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Commit 9fa941c

Browse files
Rollup merge of #95649 - ouz-a:mir-opt, r=oli-obk
New mir-opt deref_separator This adds a new mir-opt that split certain derefs into this form: `let x = (*a.b).c;` to => `tmp = a.b; let x = (*tmp).c;` Huge thanks to ``@oli-obk`` for his patient mentoring.
2 parents 76cd8f8 + 1cf6d69 commit 9fa941c

16 files changed

+193
-4
lines changed
Lines changed: 72 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,72 @@
1+
use crate::MirPass;
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use rustc_middle::mir::patch::MirPatch;
3+
use rustc_middle::mir::*;
4+
use rustc_middle::ty::TyCtxt;
5+
pub struct Derefer;
6+
7+
pub fn deref_finder<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
8+
let mut patch = MirPatch::new(body);
9+
let (basic_blocks, local_decl) = body.basic_blocks_and_local_decls_mut();
10+
for (block, data) in basic_blocks.iter_enumerated_mut() {
11+
for (i, stmt) in data.statements.iter_mut().enumerate() {
12+
match stmt.kind {
13+
StatementKind::Assign(box (og_place, Rvalue::Ref(region, borrow_knd, place))) => {
14+
for (idx, (p_ref, p_elem)) in place.iter_projections().enumerate() {
15+
if p_elem == ProjectionElem::Deref && !p_ref.projection.is_empty() {
16+
// The type that we are derefing.
17+
let ty = p_ref.ty(local_decl, tcx).ty;
18+
let temp = patch.new_temp(ty, stmt.source_info.span);
19+
20+
// Because we are assigning this right before original statement
21+
// we are using index i of statement.
22+
let loc = Location { block: block, statement_index: i };
23+
patch.add_statement(loc, StatementKind::StorageLive(temp));
24+
25+
// We are adding current p_ref's projections to our
26+
// temp value.
27+
let deref_place =
28+
Place::from(p_ref.local).project_deeper(p_ref.projection, tcx);
29+
patch.add_assign(
30+
loc,
31+
Place::from(temp),
32+
Rvalue::Use(Operand::Move(deref_place)),
33+
);
34+
35+
// We are creating a place by using our temp value's location
36+
// and copying derefed values which we need to create new statement.
37+
let temp_place =
38+
Place::from(temp).project_deeper(&place.projection[idx..], tcx);
39+
let new_stmt = Statement {
40+
source_info: stmt.source_info,
41+
kind: StatementKind::Assign(Box::new((
42+
og_place,
43+
Rvalue::Ref(region, borrow_knd, temp_place),
44+
))),
45+
};
46+
47+
// Replace current statement with newly created one.
48+
*stmt = new_stmt;
49+
50+
// Since our job with the temp is done it should be gone
51+
let loc = Location { block: block, statement_index: i + 1 };
52+
patch.add_statement(loc, StatementKind::StorageDead(temp));
53+
54+
// As all projections are off the base projection, if there are
55+
// multiple derefs in the middle of projection, it might cause
56+
// unsoundness, to not let that happen we break the loop.
57+
break;
58+
}
59+
}
60+
}
61+
_ => (),
62+
}
63+
}
64+
}
65+
patch.apply(body);
66+
}
67+
68+
impl<'tcx> MirPass<'tcx> for Derefer {
69+
fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
70+
deref_finder(tcx, body);
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}
72+
}

‎compiler/rustc_mir_transform/src/lib.rs

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -53,6 +53,7 @@ mod const_prop_lint;
5353
mod coverage;
5454
mod deaggregator;
5555
mod deduplicate_blocks;
56+
mod deref_separator;
5657
mod dest_prop;
5758
pub mod dump_mir;
5859
mod early_otherwise_branch;
@@ -431,6 +432,7 @@ fn run_post_borrowck_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tc
431432
// `Deaggregator` is conceptually part of MIR building, some backends rely on it happening
432433
// and it can help optimizations.
433434
&deaggregator::Deaggregator,
435+
&deref_separator::Derefer,
434436
&Lint(const_prop_lint::ConstProp),
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];
436438

