3 files changed, 12 insertions, 4 deletions
diff --git a/src/asm2wasm.h b/src/asm2wasm.h
index 10d065400..7cc671597 100644
--- a/src/asm2wasm.h
+++ b/src/asm2wasm.h
@@ -523,7 +523,10 @@ void Asm2WasmBuilder::processAsm(Ref ast) {
     for (unsigned i = 1; i < body->size(); i++) {
       if (body[i][0] == DEFUN) numFunctions++;
     }
-    optimizingBuilder = make_unique<OptimizingIncrementalModuleBuilder>(&wasm, numFunctions);
+    optimizingBuilder = make_unique<OptimizingIncrementalModuleBuilder>(&wasm, numFunctions, [&](PassRunner& passRunner) {
+      // run autodrop first, before optimizations
+      passRunner.add<AutoDrop>();
+    });
   }
 
   // first pass - do almost everything, but function imports and indirect calls
@@ -786,7 +789,7 @@ void Asm2WasmBuilder::processAsm(Ref ast) {
   };
   PassRunner passRunner(&wasm);
   passRunner.add<FinalizeCalls>(this);
-  passRunner.add<AutoDrop>();
+  passRunner.add<AutoDrop>(); // FinalizeCalls may cause us to require additional drops
   if (optimize) passRunner.add("vacuum"); // autodrop can add some garbage
   passRunner.run();
 
diff --git a/src/passes/pass.cpp b/src/passes/pass.cpp
index 1e7e85ccb..437b023bc 100644
--- a/src/passes/pass.cpp
+++ b/src/passes/pass.cpp
@@ -209,6 +209,9 @@ void PassRunner::run() {
 }
 
 void PassRunner::runFunction(Function* func) {
+  if (debug) {
+    std::cerr << "[PassRunner] running passes on function " << func->name << std::endl;
+  }
   for (auto* pass : passes) {
     runPassOnFunction(pass, func);
   }
diff --git a/src/wasm-module-building.h b/src/wasm-module-building.h
index ead074991..43cc493d1 100644
--- a/src/wasm-module-building.h
+++ b/src/wasm-module-building.h
@@ -73,6 +73,7 @@ static std::mutex debug;
 class OptimizingIncrementalModuleBuilder {
   Module* wasm;
   uint32_t numFunctions;
+  std::function<void (PassRunner&)> addPrePasses;
   Function* endMarker;
   std::atomic<Function*>* list;
   uint32_t nextFunction; // only used on main thread
@@ -86,8 +87,8 @@ class OptimizingIncrementalModuleBuilder {
 public:
   // numFunctions must be equal to the number of functions allocated, or higher. Knowing
   // this bounds helps avoid locking.
-  OptimizingIncrementalModuleBuilder(Module* wasm, Index numFunctions)
-      : wasm(wasm), numFunctions(numFunctions), endMarker(nullptr), list(nullptr), nextFunction(0),
+  OptimizingIncrementalModuleBuilder(Module* wasm, Index numFunctions, std::function<void (PassRunner&)> addPrePasses)
+      : wasm(wasm), numFunctions(numFunctions), addPrePasses(addPrePasses), endMarker(nullptr), list(nullptr), nextFunction(0),
         numWorkers(0), liveWorkers(0), activeWorkers(0), availableFuncs(0), finishedFuncs(0),
         finishing(false) {
     if (numFunctions == 0) {
@@ -201,6 +202,7 @@ private:
 
   void optimizeFunction(Function* func) {
     PassRunner passRunner(wasm);
+    addPrePasses(passRunner);
     passRunner.addDefaultFunctionOptimizationPasses();
     passRunner.runFunction(func);
   }