From 1ffe9059c31d17ea1b22099b0f64de0232ebadd5 Mon Sep 17 00:00:00 2001
From: Camille GILLOT <gillot.camille@gmail.com>
Date: Fri, 28 Apr 2023 16:57:40 +0000
Subject: [PATCH] Reject borrows of projections in ConstProp.
---
.../rustc_mir_transform/src/const_prop.rs | 20 ++++++++++++++-----
.../address_of_pair.fn0.ConstProp.diff | 15 +++++---------
.../const_prop_miscompile.bar.ConstProp.diff | 3 +--
.../const_prop_miscompile.foo.ConstProp.diff | 3 +--
4 files changed, 22 insertions(+), 19 deletions(-)
diff --git a/compiler/rustc_mir_transform/src/const_prop.rs b/compiler/rustc_mir_transform/src/const_prop.rs
index b3a3a25ebe8..7f995c69a48 100644
--- a/compiler/rustc_mir_transform/src/const_prop.rs
+++ b/compiler/rustc_mir_transform/src/const_prop.rs
@@ -714,13 +714,22 @@ impl CanConstProp {
}
}
-impl Visitor<'_> for CanConstProp {
+impl<'tcx> Visitor<'tcx> for CanConstProp {
+ fn visit_place(&mut self, place: &Place<'tcx>, mut context: PlaceContext, loc: Location) {
+ use rustc_middle::mir::visit::PlaceContext::*;
+
+ // Dereferencing just read the addess of `place.local`.
+ if place.projection.first() == Some(&PlaceElem::Deref) {
+ context = NonMutatingUse(NonMutatingUseContext::Copy);
+ }
+
+ self.visit_local(place.local, context, loc);
+ self.visit_projection(place.as_ref(), context, loc);
+ }
+
fn visit_local(&mut self, local: Local, context: PlaceContext, _: Location) {
use rustc_middle::mir::visit::PlaceContext::*;
match context {
- // Projections are fine, because `&mut foo.x` will be caught by
- // `MutatingUseContext::Borrow` elsewhere.
- MutatingUse(MutatingUseContext::Projection)
// These are just stores, where the storing is not propagatable, but there may be later
// mutations of the same local via `Store`
| MutatingUse(MutatingUseContext::Call)
@@ -751,7 +760,6 @@ impl Visitor<'_> for CanConstProp {
NonMutatingUse(NonMutatingUseContext::Copy)
| NonMutatingUse(NonMutatingUseContext::Move)
| NonMutatingUse(NonMutatingUseContext::Inspect)
- | NonMutatingUse(NonMutatingUseContext::Projection)
| NonMutatingUse(NonMutatingUseContext::PlaceMention)
| NonUse(_) => {}
@@ -771,6 +779,8 @@ impl Visitor<'_> for CanConstProp {
trace!("local {:?} can't be propagated because it's used: {:?}", local, context);
self.can_const_prop[local] = ConstPropMode::NoPropagation;
}
+ MutatingUse(MutatingUseContext::Projection)
+ | NonMutatingUse(NonMutatingUseContext::Projection) => bug!("visit_place should not pass {context:?} for {local:?}"),
}
}
}
diff --git a/tests/mir-opt/const_prop/address_of_pair.fn0.ConstProp.diff b/tests/mir-opt/const_prop/address_of_pair.fn0.ConstProp.diff
index 8a8e869ba03..d50b12044ce 100644
--- a/tests/mir-opt/const_prop/address_of_pair.fn0.ConstProp.diff
+++ b/tests/mir-opt/const_prop/address_of_pair.fn0.ConstProp.diff
@@ -23,25 +23,20 @@
bb0: {
StorageLive(_2); // scope 0 at $DIR/address_of_pair.rs:+1:9: +1:17
-- _2 = (const 1_i32, const false); // scope 0 at $DIR/address_of_pair.rs:+1:20: +1:30
-+ _2 = const (1_i32, false); // scope 0 at $DIR/address_of_pair.rs:+1:20: +1:30
+ _2 = (const 1_i32, const false); // scope 0 at $DIR/address_of_pair.rs:+1:20: +1:30
StorageLive(_3); // scope 1 at $DIR/address_of_pair.rs:+2:9: +2:12
_3 = &raw mut (_2.1: bool); // scope 1 at $SRC_DIR/core/src/ptr/mod.rs:LL:COL
