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Implement a generic Destination Propagation optimization on MIR #72632

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merged 20 commits into from
Sep 20, 2020
+1,919 −456
Merged

Implement a generic Destination Propagation optimization on MIR #72632

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78ff69b
Implement a destination propagation pass
jonas-schievink May 24, 2020
43ad8e4
simplify_try: print dest_prop diff and bless
jonas-schievink May 25, 2020
1649895
simplify_try: clean up test
jonas-schievink May 25, 2020
8a7b1c3
Make nrvo-simple set mir-opt-level=1
jonas-schievink May 25, 2020
8a3e2b7
Bless mir-opt tests
jonas-schievink Sep 12, 2020
812d4bb
Fix dataflow assert errors
jonas-schievink Sep 12, 2020
7dbc7f7
Add a few dest-prop MIR tests
jonas-schievink May 24, 2020
402f863
perf: walk liveness backwards in Conflicts::build
jonas-schievink Sep 12, 2020
665a98d
Fix dest-prop mir-opt tests
jonas-schievink Sep 12, 2020
ab26fb1
perf: only calculate conflicts for candidates
jonas-schievink May 26, 2020
ddd6930
perf: bail out when there's >500 candidate locals
jonas-schievink May 26, 2020
88538ad
Record intra-statement/terminator conflicts
jonas-schievink Sep 12, 2020
934634e
More logging
jonas-schievink Jun 22, 2020
484db5b
Properly inherit conflicts when merging locals
jonas-schievink Jun 24, 2020
5728834
Fix rebase fallout
jonas-schievink Jun 24, 2020
7af964f
Limit block count
jonas-schievink Jun 24, 2020
cd5d720
Fix rebase fallout
jonas-schievink Sep 12, 2020
682de94
Move inner items outside
jonas-schievink Sep 12, 2020
ffd9445
Return `Place` by value
jonas-schievink Sep 17, 2020
2f9271b
Clarify FIXME
jonas-schievink Sep 17, 2020
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2 changes: 1 addition & 1 deletion compiler/rustc_mir/src/dataflow/impls/mod.rs
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Expand Up @@ -204,7 +204,7 @@ impl<'a, 'tcx> HasMoveData<'tcx> for DefinitelyInitializedPlaces<'a, 'tcx> {

/// `EverInitializedPlaces` tracks all places that might have ever been
/// initialized upon reaching a particular point in the control flow
/// for a function, without an intervening `Storage Dead`.
/// for a function, without an intervening `StorageDead`.
///
/// This dataflow is used to determine if an immutable local variable may
/// be assigned to.
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_mir/src/lib.rs
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Expand Up @@ -6,6 +6,7 @@ Rust MIR: a lowered representation of Rust.

#![feature(nll)]
#![feature(in_band_lifetimes)]
#![feature(bindings_after_at)]
#![feature(bool_to_option)]
#![feature(box_patterns)]
#![feature(box_syntax)]
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1,057 changes: 1,057 additions & 0 deletions compiler/rustc_mir/src/transform/dest_prop.rs
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2 changes: 2 additions & 0 deletions compiler/rustc_mir/src/transform/mod.rs
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Expand Up @@ -24,6 +24,7 @@ pub mod cleanup_post_borrowck;
pub mod const_prop;
pub mod copy_prop;
pub mod deaggregator;
pub mod dest_prop;
pub mod dump_mir;
pub mod elaborate_drops;
pub mod generator;
Expand Down Expand Up @@ -467,6 +468,7 @@ fn run_optimization_passes<'tcx>(
&simplify_comparison_integral::SimplifyComparisonIntegral,
&simplify_try::SimplifyArmIdentity,
&simplify_try::SimplifyBranchSame,
&dest_prop::DestinationPropagation,
&copy_prop::CopyPropagation,
&simplify_branches::SimplifyBranches::new("after-copy-prop"),
&remove_noop_landing_pads::RemoveNoopLandingPads,
Expand Down
6 changes: 6 additions & 0 deletions compiler/rustc_mir/src/transform/nrvo.rs
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Expand Up @@ -36,6 +36,12 @@ impl<'tcx> MirPass<'tcx> for RenameReturnPlace {
return;
}

