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Auto merge of #76004 - richkadel:llvm-coverage-map-gen-6b.5, r=tmandry

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Tools, tests, and experimenting with MIR-derived coverage counters

Leverages the new mir_dump output file in HTML+CSS (from #76074) to visualize coverage code regions
and the MIR features that they came from (including overlapping spans).

See example below.

The `run-make-fulldeps/instrument-coverage` test has been refactored to maximize test coverage and reduce code duplication. The new tests support testing with and without `-Clink-dead-code`, so Rust coverage can be tested on MSVC (which, currently, only works with `link-dead-code` _disabled_).

New tests validate coverage region generation and coverage reports with multiple counters per function. Starting with a simple `if-else` branch tests, coverage tests for each additional syntax type can be added by simply dropping in a new Rust sample program.

Includes a basic, MIR-block-based implementation of coverage injection,
available via `-Zexperimental-coverage`. This implementation has known
flaws and omissions, but is simple enough to validate the new tools and
tests.

The existing `-Zinstrument-coverage` option currently enables
function-level coverage only, which at least appears to generate
accurate coverage reports at that level.

Experimental coverage is not accurate at this time. When branch coverage
works as intended, the `-Zexperimental-coverage` option should be
removed.

This PR replaces the bulk of PR #75828, with the remaining parts of
that PR distributed among other separate and indentpent PRs.

This PR depends on two of those other PRs: #76002, #76003 and #76074

Rust compiler MCP rust-lang/compiler-team#278

Relevant issue: #34701 - Implement support for LLVMs code coverage
instrumentation

![Screen-Recording-2020-08-21-at-2](https://user-images.githubusercontent.com/3827298/90972923-ff417880-e4d1-11ea-92bb-8713c6198f6d.gif)

r? @tmandry
FYI: @wesleywiser
This commit is contained in:
bors 2020-09-04 01:31:07 +00:00
commit 4ffb5c5954
28 changed files with 2070 additions and 297 deletions
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4
compiler/rustc_session/src/config.rs
View file

@ -1742,6 +1742,10 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
);
}
if debugging_opts.experimental_coverage {
debugging_opts.instrument_coverage = true;
}
if debugging_opts.instrument_coverage {
if cg.profile_generate.enabled() || cg.profile_use.is_some() {
early_error(

5
compiler/rustc_session/src/options.rs
View file

@ -893,6 +893,11 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
all statements)."),
emit_stack_sizes: bool = (false, parse_bool, [UNTRACKED],
"emit a section containing stack size metadata (default: no)"),
experimental_coverage: bool = (false, parse_bool, [TRACKED],
"enable and extend the `-Z instrument-coverage` function-level coverage \
feature, adding additional experimental (likely inaccurate) counters and \
code regions (used by `rustc` compiler developers to test new coverage \
counter placements) (default: no)"),
fewer_names: bool = (false, parse_bool, [TRACKED],
"reduce memory use by retaining fewer names within compilation artifacts (LLVM-IR) \
(default: no)"),