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simonvandelsimonvandel
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Don't need to look at the layout of the types being matched on
We only need to check that the discriminant value is the same
1 parent 4a6b728 commit 3d52e54

6 files changed

+164
-90
lines changed

‎compiler/rustc_mir/src/transform/early_otherwise_branch.rs

+2-19
Original file line numberDiff line numberDiff line change
@@ -2,8 +2,8 @@ use crate::{
22
transform::{MirPass, MirSource},
33
util::patch::MirPatch,
44
};
5+
use rustc_middle::mir::*;
56
use rustc_middle::ty::{Ty, TyCtxt};
6-
use rustc_middle::{mir::*, ty::ParamEnv};
77
use std::{borrow::Cow, fmt::Debug};
88

99
use super::simplify::simplify_cfg;
@@ -40,7 +40,7 @@ impl<'tcx> MirPass<'tcx> for EarlyOtherwiseBranch {
4040
let opts_to_apply: Vec<OptimizationToApply<'tcx>> = bbs_with_switch
4141
.flat_map(|(bb_idx, bb)| {
4242
let switch = bb.terminator();
43-
let helper = Helper { body, tcx, param_env: tcx.param_env(source.def_id()) };
43+
let helper = Helper { body, tcx };
4444
let infos = helper.go(bb, switch)?;
4545
Some(OptimizationToApply { infos, basic_block_first_switch: bb_idx })
4646
})
@@ -170,7 +170,6 @@ fn is_switch<'tcx>(terminator: &Terminator<'tcx>) -> bool {
170170
struct Helper<'a, 'tcx> {
171171
body: &'a Body<'tcx>,
172172
tcx: TyCtxt<'tcx>,
173-
param_env: ParamEnv<'tcx>,
174173
}
175174

176175
#[derive(Debug, Clone)]
@@ -267,22 +266,6 @@ impl<'a, 'tcx> Helper<'a, 'tcx> {
267266
return None;
268267
}
269268

270-
// check that the value being matched on is the same. The
271-
if this_bb_discr_info.targets_with_values.iter().find(|x| x.1 == value).is_none() {
272-
trace!("NO: values being matched on are not the same");
273-
return None;
274-
}
275-
276-
// The layouts of the two ADTs have to be equal for this optimization to apply
277-
let layout_of_adt =
278-
|ty: Ty<'tcx>| self.tcx.layout_of(self.param_env.and(ty)).ok().map(|x| x.layout);
279-
let layout_lhs = layout_of_adt(discr_info.type_adt_matched_on);
280-
let layout_rhs = layout_of_adt(this_bb_discr_info.type_adt_matched_on);
281-
if layout_lhs != layout_rhs {
282-
trace!("NO: Layouts do not match. LHS: {:?}, RHS: {:?}", layout_lhs, layout_rhs);
283-
return None;
284-
}
285-
286269
// If we reach this point, the optimization applies, and we should be able to optimize this case
287270
// store the info that is needed to apply the optimization
288271

