Add a custom `run-coverage` mode to compiletest

3 files changed, 232 insertions, 3 deletions

diff --git a/src/tools/compiletest/src/common.rs b/src/tools/compiletest/src/common.rs
index 85a8fbcffbe..81684c6f9f9 100644
--- a/src/tools/compiletest/src/common.rs
+++ b/src/tools/compiletest/src/common.rs
@@ -66,6 +66,7 @@ string_enum! {
         JsDocTest => "js-doc-test",
         MirOpt => "mir-opt",
         Assembly => "assembly",
+        RunCoverage => "run-coverage",
     }
 }
 
@@ -626,6 +627,7 @@ pub const UI_EXTENSIONS: &[&str] = &[
     UI_STDERR_64,
     UI_STDERR_32,
     UI_STDERR_16,
+    UI_COVERAGE,
 ];
 pub const UI_STDERR: &str = "stderr";
 pub const UI_STDOUT: &str = "stdout";
@@ -635,6 +637,7 @@ pub const UI_RUN_STDOUT: &str = "run.stdout";
 pub const UI_STDERR_64: &str = "64bit.stderr";
 pub const UI_STDERR_32: &str = "32bit.stderr";
 pub const UI_STDERR_16: &str = "16bit.stderr";
+pub const UI_COVERAGE: &str = "coverage";
 
 /// Absolute path to the directory where all output for all tests in the given
 /// `relative_dir` group should reside. Example:
diff --git a/src/tools/compiletest/src/header.rs b/src/tools/compiletest/src/header.rs
index 00720e1c4db..b699accf34c 100644
--- a/src/tools/compiletest/src/header.rs
+++ b/src/tools/compiletest/src/header.rs
@@ -612,10 +612,25 @@ pub fn line_directive<'line>(
 }
 
 fn iter_header<R: Read>(testfile: &Path, rdr: R, it: &mut dyn FnMut(Option<&str>, &str, usize)) {
+    iter_header_extra(testfile, rdr, &[], it)
+}
+
+fn iter_header_extra(
+    testfile: &Path,
+    rdr: impl Read,
+    extra_directives: &[&str],
+    it: &mut dyn FnMut(Option<&str>, &str, usize),
+) {
     if testfile.is_dir() {
         return;
     }
 
+    // Process any extra directives supplied by the caller (e.g. because they
+    // are implied by the test mode), with a dummy line number of 0.
+    for directive in extra_directives {
+        it(None, directive, 0);
+    }
+
     let comment = if testfile.extension().map(|e| e == "rs") == Some(true) { "//" } else { "#" };
 
     let mut rdr = BufReader::new(rdr);
@@ -894,7 +909,27 @@ pub fn make_test_description<R: Read>(
     let mut ignore_message = None;
     let mut should_fail = false;
 
-    iter_header(path, src, &mut |revision, ln, line_number| {
+    let extra_directives: &[&str] = match config.mode {
+        // The run-coverage tests are treated as having these extra directives,
+        // without needing to specify them manually in every test file.
+        // (Some of the comments below have been copied over from
+        // `tests/run-make/coverage-reports/Makefile`.)
+        Mode::RunCoverage => {
+            &[
+                "needs-profiler-support",
+                // FIXME(mati865): MinGW GCC miscompiles compiler-rt profiling library but with Clang it works
+                // properly. Since we only have GCC on the CI ignore the test for now.
+                "ignore-windows-gnu",
+                // FIXME(pietroalbini): this test currently does not work on cross-compiled
+                // targets because remote-test is not capable of sending back the *.profraw
+                // files generated by the LLVM instrumentation.
+                "ignore-cross-compile",
+            ]
+        }
+        _ => &[],
+    };
+
+    iter_header_extra(path, src, extra_directives, &mut |revision, ln, line_number| {
         if revision.is_some() && revision != cfg {
             return;
         }
diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index 91b9f668ce5..920db24a1a4 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -6,8 +6,8 @@ use crate::common::{Assembly, Incremental, JsDocTest, MirOpt, RunMake, RustdocJs
 use crate::common::{Codegen, CodegenUnits, DebugInfo, Debugger, Rustdoc};
 use crate::common::{CompareMode, FailMode, PassMode};
 use crate::common::{Config, TestPaths};
-use crate::common::{Pretty, RunPassValgrind};
-use crate::common::{UI_RUN_STDERR, UI_RUN_STDOUT};
+use crate::common::{Pretty, RunCoverage, RunPassValgrind};
+use crate::common::{UI_COVERAGE, UI_RUN_STDERR, UI_RUN_STDOUT};
 use crate::compute_diff::{write_diff, write_filtered_diff};
 use crate::errors::{self, Error, ErrorKind};
 use crate::header::TestProps;
@@ -253,6 +253,7 @@ impl<'test> TestCx<'test> {
             MirOpt => self.run_mir_opt_test(),
             Assembly => self.run_assembly_test(),
             JsDocTest => self.run_js_doc_test(),
+            RunCoverage => self.run_coverage_test(),
         }
     }
 
