4 files changed, 72 insertions, 0 deletions
diff --git a/src/asmjs/shared-constants.cpp b/src/asmjs/shared-constants.cpp
index e30fd939c..d704c8009 100644
--- a/src/asmjs/shared-constants.cpp
+++ b/src/asmjs/shared-constants.cpp
@@ -49,6 +49,7 @@ cashew::IString GLOBAL("global"),
                 FLOOR("floor"),
                 CEIL("ceil"),
                 SQRT("sqrt"),
+                POW("pow"),
                 I32_TEMP("asm2wasm_i32_temp"),
                 DEBUGGER("debugger"),
                 USE_ASM("use asm"),
diff --git a/src/asmjs/shared-constants.h b/src/asmjs/shared-constants.h
index e0c627511..7b48c3df5 100644
--- a/src/asmjs/shared-constants.h
+++ b/src/asmjs/shared-constants.h
@@ -52,6 +52,7 @@ extern cashew::IString GLOBAL,
                 FLOOR,
                 CEIL,
                 SQRT,
+                POW,
                 I32_TEMP,
                 DEBUGGER,
                 USE_ASM,
diff --git a/src/ast/localize.h b/src/ast/localize.h
new file mode 100644
index 000000000..9e7dd6653
--- /dev/null
+++ b/src/ast/localize.h
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2016 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.
+ */
+
+#ifndef wasm_ast_localizer_h
+#define wasm_ast_localizer_h
+
+#include <wasm-builder.h>
+
+namespace wasm {
+
+// Make an expression available in a local. If already in one, just
+// use that local, otherwise use a new local
+
+struct Localizer {
+  Index index;
+  Expression* expr;
+
+  Localizer(Expression* input, Function* func, Module* wasm) {
+    expr = input;
+    if (auto* get = expr->dynCast<GetLocal>()) {
+      index = get->index;
+    } else if (auto* set = expr->dynCast<SetLocal>()) {
+      index = set->index;
+    } else {
+      index = Builder::addVar(func, expr->type);
+      expr = Builder(*wasm).makeTeeLocal(index, expr);
+    }
+  }
+};
+
+} // namespace wasm
+
+#endif // wasm_ast_localizer_h
+
diff --git a/src/passes/PostEmscripten.cpp b/src/passes/PostEmscripten.cpp
index 51b8c2ec1..937a70e36 100644
--- a/src/passes/PostEmscripten.cpp
+++ b/src/passes/PostEmscripten.cpp
@@ -21,6 +21,9 @@
 
 #include <wasm.h>
 #include <pass.h>
+#include <wasm-builder.h>
+#include <ast/localize.h>
+#include <asmjs/shared-constants.h>
 
 namespace wasm {
 
@@ -88,6 +91,26 @@ struct PostEmscripten : public WalkerPass<PostWalker<PostEmscripten>> {
   void visitStore(Store* curr) {
     optimizeMemoryAccess(curr->ptr, curr->offset);
   }
+
+  void visitCallImport(CallImport* curr) {
+    // special asm.js imports can be optimized
+    auto* import = getModule()->getImport(curr->target);
+    if (import->module == GLOBAL_MATH) {
+      if (import->base == POW) {
+        if (auto* exponent = curr->operands[1]->dynCast<Const>()) {
+          if (exponent->value == Literal(double(2.0))) {
+            // This is just a square operation, do a multiply
+            Localizer localizer(curr->operands[0], getFunction(), getModule());
+            Builder builder(*getModule());
+            replaceCurrent(builder.makeBinary(MulFloat64, localizer.expr, builder.makeGetLocal(localizer.index, localizer.expr->type)));
+          } else if (exponent->value == Literal(double(0.5))) {
+            // This is just a square root operation
+            replaceCurrent(Builder(*getModule()).makeUnary(SqrtFloat64, curr->operands[0]));
+          }
+        }
+      }
+    }
+  }
 };
 
 Pass *createPostEmscriptenPass() {