if tcx.sess.opts.debugging_opts.mir_opt_level >= 2 {
// The `DestinationPropagation` pass runs at level 2, so this pass is redundant (and
// fails some asserts).
return;
}

let returned_local = match local_eligible_for_nrvo(body) {
Some(l) => l,
None => {
Expand Down
28 changes: 14 additions & 14 deletions src/test/mir-opt/const_allocation.main.ConstProp.after.32bit.mir
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Expand Up @@ -24,42 +24,42 @@ fn main() -> () {
}

alloc0 (static: FOO, size: 8, align: 4) {
╾─alloc17─╼ 03 00 00 00 │ ╾──╼....
╾─alloc14─╼ 03 00 00 00 │ ╾──╼....
}

alloc17 (size: 48, align: 4) {
alloc14 (size: 48, align: 4) {
0x00 │ 00 00 00 00 __ __ __ __ ╾─alloc4──╼ 00 00 00 00 │ ....░░░░╾──╼....
0x10 │ 00 00 00 00 __ __ __ __ ╾─alloc8──╼ 02 00 00 00 │ ....░░░░╾──╼....
0x20 │ 01 00 00 00 2a 00 00 00 ╾─alloc13─╼ 03 00 00 00 │ ....*...╾──╼....
0x10 │ 00 00 00 00 __ __ __ __ ╾─alloc7──╼ 02 00 00 00 │ ....░░░░╾──╼....
0x20 │ 01 00 00 00 2a 00 00 00 ╾─alloc11─╼ 03 00 00 00 │ ....*...╾──╼....
}

alloc4 (size: 0, align: 4) {}

alloc8 (size: 16, align: 4) {
╾─alloc7──╼ 03 00 00 00 ╾─alloc9──╼ 03 00 00 00 │ ╾──╼....╾──╼....
alloc7 (size: 16, align: 4) {
╾─alloc6──╼ 03 00 00 00 ╾─alloc8──╼ 03 00 00 00 │ ╾──╼....╾──╼....
}

alloc7 (size: 3, align: 1) {
alloc6 (size: 3, align: 1) {
66 6f 6f │ foo
}

alloc9 (size: 3, align: 1) {
alloc8 (size: 3, align: 1) {
62 61 72 │ bar
}

alloc13 (size: 24, align: 4) {
0x00 │ ╾─alloc12─╼ 03 00 00 00 ╾─alloc14─╼ 03 00 00 00 │ ╾──╼....╾──╼....
0x10 │ ╾─alloc15─╼ 04 00 00 00 │ ╾──╼....
alloc11 (size: 24, align: 4) {
0x00 │ ╾─alloc10─╼ 03 00 00 00 ╾─alloc12─╼ 03 00 00 00 │ ╾──╼....╾──╼....
0x10 │ ╾─alloc13─╼ 04 00 00 00 │ ╾──╼....
}

alloc12 (size: 3, align: 1) {
alloc10 (size: 3, align: 1) {
6d 65 68 │ meh
}

alloc14 (size: 3, align: 1) {
alloc12 (size: 3, align: 1) {
6d 6f 70 │ mop
}

alloc15 (size: 4, align: 1) {
alloc13 (size: 4, align: 1) {
6d c3 b6 70 │ m..p
}
32 changes: 16 additions & 16 deletions src/test/mir-opt/const_allocation.main.ConstProp.after.64bit.mir
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Expand Up @@ -24,46 +24,46 @@ fn main() -> () {
}

alloc0 (static: FOO, size: 16, align: 8) {
╾───────alloc17───────╼ 03 00 00 00 00 00 00 00 │ ╾──────╼........
╾───────alloc14───────╼ 03 00 00 00 00 00 00 00 │ ╾──────╼........
}

