bjoernager/rust
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Fixes reported bugs in Rust Coverage

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Fixes: #79569

Fixes: #79566
Fixes: #79565

For the first issue (#79569), I got hit a `debug_assert!()` before
encountering the reported error message (because I have `debug = true`
enabled in my config.toml).

The assertion showed me that some `SwitchInt`s can have more than one
target pointing to the same `BasicBlock`.

I had thought that was invalid, but since it seems to be possible, I'm
allowing this now.

I added a new test for this.

----

In the last two cases above, both tests (intentionally) fail to compile,
but the `InstrumentCoverage` pass is invoked anyway.

The MIR starts with an `Unreachable` `BasicBlock`, which I hadn't
encountered before. (I had assumed the `InstrumentCoverage` pass
would only be invoked with MIRs from successful compilations.)

I don't have test infrastructure set up to test coverage on files that
fail to compile, so I didn't add a new test.
This commit is contained in:
Rich Kadel 2020-12-11 18:28:37 -08:00
parent 9eb3a7ceaf
commit eb963ffe45
8 changed files with 553 additions and 18 deletions
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28
compiler/rustc_mir/src/transform/coverage/graph.rs
View file

@ -32,24 +32,28 @@ impl CoverageGraph {
// Pre-transform MIR `BasicBlock` successors and predecessors into the BasicCoverageBlock
// equivalents. Note that since the BasicCoverageBlock graph has been fully simplified, the
// each predecessor of a BCB leader_bb should be in a unique BCB, and each successor of a
// BCB last_bb should be in its own unique BCB. Therefore, collecting the BCBs using
// `bb_to_bcb` should work without requiring a deduplication step.
// each predecessor of a BCB leader_bb should be in a unique BCB. It is possible for a
// `SwitchInt` to have multiple targets to the same destination `BasicBlock`, so
// de-duplication is required. This is done without reordering the successors.
let bcbs_len = bcbs.len();
let mut seen = IndexVec::from_elem_n(false, bcbs_len);
let successors = IndexVec::from_fn_n(
|bcb| {
for b in seen.iter_mut() {
*b = false;
}
let bcb_data = &bcbs[bcb];
let bcb_successors =
let mut bcb_successors = Vec::new();
for successor in
bcb_filtered_successors(&mir_body, &bcb_data.terminator(mir_body).kind)
.filter_map(|&successor_bb| bb_to_bcb[successor_bb])
.collect::<Vec<_>>();
debug_assert!({
let mut sorted = bcb_successors.clone();
sorted.sort_unstable();
let initial_len = sorted.len();
sorted.dedup();
sorted.len() == initial_len
});
{
if !seen[successor] {
seen[successor] = true;
bcb_successors.push(successor);
}
}
bcb_successors
},
bcbs.len(),