diff --git a/src/librustc_mir/transform/const_prop.rs b/src/librustc_mir/transform/const_prop.rs index a1db06e6aa3de..a87b00263e5c4 100644 --- a/src/librustc_mir/transform/const_prop.rs +++ b/src/librustc_mir/transform/const_prop.rs @@ -34,7 +34,9 @@ use crate::interpret::{ }; use crate::transform::{MirPass, MirSource}; -/// The maximum number of bytes that we'll allocate space for a return value. +/// The maximum number of bytes that we'll allocate space for a local or the return value. +/// Needed for #66397, because otherwise we eval into large places and that can cause OOM or just +/// Severely regress performance. const MAX_ALLOC_LIMIT: u64 = 1024; /// Macro for machine-specific `InterpError` without allocation. @@ -155,14 +157,19 @@ struct ConstPropMachine<'mir, 'tcx> { written_only_inside_own_block_locals: FxHashSet, /// Locals that need to be cleared after every block terminates. only_propagate_inside_block_locals: BitSet, + can_const_prop: IndexVec, } impl<'mir, 'tcx> ConstPropMachine<'mir, 'tcx> { - fn new(only_propagate_inside_block_locals: BitSet) -> Self { + fn new( + only_propagate_inside_block_locals: BitSet, + can_const_prop: IndexVec, + ) -> Self { Self { stack: Vec::new(), written_only_inside_own_block_locals: Default::default(), only_propagate_inside_block_locals, + can_const_prop, } } } @@ -241,6 +248,9 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for ConstPropMachine<'mir, 'tcx> local: Local, ) -> InterpResult<'tcx, Result<&'a mut LocalValue, MemPlace>> { + if ecx.machine.can_const_prop[local] == ConstPropMode::NoPropagation { + throw_machine_stop_str!("tried to write to a local that is marked as not propagatable") + } if frame == 0 && ecx.machine.only_propagate_inside_block_locals.contains(local) { ecx.machine.written_only_inside_own_block_locals.insert(local); } @@ -285,7 +295,6 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for ConstPropMachine<'mir, 'tcx> struct ConstPropagator<'mir, 'tcx> { ecx: InterpCx<'mir, 'tcx, ConstPropMachine<'mir, 'tcx>>, tcx: TyCtxt<'tcx>, - can_const_prop: IndexVec, param_env: ParamEnv<'tcx>, // FIXME(eddyb) avoid cloning these two fields more than once, // by accessing them through `ecx` instead. @@ -331,7 +340,10 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { let param_env = tcx.param_env(def_id).with_reveal_all(); let span = tcx.def_span(def_id); - let can_const_prop = CanConstProp::check(body); + // FIXME: `CanConstProp::check` computes the layout of all locals, return those layouts + // so we can write them to `ecx.frame_mut().locals.layout, reducing the duplication in + // `layout_of` query invocations. + let can_const_prop = CanConstProp::check(tcx, param_env, body); let mut only_propagate_inside_block_locals = BitSet::new_empty(can_const_prop.len()); for (l, mode) in can_const_prop.iter_enumerated() { if *mode == ConstPropMode::OnlyInsideOwnBlock { @@ -342,7 +354,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { tcx, span, param_env, - ConstPropMachine::new(only_propagate_inside_block_locals), + ConstPropMachine::new(only_propagate_inside_block_locals, can_const_prop), (), ); @@ -368,7 +380,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { ecx, tcx, param_env, - can_const_prop, // FIXME(eddyb) avoid cloning these two fields more than once, // by accessing them through `ecx` instead. source_scopes: body.source_scopes.clone(), @@ -612,15 +623,9 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { fn const_prop( &mut self, rvalue: &Rvalue<'tcx>, - place_layout: TyAndLayout<'tcx>, source_info: SourceInfo, place: