1 files changed, 13 insertions, 4 deletions
diff --git a/src/pass.h b/src/pass.h
index f4b15a320..2cb661e72 100644
--- a/src/pass.h
+++ b/src/pass.h
@@ -488,10 +488,19 @@ public:
     assert(getPassRunner());
     // Parallel pass running is implemented in the PassRunner.
     if (isFunctionParallel()) {
-      // TODO: We should almost certainly be propagating pass options here, but
-      // that is a widespread change, so make sure it doesn't unacceptably
-      // regress compile times.
-      PassRunner runner(module /*, getPassOptions()*/);
+      // Reduce opt/shrink levels to a maximum of one in nested runners like
+      // these, to balance runtime. We definitely want the full levels in the
+      // main passes we run, but nested pass runners are of secondary
+      // importance.
+      // TODO Investigate the impact of allowing the levels to just pass
+      //      through. That seems to cause at least some regression in compile
+      //      times in -O3, however, but with careful measurement we may find
+      //      the benefits are worth it. For now -O1 is a reasonable compromise
+      //      as it has basically linear runtime, unlike -O2 and -O3.
+      auto options = getPassOptions();
+      options.optimizeLevel = std::min(options.optimizeLevel, 1);
+      options.shrinkLevel = std::min(options.shrinkLevel, 1);
+      PassRunner runner(module, options);
       runner.setIsNested(true);
       runner.add(create());
       runner.run();