Working expression optimization, and some improvements to branch-level source coverage
This replaces PR #78040 after reorganizing the original commits (by request) into a more logical sequence of major changes.
Most of the work is in the MIR `transform/coverage/` directory (originally, `transform/instrument_coverage.rs`).
Note this PR includes some significant additional debugging capabilities, to help myself and any future developer working on coverage improvements or issues.
In particular, there's a new Graphviz (.dot file) output for the coverage graph (the `BasicCoverageBlock` control flow graph) that provides ways to get some very good insight into the relationships between the MIR, the coverage graph BCBs, coverage spans, and counters. (There are also some cool debugging options, available via environment variable, to alter how some data in the graph appears.)
And the code for this Graphviz view is actually generic... it can be used by any implementation of the Rust `Graph` traits.
Finally (for now), I also now output information from `llvm-cov` that shows the actual counters and spans it found in the coverage map, and their counts (from the `--debug` flag). I found this to be enormously helpful in debugging some coverage issues, so I kept it in the test results as well for additional context.
`@tmandry` `@wesleywiser`
r? `@tmandry`
Here's an example of the new coverage graph:
* Within each `BasicCoverageBlock` (BCB), you can see each `CoverageSpan` and its contributing statements (MIR `Statement`s and/or `Terminator`s)
* Each `CoverageSpan` has a `Counter` or and `Expression`, and `Expression`s show their Add/Subtract operation with nested operations. (This can be changed to show the Counter and Expression IDs instead, or in addition to, the BCB.)
* The terminators of all MIR `BasicBlock`s in the BCB, including one final `Terminator`
* If an "edge counter" is required (because we need to count an edge between blocks, in some cases) the edge's Counter or Expression is shown next to its label. (Not shown in the example below.) (FYI, Edge Counters are converted into a new MIR `BasicBlock` with `Goto`)
<img width="1116" alt="Screen Shot 2020-10-17 at 12 23 29 AM" src="https://user-images.githubusercontent.com/3827298/96331095-616cb480-100f-11eb-8212-60f2d433e2d8.png">
r? `@tmandry`
FYI: `@wesleywiser`
And even though CI should now pass for MacOS, the llvm-cov show --debug
flag does not work when developing outside of CI, so I'm disabling it
for MacOS by default.
And restored missing error message from llvm-cov show
And since some CI builds disable LLVM assertions (which disables the
--debug option in llvm-cov show), I check to see if LLVM assertions are
disabled, and if so, I don't add --debug and don't check the counter
file diffs.
More portable way to make python 2/3 portable.
Strip Args line (with hardcoded paths) from debug counters output.
Ignore diff failures from llvm-cov debug output files ("counters"
files), since generic function instantiations will appear in those files
with mangled names. (Sadly, the demangler is apparently not applied to
the debug output.)
Implementing the Graph traits for the BasicCoverageBlock
graph.
optimized replacement of counters with expressions plus new BCB graphviz
* Avoid adding coverage to unreachable blocks.
* Special case for Goto at the end of the body. Make it non-reportable.
Improved debugging and formatting options (from env)
Don't automatically add counters to BCBs without CoverageSpans. They may
still get counters but only if there are dependencies from
other BCBs that have spans, I think.
Make CodeRegions optional for Counters too. It is
possible to inject counters (`llvm.instrprof.increment` intrinsic calls
without corresponding code regions in the coverage map. An expression
can still uses these counter values.
Refactored instrument_coverage.rs -> instrument_coverage/mod.rs, and
then broke up the mod into multiple files.
Compiling with coverage, with the expression optimization, works on
the json5format crate and its dependencies.
Refactored debug features from mod.rs to debug.rs
Originally, there has been a dedicated pass for renumbering
AST NodeIds to have actual values. This pass had been added by
commit a5ad4c3794.
Then, later, this step was moved to where it resides now,
macro expansion. See commit c86c8d41a2
or PR #36438.
The comment snippet, added by the original commit, has
survived the times without any change, becoming outdated
at removal of the dedicated pass.
Nowadays, grepping for the next_node_id function will show up
multiple places in the compiler that call it, but the main
rewriting that the comment talks about is still done in the
expansion step, inside an innocious looking visit_id function
that's called during macro invocation collection.
Changes from 68965 extended the kind of instances that are being
inlined. For some of those, the `instance_mir` returns a MIR body that
is already expressed in terms of the types found in substitution array,
and doesn't need further substitution.
Use `substs_for_mir_body` to take that into account.
Here's the error for rustdoc:
```
Checking rustdoc artifacts (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
error: no library targets found in package `rustdoc-tool`
```
Previously, trying to allow this would give another error!
```
warning: unknown lint: `private_intra_doc_links`
--> private.rs:1:10
|
1 | #![allow(private_intra_doc_links)]
| ^^^^^^^^^^^^^^^^^^^^^^^ help: did you mean: `broken_intra_doc_links`
|
= note: `#[warn(unknown_lints)]` on by default
warning: public documentation for `DocMe` links to private item `DontDocMe`
--> private.rs:2:11
|
2 | /// docs [DontDocMe]
| ^^^^^^^^^ this item is private
|
= note: `#[warn(private_intra_doc_links)]` on by default
= note: this link will resolve properly if you pass `--document-private-items`
```
reverse binding order in matches to allow the subbinding of copyable fields in bindings after @
Fixes#69971
### TODO
- [x] Regression tests
r? `@oli-obk`
Rollup of 15 pull requests
Successful merges:
- #76718 (Move Vec UI tests to unit tests when possible)
- #78093 (Clean up docs for 'as' keyword)
- #78425 (Move f64::NAN ui tests into `library`)
- #78465 (Change as_str → to_string in proc_macro::Ident::span() docs)
- #78584 (Add keyboard handling to the theme picker menu)
- #78716 (Array trait impl comment/doc fixes)
- #78727 ((rustdoc) fix test for trait impl display)
- #78733 (fix a couple of clippy warnings:)
- #78735 (Simplify the implementation of `get_mut` (no unsafe))
- #78738 (Move range in ui test to ops test in library/core)
- #78739 (Fix ICE on type error in async function)
- #78742 (make intern_const_alloc_recursive return error)
- #78756 (Update cargo)
- #78757 (Improve and clean up some intra-doc links)
- #78758 (Fixed typo in comment)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
(rustdoc) fix test for trait impl display
The test checks that parameters and return values with `impl Trait` types are correctly generated in rustdoc's output.
In essence, the previous version of the test checked the absence of values that would never be generated by rustdoc, so it could basically never fail. These values were adjusted to the expected output and are now required to exist in rustdoc's output. See https://github.com/rust-lang/rust/issues/55201#issuecomment-716182474 for a detailed explanation of the reasoning behind the changes.
Note that the output of rustdoc for `impl Trait`s in parameters and return values did not change since the inital test creation, so this PR only modifies the test.
Closes#55201