‎src/test/mir-opt/early_otherwise_branch.opt4.EarlyOtherwiseBranch.diff

+64
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,64 @@
1+
- // MIR for `opt4` before EarlyOtherwiseBranch
2+
+ // MIR for `opt4` after EarlyOtherwiseBranch
3+
4+
fn opt4(_1: std::result::Result<u32, ()>, _2: Option<u32>) -> u32 {
5+
debug x => _1; // in scope 0 at $DIR/early_otherwise_branch.rs:40:9: 40:10
6+
debug y => _2; // in scope 0 at $DIR/early_otherwise_branch.rs:40:29: 40:30
7+
let mut _0: u32; // return place in scope 0 at $DIR/early_otherwise_branch.rs:40:48: 40:51
8+
let mut _3: (std::result::Result<u32, ()>, std::option::Option<u32>); // in scope 0 at $DIR/early_otherwise_branch.rs:41:11: 41:17
9+
let mut _4: std::result::Result<u32, ()>; // in scope 0 at $DIR/early_otherwise_branch.rs:41:12: 41:13
10+
let mut _5: std::option::Option<u32>; // in scope 0 at $DIR/early_otherwise_branch.rs:41:15: 41:16
11+
let mut _6: isize; // in scope 0 at $DIR/early_otherwise_branch.rs:42:18: 42:25
12+
let mut _7: isize; // in scope 0 at $DIR/early_otherwise_branch.rs:42:10: 42:16
13+
+ let mut _8: isize; // in scope 0 at $DIR/early_otherwise_branch.rs:42:18: 42:25
14+
+ let mut _9: bool; // in scope 0 at $DIR/early_otherwise_branch.rs:42:18: 42:25
15+
16+
bb0: {
17+
StorageLive(_3); // scope 0 at $DIR/early_otherwise_branch.rs:41:11: 41:17
18+
StorageLive(_4); // scope 0 at $DIR/early_otherwise_branch.rs:41:12: 41:13
19+
_4 = _1; // scope 0 at $DIR/early_otherwise_branch.rs:41:12: 41:13
20+
StorageLive(_5); // scope 0 at $DIR/early_otherwise_branch.rs:41:15: 41:16
21+
_5 = _2; // scope 0 at $DIR/early_otherwise_branch.rs:41:15: 41:16
22+
(_3.0: std::result::Result<u32, ()>) = move _4; // scope 0 at $DIR/early_otherwise_branch.rs:41:11: 41:17
23+
(_3.1: std::option::Option<u32>) = move _5; // scope 0 at $DIR/early_otherwise_branch.rs:41:11: 41:17
24+
StorageDead(_5); // scope 0 at $DIR/early_otherwise_branch.rs:41:16: 41:17
25+
StorageDead(_4); // scope 0 at $DIR/early_otherwise_branch.rs:41:16: 41:17
26+
_7 = discriminant((_3.0: std::result::Result<u32, ()>)); // scope 0 at $DIR/early_otherwise_branch.rs:42:10: 42:16
27+
- switchInt(move _7) -> [1_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch.rs:42:10: 42:16
28+
+ StorageLive(_8); // scope 0 at $DIR/early_otherwise_branch.rs:42:10: 42:16
29+
+ _8 = discriminant((_3.1: std::option::Option<u32>)); // scope 0 at $DIR/early_otherwise_branch.rs:42:10: 42:16
30+
+ StorageLive(_9); // scope 0 at $DIR/early_otherwise_branch.rs:42:10: 42:16
31+
+ _9 = Ne(_8, _7); // scope 0 at $DIR/early_otherwise_branch.rs:42:10: 42:16
32+
+ StorageDead(_8); // scope 0 at $DIR/early_otherwise_branch.rs:42:10: 42:16
33+
+ switchInt(move _9) -> [false: bb4, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch.rs:42:10: 42:16
34+
}
35+
36+
bb1: {
37+
+ StorageDead(_9); // scope 0 at $DIR/early_otherwise_branch.rs:43:14: 43:15
38+
_0 = const 1_u32; // scope 0 at $DIR/early_otherwise_branch.rs:43:14: 43:15
39+
- goto -> bb4; // scope 0 at $DIR/early_otherwise_branch.rs:41:5: 44:6
40+
+ goto -> bb3; // scope 0 at $DIR/early_otherwise_branch.rs:41:5: 44:6
41+
}
42+
43+
bb2: {
44+
- _6 = discriminant((_3.1: std::option::Option<u32>)); // scope 0 at $DIR/early_otherwise_branch.rs:42:18: 42:25
45+
- switchInt(move _6) -> [1_isize: bb3, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch.rs:42:18: 42:25
46+
+ _0 = const 0_u32; // scope 0 at $DIR/early_otherwise_branch.rs:42:30: 42:31
47+
+ goto -> bb3; // scope 0 at $DIR/early_otherwise_branch.rs:41:5: 44:6
48+
}
49+
50+
bb3: {
51+
- _0 = const 0_u32; // scope 0 at $DIR/early_otherwise_branch.rs:42:30: 42:31
52+
- goto -> bb4; // scope 0 at $DIR/early_otherwise_branch.rs:41:5: 44:6
53+
+ StorageDead(_3); // scope 0 at $DIR/early_otherwise_branch.rs:45:1: 45:2
54+
+ return; // scope 0 at $DIR/early_otherwise_branch.rs:45:2: 45:2
55+
}
56+
57+
bb4: {
58+
- StorageDead(_3); // scope 0 at $DIR/early_otherwise_branch.rs:45:1: 45:2
59+
- return; // scope 0 at $DIR/early_otherwise_branch.rs:45:2: 45:2
60+
+ StorageDead(_9); // scope 0 at $DIR/early_otherwise_branch.rs:42:18: 42:25
61+
+ switchInt(_7) -> [1_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch.rs:42:18: 42:25
62+
}
63+
}
64+

