1 files changed, 67 insertions, 0 deletions
diff --git a/src/passes/DuplicateImportElimination.cpp b/src/passes/DuplicateImportElimination.cpp
new file mode 100644
index 000000000..39b126b6c
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+++ b/src/passes/DuplicateImportElimination.cpp
@@ -0,0 +1,67 @@
+/*
+ * Copyright 2019 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//
+// Removes duplicate imports.
+//
+// TODO: non-function imports too
+//
+
+#include "asm_v_wasm.h"
+#include "ir/import-utils.h"
+#include "opt-utils.h"
+#include "pass.h"
+#include "wasm.h"
+
+namespace wasm {
+
+struct DuplicateImportElimination : public Pass {
+  void run(PassRunner* runner, Module* module) override {
+    ImportInfo imports(*module);
+    std::map<Name, Name> replacements;
+    std::map<std::pair<Name, Name>, Name> seen;
+    std::vector<Name> toRemove;
+    for (auto* func : imports.importedFunctions) {
+      auto pair = std::make_pair(func->module, func->base);
+      auto iter = seen.find(pair);
+      if (iter != seen.end()) {
+        auto previousName = iter->second;
+        auto previousFunc = module->getFunction(previousName);
+        // It is ok to import the same thing with multiple types; we can only
+        // merge if the types match, of course.
+        if (getSig(previousFunc) == getSig(func)) {
+          replacements[func->name] = previousName;
+          toRemove.push_back(func->name);
+          continue;
+        }
+      }
+      seen[pair] = func->name;
+    }
+    if (!replacements.empty()) {
+      module->updateMaps();
+      OptUtils::replaceFunctions(runner, *module, replacements);
+      for (auto name : toRemove) {
+        module->removeFunction(name);
+      }
+    }
+  }
+};
+
+Pass* createDuplicateImportEliminationPass() {
+  return new DuplicateImportElimination();
+}
+
+} // namespace wasm