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merged 5 commits into from
Apr 6, 2022
Merged

New mir-opt deref_separator #95649

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4332b5f
New mir-opt deref_separator
ouz-a Apr 4, 2022
105e90f
fixed error, made function leaner and tighter
ouz-a Apr 4, 2022
904d6c8
destroy temp at the end and avoid ICE
ouz-a Apr 4, 2022
72070d8
remove region check
ouz-a Apr 5, 2022
1cf6d69
kill temp early
ouz-a Apr 5, 2022
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68 changes: 68 additions & 0 deletions compiler/rustc_mir_transform/src/deref_separator.rs
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@@ -0,0 +1,68 @@
use crate::MirPass;
use rustc_middle::mir::patch::MirPatch;
use rustc_middle::mir::*;
use rustc_middle::ty::TyCtxt;
pub struct Derefer;

pub fn deref_finder<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
let mut patch = MirPatch::new(body);
let (basic_blocks, local_decl) = body.basic_blocks_and_local_decls_mut();
for (block, data) in basic_blocks.iter_enumerated_mut() {
for (i, stmt) in data.statements.iter_mut().enumerate() {
match stmt.kind {
StatementKind::Assign(box (og_place, Rvalue::Ref(region, borrow_knd, place))) => {
for (idx, (p_ref, p_elem)) in place.iter_projections().enumerate() {
if p_elem == ProjectionElem::Deref && !p_ref.projection.is_empty() {
// The type that we are derefing
let ty = p_ref.ty(local_decl, tcx).ty;
let temp = patch.new_temp(ty, stmt.source_info.span);

// Because we are assigning this right before original statement
// we are using index i of statement
let loc = Location { block: block, statement_index: i };
patch.add_statement(loc, StatementKind::StorageLive(temp));

// We are adding current p_ref's projections to our
// temp value
let deref_place =
Place::from(p_ref.local).project_deeper(p_ref.projection, tcx);
patch.add_assign(
loc,
Place::from(temp),
Rvalue::Use(Operand::Move(deref_place)),
);

// We are creating a place by using our temp value's location
// and copying derefed values which we need to create new statement
let temp_place =
Place::from(temp).project_deeper(&place.projection[idx..], tcx);
patch.add_assign(
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This add call is now not necessary anymore, as the exact same statement is created via mutation below

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What you can add though is a storagdead statement for the temp. Maybe that'll eliminate the extra cleanup block that showed up in a bunch of tests

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mir dump looks clean now 😸

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There are still a bunch of new cleanup blocks showing up. Let's see if a storagedead resolves those.

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I thought storagedead would resolve all of those 🤔

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Sorry, misread the code. Yea, not sure what is going on, i'll investigate

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Ah, it's just MirPatch doing that eagerly even if unneeded.

loc,
og_place,
Rvalue::Ref(region, borrow_knd, temp_place),
);

let new_stmt = Statement {
source_info: stmt.source_info,
kind: StatementKind::Assign(Box::new((
og_place,
Rvalue::Ref(region, borrow_knd, temp_place),
))),
};
// Replace current statement with newly created one
*stmt = new_stmt;
}
}
}
_ => (),
}
}
}
patch.apply(body);
}

impl<'tcx> MirPass<'tcx> for Derefer {
fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
deref_finder(tcx, body);
}
}
2 changes: 2 additions & 0 deletions compiler/rustc_mir_transform/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -53,6 +53,7 @@ mod const_prop_lint;
mod coverage;
mod deaggregator;
mod deduplicate_blocks;
mod deref_separator;
mod dest_prop;
pub mod dump_mir;
mod early_otherwise_branch;
Expand Down Expand Up @@ -431,6 +432,7 @@ fn run_post_borrowck_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tc
// `Deaggregator` is conceptually part of MIR building, some backends rely on it happening
// and it can help optimizations.
&deaggregator::Deaggregator,
&deref_separator::Derefer,
&Lint(const_prop_lint::ConstProp),
];

