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https://github.com/rust-lang/rust.git
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The const propagator cannot trace references.
Thus we avoid propagation of a local the moment we encounter references to it.
This commit is contained in:
Oliver Scherer
parent
1a4e2b6f9c
commit
5fa8b08808
@ -575,8 +575,16 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
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}
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// Do not try creating references (#67862)
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Rvalue::Ref(_, _, place_ref) => {
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trace!("skipping Ref({:?})", place_ref);
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Rvalue::AddressOf(_, place) | Rvalue::Ref(_, _, place) => {
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trace!("skipping AddressOf | Ref for {:?}", place);
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// This may be creating mutable references or immutable references to cells.
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// If that happens, the pointed to value could be mutated via that reference.
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// Since we aren't tracking references, the const propagator loses track of what
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// value the local has right now.
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// Thus, all locals that have their reference taken
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// must not take part in propagation.
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Self::remove_const(&mut self.ecx, place.local);
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return None;
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}
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@ -716,6 +724,9 @@ enum ConstPropMode {
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OnlyInsideOwnBlock,
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/// The `Local` can be propagated into but reads cannot be propagated.
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OnlyPropagateInto,
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/// The `Local` cannot be part of propagation at all. Any statement
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/// referencing it either for reading or writing will not get propagated.
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NoPropagation,
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}
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struct CanConstProp {
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@ -781,7 +792,9 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
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// end of the block anyway, and inside the block we overwrite previous
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// states as applicable.
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ConstPropMode::OnlyInsideOwnBlock => {}
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other => {
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ConstPropMode::NoPropagation => {}
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ConstPropMode::OnlyPropagateInto => {}
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other @ ConstPropMode::FullConstProp => {
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trace!(
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"local {:?} can't be propagated because of multiple assignments",
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local,
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@ -813,7 +826,7 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
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| MutatingUse(MutatingUseContext::Borrow)
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| MutatingUse(MutatingUseContext::AddressOf) => {
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trace!("local {:?} can't be propagaged because it's used: {:?}", local, context);
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self.can_const_prop[local] = ConstPropMode::OnlyPropagateInto;
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self.can_const_prop[local] = ConstPropMode::NoPropagation;
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}
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}
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}
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@ -858,19 +871,22 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
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}
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}
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}
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if can_const_prop == ConstPropMode::OnlyInsideOwnBlock {
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trace!(
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"found local restricted to its block. Will remove it from const-prop after block is finished. Local: {:?}",
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place.local
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);
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self.locals_of_current_block.insert(place.local);
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}
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if can_const_prop == ConstPropMode::OnlyPropagateInto {
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trace!("can't propagate into {:?}", place);
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if place.local != RETURN_PLACE {
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Self::remove_const(&mut self.ecx, place.local);
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match can_const_prop {
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ConstPropMode::OnlyInsideOwnBlock => {
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trace!(
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"found local restricted to its block. \
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Will remove it from const-prop after block is finished. Local: {:?}",
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place.local
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);
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self.locals_of_current_block.insert(place.local);
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}
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ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => {
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trace!("can't propagate into {:?}", place);
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if place.local != RETURN_PLACE {
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Self::remove_const(&mut self.ecx, place.local);
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}
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}
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ConstPropMode::FullConstProp => {}
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}
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} else {
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// Const prop failed, so erase the destination, ensuring that whatever happens
