coverage: Remove all unstable values of -Cinstrument-coverage

Author: Zalathar

Diff for: compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs

@@ -355,21 +355,20 @@ fn add_unused_functions(cx: &CodegenCx<'_, '_>) {
 
     let tcx = cx.tcx;
 
-    let ignore_unused_generics = tcx.sess.instrument_coverage_except_unused_generics();
-
     let eligible_def_ids = tcx.mir_keys(()).iter().filter_map(|local_def_id| {
         let def_id = local_def_id.to_def_id();
         let kind = tcx.def_kind(def_id);
         // `mir_keys` will give us `DefId`s for all kinds of things, not
         // just "functions", like consts, statics, etc. Filter those out.
-        // If `ignore_unused_generics` was specified, filter out any
-        // generic functions from consideration as well.
         if !matches!(kind, DefKind::Fn | DefKind::AssocFn | DefKind::Closure) {
             return None;
         }
-        if ignore_unused_generics && tcx.generics_of(def_id).requires_monomorphization(tcx) {
-            return None;
-        }
+
+        // FIXME(79651): Consider trying to filter out dummy instantiations of
+        // unused generic functions from library crates, because they can produce
+        // "unused instantiation" in coverage reports even when they are actually
+        // used by some downstream crate in the same binary.
+
         Some(local_def_id.to_def_id())
     });
 

Diff for: compiler/rustc_monomorphize/src/partitioning.rs

@@ -175,9 +175,7 @@ where
     }
 
     // Mark one CGU for dead code, if necessary.
-    let instrument_dead_code =
-        tcx.sess.instrument_coverage() && !tcx.sess.instrument_coverage_except_unused_functions();
-    if instrument_dead_code {
+    if tcx.sess.instrument_coverage() {
         mark_code_coverage_dead_code_cgu(&mut codegen_units);
     }
 

Diff for: compiler/rustc_session/src/config.rs

@@ -134,31 +134,13 @@ pub enum LtoCli {
 /// and higher). Nevertheless, there are many variables, depending on options
 /// selected, code structure, and enabled attributes. If errors are encountered,
 /// either while compiling or when generating `llvm-cov show` reports, consider
-/// lowering the optimization level, including or excluding `-C link-dead-code`,
-/// or using `-Zunstable-options -C instrument-coverage=except-unused-functions`
-/// or `-Zunstable-options -C instrument-coverage=except-unused-generics`.
-///
-/// Note that `ExceptUnusedFunctions` means: When `mapgen.rs` generates the
-/// coverage map, it will not attempt to generate synthetic functions for unused
-/// (and not code-generated) functions (whether they are generic or not). As a
-/// result, non-codegenned functions will not be included in the coverage map,
-/// and will not appear, as covered or uncovered, in coverage reports.
-///
-/// `ExceptUnusedGenerics` will add synthetic functions to the coverage map,
-/// unless the function has type parameters.
+/// lowering the optimization level, or including/excluding `-C link-dead-code`.
 #[derive(Clone, Copy, PartialEq, Hash, Debug)]
 pub enum InstrumentCoverage {
     /// `-C instrument-coverage=no` (or `off`, `false` etc.)
     No,
     /// `-C instrument-coverage` or `-C instrument-coverage=yes`
     Yes,
-    /// Additionally, instrument branches and output branch coverage.
-    /// `-Zunstable-options -C instrument-coverage=branch`
-    Branch,
-    /// `-Zunstable-options -C instrument-coverage=except-unused-generics`
-    ExceptUnusedGenerics,
-    /// `-Zunstable-options -C instrument-coverage=except-unused-functions`
-    ExceptUnusedFunctions,
 }
 
 /// Settings for `-Z instrument-xray` flag.
@@ -2718,24 +2700,6 @@ pub fn build_session_options(early_dcx: &mut EarlyDiagCtxt, matches: &getopts::M
         }
     }
 
-    // Check for unstable values of `-C instrument-coverage`.
-    // This is what prevents them from being used on stable compilers.
-    match cg.instrument_coverage {
-        // Stable values:
-        InstrumentCoverage::Yes | InstrumentCoverage::No => {}
-        // Unstable values:
-        InstrumentCoverage::Branch
-        | InstrumentCoverage::ExceptUnusedFunctions
-        | InstrumentCoverage::ExceptUnusedGenerics => {
-            if !unstable_opts.unstable_options {
-                early_dcx.early_fatal(
-                    "`-C instrument-coverage=branch` and `-C instrument-coverage=except-*` \
-                    require `-Z unstable-options`",
-                );
-            }
-        }
-    }
-
     if cg.instrument_coverage != InstrumentCoverage::No {
         if cg.profile_generate.enabled() || cg.profile_use.is_some() {
             early_dcx.early_fatal(