alloc17 (size: 72, align: 8) {
alloc14 (size: 72, align: 8) {
0x00 │ 00 00 00 00 __ __ __ __ ╾───────alloc4────────╼ │ ....░░░░╾──────╼
0x10 │ 00 00 00 00 00 00 00 00 00 00 00 00 __ __ __ __ │ ............░░░░
0x20 │ ╾───────alloc8────────╼ 02 00 00 00 00 00 00 00 │ ╾──────╼........
0x30 │ 01 00 00 00 2a 00 00 00 ╾───────alloc13───────╼ │ ....*...╾──────╼
0x20 │ ╾───────alloc7────────╼ 02 00 00 00 00 00 00 00 │ ╾──────╼........
0x30 │ 01 00 00 00 2a 00 00 00 ╾───────alloc11───────╼ │ ....*...╾──────╼
0x40 │ 03 00 00 00 00 00 00 00 │ ........
}

alloc4 (size: 0, align: 8) {}

alloc8 (size: 32, align: 8) {
0x00 │ ╾───────alloc7────────╼ 03 00 00 00 00 00 00 00 │ ╾──────╼........
0x10 │ ╾───────alloc9────────╼ 03 00 00 00 00 00 00 00 │ ╾──────╼........
alloc7 (size: 32, align: 8) {
0x00 │ ╾───────alloc6────────╼ 03 00 00 00 00 00 00 00 │ ╾──────╼........
0x10 │ ╾───────alloc8────────╼ 03 00 00 00 00 00 00 00 │ ╾──────╼........
}

alloc7 (size: 3, align: 1) {
alloc6 (size: 3, align: 1) {
66 6f 6f │ foo
}

alloc9 (size: 3, align: 1) {
alloc8 (size: 3, align: 1) {
62 61 72 │ bar
}

alloc13 (size: 48, align: 8) {
0x00 │ ╾───────alloc12───────╼ 03 00 00 00 00 00 00 00 │ ╾──────╼........
0x10 │ ╾───────alloc14───────╼ 03 00 00 00 00 00 00 00 │ ╾──────╼........
0x20 │ ╾───────alloc15───────╼ 04 00 00 00 00 00 00 00 │ ╾──────╼........
alloc11 (size: 48, align: 8) {
0x00 │ ╾───────alloc10───────╼ 03 00 00 00 00 00 00 00 │ ╾──────╼........
0x10 │ ╾───────alloc12───────╼ 03 00 00 00 00 00 00 00 │ ╾──────╼........
0x20 │ ╾───────alloc13───────╼ 04 00 00 00 00 00 00 00 │ ╾──────╼........
}

alloc12 (size: 3, align: 1) {
alloc10 (size: 3, align: 1) {
6d 65 68 │ meh
}

alloc14 (size: 3, align: 1) {
alloc12 (size: 3, align: 1) {
6d 6f 70 │ mop
}

alloc15 (size: 4, align: 1) {
alloc13 (size: 4, align: 1) {
6d c3 b6 70 │ m..p
}
26 changes: 13 additions & 13 deletions src/test/mir-opt/const_allocation2.main.ConstProp.after.32bit.mir
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Original file line number Diff line number Diff line change
Expand Up @@ -24,41 +24,41 @@ fn main() -> () {
}

alloc0 (static: FOO, size: 8, align: 4) {
╾─alloc23─╼ 03 00 00 00 │ ╾──╼....
╾─alloc20─╼ 03 00 00 00 │ ╾──╼....
}

alloc23 (size: 48, align: 4) {
alloc20 (size: 48, align: 4) {
0x00 │ 00 00 00 00 __ __ __ __ ╾─alloc8──╼ 00 00 00 00 │ ....░░░░╾──╼....
0x10 │ 00 00 00 00 __ __ __ __ ╾─alloc13─╼ 02 00 00 00 │ ....░░░░╾──╼....
0x20 │ 01 00 00 00 2a 00 00 00 ╾─alloc21─╼ 03 00 00 00 │ ....*...╾──╼....
0x10 │ 00 00 00 00 __ __ __ __ ╾─alloc12─╼ 02 00 00 00 │ ....░░░░╾──╼....
0x20 │ 01 00 00 00 2a 00 00 00 ╾─alloc19─╼ 03 00 00 00 │ ....*...╾──╼....
}

alloc8 (size: 0, align: 4) {}

alloc13 (size: 8, align: 4) {
╾─alloc11─╼ ╾─alloc12─╼ │ ╾──╼╾──╼
alloc12 (size: 8, align: 4) {
╾─alloc10─╼ ╾─alloc11─╼ │ ╾──╼╾──╼
}

