diff --git a/compiler/rustc_mir_transform/src/ref_prop.rs b/compiler/rustc_mir_transform/src/ref_prop.rs
index dafd2ae23a635..d1bc9ee91538e 100644
--- a/compiler/rustc_mir_transform/src/ref_prop.rs
+++ b/compiler/rustc_mir_transform/src/ref_prop.rs
@@ -85,7 +85,9 @@ fn propagate_ssa<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
let ssa = SsaLocals::new(body);
let mut replacer = compute_replacement(tcx, body, &ssa);
- debug!(?replacer.targets, ?replacer.allowed_replacements, ?replacer.storage_to_remove);
+ debug!(?replacer.targets);
+ debug!(?replacer.allowed_replacements);
+ debug!(?replacer.storage_to_remove);
replacer.visit_body_preserves_cfg(body);
@@ -190,8 +192,11 @@ fn compute_replacement<'tcx>(
continue;
}
+ // Whether the current local is subject to the uniqueness rule.
+ let needs_unique = ty.is_mutable_ptr();
+
// If this a mutable reference that we cannot fully replace, mark it as unknown.
- if ty.is_mutable_ptr() && !fully_replacable_locals.contains(local) {
+ if needs_unique && !fully_replacable_locals.contains(local) {
debug!("not fully replaceable");
continue;
}
@@ -203,13 +208,14 @@ fn compute_replacement<'tcx>(
// have been visited before.
Rvalue::Use(Operand::Copy(place) | Operand::Move(place))
| Rvalue::CopyForDeref(place) => {
- if let Some(rhs) = place.as_local() {
+ if let Some(rhs) = place.as_local() && ssa.is_ssa(rhs) {
let target = targets[rhs];
- if matches!(target, Value::Pointer(..)) {
+ // Only see through immutable reference and pointers, as we do not know yet if
+ // mutable references are fully replaced.
+ if !needs_unique && matches!(target, Value::Pointer(..)) {
targets[local] = target;
- } else if ssa.is_ssa(rhs) {
- let refmut = body.local_decls[rhs].ty.is_mutable_ptr();
- targets[local] = Value::Pointer(tcx.mk_place_deref(rhs.into()), refmut);
+ } else {
+ targets[local] = Value::Pointer(tcx.mk_place_deref(rhs.into()), needs_unique);
}
}
}
@@ -217,10 +223,10 @@ fn compute_replacement<'tcx>(
let mut place = *place;
// Try to see through `place` in order to collapse reborrow chains.
if place.projection.first() == Some(&PlaceElem::Deref)
- && let Value::Pointer(target, refmut) = targets[place.local]
+ && let Value::Pointer(target, inner_needs_unique) = targets[place.local]
// Only see through immutable reference and pointers, as we do not know yet if
// mutable references are fully replaced.
- && !refmut
+ && !inner_needs_unique
// Only collapse chain if the pointee is definitely live.
&& can_perform_opt(target, location)
{
@@ -228,7 +234,7 @@ fn compute_replacement<'tcx>(
}
assert_ne!(place.local, local);
if is_constant_place(place) {
- targets[local] = Value::Pointer(place, ty.is_mutable_ptr());
+ targets[local] = Value::Pointer(place, needs_unique);
}
}
// We do not know what to do, so keep as not-a-pointer.
@@ -276,16 +282,35 @@ fn compute_replacement<'tcx>(
return;
}
- if let Value::Pointer(target, refmut) = self.targets[place.local]
- && place.projection.first() == Some(&PlaceElem::Deref)
- {
- let perform_opt = (self.can_perform_opt)(target, loc);
- if perform_opt {
- self.allowed_replacements.insert((target.local, loc));
- } else if refmut {
- // This mutable reference is not fully replacable, so drop it.
- self.targets[place.local] = Value::Unknown;
+ if place.projection.first() != Some(&PlaceElem::Deref) {
+ // This is not a dereference, nothing to do.
+ return;
+ }
+
+ let mut place = place.as_ref();
+ loop {
+ if let Value::Pointer(target, needs_unique) = self.targets[place.local] {
+ let perform_opt = (self.can_perform_opt)(target, loc);
+ debug!(?place, ?target, ?needs_unique, ?perform_opt);
+
+ // This a reborrow chain, recursively allow the replacement.
