change compiler test suit to support parallel front end robustness test

Author: SparrowLii

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

@@ -205,6 +205,7 @@ const KNOWN_DIRECTIVE_NAMES: &[&str] = &[
     "only-x86_64-pc-windows-gnu",
     "only-x86_64-pc-windows-msvc",
     "only-x86_64-unknown-linux-gnu",
+    "parallel-front-end-robustness",
     "pp-exact",
     "pretty-compare-only",
     "pretty-expanded",

src/tools/compiletest/src/header.rs

@@ -108,6 +108,9 @@ pub struct TestProps {
     pub force_host: bool,
     // Check stdout for error-pattern output as well as stderr
     pub check_stdout: bool,
+    // For parallel front end, use repeated tests to ensure
+    // there is no deadlock or other ice problems.
+    pub parallel_front_end_robustness: bool,
     // Check stdout & stderr for output of run-pass test
     pub check_run_results: bool,
     // For UI tests, allows compiler to generate arbitrary output to stdout
@@ -213,6 +216,7 @@ mod directives {
     pub const CHECK_RUN_RESULTS: &'static str = "check-run-results";
     pub const DONT_CHECK_COMPILER_STDOUT: &'static str = "dont-check-compiler-stdout";
     pub const DONT_CHECK_COMPILER_STDERR: &'static str = "dont-check-compiler-stderr";
+    pub const PARALLEL_FRONT_END_ROBUTNESS: &'static str = "parallel-front-end-robustness";
     pub const NO_PREFER_DYNAMIC: &'static str = "no-prefer-dynamic";
     pub const PRETTY_EXPANDED: &'static str = "pretty-expanded";
     pub const PRETTY_MODE: &'static str = "pretty-mode";
@@ -273,6 +277,7 @@ impl TestProps {
             dont_check_compiler_stderr: false,
             compare_output_lines_by_subset: false,
             no_prefer_dynamic: false,
+            parallel_front_end_robustness: false,
             pretty_expanded: false,
             pretty_mode: "normal".to_string(),
             pretty_compare_only: false,
@@ -494,6 +499,11 @@ impl TestProps {
                         DONT_CHECK_FAILURE_STATUS,
                         &mut self.dont_check_failure_status,
                     );
+                    config.set_name_directive(
+                        ln,
+                        PARALLEL_FRONT_END_ROBUTNESS,
+                        &mut self.parallel_front_end_robustness,
+                    );
 
                     config.set_name_directive(ln, RUN_RUSTFIX, &mut self.run_rustfix);
                     config.set_name_directive(

src/tools/compiletest/src/runtest.rs

@@ -1349,9 +1349,6 @@ impl<'test> TestCx<'test> {
         };
         rustc.arg(input_file);
 
-        // Use a single thread for efficiency and a deterministic error message order
-        rustc.arg("-Zthreads=1");
-
         // Hide libstd sources from ui tests to make sure we generate the stderr
         // output that users will see.
         // Without this, we may be producing good diagnostics in-tree but users

src/tools/compiletest/src/runtest/ui.rs

@@ -24,7 +24,24 @@ impl TestCx<'_> {
         let pm = self.pass_mode();
         let should_run = self.should_run(pm);
         let emit_metadata = self.should_emit_metadata(pm);
-        let proc_res = self.compile_test(should_run, emit_metadata);
+        let mut proc_res = self.compile_test(should_run, emit_metadata);
+
+        if self.props.parallel_front_end_robustness {
+            // Ensure there is no ice during parallel front end.
+            self.check_no_compiler_crash(&proc_res, false);
+
+            // Repeated testing due to instability in multithreaded environments.
+            for _ in 0..50 {
+                proc_res = self.compile_test(should_run, emit_metadata);
+                self.check_no_compiler_crash(&proc_res, false);
+            }
+
+            // For the parallel front end, we are currently only concerned with whether
+            // deadlock or other ice problems occur. The correctness of the output is
+            // guaranteed by other compiler tests.
+            return;
+        }
+
         self.check_if_test_should_compile(self.props.fail_mode, pm, &proc_res);
         if matches!(proc_res.truncated, Truncated::Yes)
             && !self.props.dont_check_compiler_stdout