Place<'tcx>, ) -> Option<()> { - // #66397: Don't try to eval into large places as that can cause an OOM - if place_layout.size >= Size::from_bytes(MAX_ALLOC_LIMIT) { - return None; - } - // Perform any special handling for specific Rvalue types. // Generally, checks here fall into one of two categories: // 1. Additional checking to provide useful lints to the user @@ -893,7 +898,11 @@ struct CanConstProp { impl CanConstProp { /// Returns true if `local` can be propagated - fn check(body: &Body<'_>) -> IndexVec { + fn check( + tcx: TyCtxt<'tcx>, + param_env: ParamEnv<'tcx>, + body: &Body<'tcx>, + ) -> IndexVec { let mut cpv = CanConstProp { can_const_prop: IndexVec::from_elem(ConstPropMode::FullConstProp, &body.local_decls), found_assignment: BitSet::new_empty(body.local_decls.len()), @@ -903,6 +912,16 @@ impl CanConstProp { ), }; for (local, val) in cpv.can_const_prop.iter_enumerated_mut() { + let ty = body.local_decls[local].ty; + match tcx.layout_of(param_env.and(ty)) { + Ok(layout) if layout.size < Size::from_bytes(MAX_ALLOC_LIMIT) => {} + // Either the layout fails to compute, then we can't use this local anyway + // or the local is too large, then we don't want to. + _ => { + *val = ConstPropMode::NoPropagation; + continue; + } + } // Cannot use args at all // Cannot use locals because if x < y { y - x } else { x - y } would // lint for x != y @@ -1018,61 +1037,52 @@ impl<'mir, 'tcx> MutVisitor<'tcx> for ConstPropagator<'mir, 'tcx> { let source_info = statement.source_info; self.source_info = Some(source_info); if let StatementKind::Assign(box (place, ref mut rval)) = statement.kind { - let place_ty: Ty<'tcx> = place.ty(&self.local_decls, self.tcx).ty; - if let Ok(place_layout) = self.tcx.layout_of(self.param_env.and(place_ty)) { - let can_const_prop = self.can_const_prop[place.local]; - if let Some(()) = self.const_prop(rval, place_layout, source_info, place) { - // This will return None if the above `const_prop` invocation only "wrote" a - // type whose creation requires no write. E.g. a generator whose initial state - // consists solely of uninitialized memory (so it doesn't capture any locals). - if let Some(value) = self.get_const(place) { - if self.should_const_prop(value) { - trace!("replacing {:?} with {:?}", rval, value); - self.replace_with_const(rval, value, source_info); - if can_const_prop == ConstPropMode::FullConstProp - || can_const_prop == ConstPropMode::OnlyInsideOwnBlock - { - trace!("propagated into {:?}", place); - } + let can_const_prop = self.ecx.machine.can_const_prop[place.local]; + if let Some(()) = self.const_prop(rval, source_info, place) { + // This will return None if the above `const_prop` invocation only "wrote" a + // type whose creation requires no write. E.g. a generator whose initial state + // consists solely of uninitialized memory (so it doesn't capture any locals). + if let Some(value) = self.get_const(place) { + if self.should_const_prop(value) { + trace!("replacing {:?} with {:?}", rval, value); + self.replace_with_const(rval, value, source_info); + if can_const_prop == ConstPropMode::FullConstProp + || can_const_prop == ConstPropMode::OnlyInsideOwnBlock + { + trace!("propagated into {:?}", place); } } - match can_const_prop { - ConstPropMode::OnlyInsideOwnBlock => { - trace!( - "found local restricted to its block. \ + } + match can_const_prop { + ConstPropMode::OnlyInsideOwnBlock => { + trace!( + "found local restricted to its block. \ Will remove it from const-prop after block is finished. Local: {:?}", - place.local - ); - } - ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => { - trace!