Lines changed: 60 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,60 @@
1+
- // MIR for `main` before Derefer
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+ // MIR for `main` after Derefer
3+
4+
fn main() -> () {
5+
let mut _0: (); // return place in scope 0 at $DIR/derefer_test.rs:2:11: 2:11
6+
let mut _1: (i32, i32); // in scope 0 at $DIR/derefer_test.rs:3:9: 3:14
7+
let mut _3: &mut (i32, i32); // in scope 0 at $DIR/derefer_test.rs:4:22: 4:28
8+
+ let mut _6: &mut (i32, i32); // in scope 0 at $DIR/derefer_test.rs:5:13: 5:26
9+
+ let mut _7: &mut (i32, i32); // in scope 0 at $DIR/derefer_test.rs:6:13: 6:26
10+
scope 1 {
11+
debug a => _1; // in scope 1 at $DIR/derefer_test.rs:3:9: 3:14
12+
let mut _2: (i32, &mut (i32, i32)); // in scope 1 at $DIR/derefer_test.rs:4:9: 4:14
13+
scope 2 {
14+
debug b => _2; // in scope 2 at $DIR/derefer_test.rs:4:9: 4:14
15+
let _4: &mut i32; // in scope 2 at $DIR/derefer_test.rs:5:9: 5:10
16+
scope 3 {
17+
debug x => _4; // in scope 3 at $DIR/derefer_test.rs:5:9: 5:10
18+
let _5: &mut i32; // in scope 3 at $DIR/derefer_test.rs:6:9: 6:10
19+
scope 4 {
20+
debug y => _5; // in scope 4 at $DIR/derefer_test.rs:6:9: 6:10
21+
}
22+
}
23+
}
24+
}
25+
26+
bb0: {
27+
StorageLive(_1); // scope 0 at $DIR/derefer_test.rs:3:9: 3:14
28+
(_1.0: i32) = const 42_i32; // scope 0 at $DIR/derefer_test.rs:3:17: 3:24
29+
(_1.1: i32) = const 43_i32; // scope 0 at $DIR/derefer_test.rs:3:17: 3:24
30+
StorageLive(_2); // scope 1 at $DIR/derefer_test.rs:4:9: 4:14
31+
StorageLive(_3); // scope 1 at $DIR/derefer_test.rs:4:22: 4:28
32+
_3 = &mut _1; // scope 1 at $DIR/derefer_test.rs:4:22: 4:28
33+
(_2.0: i32) = const 99_i32; // scope 1 at $DIR/derefer_test.rs:4:17: 4:29
34+
(_2.1: &mut (i32, i32)) = move _3; // scope 1 at $DIR/derefer_test.rs:4:17: 4:29
35+
StorageDead(_3); // scope 1 at $DIR/derefer_test.rs:4:28: 4:29
36+
StorageLive(_4); // scope 2 at $DIR/derefer_test.rs:5:9: 5:10
37+
- _4 = &mut ((*(_2.1: &mut (i32, i32))).0: i32); // scope 2 at $DIR/derefer_test.rs:5:13: 5:26
38+
+ StorageLive(_6); // scope 2 at $DIR/derefer_test.rs:5:13: 5:26
39+
+ _6 = move (_2.1: &mut (i32, i32)); // scope 2 at $DIR/derefer_test.rs:5:13: 5:26
40+
+ _4 = &mut ((*_6).0: i32); // scope 2 at $DIR/derefer_test.rs:5:13: 5:26
41+
+ StorageDead(_6); // scope 3 at $DIR/derefer_test.rs:6:9: 6:10
42+
StorageLive(_5); // scope 3 at $DIR/derefer_test.rs:6:9: 6:10
43+
- _5 = &mut ((*(_2.1: &mut (i32, i32))).1: i32); // scope 3 at $DIR/derefer_test.rs:6:13: 6:26
44+
+ StorageLive(_7); // scope 3 at $DIR/derefer_test.rs:6:13: 6:26
45+
+ _7 = move (_2.1: &mut (i32, i32)); // scope 3 at $DIR/derefer_test.rs:6:13: 6:26
46+
+ _5 = &mut ((*_7).1: i32); // scope 3 at $DIR/derefer_test.rs:6:13: 6:26
47+
+ StorageDead(_7); // scope 0 at $DIR/derefer_test.rs:2:11: 7:2
48+
_0 = const (); // scope 0 at $DIR/derefer_test.rs:2:11: 7:2
49+
StorageDead(_5); // scope 3 at $DIR/derefer_test.rs:7:1: 7:2
50+
StorageDead(_4); // scope 2 at $DIR/derefer_test.rs:7:1: 7:2
51+
StorageDead(_2); // scope 1 at $DIR/derefer_test.rs:7:1: 7:2
52+
StorageDead(_1); // scope 0 at $DIR/derefer_test.rs:7:1: 7:2
53+
return; // scope 0 at $DIR/derefer_test.rs:7:2: 7:2
54+
+ }
55+
+
56+
+ bb1 (cleanup): {
57+
+ resume; // scope 0 at $DIR/derefer_test.rs:2:1: 7:2
58+
}
59+
}
60+