-- _2 = (const 1_i32, const false); // scope 2 at $DIR/address_of_pair.rs:+3:5: +3:22
-+ _2 = const (1_i32, false); // scope 2 at $DIR/address_of_pair.rs:+3:5: +3:22
+ _2 = (const 1_i32, const false); // scope 2 at $DIR/address_of_pair.rs:+3:5: +3:22
StorageLive(_4); // scope 2 at $DIR/address_of_pair.rs:+4:5: +6:6
(*_3) = const true; // scope 3 at $DIR/address_of_pair.rs:+5:9: +5:20
_4 = const (); // scope 3 at $DIR/address_of_pair.rs:+4:5: +6:6
StorageDead(_4); // scope 2 at $DIR/address_of_pair.rs:+6:5: +6:6
StorageLive(_5); // scope 2 at $DIR/address_of_pair.rs:+7:9: +7:12
StorageLive(_6); // scope 2 at $DIR/address_of_pair.rs:+7:16: +7:22
-- _6 = (_2.1: bool); // scope 2 at $DIR/address_of_pair.rs:+7:16: +7:22
-- _5 = Not(move _6); // scope 2 at $DIR/address_of_pair.rs:+7:15: +7:22
-+ _6 = const false; // scope 2 at $DIR/address_of_pair.rs:+7:16: +7:22
-+ _5 = const true; // scope 2 at $DIR/address_of_pair.rs:+7:15: +7:22
+ _6 = (_2.1: bool); // scope 2 at $DIR/address_of_pair.rs:+7:16: +7:22
+ _5 = Not(move _6); // scope 2 at $DIR/address_of_pair.rs:+7:15: +7:22
StorageDead(_6); // scope 2 at $DIR/address_of_pair.rs:+7:21: +7:22
-- _0 = _5; // scope 4 at $DIR/address_of_pair.rs:+8:12: +8:15
-+ _0 = const true; // scope 4 at $DIR/address_of_pair.rs:+8:12: +8:15
+ _0 = _5; // scope 4 at $DIR/address_of_pair.rs:+8:12: +8:15
StorageDead(_5); // scope 2 at $DIR/address_of_pair.rs:+9:1: +9:2
StorageDead(_3); // scope 1 at $DIR/address_of_pair.rs:+9:1: +9:2
StorageDead(_2); // scope 0 at $DIR/address_of_pair.rs:+9:1: +9:2
diff --git a/tests/mir-opt/const_prop_miscompile.bar.ConstProp.diff b/tests/mir-opt/const_prop_miscompile.bar.ConstProp.diff
index def9fc6428f..a5f52d08957 100644
--- a/tests/mir-opt/const_prop_miscompile.bar.ConstProp.diff
+++ b/tests/mir-opt/const_prop_miscompile.bar.ConstProp.diff
@@ -19,8 +19,7 @@
bb0: {
StorageLive(_1); // scope 0 at $DIR/const_prop_miscompile.rs:+1:9: +1:14
-- _1 = (const 1_i32,); // scope 0 at $DIR/const_prop_miscompile.rs:+1:17: +1:21
-+ _1 = const (1_i32,); // scope 0 at $DIR/const_prop_miscompile.rs:+1:17: +1:21
+ _1 = (const 1_i32,); // scope 0 at $DIR/const_prop_miscompile.rs:+1:17: +1:21
StorageLive(_2); // scope 1 at $DIR/const_prop_miscompile.rs:+2:5: +4:6
StorageLive(_3); // scope 2 at $DIR/const_prop_miscompile.rs:+3:10: +3:22
_3 = &raw mut (_1.0: i32); // scope 2 at $DIR/const_prop_miscompile.rs:+3:10: +3:22
diff --git a/tests/mir-opt/const_prop_miscompile.foo.ConstProp.diff b/tests/mir-opt/const_prop_miscompile.foo.ConstProp.diff
index b54c10a140f..42ddc2a5620 100644
--- a/tests/mir-opt/const_prop_miscompile.foo.ConstProp.diff
+++ b/tests/mir-opt/const_prop_miscompile.foo.ConstProp.diff
@@ -16,8 +16,7 @@
bb0: {
StorageLive(_1); // scope 0 at $DIR/const_prop_miscompile.rs:+1:9: +1:14
-- _1 = (const 1_i32,); // scope 0 at $DIR/const_prop_miscompile.rs:+1:17: +1:21
-+ _1 = const (1_i32,); // scope 0 at $DIR/const_prop_miscompile.rs:+1:17: +1:21
+ _1 = (const 1_i32,); // scope 0 at $DIR/const_prop_miscompile.rs:+1:17: +1:21
StorageLive(_2); // scope 1 at $DIR/const_prop_miscompile.rs:+2:6: +2:14
_2 = &mut (_1.0: i32); // scope 1 at $DIR/const_prop_miscompile.rs:+2:6: +2:14
(*_2) = const 5_i32; // scope 1 at $DIR/const_prop_miscompile.rs:+2:5: +2:18