+ //
+ // This also allows to detect cases where `target.local` is not replacable,
+ // and mark it as such.
+ if let &[PlaceElem::Deref] = &target.projection[..] {
+ assert!(perform_opt);
+ self.allowed_replacements.insert((target.local, loc));
+ place.local = target.local;
+ continue;
+ } else if perform_opt {
+ self.allowed_replacements.insert((target.local, loc));
+ } else if needs_unique {
+ // This mutable reference is not fully replacable, so drop it.
+ self.targets[place.local] = Value::Unknown;
+ }
}
+
+ break;
}
}
}
@@ -326,18 +351,23 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'tcx> {
}
fn visit_place(&mut self, place: &mut Place<'tcx>, ctxt: PlaceContext, loc: Location) {
- if let Value::Pointer(target, _) = self.targets[place.local]
- && place.projection.first() == Some(&PlaceElem::Deref)
- {
- let perform_opt = matches!(ctxt, PlaceContext::NonUse(_))
- || self.allowed_replacements.contains(&(target.local, loc));
-
- if perform_opt {
- *place = target.project_deeper(&place.projection[1..], self.tcx);
- self.any_replacement = true;
+ if place.projection.first() != Some(&PlaceElem::Deref) {
+ return;
+ }
+
+ loop {
+ if let Value::Pointer(target, _) = self.targets[place.local] {
+ let perform_opt = matches!(ctxt, PlaceContext::NonUse(_))
+ || self.allowed_replacements.contains(&(target.local, loc));
+
+ if perform_opt {
+ *place = target.project_deeper(&place.projection[1..], self.tcx);
+ self.any_replacement = true;
+ continue;
+ }
}
- } else {
- self.super_place(place, ctxt, loc);
+
+ break;
}
}
diff --git a/tests/mir-opt/reference_prop.mut_raw_then_mut_shr.ReferencePropagation.diff b/tests/mir-opt/reference_prop.mut_raw_then_mut_shr.ReferencePropagation.diff
new file mode 100644
index 0000000000000..af8ee2411d36d
--- /dev/null
+++ b/tests/mir-opt/reference_prop.mut_raw_then_mut_shr.ReferencePropagation.diff
@@ -0,0 +1,74 @@
+- // MIR for `mut_raw_then_mut_shr` before ReferencePropagation
++ // MIR for `mut_raw_then_mut_shr` after ReferencePropagation
+
+ fn mut_raw_then_mut_shr() -> (i32, i32) {
+ let mut _0: (i32, i32); // return place in scope 0 at $DIR/reference_prop.rs:+0:30: +0:40
+ let mut _1: i32; // in scope 0 at $DIR/reference_prop.rs:+1:9: +1:14
+ let mut _4: *mut i32; // in scope 0 at $DIR/reference_prop.rs:+3:16: +3:36
+ let mut _5: &mut i32; // in scope 0 at $DIR/reference_prop.rs:+3:16: +3:26
+ let _8: (); // in scope 0 at $DIR/reference_prop.rs:+7:5: +7:26
+ let mut _9: i32; // in scope 0 at $DIR/reference_prop.rs:+8:6: +8:7
+ let mut _10: i32; // in scope 0 at $DIR/reference_prop.rs:+8:9: +8:10
+ scope 1 {
+ debug x => _1; // in scope 1 at $DIR/reference_prop.rs:+1:9: +1:14
+ let _2: &mut i32; // in scope 1 at $DIR/reference_prop.rs:+2:9: +2:13
+ scope 2 {
+ debug xref => _2; // in scope 2 at $DIR/reference_prop.rs:+2:9: +2:13
+ let _3: *mut i32; // in scope 2 at $DIR/reference_prop.rs:+3:9: +3:13
+ scope 3 {
+ debug xraw => _3; // in scope 3 at $DIR/reference_prop.rs:+3:9: +3:13