("can't propagate into {:?}", place); - if place.local != RETURN_PLACE { - Self::remove_const(&mut self.ecx, place.local); - } + place.local + ); + } + ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => { + trace!("can't propagate into {:?}", place); + if place.local != RETURN_PLACE { + Self::remove_const(&mut self.ecx, place.local); } - ConstPropMode::FullConstProp => {} } - } else { - // Const prop failed, so erase the destination, ensuring that whatever happens - // from here on, does not know about the previous value. - // This is important in case we have - // ```rust - // let mut x = 42; - // x = SOME_MUTABLE_STATIC; - // // x must now be undefined - // ``` - // FIXME: we overzealously erase the entire local, because that's easier to - // implement. - trace!( - "propagation into {:?} failed. - Nuking the entire site from orbit, it's the only way to be sure", - place, - ); - Self::remove_const(&mut self.ecx, place.local); + ConstPropMode::FullConstProp => {} } } else { + // Const prop failed, so erase the destination, ensuring that whatever happens + // from here on, does not know about the previous value. + // This is important in case we have + // ```rust + // let mut x = 42; + // x = SOME_MUTABLE_STATIC; + // // x must now be undefined + // ``` + // FIXME: we overzealously erase the entire local, because that's easier to + // implement. trace!( - "cannot propagate into {:?}, because the type of the local is generic.", + "propagation into {:?} failed. + Nuking the entire site from orbit, it's the only way to be sure", place, ); Self::remove_const(&mut self.ecx, place.local); diff --git a/src/test/mir-opt/const_prop/large_array_index.main.ConstProp.diff.32bit b/src/test/mir-opt/const_prop/large_array_index.main.ConstProp.diff.32bit new file mode 100644 index 0000000000000..721766f984971 --- /dev/null +++ b/src/test/mir-opt/const_prop/large_array_index.main.ConstProp.diff.32bit @@ -0,0 +1,85 @@ +- // MIR for `main` before ConstProp ++ // MIR for `main` after ConstProp + + fn main() -> () { + let mut _0: (); // return place in scope 0 at $DIR/large_array_index.rs:4:11: 4:11 + let _1: u8; // in scope 0 at $DIR/large_array_index.rs:6:9: 6:10 + let mut _2: [u8; 5000]; // in scope 0 at $DIR/large_array_index.rs:6:17: 6:29 + let _3: usize; // in scope 0 at $DIR/large_array_index.rs:6:30: 6:31 + let mut _4: usize; // in scope 0 at $DIR/large_array_index.rs:6:17: 6:32 + let mut _5: bool; // in scope 0 at $DIR/large_array_index.rs:6:17: 6:32 + scope 1 { + debug x => _1; // in scope 1 at $DIR/large_array_index.rs:6:9: 6:10 + } + + bb0: { + StorageLive(_1); // scope 0 at $DIR/large_array_index.rs:6:9: 6:10 + StorageLive(_2); // scope 0 at $DIR/large_array_index.rs:6:17: 6:29 + _2 = [const 0_u8; 5000]; // scope 0 at $DIR/large_array_index.rs:6:17: 6:29 + // ty::Const + // + ty: u8 + // + val: Value(Scalar(0x00)) + // mir::Constant + // + span: $DIR/large_array_index.rs:6:18: 6:22 + // + literal: Const { ty: u8, val: Value(Scalar(0x00)) } + StorageLive(_3); // scope 0 at $DIR/large_array_index.rs:6:30: 6:31 + _3 = const 2_usize; // scope 0 at $DIR/large_array_index.rs:6:30: 6:31 + // ty::Const + // + ty: usize + // + val: Value(Scalar(0x00000002)) + // mir::Constant + // + span: $DIR/large_array_index.rs:6:30: 6:31 + // + literal: Const { ty: usize, val: Value(Scalar(0x00000002)) } + _4 = const 5000_usize; // scope 0 at $DIR/large_array_index.rs:6:17: 6:32 + // ty::Const + // + ty: usize + // + val: Value(Scalar(0x00001388)) + // mir::Constant + // + span: $DIR/large_array_index.rs:6:17: 6:32 + // + literal: Const { ty: