5 files changed, 50 insertions, 22 deletions

diff --git a/src/ir/module-splitting.cpp b/src/ir/module-splitting.cpp
index 22f8b301f..adda1f4a6 100644
--- a/src/ir/module-splitting.cpp
+++ b/src/ir/module-splitting.cpp
@@ -94,10 +94,9 @@ template<class F> void forEachElement(Module& module, F f) {
     } else if (auto* g = segment->offset->dynCast<GlobalGet>()) {
       base = g->name;
     }
-    ElementUtils::iterElementSegmentFunctionNames(
-      segment, [&](Name& entry, Index i) {
-        f(segment->table, base, offset + i, entry);
-      });
+    for (Index i = 0; i < segment->data.size(); ++i) {
+      f(segment->table, base, offset + i, segment->data[i]);
+    }
   });
 }
 
@@ -209,9 +208,12 @@ TableSlotManager::TableSlotManager(Module& module) : module(module) {
   }
 
   // Initialize funcIndices with the functions already in the table.
-  forEachElement(module, [&](Name table, Name base, Index offset, Name func) {
-    addSlot(func, {table, base, offset});
-  });
+  forEachElement(module,
+                 [&](Name table, Name base, Index offset, Expression* elem) {
+                   if (auto* func = elem->dynCast<RefFunc>()) {
+                     addSlot(func->func, {table, base, offset});
+                   }
+                 });
 }
 
 Table* TableSlotManager::makeTable() {
@@ -693,21 +695,32 @@ void ModuleSplitter::setupTablePatching() {
   // Replace table references to secondary functions with an imported
   // placeholder that encodes the table index in its name:
   // `importNamespace`.`index`.
-  forEachElement(primary, [&](Name, Name, Index index, Name& elem) {
-    if (secondaryFuncs.count(elem)) {
-      placeholderMap[index] = elem;
-      auto* secondaryFunc = secondary.getFunction(elem);
-      replacedElems[index] = secondaryFunc;
-      auto placeholder = std::make_unique<Function>();
-      placeholder->module = config.placeholderNamespace;
-      placeholder->base = std::to_string(index);
-      placeholder->name = Names::getValidFunctionName(
-        primary, std::string("placeholder_") + placeholder->base.toString());
-      placeholder->hasExplicitName = true;
-      placeholder->type = secondaryFunc->type;
-      elem = placeholder->name;
-      primary.addFunction(std::move(placeholder));
+  forEachElement(primary, [&](Name, Name, Index index, Expression*& elem) {
+    auto* ref = elem->dynCast<RefFunc>();
+    if (!ref) {
+      return;
+    }
+    if (!secondaryFuncs.count(ref->func)) {
+      return;
+    }
+    placeholderMap[index] = ref->func;
+    auto* secondaryFunc = secondary.getFunction(ref->func);
+    replacedElems[index] = secondaryFunc;
+    if (!config.usePlaceholders) {
+      // TODO: This can create active element segments with lots of nulls. We
+      // should optimize them like we do data segments with zeros.
+      elem = Builder(primary).makeRefNull(HeapType::nofunc);
+      return;
     }
+    auto placeholder = std::make_unique<Function>();
+    placeholder->module = config.placeholderNamespace;
+    placeholder->base = std::to_string(index);
+    placeholder->name = Names::getValidFunctionName(
+      primary, std::string("placeholder_") + placeholder->base.toString());
+    placeholder->hasExplicitName = true;
+    placeholder->type = secondaryFunc->type;
+    elem = Builder(primary).makeRefFunc(placeholder->name, placeholder->type);
+    primary.addFunction(std::move(placeholder));
   });
 
   if (replacedElems.size() == 0) {
diff --git a/src/ir/module-splitting.h b/src/ir/module-splitting.h
index dc5bb1998..620993d2d 100644
--- a/src/ir/module-splitting.h
+++ b/src/ir/module-splitting.h
@@ -52,11 +52,15 @@ struct Config {
   // exists. May or may not include imported functions, which are always kept in
   // the primary module regardless.
   std::set<Name> primaryFuncs;
+  // Whether to import placeholder functions into the primary module that will
+  // be called when a secondary function is called before the secondary module
+  // has been loaded.
+  bool usePlaceholders = true;
   // The namespace from which to import primary functions into the secondary
   // module.
   Name importNamespace = "primary";
   // The namespace from which to import placeholder functions into the primary
-  // module.
+  // module. Ignored if `usePlaceholders` is false.
   Name placeholderNamespace = "placeholder";
   // The prefix to attach to the name of any newly created exports. This can be
   // used to differentiate between "real" exports of the module and exports that
diff --git a/src/tools/wasm-split/split-options.cpp b/src/tools/wasm-split/split-options.cpp
index 9a9351998..825efddd9 100644
--- a/src/tools/wasm-split/split-options.cpp
+++ b/src/tools/wasm-split/split-options.cpp
@@ -177,6 +177,15 @@ WasmSplitOptions::WasmSplitOptions()
          Options::Arguments::Zero,
          [&](Options* o, const std::string& argument) { symbolMap = true; })
     .add(
+      "--no-placeholders",
+      "",
+      "Do not import placeholder functions. Calls to secondary functions will "
+      "fail before the secondary module has been instantiated.",
+      WasmSplitOption,
+      {Mode::Split},
+      Options::Arguments::Zero,
+      [&](Options* o, const std::string& argument) { usePlaceholders = false; })
+    .add(
       "--placeholdermap",
       "",
       "Write a file mapping placeholder indices to the function names.",
diff --git a/src/tools/wasm-split/split-options.h b/src/tools/wasm-split/split-options.h
index 6aa5b0011..b8129f29b 100644
--- a/src/tools/wasm-split/split-options.h
+++ b/src/tools/wasm-split/split-options.h
@@ -41,6 +41,7 @@ struct WasmSplitOptions : ToolOptions {
   };
   StorageKind storageKind = StorageKind::InGlobals;
 
+  bool usePlaceholders = true;
   bool unescape = false;
   bool verbose = false;
   bool emitBinary = true;
diff --git a/src/tools/wasm-split/wasm-split.cpp b/src/tools/wasm-split/wasm-split.cpp
index c1ec6052f..cb148090d 100644
--- a/src/tools/wasm-split/wasm-split.cpp
+++ b/src/tools/wasm-split/wasm-split.cpp
@@ -329,6 +329,7 @@ void splitModule(const WasmSplitOptions& options) {
   if (options.exportPrefix.size()) {
     config.newExportPrefix = options.exportPrefix;
   }
+  config.usePlaceholders = options.usePlaceholders;
   config.minimizeNewExportNames = !options.passOptions.debugInfo;
   config.jspi = options.jspi;
   auto splitResults = ModuleSplitting::splitFunctions(wasm, config);