+ let _6: &i32; // in scope 3 at $DIR/reference_prop.rs:+4:9: +4:13
+ scope 4 {
+ debug xshr => _6; // in scope 4 at $DIR/reference_prop.rs:+4:9: +4:13
+ let _7: i32; // in scope 4 at $DIR/reference_prop.rs:+6:9: +6:10
+ scope 5 {
+ debug a => _7; // in scope 5 at $DIR/reference_prop.rs:+6:9: +6:10
+ scope 6 {
+ }
+ }
+ }
+ }
+ }
+ }
+
+ bb0: {
+ StorageLive(_1); // scope 0 at $DIR/reference_prop.rs:+1:9: +1:14
+ _1 = const 2_i32; // scope 0 at $DIR/reference_prop.rs:+1:17: +1:18
+- StorageLive(_2); // scope 1 at $DIR/reference_prop.rs:+2:9: +2:13
+ _2 = &mut _1; // scope 1 at $DIR/reference_prop.rs:+2:16: +2:22
+ StorageLive(_3); // scope 2 at $DIR/reference_prop.rs:+3:9: +3:13
+- StorageLive(_4); // scope 2 at $DIR/reference_prop.rs:+3:16: +3:36
+- StorageLive(_5); // scope 2 at $DIR/reference_prop.rs:+3:16: +3:26
+- _5 = &mut (*_2); // scope 2 at $DIR/reference_prop.rs:+3:16: +3:26
+- _4 = &raw mut (*_5); // scope 2 at $DIR/reference_prop.rs:+3:16: +3:26
++ _4 = &raw mut _1; // scope 2 at $DIR/reference_prop.rs:+3:16: +3:26
+ _3 = _4; // scope 2 at $DIR/reference_prop.rs:+3:16: +3:36
+- StorageDead(_5); // scope 2 at $DIR/reference_prop.rs:+3:36: +3:37
+- StorageDead(_4); // scope 2 at $DIR/reference_prop.rs:+3:36: +3:37
+ StorageLive(_6); // scope 3 at $DIR/reference_prop.rs:+4:9: +4:13
+- _6 = &(*_2); // scope 3 at $DIR/reference_prop.rs:+4:16: +4:22
++ _6 = &_1; // scope 3 at $DIR/reference_prop.rs:+4:16: +4:22
+ StorageLive(_7); // scope 4 at $DIR/reference_prop.rs:+6:9: +6:10
+- _7 = (*_6); // scope 4 at $DIR/reference_prop.rs:+6:13: +6:18
+- StorageLive(_8); // scope 5 at $DIR/reference_prop.rs:+7:5: +7:26
+- (*_3) = const 4_i32; // scope 6 at $DIR/reference_prop.rs:+7:14: +7:23
+- _8 = const (); // scope 6 at $DIR/reference_prop.rs:+7:5: +7:26
+- StorageDead(_8); // scope 5 at $DIR/reference_prop.rs:+7:25: +7:26
++ _7 = _1; // scope 4 at $DIR/reference_prop.rs:+6:13: +6:18
++ _1 = const 4_i32; // scope 6 at $DIR/reference_prop.rs:+7:14: +7:23
+ StorageLive(_9); // scope 5 at $DIR/reference_prop.rs:+8:6: +8:7
+ _9 = _7; // scope 5 at $DIR/reference_prop.rs:+8:6: +8:7
+ StorageLive(_10); // scope 5 at $DIR/reference_prop.rs:+8:9: +8:10
+ _10 = _1; // scope 5 at $DIR/reference_prop.rs:+8:9: +8:10
+ _0 = (move _9, move _10); // scope 5 at $DIR/reference_prop.rs:+8:5: +8:11
+ StorageDead(_10); // scope 5 at $DIR/reference_prop.rs:+8:10: +8:11
+ StorageDead(_9); // scope 5 at $DIR/reference_prop.rs:+8:10: +8:11
+ StorageDead(_7); // scope 4 at $DIR/reference_prop.rs:+9:1: +9:2
+ StorageDead(_6); // scope 3 at $DIR/reference_prop.rs:+9:1: +9:2
+ StorageDead(_3); // scope 2 at $DIR/reference_prop.rs:+9:1: +9:2
+- StorageDead(_2); // scope 1 at $DIR/reference_prop.rs:+9:1: +9:2
+ StorageDead(_1); // scope 0 at $DIR/reference_prop.rs:+9:1: +9:2
+ return; // scope 0 at $DIR/reference_prop.rs:+9:2: +9:2
+ }
+ }
+
diff --git a/tests/mir-opt/reference_prop.read_through_raw.ReferencePropagation.diff b/tests/mir-opt/reference_prop.read_through_raw.ReferencePropagation.diff