usize, val: Value(Scalar(0x00001388)) } +- _5 = Lt(_3, _4); // scope 0 at $DIR/large_array_index.rs:6:17: 6:32 +- assert(move _5, "index out of bounds: the len is {} but the index is {}", move _4, _3) -> bb1; // scope 0 at $DIR/large_array_index.rs:6:17: 6:32 ++ _5 = const true; // scope 0 at $DIR/large_array_index.rs:6:17: 6:32 ++ // ty::Const ++ // + ty: bool ++ // + val: Value(Scalar(0x01)) ++ // mir::Constant ++ // + span: $DIR/large_array_index.rs:6:17: 6:32 ++ // + literal: Const { ty: bool, val: Value(Scalar(0x01)) } ++ assert(const true, "index out of bounds: the len is {} but the index is {}", const 5000_usize, const 2_usize) -> bb1; // scope 0 at $DIR/large_array_index.rs:6:17: 6:32 ++ // ty::Const ++ // + ty: bool ++ // + val: Value(Scalar(0x01)) ++ // mir::Constant ++ // + span: $DIR/large_array_index.rs:6:17: 6:32 ++ // + literal: Const { ty: bool, val: Value(Scalar(0x01)) } ++ // ty::Const ++ // + ty: usize ++ // + val: Value(Scalar(0x00001388)) ++ // mir::Constant ++ // + span: $DIR/large_array_index.rs:6:17: 6:32 ++ // + literal: Const { ty: usize, val: Value(Scalar(0x00001388)) } ++ // ty::Const ++ // + ty: usize ++ // + val: Value(Scalar(0x00000002)) ++ // mir::Constant ++ // + span: $DIR/large_array_index.rs:6:17: 6:32 ++ // + literal: Const { ty: usize, val: Value(Scalar(0x00000002)) } + } + + bb1: { + _1 = _2[_3]; // scope 0 at $DIR/large_array_index.rs:6:17: 6:32 + StorageDead(_3); // scope 0 at $DIR/large_array_index.rs:6:32: 6:33 + StorageDead(_2); // scope 0 at $DIR/large_array_index.rs:6:32: 6:33 + _0 = const (); // scope 0 at $DIR/large_array_index.rs:4:11: 7:2 + // ty::Const + // + ty: () + // + val: Value(Scalar()) + // mir::Constant + // + span: $DIR/large_array_index.rs:4:11: 7:2 + // + literal: Const { ty: (), val: Value(Scalar()) } + StorageDead(_1); // scope 0 at $DIR/large_array_index.rs:7:1: 7:2 + return; // scope 0 at $DIR/large_array_index.rs:7:2: 7:2 + } + } + diff --git a/src/test/mir-opt/const_prop/large_array_index.main.ConstProp.diff.64bit b/src/test/mir-opt/const_prop/large_array_index.main.ConstProp.diff.64bit new file mode 100644 index 0000000000000..eae2ce6671cc1 --- /dev/null +++ b/src/test/mir-opt/const_prop/large_array_index.main.ConstProp.diff.64bit @@ -0,0 +1,85 @@ +- // MIR for `main` before ConstProp ++ // MIR for `main` after ConstProp + + fn main() -> () { + let mut _0: (); // return place in scope 0 at $DIR/large_array_index.rs:4:11: 4:11 + let _1: u8; // in scope 0 at $DIR/large_array_index.rs:6:9: 6:10 + let mut _2: [u8; 5000]; // in scope 0 at $DIR/large_array_index.rs:6:17: 6:29 + let _3: usize; // in scope 0 at $DIR/large_array_index.rs:6:30: 6:31 + let mut _4: usize; // in scope 0 at $DIR/large_array_index.rs:6:17: 6:32 + let mut _5: bool; // in scope 0 at $DIR/large_array_index.rs:6:17: 6:32 + scope 1 { + debug x => _1; // in scope 1 at $DIR/large_array_index.rs:6:9: 6:10 + } + + bb0: { + StorageLive(_1); // scope 0 at $DIR/large_array_index.rs:6:9: 6:10 + StorageLive(_2); // scope 0 at $DIR/large_array_index.rs:6:17: 6:29 + _2 = [const 0_u8; 5000]; // scope 0 at $DIR/large_array_index.rs:6:17: 6:29 + // ty::Const + // + ty: u8 + // + val: Value(Scalar(0x00)) + // mir::Constant + // + span: $DIR/large_array_index.rs:6:18: 6:22 + // + literal: Const { ty: u8, val: Value(Scalar(0x00)) } + StorageLive(_3); // scope 0 at $DIR/large_array_index.rs:6:30: 6:31 + _3 = const 2_usize; // scope 0 at $DIR/large_array_index.rs:6:30: 6:31 + // ty::Const + // + ty: usize + // + val: Value(Scalar(0x0000000000000002)) + // mir::Constant + // + span: $DIR/large_array_index.rs:6:30: 