‎src/test/mir-opt/early_otherwise_branch.opt5.EarlyOtherwiseBranch.diff

+77
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,77 @@
1+
- // MIR for `opt5` before EarlyOtherwiseBranch
2+
+ // MIR for `opt5` after EarlyOtherwiseBranch
3+
4+
fn opt5(_1: Option<u32>, _2: Option<bool>) -> u32 {
5+
debug x => _1; // in scope 0 at $DIR/early_otherwise_branch.rs:49:9: 49:10
6+
debug y => _2; // in scope 0 at $DIR/early_otherwise_branch.rs:49:25: 49:26
7+
let mut _0: u32; // return place in scope 0 at $DIR/early_otherwise_branch.rs:49:45: 49:48
8+
let mut _3: (std::option::Option<u32>, std::option::Option<bool>); // in scope 0 at $DIR/early_otherwise_branch.rs:50:11: 50:17
9+
let mut _4: std::option::Option<u32>; // in scope 0 at $DIR/early_otherwise_branch.rs:50:12: 50:13
10+
let mut _5: std::option::Option<bool>; // in scope 0 at $DIR/early_otherwise_branch.rs:50:15: 50:16
11+
let mut _6: isize; // in scope 0 at $DIR/early_otherwise_branch.rs:51:19: 51:26
12+
let mut _7: isize; // in scope 0 at $DIR/early_otherwise_branch.rs:51:10: 51:17
13+
let _8: u32; // in scope 0 at $DIR/early_otherwise_branch.rs:51:15: 51:16
14+
let _9: bool; // in scope 0 at $DIR/early_otherwise_branch.rs:51:24: 51:25
15+
+ let mut _10: isize; // in scope 0 at $DIR/early_otherwise_branch.rs:51:19: 51:26
16+
+ let mut _11: bool; // in scope 0 at $DIR/early_otherwise_branch.rs:51:19: 51:26
17+
scope 1 {
18+
debug a => _8; // in scope 1 at $DIR/early_otherwise_branch.rs:51:15: 51:16
19+
debug b => _9; // in scope 1 at $DIR/early_otherwise_branch.rs:51:24: 51:25
20+
}
21+
22+
bb0: {
23+
StorageLive(_3); // scope 0 at $DIR/early_otherwise_branch.rs:50:11: 50:17
24+
StorageLive(_4); // scope 0 at $DIR/early_otherwise_branch.rs:50:12: 50:13
25+
_4 = _1; // scope 0 at $DIR/early_otherwise_branch.rs:50:12: 50:13
26+
StorageLive(_5); // scope 0 at $DIR/early_otherwise_branch.rs:50:15: 50:16
27+
_5 = _2; // scope 0 at $DIR/early_otherwise_branch.rs:50:15: 50:16
28+
(_3.0: std::option::Option<u32>) = move _4; // scope 0 at $DIR/early_otherwise_branch.rs:50:11: 50:17
29+
(_3.1: std::option::Option<bool>) = move _5; // scope 0 at $DIR/early_otherwise_branch.rs:50:11: 50:17
30+
StorageDead(_5); // scope 0 at $DIR/early_otherwise_branch.rs:50:16: 50:17
31+
StorageDead(_4); // scope 0 at $DIR/early_otherwise_branch.rs:50:16: 50:17
32+
_7 = discriminant((_3.0: std::option::Option<u32>)); // scope 0 at $DIR/early_otherwise_branch.rs:51:10: 51:17
33+
- switchInt(move _7) -> [1_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch.rs:51:10: 51:17
34+
+ StorageLive(_10); // scope 0 at $DIR/early_otherwise_branch.rs:51:10: 51:17
35+
+ _10 = discriminant((_3.1: std::option::Option<bool>)); // scope 0 at $DIR/early_otherwise_branch.rs:51:10: 51:17
36+
+ StorageLive(_11); // scope 0 at $DIR/early_otherwise_branch.rs:51:10: 51:17
37+
+ _11 = Ne(_10, _7); // scope 0 at $DIR/early_otherwise_branch.rs:51:10: 51:17
38+
+ StorageDead(_10); // scope 0 at $DIR/early_otherwise_branch.rs:51:10: 51:17
39+
+ switchInt(move _11) -> [false: bb4, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch.rs:51:10: 51:17
40+
}
41+
42+
bb1: {
43+
+ StorageDead(_11); // scope 0 at $DIR/early_otherwise_branch.rs:52:14: 52:15
44+
_0 = const 1_u32; // scope 0 at $DIR/early_otherwise_branch.rs:52:14: 52:15
45+
- goto -> bb4; // scope 0 at $DIR/early_otherwise_branch.rs:50:5: 53:6
46+
+ goto -> bb3; // scope 0 at $DIR/early_otherwise_branch.rs:50:5: 53:6
47+
}
48+
49+
bb2: {
50+
- _6 = discriminant((_3.1: std::option::Option<bool>)); // scope 0 at $DIR/early_otherwise_branch.rs:51:19: 51:26
51+
- switchInt(move _6) -> [1_isize: bb3, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch.rs:51:19: 51:26
52+
- }
53+
-
54+
- bb3: {
55+
StorageLive(_8); // scope 0 at $DIR/early_otherwise_branch.rs:51:15: 51:16
56+
_8 = (((_3.0: std::option::Option<u32>) as Some).0: u32); // scope 0 at $DIR/early_otherwise_branch.rs:51:15: 51:16
57+
StorageLive(_9); // scope 0 at $DIR/early_otherwise_branch.rs:51:24: 51:25
58+
_9 = (((_3.1: std::option::Option<bool>) as Some).0: bool); // scope 0 at $DIR/early_otherwise_branch.rs:51:24: 51:25
59+
_0 = const 0_u32; // scope 1 at $DIR/early_otherwise_branch.rs:51:31: 51:32
60+
StorageDead(_9); // scope 0 at $DIR/early_otherwise_branch.rs:51:31: 51:32
61+
StorageDead(_8); // scope 0 at $DIR/early_otherwise_branch.rs:51:31: 51:32
62+
- goto -> bb4; // scope 0 at $DIR/early_otherwise_branch.rs:50:5: 53:6
63+
+ goto -> bb3; // scope 0 at $DIR/early_otherwise_branch.rs:50:5: 53:6
64+
}
65+
66+
- bb4: {
67+
+ bb3: {
68+
StorageDead(_3); // scope 0 at $DIR/early_otherwise_branch.rs:54:1: 54:2
69+
return; // scope 0 at $DIR/early_otherwise_branch.rs:54:2: 54:2
70+
+ }
71+
+
72+
+ bb4: {
73+
+ StorageDead(_11); // scope 0 at $DIR/early_otherwise_branch.rs:51:19: 51:26
74+
+ switchInt(_7) -> [1_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch.rs:51:19: 51:26
75+
}
76+
}
77+