‎src/test/mir-opt/derefer_test.rs

Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,7 @@
1+
// EMIT_MIR derefer_test.main.Derefer.diff
2+
fn main() {
3+
let mut a = (42,43);
4+
let mut b = (99, &mut a);
5+
let x = &mut (*b.1).0;
6+
let y = &mut (*b.1).1;
7+
}

‎src/test/mir-opt/inline/issue_58867_inline_as_ref_as_mut.b.Inline.after.mir

Lines changed: 5 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -10,6 +10,7 @@ fn b(_1: &mut Box<T>) -> &mut T {
1010
debug self => _4; // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
1111
let mut _5: &mut T; // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
1212
let mut _6: &mut T; // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
13+
let mut _7: std::boxed::Box<T>; // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
1314
}
1415

1516
bb0: {
@@ -19,7 +20,10 @@ fn b(_1: &mut Box<T>) -> &mut T {
1920
_4 = &mut (*_1); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:8:5: 8:15
2021
StorageLive(_5); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
2122
StorageLive(_6); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
22-
_6 = &mut (*(*_4)); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
23+
StorageLive(_7); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
24+
_7 = move (*_4); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
25+
_6 = &mut (*_7); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
26+
StorageDead(_7); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
2327
_5 = &mut (*_6); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
2428
_3 = &mut (*_5); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
2529
StorageDead(_6); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL

‎src/test/mir-opt/inline/issue_58867_inline_as_ref_as_mut.d.Inline.after.mir

Lines changed: 5 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,13 +7,17 @@ fn d(_1: &Box<T>) -> &T {
77
let mut _3: &std::boxed::Box<T>; // in scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:18:5: 18:15
88
scope 1 (inlined <Box<T> as AsRef<T>>::as_ref) { // at $DIR/issue-58867-inline-as-ref-as-mut.rs:18:5: 18:15
99
debug self => _3; // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
10+
let mut _4: std::boxed::Box<T>; // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
1011
}
1112

1213
bb0: {
1314
StorageLive(_2); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:18:5: 18:15
1415
StorageLive(_3); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:18:5: 18:15
1516
_3 = &(*_1); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:18:5: 18:15
16-
_2 = &(*(*_3)); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
17+
StorageLive(_4); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
18+
_4 = move (*_3); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
19+
_2 = &(*_4); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
20+
StorageDead(_4); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
1721
_0 = &(*_2); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:18:5: 18:15
1822
StorageDead(_3); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:18:14: 18:15
1923
StorageDead(_2); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:19:1: 19:2

‎src/test/mir-opt/lower_array_len.array_bound.NormalizeArrayLen.diff

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -64,5 +64,9 @@
6464
StorageDead(_3); // scope 0 at $DIR/lower_array_len.rs:11:5: 11:6
6565
return; // scope 0 at $DIR/lower_array_len.rs:12:2: 12:2
6666
}
67+
68+
bb6 (cleanup): {
69+
resume; // scope 0 at $DIR/lower_array_len.rs:6:1: 12:2
70+
}
6771
}
6872

‎src/test/mir-opt/lower_array_len.array_bound_mut.NormalizeArrayLen.diff

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -77,5 +77,9 @@
7777
StorageDead(_3); // scope 0 at $DIR/lower_array_len.rs:24:5: 24:6
7878
return; // scope 0 at $DIR/lower_array_len.rs:25:2: 25:2
7979
}
80+
81+
bb7 (cleanup): {
82+
resume; // scope 0 at $DIR/lower_array_len.rs:17:1: 25:2
83+
}
8084
}
8185

‎src/test/mir-opt/lower_array_len.array_len.NormalizeArrayLen.diff

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -26,5 +26,9 @@
2626
StorageDead(_2); // scope 0 at $DIR/lower_array_len.rs:31:13: 31:14
2727
return; // scope 0 at $DIR/lower_array_len.rs:32:2: 32:2
2828
}
29+
30+
bb2 (cleanup): {
31+
resume; // scope 0 at $DIR/lower_array_len.rs:30:1: 32:2
32+
}
2933
}
3034

‎src/test/mir-opt/lower_array_len.array_len_by_value.NormalizeArrayLen.diff

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -26,5 +26,9 @@
2626
StorageDead(_2); // scope 0 at $DIR/lower_array_len.rs:38:13: 38:14
2727
return; // scope 0 at $DIR/lower_array_len.rs:39:2: 39:2
2828
}
29+
30+
bb2 (cleanup): {
31+
resume; // scope 0 at $DIR/lower_array_len.rs:37:1: 39:2
32+
}
2933
}
3034

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