Expand Down
60 changes: 60 additions & 0 deletions src/test/mir-opt/derefer_test.main.Derefer.diff
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@@ -0,0 +1,60 @@
- // MIR for `main` before Derefer
+ // MIR for `main` after Derefer

fn main() -> () {
let mut _0: (); // return place in scope 0 at $DIR/derefer_test.rs:2:11: 2:11
let mut _1: (i32, i32); // in scope 0 at $DIR/derefer_test.rs:3:9: 3:14
let mut _3: &mut (i32, i32); // in scope 0 at $DIR/derefer_test.rs:4:22: 4:28
+ let mut _6: &mut (i32, i32); // in scope 0 at $DIR/derefer_test.rs:5:13: 5:26
+ let mut _7: &mut (i32, i32); // in scope 0 at $DIR/derefer_test.rs:6:13: 6:26
scope 1 {
debug a => _1; // in scope 1 at $DIR/derefer_test.rs:3:9: 3:14
let mut _2: (i32, &mut (i32, i32)); // in scope 1 at $DIR/derefer_test.rs:4:9: 4:14
scope 2 {
debug b => _2; // in scope 2 at $DIR/derefer_test.rs:4:9: 4:14
let _4: &mut i32; // in scope 2 at $DIR/derefer_test.rs:5:9: 5:10
scope 3 {
debug x => _4; // in scope 3 at $DIR/derefer_test.rs:5:9: 5:10
let _5: &mut i32; // in scope 3 at $DIR/derefer_test.rs:6:9: 6:10
scope 4 {
debug y => _5; // in scope 4 at $DIR/derefer_test.rs:6:9: 6:10
}
}
}
}

bb0: {
StorageLive(_1); // scope 0 at $DIR/derefer_test.rs:3:9: 3:14
(_1.0: i32) = const 42_i32; // scope 0 at $DIR/derefer_test.rs:3:17: 3:24
(_1.1: i32) = const 43_i32; // scope 0 at $DIR/derefer_test.rs:3:17: 3:24
StorageLive(_2); // scope 1 at $DIR/derefer_test.rs:4:9: 4:14
StorageLive(_3); // scope 1 at $DIR/derefer_test.rs:4:22: 4:28
_3 = &mut _1; // scope 1 at $DIR/derefer_test.rs:4:22: 4:28
(_2.0: i32) = const 99_i32; // scope 1 at $DIR/derefer_test.rs:4:17: 4:29
(_2.1: &mut (i32, i32)) = move _3; // scope 1 at $DIR/derefer_test.rs:4:17: 4:29
StorageDead(_3); // scope 1 at $DIR/derefer_test.rs:4:28: 4:29
StorageLive(_4); // scope 2 at $DIR/derefer_test.rs:5:9: 5:10
- _4 = &mut ((*(_2.1: &mut (i32, i32))).0: i32); // scope 2 at $DIR/derefer_test.rs:5:13: 5:26
+ StorageLive(_6); // scope 2 at $DIR/derefer_test.rs:5:13: 5:26
+ _6 = move (_2.1: &mut (i32, i32)); // scope 2 at $DIR/derefer_test.rs:5:13: 5:26
+ _4 = &mut ((*_6).0: i32); // scope 2 at $DIR/derefer_test.rs:5:13: 5:26
+ _4 = &mut ((*_6).0: i32); // scope 2 at $DIR/derefer_test.rs:5:13: 5:26
StorageLive(_5); // scope 3 at $DIR/derefer_test.rs:6:9: 6:10
- _5 = &mut ((*(_2.1: &mut (i32, i32))).1: i32); // scope 3 at $DIR/derefer_test.rs:6:13: 6:26
+ StorageLive(_7); // scope 3 at $DIR/derefer_test.rs:6:13: 6:26
+ _7 = move (_2.1: &mut (i32, i32)); // scope 3 at $DIR/derefer_test.rs:6:13: 6:26
+ _5 = &mut ((*_7).1: i32); // scope 3 at $DIR/derefer_test.rs:6:13: 6:26
+ _5 = &mut ((*_7).1: i32); // scope 3 at $DIR/derefer_test.rs:6:13: 6:26
_0 = const (); // scope 0 at $DIR/derefer_test.rs:2:11: 7:2
StorageDead(_5); // scope 3 at $DIR/derefer_test.rs:7:1: 7:2
StorageDead(_4); // scope 2 at $DIR/derefer_test.rs:7:1: 7:2
StorageDead(_2); // scope 1 at $DIR/derefer_test.rs:7:1: 7:2
StorageDead(_1); // scope 0 at $DIR/derefer_test.rs:7:1: 7:2
return; // scope 0 at $DIR/derefer_test.rs:7:2: 7:2
+ }
+
+ bb1 (cleanup): {
+ resume; // scope 0 at $DIR/derefer_test.rs:2:1: 7:2
}
}

