2 files changed, 65 insertions, 0 deletions
diff --git a/src/tools/compiletest/src/header.rs b/src/tools/compiletest/src/header.rs
index 48149e3b897..8c96554738e 100644
--- a/src/tools/compiletest/src/header.rs
+++ b/src/tools/compiletest/src/header.rs
@@ -934,6 +934,9 @@ fn iter_header(
 
 impl Config {
     fn parse_and_update_revisions(&self, testfile: &Path, line: &str, existing: &mut Vec<String>) {
+        const FORBIDDEN_REVISION_NAMES: [&str; 9] =
+            ["CHECK", "COM", "NEXT", "SAME", "EMPTY", "NOT", "COUNT", "DAG", "LABEL"];
+
         if let Some(raw) = self.parse_name_value_directive(line, "revisions") {
             if self.mode == Mode::RunMake {
                 panic!("`run-make` tests do not support revisions: {}", testfile.display());
@@ -948,6 +951,15 @@ impl Config {
                         raw,
                         testfile.display()
                     );
+                } else if matches!(self.mode, Mode::Assembly | Mode::Codegen | Mode::MirOpt)
+                    && FORBIDDEN_REVISION_NAMES.contains(&revision.as_str())
+                {
+                    panic!(
+                        "revision name `{revision}` is not permitted in a test suite that uses `FileCheck` annotations\n\
+                         as it is confusing when used as custom `FileCheck` prefix: `{revision}` in line `{}`: {}",
+                        raw,
+                        testfile.display()
+                    );
                 }
                 existing.push(revision);
             }
diff --git a/src/tools/compiletest/src/header/tests.rs b/src/tools/compiletest/src/header/tests.rs
index 618b66dfd4c..25bb1a5f428 100644
--- a/src/tools/compiletest/src/header/tests.rs
+++ b/src/tools/compiletest/src/header/tests.rs
@@ -554,6 +554,59 @@ fn test_duplicate_revisions() {
 }
 
 #[test]
+#[should_panic(
+    expected = "revision name `CHECK` is not permitted in a test suite that uses `FileCheck` annotations"
+)]
+fn test_assembly_mode_forbidden_revisions() {
+    let config = cfg().mode("assembly").build();
+    parse_rs(&config, "//@ revisions: CHECK");
+}
+
+#[test]
+#[should_panic(
+    expected = "revision name `CHECK` is not permitted in a test suite that uses `FileCheck` annotations"
+)]
+fn test_codegen_mode_forbidden_revisions() {
+    let config = cfg().mode("codegen").build();
+    parse_rs(&config, "//@ revisions: CHECK");
+}
+
+#[test]
+#[should_panic(
+    expected = "revision name `CHECK` is not permitted in a test suite that uses `FileCheck` annotations"
+)]
+fn test_miropt_mode_forbidden_revisions() {
+    let config = cfg().mode("mir-opt").build();
+    parse_rs(&config, "//@ revisions: CHECK");
+}
+
+#[test]
+fn test_forbidden_revisions_allowed_in_non_filecheck_dir() {
+    let revisions = ["CHECK", "COM", "NEXT", "SAME", "EMPTY", "NOT", "COUNT", "DAG", "LABEL"];
+    let modes = [
+        "pretty",
+        "debuginfo",
+        "rustdoc",
+        "rustdoc-json",
+        "codegen-units",
+        "incremental",
+        "ui",
+        "js-doc-test",
+        "coverage-map",
+        "coverage-run",
+        "crashes",
+    ];
+
+    for rev in revisions {
+        let content = format!("//@ revisions: {rev}");
+        for mode in modes {
+            let config = cfg().mode(mode).build();
+            parse_rs(&config, &content);
+        }
+    }
+}
+
+#[test]
 fn ignore_arch() {
     let archs = [
         ("x86_64-unknown-linux-gnu", "x86_64"),