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@ -890,6 +906,12 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
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);
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Self::remove_const(&mut self.ecx, place.local);
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}
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} else {
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trace!(
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"cannot propagate into {:?}, because the type of the local is generic.",
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place,
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);
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Self::remove_const(&mut self.ecx, place.local);
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}
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} else {
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match statement.kind {
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@ -46,22 +46,8 @@
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// mir::Constant
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// + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:23: 7:24
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// + literal: Const { ty: usize, val: Value(Scalar(0x00000003)) }
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- _7 = Len((*_1)); // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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- _8 = Lt(_6, _7); // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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+ _7 = const 3usize; // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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+ // ty::Const
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+ // + ty: usize
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+ // + val: Value(Scalar(0x00000003))
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+ // mir::Constant
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+ // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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+ // + literal: Const { ty: usize, val: Value(Scalar(0x00000003)) }
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+ _8 = const false; // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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+ // ty::Const
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+ // + ty: bool
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+ // + val: Value(Scalar(0x00))
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+ // mir::Constant
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+ // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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+ // + literal: Const { ty: bool, val: Value(Scalar(0x00)) }
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_7 = Len((*_1)); // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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_8 = Lt(_6, _7); // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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assert(move _8, "index out of bounds: the len is {} but the index is {}", move _7, _6) -> bb1; // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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}
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@ -46,22 +46,8 @@
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// mir::Constant
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// + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:23: 7:24
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// + literal: Const { ty: usize, val: Value(Scalar(0x0000000000000003)) }
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- _7 = Len((*_1)); // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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- _8 = Lt(_6, _7); // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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+ _7 = const 3usize; // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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+ // ty::Const
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+ // + ty: usize
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+ // + val: Value(Scalar(0x0000000000000003))
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+ // mir::Constant
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+ // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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+ // + literal: Const { ty: usize, val: Value(Scalar(0x0000000000000003)) }
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+ _8 = const false; // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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+ // ty::Const
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+ // + ty: bool
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+ // + val: Value(Scalar(0x00))
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+ // mir::Constant
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+ // + span: $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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+ // + literal: Const { ty: bool, val: Value(Scalar(0x00)) }
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_7 = Len((*_1)); // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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_8 = Lt(_6, _7); // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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assert(move _8, "index out of bounds: the len is {} but the index is {}", move _7, _6) -> bb1; // scope 2 at $DIR/bad_op_unsafe_oob_for_slices.rs:7:18: 7:25
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}
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22
src/test/mir-opt/const_prop_miscompile.rs
Normal file
22
src/test/mir-opt/const_prop_miscompile.rs
Normal file
@ -0,0 +1,22 @@
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#![feature(raw_ref_op)]
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// EMIT_MIR rustc.foo.ConstProp.diff
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fn foo() {
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let mut u = (1,);
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*&mut u.0 = 5;
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let y = { u.0 } == 5;
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}
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// EMIT_MIR rustc.bar.ConstProp.diff
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fn bar() {
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let mut v = (1,);
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unsafe {
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*&raw mut v.0 = 5;
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}
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let y = { v.0 } == 5;
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}
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fn main() {
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foo();
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bar();