7 changes: 7 additions & 0 deletions src/test/mir-opt/derefer_test.rs
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@@ -0,0 +1,7 @@
// EMIT_MIR derefer_test.main.Derefer.diff
fn main() {
let mut a = (42,43);
let mut b = (99, &mut a);
let x = &mut (*b.1).0;
let y = &mut (*b.1).1;
}
6 changes: 5 additions & 1 deletion src/test/mir-opt/inline/issue_58867_inline_as_ref_as_mut.b.Inline.after.mir
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Expand Up @@ -10,6 +10,7 @@ fn b(_1: &mut Box<T>) -> &mut T {
debug self => _4; // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
let mut _5: &mut T; // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
let mut _6: &mut T; // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
let mut _7: std::boxed::Box<T>; // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
}

bb0: {
Expand All @@ -19,7 +20,10 @@ fn b(_1: &mut Box<T>) -> &mut T {
_4 = &mut (*_1); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:8:5: 8:15
StorageLive(_5); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
StorageLive(_6); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
_6 = &mut (*(*_4)); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
StorageLive(_7); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
_7 = move (*_4); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
_6 = &mut (*_7); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
_6 = &mut (*_7); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
_5 = &mut (*_6); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
_3 = &mut (*_5); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
StorageDead(_6); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
Expand Down
6 changes: 5 additions & 1 deletion src/test/mir-opt/inline/issue_58867_inline_as_ref_as_mut.d.Inline.after.mir
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Expand Up @@ -7,13 +7,17 @@ fn d(_1: &Box<T>) -> &T {
let mut _3: &std::boxed::Box<T>; // in scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:18:5: 18:15
scope 1 (inlined <Box<T> as AsRef<T>>::as_ref) { // at $DIR/issue-58867-inline-as-ref-as-mut.rs:18:5: 18:15
debug self => _3; // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
let mut _4: std::boxed::Box<T>; // in scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
}

bb0: {
StorageLive(_2); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:18:5: 18:15
StorageLive(_3); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:18:5: 18:15
_3 = &(*_1); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:18:5: 18:15
_2 = &(*(*_3)); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
StorageLive(_4); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
_4 = move (*_3); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
_2 = &(*_4); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
_2 = &(*_4); // scope 1 at $SRC_DIR/alloc/src/boxed.rs:LL:COL
_0 = &(*_2); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:18:5: 18:15
StorageDead(_3); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:18:14: 18:15
StorageDead(_2); // scope 0 at $DIR/issue-58867-inline-as-ref-as-mut.rs:19:1: 19:2
Expand Down
4 changes: 4 additions & 0 deletions src/test/mir-opt/lower_array_len.array_bound.NormalizeArrayLen.diff
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Expand Up @@ -64,5 +64,9 @@
StorageDead(_3); // scope 0 at $DIR/lower_array_len.rs:11:5: 11:6
return; // scope 0 at $DIR/lower_array_len.rs:12:2: 12:2
}

bb6 (cleanup): {
resume; // scope 0 at $DIR/lower_array_len.rs:6:1: 12:2
}
}

4 changes: 4 additions & 0 deletions src/test/mir-opt/lower_array_len.array_bound_mut.NormalizeArrayLen.diff
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Expand Up @@ -77,5 +77,9 @@
StorageDead(_3); // scope 0 at $DIR/lower_array_len.rs:24:5: 24:6
return; // scope 0 at $DIR/lower_array_len.rs:25:2: 25:2
}

bb7 (cleanup): {
resume; // scope 0 at $DIR/lower_array_len.rs:17:1: 25:2
}
}

4 changes: 4 additions & 0 deletions src/test/mir-opt/lower_array_len.array_len.NormalizeArrayLen.diff
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Expand Up @@ -26,5 +26,9 @@
StorageDead(_2); // scope 0 at $DIR/lower_array_len.rs:31:13: 31:14
return; // scope 0 at $DIR/lower_array_len.rs:32:2: 32:2
}