alloc11 (size: 1, align: 1) {
alloc10 (size: 1, align: 1) {
05 │ .
}

alloc12 (size: 1, align: 1) {
alloc11 (size: 1, align: 1) {
06 │ .
}

alloc21 (size: 12, align: 4) {
╾─a17+0x3─╼ ╾─alloc18─╼ ╾─a20+0x2─╼ │ ╾──╼╾──╼╾──╼
alloc19 (size: 12, align: 4) {
╾─a15+0x3─╼ ╾─alloc16─╼ ╾─a18+0x2─╼ │ ╾──╼╾──╼╾──╼
}

alloc17 (size: 4, align: 1) {
alloc15 (size: 4, align: 1) {
2a 45 15 6f │ *E.o
}

alloc18 (size: 1, align: 1) {
alloc16 (size: 1, align: 1) {
2a │ *
}

alloc20 (size: 4, align: 1) {
alloc18 (size: 4, align: 1) {
2a 45 15 6f │ *E.o
}
28 changes: 14 additions & 14 deletions src/test/mir-opt/const_allocation2.main.ConstProp.after.64bit.mir
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Expand Up @@ -24,44 +24,44 @@ fn main() -> () {
}

alloc0 (static: FOO, size: 16, align: 8) {
╾───────alloc23───────╼ 03 00 00 00 00 00 00 00 │ ╾──────╼........
╾───────alloc20───────╼ 03 00 00 00 00 00 00 00 │ ╾──────╼........
}

alloc23 (size: 72, align: 8) {
alloc20 (size: 72, align: 8) {
0x00 │ 00 00 00 00 __ __ __ __ ╾───────alloc8────────╼ │ ....░░░░╾──────╼
0x10 │ 00 00 00 00 00 00 00 00 00 00 00 00 __ __ __ __ │ ............░░░░
0x20 │ ╾───────alloc13───────╼ 02 00 00 00 00 00 00 00 │ ╾──────╼........
0x30 │ 01 00 00 00 2a 00 00 00 ╾───────alloc21───────╼ │ ....*...╾──────╼
0x20 │ ╾───────alloc12───────╼ 02 00 00 00 00 00 00 00 │ ╾──────╼........
0x30 │ 01 00 00 00 2a 00 00 00 ╾───────alloc19───────╼ │ ....*...╾──────╼
0x40 │ 03 00 00 00 00 00 00 00 │ ........
}

alloc8 (size: 0, align: 8) {}

alloc13 (size: 16, align: 8) {
╾───────alloc11───────╼ ╾───────alloc12───────╼ │ ╾──────╼╾──────╼
alloc12 (size: 16, align: 8) {
╾───────alloc10───────╼ ╾───────alloc11───────╼ │ ╾──────╼╾──────╼
}

alloc11 (size: 1, align: 1) {
alloc10 (size: 1, align: 1) {
05 │ .
}

alloc12 (size: 1, align: 1) {
alloc11 (size: 1, align: 1) {
06 │ .
}

alloc21 (size: 24, align: 8) {
0x00 │ ╾─────alloc17+0x3─────╼ ╾───────alloc18───────╼ │ ╾──────╼╾──────╼
0x10 │ ╾─────alloc20+0x2─────╼ │ ╾──────╼
alloc19 (size: 24, align: 8) {
0x00 │ ╾─────alloc15+0x3─────╼ ╾───────alloc16───────╼ │ ╾──────╼╾──────╼
0x10 │ ╾─────alloc18+0x2─────╼ │ ╾──────╼
}

alloc17 (size: 4, align: 1) {
alloc15 (size: 4, align: 1) {
2a 45 15 6f │ *E.o
}

alloc18 (size: 1, align: 1) {
alloc16 (size: 1, align: 1) {
2a │ *
}

alloc20 (size: 4, align: 1) {
alloc18 (size: 4, align: 1) {
2a 45 15 6f │ *E.o
}
4 changes: 2 additions & 2 deletions src/test/mir-opt/const_allocation3.main.ConstProp.after.32bit.mir
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Expand Up @@ -24,10 +24,10 @@ fn main() -> () {
}

