Rollup merge of #120656 - Zalathar:filecheck-flags, r=wesleywiser

Allow tests to specify a `//@ filecheck-flags:` header

This allows individual codegen/assembly/mir-opt tests to pass extra flags to the LLVM `filecheck` tool as needed.

---

The original motivation was noticing that `tests/run-make/instrument-coverage` was very close to being an ordinary codegen test, except that it needs some extra logic to set up platform-specific variables to be passed into filecheck.

I then saw the comment in `verify_with_filecheck` indicating that a `filecheck-flags` header might be useful for other purposes as well.

2 files changed, 31 insertions, 16 deletions

diff --git a/src/tools/compiletest/src/header.rs b/src/tools/compiletest/src/header.rs
index c76cba824a3..6de445a5783 100644
--- a/src/tools/compiletest/src/header.rs
+++ b/src/tools/compiletest/src/header.rs
@@ -197,6 +197,8 @@ pub struct TestProps {
     /// Extra flags to pass to `llvm-cov` when producing coverage reports.
     /// Only used by the "coverage-run" test mode.
     pub llvm_cov_flags: Vec<String>,
+    /// Extra flags to pass to LLVM's `filecheck` tool, in tests that use it.
+    pub filecheck_flags: Vec<String>,
 }
 
 mod directives {
@@ -236,6 +238,7 @@ mod directives {
     pub const REMAP_SRC_BASE: &'static str = "remap-src-base";
     pub const COMPARE_OUTPUT_LINES_BY_SUBSET: &'static str = "compare-output-lines-by-subset";
     pub const LLVM_COV_FLAGS: &'static str = "llvm-cov-flags";
+    pub const FILECHECK_FLAGS: &'static str = "filecheck-flags";
     // This isn't a real directive, just one that is probably mistyped often
     pub const INCORRECT_COMPILER_FLAGS: &'static str = "compiler-flags";
 }
@@ -286,6 +289,7 @@ impl TestProps {
             mir_unit_test: None,
             remap_src_base: false,
             llvm_cov_flags: vec![],
+            filecheck_flags: vec![],
         }
     }
 
@@ -542,6 +546,10 @@ impl TestProps {
                     if let Some(flags) = config.parse_name_value_directive(ln, LLVM_COV_FLAGS) {
                         self.llvm_cov_flags.extend(split_flags(&flags));
                     }
+
+                    if let Some(flags) = config.parse_name_value_directive(ln, FILECHECK_FLAGS) {
+                        self.filecheck_flags.extend(split_flags(&flags));
+                    }
                 },
             );
 
diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index 61211a7d675..f1ba9ab4767 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -2909,25 +2909,32 @@ impl<'test> TestCx<'test> {
     fn verify_with_filecheck(&self, output: &Path) -> ProcRes {
         let mut filecheck = Command::new(self.config.llvm_filecheck.as_ref().unwrap());
         filecheck.arg("--input-file").arg(output).arg(&self.testpaths.file);
-        // It would be more appropriate to make most of the arguments configurable through
-        // a comment-attribute similar to `compile-flags`. For example, --check-prefixes is a very
-        // useful flag.
-        //
-        // For now, though…
-        let prefix_for_target =
-            if self.config.target.contains("msvc") { "MSVC" } else { "NONMSVC" };
-        let prefixes = if let Some(rev) = self.revision {
-            format!("CHECK,{},{}", prefix_for_target, rev)
-        } else {
-            format!("CHECK,{}", prefix_for_target)
-        };
-        if self.config.llvm_version.unwrap_or(0) >= 130000 {
-            filecheck.args(&["--allow-unused-prefixes", "--check-prefixes", &prefixes]);
-        } else {
-            filecheck.args(&["--check-prefixes", &prefixes]);
+
+        // FIXME: Consider making some of these prefix flags opt-in per test,
+        // via `filecheck-flags` or by adding new header directives.
+
+        // Because we use custom prefixes, we also have to register the default prefix.
+        filecheck.arg("--check-prefix=CHECK");
+
+        // Some tests use the current revision name as a check prefix.
+        if let Some(rev) = self.revision {
+            filecheck.arg("--check-prefix").arg(rev);
         }
+
+        // Some tests also expect either the MSVC or NONMSVC prefix to be defined.
+        let msvc_or_not = if self.config.target.contains("msvc") { "MSVC" } else { "NONMSVC" };
+        filecheck.arg("--check-prefix").arg(msvc_or_not);
+
+        // The filecheck tool normally fails if a prefix is defined but not used.
+        // However, we define several prefixes globally for all tests.
+        filecheck.arg("--allow-unused-prefixes");
+
         // Provide more context on failures.
         filecheck.args(&["--dump-input-context", "100"]);
+
+        // Add custom flags supplied by the `filecheck-flags:` test header.
+        filecheck.args(&self.props.filecheck_flags);
+
         self.compose_and_run(filecheck, "", None, None)
     }