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}
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@ -0,0 +1,75 @@
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- // MIR for `bar` before ConstProp
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+ // MIR for `bar` after ConstProp
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fn bar() -> () {
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let mut _0: (); // return place in scope 0 at $DIR/const_prop_miscompile.rs:11:10: 11:10
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let mut _1: (i32,); // in scope 0 at $DIR/const_prop_miscompile.rs:12:9: 12:14
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let _2: (); // in scope 0 at $DIR/const_prop_miscompile.rs:13:5: 15:6
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let mut _3: *mut i32; // in scope 0 at $DIR/const_prop_miscompile.rs:14:10: 14:22
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let mut _5: i32; // in scope 0 at $DIR/const_prop_miscompile.rs:16:13: 16:20
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scope 1 {
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debug v => _1; // in scope 1 at $DIR/const_prop_miscompile.rs:12:9: 12:14
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let _4: bool; // in scope 1 at $DIR/const_prop_miscompile.rs:16:9: 16:10
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scope 2 {
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}
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scope 3 {
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debug y => _4; // in scope 3 at $DIR/const_prop_miscompile.rs:16:9: 16:10
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}
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}
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bb0: {
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StorageLive(_1); // scope 0 at $DIR/const_prop_miscompile.rs:12:9: 12:14
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- _1 = (const 1i32,); // scope 0 at $DIR/const_prop_miscompile.rs:12:17: 12:21
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+ _1 = const (1i32,); // scope 0 at $DIR/const_prop_miscompile.rs:12:17: 12:21
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// ty::Const
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- // + ty: i32
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+ // + ty: (i32,)
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// + val: Value(Scalar(0x00000001))
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// mir::Constant
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- // + span: $DIR/const_prop_miscompile.rs:12:18: 12:19
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- // + literal: Const { ty: i32, val: Value(Scalar(0x00000001)) }
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+ // + span: $DIR/const_prop_miscompile.rs:12:17: 12:21
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+ // + literal: Const { ty: (i32,), val: Value(Scalar(0x00000001)) }
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StorageLive(_2); // scope 1 at $DIR/const_prop_miscompile.rs:13:5: 15:6
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StorageLive(_3); // scope 2 at $DIR/const_prop_miscompile.rs:14:10: 14:22
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_3 = &raw mut (_1.0: i32); // scope 2 at $DIR/const_prop_miscompile.rs:14:10: 14:22
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(*_3) = const 5i32; // scope 2 at $DIR/const_prop_miscompile.rs:14:9: 14:26
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// ty::Const
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// + ty: i32
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// + val: Value(Scalar(0x00000005))
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// mir::Constant
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// + span: $DIR/const_prop_miscompile.rs:14:25: 14:26
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// + literal: Const { ty: i32, val: Value(Scalar(0x00000005)) }
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StorageDead(_3); // scope 2 at $DIR/const_prop_miscompile.rs:14:26: 14:27
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_2 = const (); // scope 2 at $DIR/const_prop_miscompile.rs:13:5: 15:6
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// ty::Const
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// + ty: ()
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// + val: Value(Scalar(<ZST>))
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// mir::Constant
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// + span: $DIR/const_prop_miscompile.rs:13:5: 15:6
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// + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
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StorageDead(_2); // scope 1 at $DIR/const_prop_miscompile.rs:15:5: 15:6
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StorageLive(_4); // scope 1 at $DIR/const_prop_miscompile.rs:16:9: 16:10
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StorageLive(_5); // scope 1 at $DIR/const_prop_miscompile.rs:16:13: 16:20
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_5 = (_1.0: i32); // scope 1 at $DIR/const_prop_miscompile.rs:16:15: 16:18
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_4 = Eq(move _5, const 5i32); // scope 1 at $DIR/const_prop_miscompile.rs:16:13: 16:25
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// ty::Const
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// + ty: i32
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// + val: Value(Scalar(0x00000005))
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// mir::Constant
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// + span: $DIR/const_prop_miscompile.rs:16:24: 16:25
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// + literal: Const { ty: i32, val: Value(Scalar(0x00000005)) }
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StorageDead(_5); // scope 1 at $DIR/const_prop_miscompile.rs:16:24: 16:25
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_0 = const (); // scope 0 at $DIR/const_prop_miscompile.rs:11:10: 17:2
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// ty::Const
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// + ty: ()
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// + val: Value(Scalar(<ZST>))
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// mir::Constant
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// + span: $DIR/const_prop_miscompile.rs:11:10: 17:2
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// + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
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StorageDead(_4); // scope 1 at $DIR/const_prop_miscompile.rs:17:1: 17:2
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StorageDead(_1); // scope 0 at $DIR/const_prop_miscompile.rs:17:1: 17:2
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return; // scope 0 at $DIR/const_prop_miscompile.rs:17:2: 17:2
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}
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}
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@ -0,0 +1,63 @@
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- // MIR for `foo` before ConstProp
