diff options
Diffstat (limited to 'compiler/rustc_session/src')
| -rw-r--r-- | compiler/rustc_session/src/config.rs | 17 | ||||
| -rw-r--r-- | compiler/rustc_session/src/options.rs | 6 | ||||
| -rw-r--r-- | compiler/rustc_session/src/session.rs | 48 |
3 files changed, 41 insertions, 30 deletions
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs index 1808a0ca59b..0a2a535598a 100644 --- a/compiler/rustc_session/src/config.rs +++ b/compiler/rustc_session/src/config.rs @@ -1718,20 +1718,11 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options { ); } - // `-Z instrument-coverage` implies: - // * `-Z symbol-mangling-version=v0` - to ensure consistent and reversible name mangling. - // Note, LLVM coverage tools can analyze coverage over multiple runs, including some - // changes to source code; so mangled names must be consistent across compilations. - // * `-C link-dead-code` - so unexecuted code is still counted as zero, rather than be - // optimized out. Note that instrumenting dead code can be explicitly disabled with: - // `-Z instrument-coverage -C link-dead-code=no`. + // `-Z instrument-coverage` implies `-Z symbol-mangling-version=v0` - to ensure consistent + // and reversible name mangling. Note, LLVM coverage tools can analyze coverage over + // multiple runs, including some changes to source code; so mangled names must be consistent + // across compilations. debugging_opts.symbol_mangling_version = SymbolManglingVersion::V0; - if cg.link_dead_code == None { - // FIXME(richkadel): Investigate if the `instrument-coverage` implementation can - // inject ["zero counters"](https://llvm.org/docs/CoverageMappingFormat.html#counter) - // in the coverage map when "dead code" is removed, rather than forcing `link-dead-code`. - cg.link_dead_code = Some(true); - } } if !cg.embed_bitcode { diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs index d05f1a3f34b..988d3d39bd5 100644 --- a/compiler/rustc_session/src/options.rs +++ b/compiler/rustc_session/src/options.rs @@ -885,9 +885,9 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options, "instrument the generated code to support LLVM source-based code coverage \ reports (note, the compiler build config must include `profiler = true`, \ and is mutually exclusive with `-C profile-generate`/`-C profile-use`); \ - implies `-C link-dead-code` (unless explicitly disabled)` and \ - `-Z symbol-mangling-version=v0`; and disables/overrides some optimization \ - options (default: no)"), + implies `-C link-dead-code` (unless targeting MSVC, or explicitly disabled) \ + and `-Z symbol-mangling-version=v0`; disables/overrides some Rust \ + optimizations (default: no)"), instrument_mcount: bool = (false, parse_bool, [TRACKED], "insert function instrument code for mcount-based tracing (default: no)"), keep_hygiene_data: bool = (false, parse_bool, [UNTRACKED], diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs index c006e593e47..e007c321d3d 100644 --- a/compiler/rustc_session/src/session.rs +++ b/compiler/rustc_session/src/session.rs @@ -1021,6 +1021,40 @@ impl Session { || self.opts.debugging_opts.sanitizer.intersects(SanitizerSet::ADDRESS | SanitizerSet::MEMORY) } + pub fn link_dead_code(&self) -> bool { + match self.opts.cg.link_dead_code { + Some(explicitly_set) => explicitly_set, + None => { + self.opts.debugging_opts.instrument_coverage + && !self.target.target.options.is_like_msvc + // Issue #76038: (rustc `-Clink-dead-code` causes MSVC linker to produce invalid + // binaries when LLVM InstrProf counters are enabled). As described by this issue, + // the "link dead code" option produces incorrect binaries when compiled and linked + // under MSVC. The resulting Rust programs typically crash with a segmentation + // fault, or produce an empty "*.profraw" file (profiling counter results normally + // generated during program exit). + // + // If not targeting MSVC, `-Z instrument-coverage` implies `-C link-dead-code`, so + // unexecuted code is still counted as zero, rather than be optimized out. Note that + // instrumenting dead code can be explicitly disabled with: + // + // `-Z instrument-coverage -C link-dead-code=no`. + // + // FIXME(richkadel): Investigate if `instrument-coverage` implementation can inject + // [zero counters](https://llvm.org/docs/CoverageMappingFormat.html#counter) in the + // coverage map when "dead code" is removed, rather than forcing `link-dead-code`. + // This may not be possible, however, if (as it seems to appear) the "dead code" + // that would otherwise not be linked is only identified as "dead" by the native + // linker. If that's the case, I believe it is too late for the Rust compiler to + // leverage any information it might be able to get from the linker regarding what + // code is dead, to be able to add those counters. + // + // On the other hand, if any Rust compiler passes are optimizing out dead code blocks + // we should inject "zero" counters for those code regions. + } + } + } + pub fn mark_attr_known(&self, attr: &Attribute) { self.known_attrs.lock().mark(attr) } @@ -1428,20 +1462,6 @@ fn validate_commandline_args_with_session_available(sess: &Session) { ); } - // FIXME(richkadel): See `src/test/run-make-fulldeps/instrument-coverage/Makefile`. After - // compiling with `-Zinstrument-coverage`, the resulting binary generates a segfault during - // the program's exit process (likely while attempting to generate the coverage stats in - // the "*.profraw" file). An investigation to resolve the problem on Windows is ongoing, - // but until this is resolved, the option is disabled on Windows, and the test is skipped - // when targeting `MSVC`. - if sess.opts.debugging_opts.instrument_coverage && sess.target.target.options.is_like_msvc { - sess.warn( - "Rust source-based code coverage instrumentation (with `-Z instrument-coverage`) \ - is not yet supported on Windows when targeting MSVC. The resulting binaries will \ - still be instrumented for experimentation purposes, but may not execute correctly.", - ); - } - const ASAN_SUPPORTED_TARGETS: &[&str] = &[ "aarch64-fuchsia", "aarch64-unknown-linux-gnu", |