs:29:2: 29:2
+ }
+
+ bb8: {
+ bb7: {
+ StorageDead(_35); // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:21: 23:30
+ switchInt(_11) -> [0_isize: bb2, 1_isize: bb3, 2_isize: bb4, 3_isize: bb5, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch_68867.rs:23:21: 23:30
}
Expand Down
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