alloc0 (static: FOO, size: 4, align: 4) {
╾─alloc9──╼ │ ╾──╼
╾─alloc3──╼ │ ╾──╼
}

alloc9 (size: 168, align: 1) {
alloc3 (size: 168, align: 1) {
0x00 │ ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab │ ................
0x10 │ ab ab ab ab ab ab ab ab ab ab ab ab ╾─alloc4──╼ │ ............╾──╼
0x20 │ 01 ef cd ab 00 00 00 00 00 00 00 00 00 00 00 00 │ ................
Expand Down
4 changes: 2 additions & 2 deletions src/test/mir-opt/const_allocation3.main.ConstProp.after.64bit.mir
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Expand Up @@ -24,10 +24,10 @@ fn main() -> () {
}

alloc0 (static: FOO, size: 8, align: 8) {
╾───────alloc9────────╼ │ ╾──────╼
╾───────alloc3────────╼ │ ╾──────╼
}

alloc9 (size: 180, align: 1) {
alloc3 (size: 180, align: 1) {
0x00 │ ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab │ ................
0x10 │ ab ab ab ab ab ab ab ab ab ab ab ab ╾──alloc4── │ ............╾───
0x20 │ ──────────╼ 01 ef cd ab 00 00 00 00 00 00 00 00 │ ───╼............
Expand Down
15 changes: 5 additions & 10 deletions src/test/mir-opt/copy_propagation.test.CopyPropagation.diff
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Expand Up @@ -6,19 +6,14 @@
let mut _0: u32; // return place in scope 0 at $DIR/copy_propagation.rs:3:20: 3:23
let _2: u32; // in scope 0 at $DIR/copy_propagation.rs:4:9: 4:10
scope 1 {
- debug y => _2; // in scope 1 at $DIR/copy_propagation.rs:4:9: 4:10
+ debug y => _1; // in scope 1 at $DIR/copy_propagation.rs:4:9: 4:10
debug y => _0; // in scope 1 at $DIR/copy_propagation.rs:4:9: 4:10
}

bb0: {
- StorageLive(_2); // scope 0 at $DIR/copy_propagation.rs:4:9: 4:10
- _2 = _1; // scope 0 at $DIR/copy_propagation.rs:4:13: 4:14
- _0 = _2; // scope 1 at $DIR/copy_propagation.rs:5:5: 5:6
- StorageDead(_2); // scope 0 at $DIR/copy_propagation.rs:6:1: 6:2
+ nop; // scope 0 at $DIR/copy_propagation.rs:4:9: 4:10
+ nop; // scope 0 at $DIR/copy_propagation.rs:4:13: 4:14
+ _0 = _1; // scope 1 at $DIR/copy_propagation.rs:5:5: 5:6
+ nop; // scope 0 at $DIR/copy_propagation.rs:6:1: 6:2
nop; // scope 0 at $DIR/copy_propagation.rs:4:9: 4:10
_0 = _1; // scope 0 at $DIR/copy_propagation.rs:4:13: 4:14
nop; // scope 1 at $DIR/copy_propagation.rs:5:5: 5:6
nop; // scope 0 at $DIR/copy_propagation.rs:6:1: 6:2
return; // scope 0 at $DIR/copy_propagation.rs:6:2: 6:2
}
}
Expand Down
10 changes: 5 additions & 5 deletions src/test/mir-opt/copy_propagation_arg.arg_src.CopyPropagation.diff
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Expand Up @@ -6,15 +6,15 @@
let mut _0: i32; // return place in scope 0 at $DIR/copy_propagation_arg.rs:27:27: 27:30
let _2: i32; // in scope 0 at $DIR/copy_propagation_arg.rs:28:9: 28:10
scope 1 {
debug y => _2; // in scope 1 at $DIR/copy_propagation_arg.rs:28:9: 28:10
debug y => _0; // in scope 1 at $DIR/copy_propagation_arg.rs:28:9: 28:10
}