index a7d505c69066b..75c1f8f57ccae 100644
--- a/tests/mir-opt/reference_prop.read_through_raw.ReferencePropagation.diff
+++ b/tests/mir-opt/reference_prop.read_through_raw.ReferencePropagation.diff
@@ -9,15 +9,14 @@
let mut _5: *mut usize; // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
bb0: {
- _2 = &mut (*_1); // scope 0 at $DIR/reference_prop.rs:+10:13: +10:25
+- _2 = &mut (*_1); // scope 0 at $DIR/reference_prop.rs:+10:13: +10:25
- _3 = &mut (*_2); // scope 0 at $DIR/reference_prop.rs:+11:13: +11:26
- _4 = &raw mut (*_2); // scope 0 at $DIR/reference_prop.rs:+12:13: +12:30
- _5 = &raw mut (*_3); // scope 0 at $DIR/reference_prop.rs:+13:13: +13:30
- _0 = (*_4); // scope 0 at $DIR/reference_prop.rs:+15:13: +15:22
- _0 = (*_5); // scope 0 at $DIR/reference_prop.rs:+16:13: +16:22
-+ _3 = &mut (*_1); // scope 0 at $DIR/reference_prop.rs:+11:13: +11:26
-+ _0 = (*_2); // scope 0 at $DIR/reference_prop.rs:+15:13: +15:22
-+ _0 = (*_3); // scope 0 at $DIR/reference_prop.rs:+16:13: +16:22
++ _0 = (*_1); // scope 0 at $DIR/reference_prop.rs:+15:13: +15:22
++ _0 = (*_1); // scope 0 at $DIR/reference_prop.rs:+16:13: +16:22
return; // scope 0 at $DIR/reference_prop.rs:+17:13: +17:21
}
}
diff --git a/tests/mir-opt/reference_prop.rs b/tests/mir-opt/reference_prop.rs
index e3e5d791464eb..93f8d1df8e85a 100644
--- a/tests/mir-opt/reference_prop.rs
+++ b/tests/mir-opt/reference_prop.rs
@@ -433,6 +433,29 @@ fn maybe_dead(m: bool) {
)
}
+fn mut_raw_then_mut_shr() -> (i32, i32) {
+ let mut x = 2;
+ let xref = &mut x;
+ let xraw = &mut *xref as *mut _;
+ let xshr = &*xref;
+ // Verify that we completely replace with `x` in both cases.
+ let a = *xshr;
+ unsafe { *xraw = 4; }
+ (a, x)
+}
+
+fn unique_with_copies() {
+ let y = {
+ let mut a = 0;
+ let x = &raw mut a;
+ // `*y` is not replacable below, so we must not replace `*x`.
+ unsafe { opaque(*x) };
+ x
+ };
+ // But rewriting as `*x` is ok.
+ unsafe { opaque(*y) };
+}
+
fn main() {
let mut x = 5_usize;
let mut y = 7_usize;
@@ -444,6 +467,8 @@ fn main() {
multiple_storage();
dominate_storage();
maybe_dead(true);
+ mut_raw_then_mut_shr();
+ unique_with_copies();
}
// EMIT_MIR reference_prop.reference_propagation.ReferencePropagation.diff
@@ -454,3 +479,5 @@ fn main() {
// EMIT_MIR reference_prop.multiple_storage.ReferencePropagation.diff
// EMIT_MIR reference_prop.dominate_storage.ReferencePropagation.diff
// EMIT_MIR reference_prop.maybe_dead.ReferencePropagation.diff
+// EMIT_MIR reference_prop.mut_raw_then_mut_shr.ReferencePropagation.diff
+// EMIT_MIR reference_prop.unique_with_copies.ReferencePropagation.diff
diff --git a/tests/mir-opt/reference_prop.unique_with_copies.ReferencePropagation.diff b/tests/mir-opt/reference_prop.unique_with_copies.ReferencePropagation.diff
new file mode 100644
index 0000000000000..2cda2409e8093
--- /dev/null
+++ b/tests/mir-opt/reference_prop.unique_with_copies.ReferencePropagation.diff
@@ -0,0 +1,66 @@
+- // MIR for `unique_with_copies` before ReferencePropagation