Diff for: compiler/rustc_session/src/options.rs

@@ -395,7 +395,7 @@ mod desc {
     pub const parse_linker_flavor: &str = ::rustc_target::spec::LinkerFlavorCli::one_of();
     pub const parse_optimization_fuel: &str = "crate=integer";
     pub const parse_dump_mono_stats: &str = "`markdown` (default) or `json`";
-    pub const parse_instrument_coverage: &str = "either a boolean (`yes`, `no`, `on`, `off`, etc) or (unstable) one of `branch`, `except-unused-generics`, `except-unused-functions`";
+    pub const parse_instrument_coverage: &str = parse_bool;
     pub const parse_instrument_xray: &str = "either a boolean (`yes`, `no`, `on`, `off`, etc), or a comma separated list of settings: `always` or `never` (mutually exclusive), `ignore-loops`, `instruction-threshold=N`, `skip-entry`, `skip-exit`";
     pub const parse_unpretty: &str = "`string` or `string=string`";
     pub const parse_treat_err_as_bug: &str = "either no value or a non-negative number";
@@ -928,15 +928,10 @@ mod parse {
             return true;
         };
 
+        // Parse values that have historically been accepted by stable compilers,
+        // even though they're currently just aliases for boolean values.
         *slot = match v {
             "all" => InstrumentCoverage::Yes,
-            "branch" => InstrumentCoverage::Branch,
-            "except-unused-generics" | "except_unused_generics" => {
-                InstrumentCoverage::ExceptUnusedGenerics
-            }
-            "except-unused-functions" | "except_unused_functions" => {
-                InstrumentCoverage::ExceptUnusedFunctions
-            }
             "0" => InstrumentCoverage::No,
             _ => return false,
         };
@@ -1445,14 +1440,9 @@ options! {
         "set the threshold for inlining a function"),
     #[rustc_lint_opt_deny_field_access("use `Session::instrument_coverage` instead of this field")]
     instrument_coverage: InstrumentCoverage = (InstrumentCoverage::No, parse_instrument_coverage, [TRACKED],
-        "instrument the generated code to support LLVM source-based code coverage \
-        reports (note, the compiler build config must include `profiler = true`); \
-        implies `-C symbol-mangling-version=v0`. Optional values are:
-        `=no` `=n` `=off` `=false` (default)
-        `=yes` `=y` `=on` `=true` (implicit value)
-        `=branch` (unstable)
-        `=except-unused-generics` (unstable)
-        `=except-unused-functions` (unstable)"),
+        "instrument the generated code to support LLVM source-based code coverage reports \
+        (note, the compiler build config must include `profiler = true`); \
+        implies `-C symbol-mangling-version=v0`"),
     link_arg: (/* redirected to link_args */) = ((), parse_string_push, [UNTRACKED],
         "a single extra argument to append to the linker invocation (can be used several times)"),
     link_args: Vec<String> = (Vec::new(), parse_list, [UNTRACKED],

Diff for: compiler/rustc_session/src/session.rs

@@ -352,18 +352,6 @@ impl Session {
         self.opts.cg.instrument_coverage() != InstrumentCoverage::No
     }
 
-    pub fn instrument_coverage_branch(&self) -> bool {
-        self.opts.cg.instrument_coverage() == InstrumentCoverage::Branch
-    }
-
-    pub fn instrument_coverage_except_unused_generics(&self) -> bool {
-        self.opts.cg.instrument_coverage() == InstrumentCoverage::ExceptUnusedGenerics
-    }
-
-    pub fn instrument_coverage_except_unused_functions(&self) -> bool {
-        self.opts.cg.instrument_coverage() == InstrumentCoverage::ExceptUnusedFunctions
-    }
-
     pub fn is_sanitizer_cfi_enabled(&self) -> bool {
         self.opts.unstable_opts.sanitizer.contains(SanitizerSet::CFI)
     }

Diff for: src/doc/rustc/src/instrument-coverage.md

@@ -346,15 +346,6 @@ $ llvm-cov report \
   more fine-grained coverage options are added.
   Using this value is currently not recommended.
 