bb0: {
StorageLive(_2); // scope 0 at $DIR/copy_propagation_arg.rs:28:9: 28:10
_2 = _1; // scope 0 at $DIR/copy_propagation_arg.rs:28:13: 28:14
nop; // scope 0 at $DIR/copy_propagation_arg.rs:28:9: 28:10
_0 = _1; // scope 0 at $DIR/copy_propagation_arg.rs:28:13: 28:14
_1 = const 123_i32; // scope 1 at $DIR/copy_propagation_arg.rs:29:5: 29:12
_0 = _2; // scope 1 at $DIR/copy_propagation_arg.rs:30:5: 30:6
StorageDead(_2); // scope 0 at $DIR/copy_propagation_arg.rs:31:1: 31:2
nop; // scope 1 at $DIR/copy_propagation_arg.rs:30:5: 30:6
nop; // scope 0 at $DIR/copy_propagation_arg.rs:31:1: 31:2
return; // scope 0 at $DIR/copy_propagation_arg.rs:31:2: 31:2
}
}
Expand Down
8 changes: 4 additions & 4 deletions src/test/mir-opt/copy_propagation_arg.baz.CopyPropagation.diff
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Expand Up @@ -7,10 +7,10 @@
let mut _2: i32; // in scope 0 at $DIR/copy_propagation_arg.rs:23:9: 23:10

bb0: {
StorageLive(_2); // scope 0 at $DIR/copy_propagation_arg.rs:23:9: 23:10
_2 = _1; // scope 0 at $DIR/copy_propagation_arg.rs:23:9: 23:10
_1 = move _2; // scope 0 at $DIR/copy_propagation_arg.rs:23:5: 23:10
StorageDead(_2); // scope 0 at $DIR/copy_propagation_arg.rs:23:9: 23:10
nop; // scope 0 at $DIR/copy_propagation_arg.rs:23:9: 23:10
nop; // scope 0 at $DIR/copy_propagation_arg.rs:23:9: 23:10
nop; // scope 0 at $DIR/copy_propagation_arg.rs:23:5: 23:10
nop; // scope 0 at $DIR/copy_propagation_arg.rs:23:9: 23:10
_0 = const (); // scope 0 at $DIR/copy_propagation_arg.rs:21:20: 24:2
return; // scope 0 at $DIR/copy_propagation_arg.rs:24:2: 24:2
}
Expand Down
8 changes: 4 additions & 4 deletions src/test/mir-opt/copy_propagation_arg.foo.CopyPropagation.diff
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Expand Up @@ -8,19 +8,19 @@
let mut _3: u8; // in scope 0 at $DIR/copy_propagation_arg.rs:11:15: 11:16

bb0: {
StorageLive(_2); // scope 0 at $DIR/copy_propagation_arg.rs:11:9: 11:17
nop; // scope 0 at $DIR/copy_propagation_arg.rs:11:9: 11:17
StorageLive(_3); // scope 0 at $DIR/copy_propagation_arg.rs:11:15: 11:16
_3 = _1; // scope 0 at $DIR/copy_propagation_arg.rs:11:15: 11:16
_2 = dummy(move _3) -> bb1; // scope 0 at $DIR/copy_propagation_arg.rs:11:9: 11:17
_1 = dummy(move _3) -> bb1; // scope 0 at $DIR/copy_propagation_arg.rs:11:9: 11:17
// mir::Constant
// + span: $DIR/copy_propagation_arg.rs:11:9: 11:14
// + literal: Const { ty: fn(u8) -> u8 {dummy}, val: Value(Scalar(<ZST>)) }
}

bb1: {
StorageDead(_3); // scope 0 at $DIR/copy_propagation_arg.rs:11:16: 11:17
_1 = move _2; // scope 0 at $DIR/copy_propagation_arg.rs:11:5: 11:17
StorageDead(_2); // scope 0 at $DIR/copy_propagation_arg.rs:11:16: 11:17
nop; // scope 0 at $DIR/copy_propagation_arg.rs:11:5: 11:17
nop; // scope 0 at $DIR/copy_propagation_arg.rs:11:16: 11:17
_0 = const (); // scope 0 at $DIR/copy_propagation_arg.rs:9:19: 12:2
return; // scope 0 at $DIR/copy_propagation_arg.rs:12:2: 12:2
}
Expand Down
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