@@ -465,6 +466,184 @@ impl<'test> TestCx<'test> {
         }
     }
 
+    fn run_coverage_test(&self) {
+        let should_run = self.run_if_enabled();
+        let proc_res = self.compile_test(should_run, Emit::None);
+
+        if !proc_res.status.success() {
+            self.fatal_proc_rec("compilation failed!", &proc_res);
+        }
+        drop(proc_res);
+
+        if let WillExecute::Disabled = should_run {
+            return;
+        }
+
+        let profraw_path = self.output_base_dir().join("default.profraw");
+        let profdata_path = self.output_base_dir().join("default.profdata");
+
+        // Delete any existing profraw/profdata files to rule out unintended
+        // interference between repeated test runs.
+        if profraw_path.exists() {
+            std::fs::remove_file(&profraw_path).unwrap();
+        }
+        if profdata_path.exists() {
+            std::fs::remove_file(&profdata_path).unwrap();
+        }
+
+        let proc_res = self.exec_compiled_test_general(
+            &[("LLVM_PROFILE_FILE", &profraw_path.to_str().unwrap())],
+            false,
+        );
+        if self.props.failure_status.is_some() {
+            self.check_correct_failure_status(&proc_res);
+        } else if !proc_res.status.success() {
+            self.fatal_proc_rec("test run failed!", &proc_res);
+        }
+        drop(proc_res);
+
+        // Run `llvm-profdata merge` to index the raw coverage output.
+        let proc_res = self.run_llvm_tool("llvm-profdata", |cmd| {
+            cmd.args(["merge", "--sparse", "--output"]);
+            cmd.arg(&profdata_path);
+            cmd.arg(&profraw_path);
+        });
+        if !proc_res.status.success() {
+            self.fatal_proc_rec("llvm-profdata merge failed!", &proc_res);
+        }
+        drop(proc_res);
+
+        // Run `llvm-cov show` to produce a coverage report in text format.
+        let proc_res = self.run_llvm_tool("llvm-cov", |cmd| {
+            cmd.args(["show", "--format=text", "--show-line-counts-or-regions"]);
+
+            cmd.arg("--Xdemangler");
+            cmd.arg(self.config.rust_demangler_path.as_ref().unwrap());
+
+            cmd.arg("--instr-profile");
+            cmd.arg(&profdata_path);
+
+            cmd.arg("--object");
+            cmd.arg(&self.make_exe_name());
+        });
+        if !proc_res.status.success() {
+            self.fatal_proc_rec("llvm-cov show failed!", &proc_res);
+        }
+
+        let kind = UI_COVERAGE;
+
+        let expected_coverage = self.load_expected_output(kind);
+        let normalized_actual_coverage =
+            self.normalize_coverage_output(&proc_res.stdout).unwrap_or_else(|err| {
+                self.fatal_proc_rec(&err, &proc_res);
+            });
+
+        let coverage_errors = self.compare_output(
+            kind,
+            &normalized_actual_coverage,
+            &expected_coverage,
+            self.props.compare_output_lines_by_subset,
+        );
+
+        if coverage_errors > 0 {
+            self.fatal_proc_rec(
+                &format!("{} errors occurred comparing coverage output.", coverage_errors),
+                &proc_res,
+            );
+        }
+    }
+
+    fn run_llvm_tool(&self, name: &str, configure_cmd_fn: impl FnOnce(&mut Command)) -> ProcRes {
+        let tool_path = self
+            .config
+            .llvm_bin_dir
+            .as_ref()
+            .expect("this test expects the LLVM bin dir to be available")
+            .join(name);
+
+        let mut cmd = Command::new(tool_path);
+        configure_cmd_fn(&mut cmd);
+
+        let output = cmd.output().unwrap_or_else(|_| panic!("failed to exec `{cmd:?}`"));
+
+        let proc_res = ProcRes {
+            status: output.status,
+            stdout: String::from_utf8(output.stdout).unwrap(),
+            stderr: String::from_utf8(output.stderr).unwrap(),
+            cmdline: format!("{cmd:?}"),
+        };
+        self.dump_output(&proc_res.stdout, &proc_res.stderr);
+
+        proc_res
+    }
+
+    fn normalize_coverage_output(&self, coverage: &str) -> Result<String, String> {
+        let normalized = self.normalize_output(coverage, &[]);
+
+        let mut lines = normalized.lines().collect::<Vec<_>>();
+
+        Self::sort_coverage_subviews(&mut lines)?;
+
