start work on SimplifyLocals

1 files changed, 43 insertions, 0 deletions

diff --git a/src/passes/SimplifyLocals.cpp b/src/passes/SimplifyLocals.cpp
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+++ b/src/passes/SimplifyLocals.cpp
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+/*
+ * Copyright 2015 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.
+ */
+
+//
+// Miscellaneous locals-related optimizations
+//
+
+#include <wasm.h>
+#include <pass.h>
+
+namespace wasm {
+
+struct SimplifyLocals : public Pass {
+  void visitBlock(Block *curr) override {
+    // look for pairs of setlocal-getlocal, which can be just a setlocal (since it returns a value)
+    for (size_t i = 0; i < curr->list.size() - 1; i++) {
+      auto set = curr->list[i]->dyn_cast<SetLocal>();
+      if (!set) continue;
+      auto get = curr->list[i + 1]->dyn_cast<GetLocal>();
+      if (!get) continue;
+      if (set->name != get->name) continue;
+      curr->list.erase(curr->list.begin() + i + 1);
+      i -= 1;
+    }
+  }
+};
+
+static RegisterPass<SimplifyLocals> registerPass("simplify-locals", "miscellaneous locals-related optimizations");
+
+} // namespace wasm