add has_enzyme/needs-enzyme to the test infra

src/bootstrap/src/core/build_steps/test.rs

@@ -1792,6 +1792,10 @@ NOTE: if you're sure you want to do this, please open an issue as to why. In the
         cmd.arg("--host").arg(&*compiler.host.triple);
         cmd.arg("--llvm-filecheck").arg(builder.llvm_filecheck(builder.config.build));
 
+        if builder.build.config.llvm_enzyme {
+            cmd.arg("--has-enzyme");
+        }
+
         if builder.config.cmd.bless() {
             cmd.arg("--bless");
         }

src/tools/compiletest/src/command-list.rs

@@ -139,6 +139,7 @@ const KNOWN_DIRECTIVE_NAMES: &[&str] = &[
     "needs-deterministic-layouts",
     "needs-dlltool",
     "needs-dynamic-linking",
+    "needs-enzyme",
     "needs-force-clang-based-tests",
     "needs-git-hash",
     "needs-llvm-components",

src/tools/compiletest/src/common.rs

@@ -349,6 +349,9 @@ pub struct Config {
     /// whether to run `tidy` when a rustdoc test fails
     pub has_tidy: bool,
 
+    /// whether to run `enzyme` autodiff tests
+    pub has_enzyme: bool,
+
     /// The current Rust channel
     pub channel: String,
 

src/tools/compiletest/src/header.rs

@@ -218,6 +218,8 @@ pub struct TestProps {
     pub filecheck_flags: Vec<String>,
     /// Don't automatically insert any `--check-cfg` args
     pub no_auto_check_cfg: bool,
+    /// Run tests which require enzyme being build
+    pub has_enzyme: bool,
 }
 
 mod directives {
@@ -322,6 +324,7 @@ impl TestProps {
             llvm_cov_flags: vec![],
             filecheck_flags: vec![],
             no_auto_check_cfg: false,
+            has_enzyme: false,
         }
     }
 

src/tools/compiletest/src/header/needs.rs

@@ -79,6 +79,11 @@ pub(super) fn handle_needs(
             condition: cache.sanitizer_safestack,
             ignore_reason: "ignored on targets without SafeStack support",
         },
+        Need {
+            name: "needs-enzyme",
+            condition: config.has_enzyme,
+            ignore_reason: "ignored when LLVM Enzyme is disabled",
+        },
         Need {
             name: "needs-run-enabled",
             condition: config.run_enabled(),

src/tools/compiletest/src/lib.rs

@@ -83,6 +83,7 @@ pub fn parse_config(args: Vec<String>) -> Config {
         )
         .optopt("", "run", "whether to execute run-* tests", "auto | always | never")
         .optflag("", "ignored", "run tests marked as ignored")
+        .optflag("", "has-enzyme", "run tests that require enzyme")
         .optflag("", "with-debug-assertions", "whether to run tests with `ignore-debug` header")
         .optmulti(
             "",
@@ -233,6 +234,7 @@ pub fn parse_config(args: Vec<String>) -> Config {
         // Avoid spawning an external command when we know tidy won't be used.
         false
     };
+    let has_enzyme = matches.opt_present("has-enzyme");
     let filters = if mode == Mode::RunMake {
         matches
             .free
@@ -331,6 +333,7 @@ pub fn parse_config(args: Vec<String>) -> Config {
             .map(|s| s.parse().expect("invalid --compare-mode provided")),
         rustfix_coverage: matches.opt_present("rustfix-coverage"),
         has_tidy,
+        has_enzyme,
         channel: matches.opt_str("channel").unwrap(),
         git_hash: matches.opt_present("git-hash"),
         edition: matches.opt_str("edition"),