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Add some more sanity tests and add a debug log message for it
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3 files changed

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‎src/librustc_mir/transform/const_prop.rs

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Original file line numberDiff line numberDiff line change
@@ -893,6 +893,11 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> {
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// ```
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// FIXME: we overzealously erase the entire local, because that's easier to
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// implement.
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trace!(
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"propagation into {:?} failed.
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Nuking the entire site from orbit, it's the only way to be sure",
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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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}

‎src/test/mir-opt/const_prop/mutable_variable_unprop_assign.rs

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@@ -0,0 +1,15 @@
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// compile-flags: -O
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// EMIT_MIR rustc.main.ConstProp.diff
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fn main() {
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let a = foo();
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let mut x: (i32, i32) = (1, 2);
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x.1 = a;
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let y = x.1;
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let z = x.0; // this could theoretically be allowed, but we can't handle it right now
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}
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#[inline(never)]
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fn foo() -> i32 {
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unimplemented!()
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}

‎src/test/mir-opt/const_prop/mutable_variable_unprop_assign/rustc.main.ConstProp.diff

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- // MIR for `main` before ConstProp
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+ // MIR for `main` after ConstProp
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fn main() -> () {
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let mut _0: (); // return place in scope 0 at $DIR/mutable_variable_unprop_assign.rs:4:11: 4:11
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let _1: i32; // in scope 0 at $DIR/mutable_variable_unprop_assign.rs:5:9: 5:10
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let mut _3: i32; // in scope 0 at $DIR/mutable_variable_unprop_assign.rs:7:11: 7:12
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scope 1 {
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debug a => _1; // in scope 1 at $DIR/mutable_variable_unprop_assign.rs:5:9: 5:10
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let mut _2: (i32, i32) as UserTypeProjection { base: UserType(0), projs: [] }; // in scope 1 at $DIR/mutable_variable_unprop_assign.rs:6:9: 6:14
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scope 2 {
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debug x => _2; // in scope 2 at $DIR/mutable_variable_unprop_assign.rs:6:9: 6:14
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let _4: i32; // in scope 2 at $DIR/mutable_variable_unprop_assign.rs:8:9: 8:10
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scope 3 {
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debug y => _4; // in scope 3 at $DIR/mutable_variable_unprop_assign.rs:8:9: 8:10
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let _5: i32; // in scope 3 at $DIR/mutable_variable_unprop_assign.rs:9:9: 9:10
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scope 4 {
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debug z => _5; // in scope 4 at $DIR/mutable_variable_unprop_assign.rs:9:9: 9:10
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}
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}
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}
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}
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bb0: {
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StorageLive(_1); // scope 0 at $DIR/mutable_variable_unprop_assign.rs:5:9: 5:10
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_1 = const foo() -> bb1; // scope 0 at $DIR/mutable_variable_unprop_assign.rs:5:13: 5:18
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// ty::Const
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// + ty: fn() -> i32 {foo}
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// + val: Value(Scalar(<ZST>))
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// mir::Constant
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// + span: $DIR/mutable_variable_unprop_assign.rs:5:13: 5:16
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// + literal: Const { ty: fn() -> i32 {foo}, val: Value(Scalar(<ZST>)) }
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}
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bb1: {
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StorageLive(_2); // scope 1 at $DIR/mutable_variable_unprop_assign.rs:6:9: 6:14
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_2 = (const 1i32, const 2i32); // scope 1 at $DIR/mutable_variable_unprop_assign.rs:6:29: 6:35
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// ty::Const
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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/mutable_variable_unprop_assign.rs:6:30: 6:31
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+ // + span: $DIR/mutable_variable_unprop_assign.rs:6:29: 6:35
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// + literal: Const { ty: i32, val: Value(Scalar(0x00000001)) }
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// ty::Const
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// + ty: i32
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// + val: Value(Scalar(0x00000002))
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// mir::Constant
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- // + span: $DIR/mutable_variable_unprop_assign.rs:6:33: 6:34
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+ // + span: $DIR/mutable_variable_unprop_assign.rs:6:29: 6:35
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// + literal: Const { ty: i32, val: Value(Scalar(0x00000002)) }
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StorageLive(_3); // scope 2 at $DIR/mutable_variable_unprop_assign.rs:7:11: 7:12
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_3 = _1; // scope 2 at $DIR/mutable_variable_unprop_assign.rs:7:11: 7:12
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(_2.1: i32) = move _3; // scope 2 at $DIR/mutable_variable_unprop_assign.rs:7:5: 7:12
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StorageDead(_3); // scope 2 at $DIR/mutable_variable_unprop_assign.rs:7:11: 7:12
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StorageLive(_4); // scope 2 at $DIR/mutable_variable_unprop_assign.rs:8:9: 8:10
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_4 = (_2.1: i32); // scope 2 at $DIR/mutable_variable_unprop_assign.rs:8:13: 8:16
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StorageLive(_5); // scope 3 at $DIR/mutable_variable_unprop_assign.rs:9:9: 9:10
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_5 = (_2.0: i32); // scope 3 at $DIR/mutable_variable_unprop_assign.rs:9:13: 9:16
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_0 = const (); // scope 0 at $DIR/mutable_variable_unprop_assign.rs:4:11: 10:2
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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/mutable_variable_unprop_assign.rs:4:11: 10:2
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// + literal: Const { ty: (), val: Value(Scalar(<ZST>)) }
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StorageDead(_5); // scope 3 at $DIR/mutable_variable_unprop_assign.rs:10:1: 10:2
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StorageDead(_4); // scope 2 at $DIR/mutable_variable_unprop_assign.rs:10:1: 10:2
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StorageDead(_2); // scope 1 at $DIR/mutable_variable_unprop_assign.rs:10:1: 10:2
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StorageDead(_1); // scope 0 at $DIR/mutable_variable_unprop_assign.rs:10:1: 10:2
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return; // scope 0 at $DIR/mutable_variable_unprop_assign.rs:10:2: 10:2
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}
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}
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