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+ // MIR for `foo` after ConstProp
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fn foo() -> () {
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let mut _0: (); // return place in scope 0 at $DIR/const_prop_miscompile.rs:4:10: 4:10
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let mut _1: (i32,); // in scope 0 at $DIR/const_prop_miscompile.rs:5:9: 5:14
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let mut _2: &mut i32; // in scope 0 at $DIR/const_prop_miscompile.rs:6:6: 6:14
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let mut _4: i32; // in scope 0 at $DIR/const_prop_miscompile.rs:7:13: 7:20
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scope 1 {
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debug u => _1; // in scope 1 at $DIR/const_prop_miscompile.rs:5:9: 5:14
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let _3: bool; // in scope 1 at $DIR/const_prop_miscompile.rs:7:9: 7:10
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scope 2 {
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debug y => _3; // in scope 2 at $DIR/const_prop_miscompile.rs:7:9: 7:10
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}
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}
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bb0: {
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StorageLive(_1); // scope 0 at $DIR/const_prop_miscompile.rs:5:9: 5:14
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- _1 = (const 1i32,); // scope 0 at $DIR/const_prop_miscompile.rs:5:17: 5:21
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+ _1 = const (1i32,); // scope 0 at $DIR/const_prop_miscompile.rs:5:17: 5:21
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// ty::Const
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- // + ty: i32
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+ // + ty: (i32,)
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// + val: Value(Scalar(0x00000001))
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// mir::Constant
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- // + span: $DIR/const_prop_miscompile.rs:5:18: 5:19
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- // + literal: Const { ty: i32, val: Value(Scalar(0x00000001)) }
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+ // + span: $DIR/const_prop_miscompile.rs:5:17: 5:21
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+ // + literal: Const { ty: (i32,), val: Value(Scalar(0x00000001)) }
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StorageLive(_2); // scope 1 at $DIR/const_prop_miscompile.rs:6:6: 6:14
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_2 = &mut (_1.0: i32); // scope 1 at $DIR/const_prop_miscompile.rs:6:6: 6:14
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(*_2) = const 5i32; // scope 1 at $DIR/const_prop_miscompile.rs:6:5: 6:18
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// ty::Const
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// + ty: i32
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// + val: Value(Scalar(0x00000005))
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// mir::Constant
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// + span: $DIR/const_prop_miscompile.rs:6:17: 6:18
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// + literal: Const { ty: i32, val: Value(Scalar(0x00000005)) }
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StorageDead(_2); // scope 1 at $DIR/const_prop_miscompile.rs:6:18: 6:19
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StorageLive(_3); // scope 1 at $DIR/const_prop_miscompile.rs:7:9: 7:10
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StorageLive(_4); // scope 1 at $DIR/const_prop_miscompile.rs:7:13: 7:20
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_4 = (_1.0: i32); // scope 1 at $DIR/const_prop_miscompile.rs:7:15: 7:18
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_3 = Eq(move _4, const 5i32); // scope 1 at $DIR/const_prop_miscompile.rs:7:13: 7:25
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// ty::Const
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// + ty: i32
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// + val: Value(Scalar(0x00000005))
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// mir::Constant
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// + span: $DIR/const_prop_miscompile.rs:7:24: 7:25
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// + literal: Const { ty: i32, val: Value(Scalar(0x00000005)) }
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StorageDead(_4); // scope 1 at $DIR/const_prop_miscompile.rs:7:24: 7:25
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_0 = const (); // scope 0 at $DIR/const_prop_miscompile.rs:4:10: 8:2
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// ty::Const
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// + ty: ()
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// + val: Value(Scalar(<ZST>))
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// mir::Constant
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// + span: $DIR/const_prop_miscompile.rs:4:10: 8:2
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// + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
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StorageDead(_3); // scope 1 at $DIR/const_prop_miscompile.rs:8:1: 8:2
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StorageDead(_1); // scope 0 at $DIR/const_prop_miscompile.rs:8:1: 8:2
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return; // scope 0 at $DIR/const_prop_miscompile.rs:8:2: 8:2
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}
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}
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@ -19,6 +19,6 @@ fn mod_by_zero() {
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fn oob_error_for_slices() {
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let a: *const [_] = &[1, 2, 3];
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unsafe {
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let _b = (*a)[3]; //~ ERROR this operation will panic at runtime [unconditional_panic]
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let _b = (*a)[3];
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}
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}
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@ -12,11 +12,5 @@ error: this operation will panic at runtime
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LL | let _z = 1 % y;
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| ^^^^^ attempt to calculate the remainder with a divisor of zero
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error: this operation will panic at runtime
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--> $DIR/mir_detects_invalid_ops.rs:22:18
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LL | let _b = (*a)[3];
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| ^^^^^^^ index out of bounds: the len is 3 but the index is 3
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error: aborting due to 3 previous errors
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error: aborting due to 2 previous errors
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