bb2 (cleanup): {
resume; // scope 0 at $DIR/lower_array_len.rs:30:1: 32:2
}
}

4 changes: 4 additions & 0 deletions src/test/mir-opt/lower_array_len.array_len_by_value.NormalizeArrayLen.diff
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Expand Up @@ -26,5 +26,9 @@
StorageDead(_2); // scope 0 at $DIR/lower_array_len.rs:38:13: 38:14
return; // scope 0 at $DIR/lower_array_len.rs:39:2: 39:2
}

bb2 (cleanup): {
resume; // scope 0 at $DIR/lower_array_len.rs:37:1: 39:2
}
}

4 changes: 4 additions & 0 deletions src/test/mir-opt/lower_slice_len.bound.LowerSliceLenCalls.diff
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Expand Up @@ -59,5 +59,9 @@
StorageDead(_3); // scope 0 at $DIR/lower_slice_len.rs:9:5: 9:6
return; // scope 0 at $DIR/lower_slice_len.rs:10:2: 10:2
}

bb6 (cleanup): {
resume; // scope 0 at $DIR/lower_slice_len.rs:4:1: 10:2
}
}

8 changes: 6 additions & 2 deletions ...t/uninhabited_fallthrough_elimination.eliminate_fallthrough.UninhabitedEnumBranching.diff
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Expand Up @@ -9,7 +9,7 @@
bb0: {
_2 = discriminant(_1); // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:22:11: 22:12
- switchInt(move _2) -> [1_isize: bb3, 2_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:22:5: 22:12
+ switchInt(move _2) -> [1_isize: bb3, 2_isize: bb2, otherwise: bb5]; // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:22:5: 22:12
+ switchInt(move _2) -> [1_isize: bb3, 2_isize: bb2, otherwise: bb6]; // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:22:5: 22:12
}

bb1: {
Expand All @@ -29,9 +29,13 @@

bb4: {
return; // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:27:2: 27:2
}

bb5 (cleanup): {
resume; // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:21:1: 27:2
+ }
+
+ bb5: {
+ bb6: {
+ unreachable; // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:25:14: 25:15
}
}
Expand Down
4 changes: 4 additions & 0 deletions ...ir-opt/uninhabited_fallthrough_elimination.keep_fallthrough.UninhabitedEnumBranching.diff
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Expand Up @@ -30,5 +30,9 @@
bb4: {
return; // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:18:2: 18:2
}

bb5 (cleanup): {
resume; // scope 0 at $DIR/uninhabited_fallthrough_elimination.rs:12:1: 18:2
}
}

4 changes: 4 additions & 0 deletions src/test/mir-opt/unreachable.main.UnreachablePropagation.diff
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Expand Up @@ -64,6 +64,10 @@
_0 = const (); // scope 0 at $DIR/unreachable.rs:19:6: 19:6
StorageDead(_1); // scope 0 at $DIR/unreachable.rs:20:1: 20:2
return; // scope 0 at $DIR/unreachable.rs:20:2: 20:2
- }
-
- bb7 (cleanup): {
- resume; // scope 0 at $DIR/unreachable.rs:8:1: 20:2
}
}

4 changes: 4 additions & 0 deletions src/test/mir-opt/unreachable_diverging.main.UnreachablePropagation.diff
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Expand Up @@ -69,6 +69,10 @@
StorageDead(_1); // scope 0 at $DIR/unreachable_diverging.rs:20:1: 20:2
StorageDead(_2); // scope 0 at $DIR/unreachable_diverging.rs:20:1: 20:2
return; // scope 0 at $DIR/unreachable_diverging.rs:20:2: 20:2
- }
-
- bb7 (cleanup): {
- resume; // scope 0 at $DIR/unreachable_diverging.rs:12:1: 20:2
}
}

4 changes: 4 additions & 0 deletions src/test/run-make/const_fn_mir/dump.mir
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Expand Up @@ -23,6 +23,10 @@ fn foo() -> i32 {
_0 = move (_1.0: i32); // scope 0 at main.rs:5:5: 5:10
return; // scope 0 at main.rs:6:2: 6:2
}

bb2 (cleanup): {
resume; // scope 0 at main.rs:4:1: 6:2
}
}

fn main() -> () {
Expand Down