++ // MIR for `unique_with_copies` after ReferencePropagation
+
+ fn unique_with_copies() -> () {
+ let mut _0: (); // return place in scope 0 at $DIR/reference_prop.rs:+0:25: +0:25
+ let _1: *mut i32; // in scope 0 at $DIR/reference_prop.rs:+1:9: +1:10
+ let mut _2: i32; // in scope 0 at $DIR/reference_prop.rs:+2:13: +2:18
+ let _4: (); // in scope 0 at $DIR/reference_prop.rs:+5:18: +5:28
+ let mut _5: i32; // in scope 0 at $DIR/reference_prop.rs:+5:25: +5:27
+ let _6: (); // in scope 0 at $DIR/reference_prop.rs:+9:14: +9:24
+ let mut _7: i32; // in scope 0 at $DIR/reference_prop.rs:+9:21: +9:23
+ scope 1 {
+ debug y => _1; // in scope 1 at $DIR/reference_prop.rs:+1:9: +1:10
+ scope 5 {
+ }
+ }
+ scope 2 {
+ debug a => _2; // in scope 2 at $DIR/reference_prop.rs:+2:13: +2:18
+ let _3: *mut i32; // in scope 2 at $DIR/reference_prop.rs:+3:13: +3:14
+ scope 3 {
+ debug x => _3; // in scope 3 at $DIR/reference_prop.rs:+3:13: +3:14
+ scope 4 {
+ }
+ }
+ }
+
+ bb0: {
+ StorageLive(_1); // scope 0 at $DIR/reference_prop.rs:+1:9: +1:10
+ StorageLive(_2); // scope 0 at $DIR/reference_prop.rs:+2:13: +2:18
+ _2 = const 0_i32; // scope 0 at $DIR/reference_prop.rs:+2:21: +2:22
+- StorageLive(_3); // scope 2 at $DIR/reference_prop.rs:+3:13: +3:14
+ _3 = &raw mut _2; // scope 2 at $DIR/reference_prop.rs:+3:17: +3:27
+ StorageLive(_4); // scope 3 at $DIR/reference_prop.rs:+5:9: +5:30
+ StorageLive(_5); // scope 4 at $DIR/reference_prop.rs:+5:25: +5:27
+ _5 = (*_3); // scope 4 at $DIR/reference_prop.rs:+5:25: +5:27
+ _4 = opaque::<i32>(move _5) -> bb1; // scope 4 at $DIR/reference_prop.rs:+5:18: +5:28
+ // mir::Constant
+ // + span: $DIR/reference_prop.rs:452:18: 452:24
+ // + literal: Const { ty: fn(i32) {opaque::<i32>}, val: Value(<ZST>) }
+ }
+
+ bb1: {
+ StorageDead(_5); // scope 4 at $DIR/reference_prop.rs:+5:27: +5:28
+ StorageDead(_4); // scope 3 at $DIR/reference_prop.rs:+5:30: +5:31
+ _1 = _3; // scope 3 at $DIR/reference_prop.rs:+6:9: +6:10
+- StorageDead(_3); // scope 2 at $DIR/reference_prop.rs:+7:5: +7:6
+ StorageDead(_2); // scope 0 at $DIR/reference_prop.rs:+7:5: +7:6
+ StorageLive(_6); // scope 1 at $DIR/reference_prop.rs:+9:5: +9:26
+ StorageLive(_7); // scope 5 at $DIR/reference_prop.rs:+9:21: +9:23
+- _7 = (*_1); // scope 5 at $DIR/reference_prop.rs:+9:21: +9:23
++ _7 = (*_3); // scope 5 at $DIR/reference_prop.rs:+9:21: +9:23
+ _6 = opaque::<i32>(move _7) -> bb2; // scope 5 at $DIR/reference_prop.rs:+9:14: +9:24
+ // mir::Constant
+ // + span: $DIR/reference_prop.rs:456:14: 456:20
+ // + literal: Const { ty: fn(i32) {opaque::<i32>}, val: Value(<ZST>) }
+ }
+
+ bb2: {
+ StorageDead(_7); // scope 5 at $DIR/reference_prop.rs:+9:23: +9:24
+ StorageDead(_6); // scope 1 at $DIR/reference_prop.rs:+9:26: +9:27
+ _0 = const (); // scope 0 at $DIR/reference_prop.rs:+0:25: +10:2
+ StorageDead(_1); // scope 0 at $DIR/reference_prop.rs:+10:1: +10:2
+ return; // scope 0 at $DIR/reference_prop.rs:+10:2: +10:2
+ }
+ }
+