‎src/test/mir-opt/early_otherwise_branch.rs

+21-1
Original file line numberDiff line numberDiff line change
@@ -26,7 +26,7 @@ enum MyOption2<T> {
2626
None,
2727
}
2828

29-
// must optimize as the tag encoding of the discriminant are the same
29+
// must optimize as the discriminant values are the same
3030
// EMIT_MIR early_otherwise_branch.opt3.EarlyOtherwiseBranch.diff
3131
fn opt3(x: MyOption1<u32>, y: MyOption2<u32>) -> u32 {
3232
match (x, y) {
@@ -35,8 +35,28 @@ fn opt3(x: MyOption1<u32>, y: MyOption2<u32>) -> u32 {
3535
}
3636
}
3737

38+
// must optimize as the discriminant values are the same
39+
// EMIT_MIR early_otherwise_branch.opt4.EarlyOtherwiseBranch.diff
40+
fn opt4(x: Result<u32, ()>, y: Option<u32>) -> u32 {
41+
match (x, y) {
42+
(Err(_), Some(_)) => 0,
43+
_ => 1,
44+
}
45+
}
46+
47+
// must optimize as the discriminant values are the same
48+
// EMIT_MIR early_otherwise_branch.opt5.EarlyOtherwiseBranch.diff
49+
fn opt5(x: Option<u32>, y: Option<bool>) -> u32 {
50+
match (x, y) {
51+
(Some(a), Some(b)) => 0,
52+
_ => 1,
53+
}
54+
}
55+
3856
fn main() {
3957
opt1(None, Some(0));
4058
opt2(None, Some(0));
4159
opt3(MyOption1::None, MyOption2::Some(0));
60+
opt4(Ok(0), None);
61+
opt5(None, Some(true));
4262
}

‎src/test/mir-opt/early_otherwise_branch_noopt.noopt2.EarlyOtherwiseBranch.diff

-60
This file was deleted.

‎src/test/mir-opt/early_otherwise_branch_noopt.rs

-10
Original file line numberDiff line numberDiff line change
@@ -13,16 +13,6 @@ fn noopt1(x: Option<u32>, y: Option<u32>) -> u32 {
1313
}
1414
}
1515

16-
// must not optimize as the tag encodings of the discriminant are not the same
17-
// EMIT_MIR early_otherwise_branch_noopt.noopt2.EarlyOtherwiseBranch.diff
18-
fn noopt2(x: Option<u32>, y: Option<bool>) -> u32 {
19-
match (x, y) {
20-
(Some(a), Some(b)) => 0,
21-
_ => 1,
22-
}
23-
}
24-
2516
fn main() {
2617
noopt1(None, Some(0));
27-
noopt2(None, Some(true));
2818
}

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