6:31 + // + literal: Const { ty: usize, val: Value(Scalar(0x0000000000000002)) } + _4 = const 5000_usize; // scope 0 at $DIR/large_array_index.rs:6:17: 6:32 + // ty::Const + // + ty: usize + // + val: Value(Scalar(0x0000000000001388)) + // mir::Constant + // + span: $DIR/large_array_index.rs:6:17: 6:32 + // + literal: Const { ty: usize, val: Value(Scalar(0x0000000000001388)) } +- _5 = Lt(_3, _4); // scope 0 at $DIR/large_array_index.rs:6:17: 6:32 +- assert(move _5, "index out of bounds: the len is {} but the index is {}", move _4, _3) -> bb1; // scope 0 at $DIR/large_array_index.rs:6:17: 6:32 ++ _5 = const true; // scope 0 at $DIR/large_array_index.rs:6:17: 6:32 ++ // ty::Const ++ // + ty: bool ++ // + val: Value(Scalar(0x01)) ++ // mir::Constant ++ // + span: $DIR/large_array_index.rs:6:17: 6:32 ++ // + literal: Const { ty: bool, val: Value(Scalar(0x01)) } ++ assert(const true, "index out of bounds: the len is {} but the index is {}", const 5000_usize, const 2_usize) -> bb1; // scope 0 at $DIR/large_array_index.rs:6:17: 6:32 ++ // ty::Const ++ // + ty: bool ++ // + val: Value(Scalar(0x01)) ++ // mir::Constant ++ // + span: $DIR/large_array_index.rs:6:17: 6:32 ++ // + literal: Const { ty: bool, val: Value(Scalar(0x01)) } ++ // ty::Const ++ // + ty: usize ++ // + val: Value(Scalar(0x0000000000001388)) ++ // mir::Constant ++ // + span: $DIR/large_array_index.rs:6:17: 6:32 ++ // + literal: Const { ty: usize, val: Value(Scalar(0x0000000000001388)) } ++ // ty::Const ++ // + ty: usize ++ // + val: Value(Scalar(0x0000000000000002)) ++ // mir::Constant ++ // + span: $DIR/large_array_index.rs:6:17: 6:32 ++ // + literal: Const { ty: usize, val: Value(Scalar(0x0000000000000002)) } + } + + bb1: { + _1 = _2[_3]; // scope 0 at $DIR/large_array_index.rs:6:17: 6:32 + StorageDead(_3); // scope 0 at $DIR/large_array_index.rs:6:32: 6:33 + StorageDead(_2); // scope 0 at $DIR/large_array_index.rs:6:32: 6:33 + _0 = const (); // scope 0 at $DIR/large_array_index.rs:4:11: 7:2 + // ty::Const + // + ty: () + // + val: Value(Scalar()) + // mir::Constant + // + span: $DIR/large_array_index.rs:4:11: 7:2 + // + literal: Const { ty: (), val: Value(Scalar()) } + StorageDead(_1); // scope 0 at $DIR/large_array_index.rs:7:1: 7:2 + return; // scope 0 at $DIR/large_array_index.rs:7:2: 7:2 + } + } + diff --git a/src/test/mir-opt/const_prop/large_array_index.rs b/src/test/mir-opt/const_prop/large_array_index.rs new file mode 100644 index 0000000000000..48d134376db62 --- /dev/null +++ b/src/test/mir-opt/const_prop/large_array_index.rs @@ -0,0 +1,7 @@ +// EMIT_MIR_FOR_EACH_BIT_WIDTH + +// EMIT_MIR large_array_index.main.ConstProp.diff +fn main() { + // check that we don't propagate this, because it's too large + let x: u8 = [0_u8; 5000][2]; +} diff --git a/src/test/mir-opt/const_prop/mutable_variable_aggregate_mut_ref.main.ConstProp.diff b/src/test/mir-opt/const_prop/mutable_variable_aggregate_mut_ref.main.ConstProp.diff index e78bc31b77480..6e2ee0957ab33 100644 --- a/src/test/mir-opt/const_prop/mutable_variable_aggregate_mut_ref.main.ConstProp.diff +++ b/src/test/mir-opt/const_prop/mutable_variable_aggregate_mut_ref.main.ConstProp.diff @@ -23,15 +23,13 @@ // + ty: i32 // + val: Value(Scalar(0x0000002a)) // mir::Constant -- // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:18: 5:20 -+ // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:17: 5:25 + // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:18: 5:20 // + literal: Const { ty: i32, val: Value(Scalar(0x0000002a)) } // ty::Const // + ty: i32 // + val: Value(Scalar(0x0000002b)) // mir::Constant -- // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:22: 5:24 -+ // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:17: 5:25 + // + span: $DIR/mutable_variable_aggregate_mut_ref.rs:5:22: 5:24 // + literal: Const { ty: i32, val: Value(Scalar(0x0000002b)) } StorageLive(_2); // scope 1 at $DIR/mutable_variable_aggregate_mut_ref.rs:6:9: 6:10 _2 = &mut _1; // scope 1 at $DIR/mutable_variable_aggregate_mut_ref.rs:6:13: 6:19 diff --git a/src/test/ui/recursion/issue-26548-recursion-via-normalize.stderr b/src/test/ui/recursion/issue-26548-recursion-via-normalize.stderr index be55890c08c88..7f197a238e5a0 100644 --- a/src/test/ui/recursion/issue-26548-recursion-via-normalize.stderr +++ b/src/test/ui/recursion/issue-26548-recursion-via-normalize.stderr @@ -1,7 +1,7 @@ -error[E0391]: cycle detected when computing layout of `std::option::Option` +error[E0391]: cycle detected when computing layout of `S` | - = note: ...which requires computing layout of `S`... - = note: ...which again requires computing layout of `std::option::Option`, completing the cycle + = note: ...which requires computing layout of `std::option::Option`... + = note: ...which again requires computing layout of `S`, completing the cycle note: cycle used when optimizing MIR for `main` --> $DIR/issue-26548-recursion-via-normalize.rs:15:1 | diff --git a/src/tools/clippy/tests/ui/indexing_slicing_index.stderr b/src/tools/clippy/tests/ui/indexing_slicing_index.stderr index ac5f0d0a39e89..2b3f9be2dfb9b 100644 --- a/src/tools/clippy/tests/ui/indexing_slicing_index.stderr +++ b/src/tools/clippy/tests/ui/indexing_slicing_index.stderr @@ -1,23 +1,3 @@ -error: this operation will panic at runtime - --> $DIR/indexing_slicing_index.rs:11:5 - | -LL | x[4]; // Ok, let rustc's `const_err` lint handle `usize` indexing on arrays. - | ^^^^ index out of bounds: the len is 4 but the index is 4 - | - = note: `#[deny(unconditional_panic)]` on by default - -error: this operation will panic at runtime - --> $DIR/indexing_slicing_index.rs:12:5 - | -LL | x[1 << 3]; // Ok, let rustc's `const_err` lint handle `usize` indexing on arrays. - | ^^^^^^^^^ index out of bounds: the len is 4 but the index is 8 - -error: this operation will panic at runtime - --> $DIR/indexing_slicing_index.rs:27:5 - | -LL | x[N]; // Ok, let rustc's `const_err` lint handle `usize` indexing on arrays. - | ^^^^ index out of bounds: the len is 4 but the index is 15 - error: indexing may panic. --> $DIR/indexing_slicing_index.rs:10:5 | @@ -75,5 +55,5 @@ LL | v[M]; | = help: Consider using `.get(n)` or `.get_mut(n)` instead -error: aborting due to 10 previous errors +error: aborting due to 7 previous errors diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs index 9354cc16a9ae9..b97ca9e3a0f27 100644 --- a/src/tools/compiletest/src/runtest.rs +++ b/src/tools/compiletest/src/runtest.rs @@ -3239,8 +3239,19 @@ impl<'test> TestCx<'test> { } fn diff_mir_files(&self, before: PathBuf, after: PathBuf) -> String { - let before = self.get_mir_dump_dir().join(before); - let after = self.get_mir_dump_dir().join(after); + let to_full_path = |path: PathBuf| { + let full = self.get_mir_dump_dir().join(&path); + if !full.exists() { + panic!( + "the mir dump file for {} does not exist (requested in {})", + path.display(), + self.testpaths.file.display(), + ); + } + full + }; + let before = to_full_path(before); + let after = to_full_path(after); debug!("comparing the contents of: {} with {}", before.display(), after.display()); let before = fs::read_to_string(before).unwrap(); let after = fs::read_to_string(after).unwrap();