-### Unstable values
-
-- `-Z unstable-options -C instrument-coverage=branch`:
-  Placeholder for potential branch coverage support in the future.
-- `-Z unstable-options -C instrument-coverage=except-unused-generics`:
-  Instrument all functions except unused generics.
-- `-Z unstable-options -C instrument-coverage=except-unused-functions`:
-  Instrument only used (called) functions and instantiated generic functions.
-
 ## Other references
 
 Rust's implementation and workflow for source-based code coverage is based on the same library and tools used to implement [source-based code coverage in Clang]. (This document is partially based on the Clang guide.)

Diff for: tests/coverage/auxiliary/used_crate.rs

@@ -76,13 +76,8 @@ fn use_this_lib_crate() {
 // ```
 //
 // The notice is triggered because the function is unused by the library itself,
-// and when the library is compiled, a synthetic function is generated, so
-// unused function coverage can be reported. Coverage can be skipped for unused
-// generic functions with:
-//
-// ```shell
-// $ `rustc -Zunstable-options -C instrument-coverage=except-unused-generics ...`
-// ```
+// so when the library is compiled, an "unused" set of mappings for that function
+// is included in the library's coverage metadata.
 //
 // Even though this function is used by `uses_crate.rs` (and
 // counted), with substitutions for `T`, those instantiations are only generated
@@ -98,6 +93,6 @@ fn use_this_lib_crate() {
 // another binary that never used this generic function, then it would be valid
 // to show the unused generic, with unknown substitution (`_`).
 //
-// The alternative is to exclude all generics from being included in the "unused
-// functions" list, which would then omit coverage results for
-// `unused_generic_function<T>()`, below.
+// The alternative would be to exclude all generics from being included in the
+// "unused functions" list, which would then omit coverage results for
+// `unused_generic_function<T>()`.

Diff for: tests/coverage/uses_crate.coverage

@@ -124,13 +124,8 @@ $DIR/auxiliary/used_crate.rs:
    LL|       |// ```
    LL|       |//
    LL|       |// The notice is triggered because the function is unused by the library itself,
-   LL|       |// and when the library is compiled, a synthetic function is generated, so
-   LL|       |// unused function coverage can be reported. Coverage can be skipped for unused
-   LL|       |// generic functions with:
-   LL|       |//
-   LL|       |// ```shell
-   LL|       |// $ `rustc -Zunstable-options -C instrument-coverage=except-unused-generics ...`
-   LL|       |// ```
+   LL|       |// so when the library is compiled, an "unused" set of mappings for that function
+   LL|       |// is included in the library's coverage metadata.
    LL|       |//
    LL|       |// Even though this function is used by `uses_crate.rs` (and
    LL|       |// counted), with substitutions for `T`, those instantiations are only generated
@@ -146,9 +141,9 @@ $DIR/auxiliary/used_crate.rs:
    LL|       |// another binary that never used this generic function, then it would be valid
    LL|       |// to show the unused generic, with unknown substitution (`_`).
    LL|       |//
-   LL|       |// The alternative is to exclude all generics from being included in the "unused
-   LL|       |// functions" list, which would then omit coverage results for
-   LL|       |// `unused_generic_function<T>()`, below.
+   LL|       |// The alternative would be to exclude all generics from being included in the
+   LL|       |// "unused functions" list, which would then omit coverage results for
+   LL|       |// `unused_generic_function<T>()`.
 
 $DIR/uses_crate.rs:
    LL|       |// This test was failing on Linux for a while due to #110393 somehow making

Diff for: tests/ui/instrument-coverage/bad-value.bad.stderr

@@ -1,2 +1,2 @@
-error: incorrect value `bad-value` for codegen option `instrument-coverage` - either a boolean (`yes`, `no`, `on`, `off`, etc) or (unstable) one of `branch`, `except-unused-generics`, `except-unused-functions` was expected
+error: incorrect value `bad-value` for codegen option `instrument-coverage` - one of: `y`, `yes`, `on`, `true`, `n`, `no`, `off` or `false` was expected
 

Diff for: tests/ui/instrument-coverage/bad-value.blank.stderr

@@ -1,2 +1,2 @@
-error: incorrect value `` for codegen option `instrument-coverage` - either a boolean (`yes`, `no`, `on`, `off`, etc) or (unstable) one of `branch`, `except-unused-generics`, `except-unused-functions` was expected
+error: incorrect value `` for codegen option `instrument-coverage` - one of: `y`, `yes`, `on`, `true`, `n`, `no`, `off` or `false` was expected