+        let joined_lines = lines.iter().flat_map(|line| [line, "\n"]).collect::<String>();
+        Ok(joined_lines)
+    }
+
+    fn sort_coverage_subviews(coverage_lines: &mut Vec<&str>) -> Result<(), String> {
+        let mut output_lines = Vec::new();
+
+        // We accumulate a list of zero or more "subviews", where each
+        // subview is a list of one or more lines.
+        let mut subviews: Vec<Vec<&str>> = Vec::new();
+
+        fn flush<'a>(subviews: &mut Vec<Vec<&'a str>>, output_lines: &mut Vec<&'a str>) {
+            if subviews.is_empty() {
+                return;
+            }
+
+            // Take and clear the list of accumulated subviews.
+            let mut subviews = std::mem::take(subviews);
+
+            // The last "subview" should be just a boundary line on its own,
+            // so exclude it when sorting the other subviews.
+            let except_last = subviews.len() - 1;
+            (&mut subviews[..except_last]).sort();
+
+            for view in subviews {
+                for line in view {
+                    output_lines.push(line);
+                }
+            }
+        }
+
+        for (line, line_num) in coverage_lines.iter().zip(1..) {
+            if line.starts_with("  ------------------") {
+                // This is a subview boundary line, so start a new subview.
+                subviews.push(vec![line]);
+            } else if line.starts_with("  |") {
+                // Add this line to the current subview.
+                subviews
+                    .last_mut()
+                    .ok_or(format!(
+                        "unexpected subview line outside of a subview on line {line_num}"
+                    ))?
+                    .push(line);
+            } else {
+                // This line is not part of a subview, so sort and print any
+                // accumulated subviews, and then print the line as-is.
+                flush(&mut subviews, &mut output_lines);
+                output_lines.push(line);
+            }
+        }
+
+        flush(&mut subviews, &mut output_lines);
+        assert!(subviews.is_empty());
+
+        assert_eq!(output_lines.len(), coverage_lines.len());
+        *coverage_lines = output_lines;
+
+        Ok(())
+    }
+
     fn run_pretty_test(&self) {
         if self.props.pp_exact.is_some() {
             logv(self.config, "testing for exact pretty-printing".to_owned());
@@ -1822,6 +2001,7 @@ impl<'test> TestCx<'test> {
             || self.is_vxworks_pure_static()
             || self.config.target.contains("bpf")
             || !self.config.target_cfg().dynamic_linking
+            || self.config.mode == RunCoverage
         {
             // We primarily compile all auxiliary libraries as dynamic libraries
             // to avoid code size bloat and large binaries as much as possible
@@ -1832,6 +2012,10 @@ impl<'test> TestCx<'test> {
             // dynamic libraries so we just go back to building a normal library. Note,
             // however, that for MUSL if the library is built with `force_host` then
             // it's ok to be a dylib as the host should always support dylibs.
+            //
+            // Coverage tests want static linking by default so that coverage
+            // mappings in auxiliary libraries can be merged into the final
+            // executable.
             (false, Some("lib"))
         } else {
             (true, Some("dylib"))
@@ -2009,6 +2193,10 @@ impl<'test> TestCx<'test> {
                     }
                 }
                 DebugInfo => { /* debuginfo tests must be unoptimized */ }
+                RunCoverage => {
+                    // Coverage reports are affected by optimization level, and
+                    // the current snapshots assume no optimization by default.
+                }
                 _ => {
                     rustc.arg("-O");
                 }
@@ -2075,6 +2263,9 @@ impl<'test> TestCx<'test> {
 
                 rustc.arg(dir_opt);
             }
+            RunCoverage => {
+                rustc.arg("-Cinstrument-coverage");
+            }
             RunPassValgrind | Pretty | DebugInfo | Codegen | Rustdoc | RustdocJson | RunMake
             | CodegenUnits | JsDocTest | Assembly => {
                 // do not use JSON output