coverage: Add a synthetic test for when all spans are discarded
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837a25dd41
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8 changed files with 67 additions and 3 deletions
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@ -132,6 +132,7 @@ fn fill_region_tables<'tcx>(
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let make_cov_span = |span: Span| {
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spans::make_coverage_span(local_file_id, source_map, fn_cov_info, &source_file, span)
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};
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let discard_all = tcx.sess.coverage_discard_all_spans_in_codegen();
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// For each counter/region pair in this function+file, convert it to a
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// form suitable for FFI.
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@ -141,7 +142,17 @@ fn fill_region_tables<'tcx>(
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// MIR opts, replace those occurrences with zero.
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let kind = kind.map_terms(|term| if is_zero_term(term) { CovTerm::Zero } else { term });
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// Convert the `Span` into coordinates that we can pass to LLVM, or
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// discard the span if conversion fails. In rare, cases _all_ of a
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// function's spans are discarded, and the rest of coverage codegen
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// needs to handle that gracefully to avoid a repeat of #133606.
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// We don't have a good test case for triggering that organically, so
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// instead we set `-Zcoverage-options=discard-all-spans-in-codegen`
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// to force it to occur.
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let Some(cov_span) = make_cov_span(span) else { continue };
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if discard_all {
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continue;
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}
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match kind {
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MappingKind::Code(term) => {
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@ -766,7 +766,11 @@ fn test_unstable_options_tracking_hash() {
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})
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);
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tracked!(codegen_backend, Some("abc".to_string()));
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tracked!(coverage_options, CoverageOptions { level: CoverageLevel::Mcdc, no_mir_spans: true });
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tracked!(coverage_options, CoverageOptions {
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level: CoverageLevel::Mcdc,
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no_mir_spans: true,
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discard_all_spans_in_codegen: true
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});
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tracked!(crate_attr, vec!["abc".to_string()]);
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tracked!(cross_crate_inline_threshold, InliningThreshold::Always);
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tracked!(debug_info_for_profiling, true);
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@ -147,18 +147,24 @@ pub enum InstrumentCoverage {
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Yes,
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}
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/// Individual flag values controlled by `-Z coverage-options`.
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/// Individual flag values controlled by `-Zcoverage-options`.
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#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, Default)]
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pub struct CoverageOptions {
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pub level: CoverageLevel,
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/// `-Z coverage-options=no-mir-spans`: Don't extract block coverage spans
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/// `-Zcoverage-options=no-mir-spans`: Don't extract block coverage spans
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/// from MIR statements/terminators, making it easier to inspect/debug
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/// branch and MC/DC coverage mappings.
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///
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/// For internal debugging only. If other code changes would make it hard
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/// to keep supporting this flag, remove it.
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pub no_mir_spans: bool,
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/// `-Zcoverage-options=discard-all-spans-in-codegen`: During codgen,
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/// discard all coverage spans as though they were invalid. Needed by
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/// regression tests for #133606, because we don't have an easy way to
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/// reproduce it from actual source code.
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pub discard_all_spans_in_codegen: bool,
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}
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/// Controls whether branch coverage or MC/DC coverage is enabled.
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@ -1037,6 +1037,7 @@ pub mod parse {
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"condition" => slot.level = CoverageLevel::Condition,
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"mcdc" => slot.level = CoverageLevel::Mcdc,
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"no-mir-spans" => slot.no_mir_spans = true,
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"discard-all-spans-in-codegen" => slot.discard_all_spans_in_codegen = true,
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_ => return false,
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}
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}
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@ -352,6 +352,11 @@ impl Session {
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self.opts.unstable_opts.coverage_options.no_mir_spans
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}
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/// True if `-Zcoverage-options=discard-all-spans-in-codegen` was passed.
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pub fn coverage_discard_all_spans_in_codegen(&self) -> bool {
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self.opts.unstable_opts.coverage_options.discard_all_spans_in_codegen
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}
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pub fn is_sanitizer_cfi_enabled(&self) -> bool {
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self.opts.unstable_opts.sanitizer.contains(SanitizerSet::CFI)
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}
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6
tests/coverage/auxiliary/discard_all_helper.rs
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6
tests/coverage/auxiliary/discard_all_helper.rs
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@ -0,0 +1,6 @@
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//@ edition: 2021
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// Force this function to be generated in its home crate, so that it ends up
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// with normal coverage metadata.
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#[inline(never)]
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pub fn external_function() {}
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7
tests/coverage/discard-all-issue-133606.coverage
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7
tests/coverage/discard-all-issue-133606.coverage
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@ -0,0 +1,7 @@
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LL| |//@ edition: 2021
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LL| |
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LL| |// Force this function to be generated in its home crate, so that it ends up
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LL| |// with normal coverage metadata.
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LL| |#[inline(never)]
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LL| 1|pub fn external_function() {}
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24
tests/coverage/discard-all-issue-133606.rs
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24
tests/coverage/discard-all-issue-133606.rs
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@ -0,0 +1,24 @@
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//! Regression test for <https://github.com/rust-lang/rust/issues/133606>.
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//!
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//! In rare cases, all of a function's coverage spans are discarded at a late
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//! stage during codegen. When that happens, the subsequent code needs to take
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//! special care to avoid emitting coverage metadata that would cause `llvm-cov`
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//! to fail with a fatal error.
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//!
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//! We currently don't know of a concise way to reproduce that scenario with
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//! ordinary Rust source code, so instead we set a special testing-only flag to
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//! force it to occur.
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//@ edition: 2021
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//@ compile-flags: -Zcoverage-options=discard-all-spans-in-codegen
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// The `llvm-cov` tool will complain if the test binary ends up having no
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// coverage metadata at all. To prevent that, we also link to instrumented
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// code in an auxiliary crate that doesn't have the special flag set.
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//@ aux-build: discard_all_helper.rs
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extern crate discard_all_helper;
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fn main() {
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discard_all_helper::external_function();
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}
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