3 files changed, 79 insertions, 3 deletions

diff --git a/src/asm2wasm.h b/src/asm2wasm.h
index 5bdb2a9bf..377b6b20b 100644
--- a/src/asm2wasm.h
+++ b/src/asm2wasm.h
@@ -954,9 +954,15 @@ void Asm2WasmBuilder::processAsm(Ref ast) {
     void visitCallIndirect(CallIndirect* curr) {
       // we already call into target = something + offset, where offset is a callImport with the name of the table. replace that with the table offset
       auto add = curr->target->cast<Binary>();
-      auto offset = add->right->cast<CallImport>();
-      auto tableName = offset->target;
-      add->right = parent->builder.makeConst(Literal((int32_t)parent->functionTableStarts[tableName]));
+      if (add->right->is<CallImport>()) {
+        auto offset = add->right->cast<CallImport>();
+        auto tableName = offset->target;
+        add->right = parent->builder.makeConst(Literal((int32_t)parent->functionTableStarts[tableName]));
+      } else {
+        auto offset = add->left->cast<CallImport>();
+        auto tableName = offset->target;
+        add->left = parent->builder.makeConst(Literal((int32_t)parent->functionTableStarts[tableName]));
+      }
     }
   };
 
diff --git a/src/ast/properties.h b/src/ast/properties.h
new file mode 100644
index 000000000..9834c73d0
--- /dev/null
+++ b/src/ast/properties.h
@@ -0,0 +1,60 @@
+/*
+ * 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_properties_h
+#define wasm_ast_properties_h
+
+#include "wasm.h"
+
+namespace wasm {
+
+struct Properties {
+  static bool emitsBoolean(Expression* curr) {
+    if (auto* unary = curr->dynCast<Unary>()) {
+      return unary->isRelational();
+    } else if (auto* binary = curr->dynCast<Binary>()) {
+      return binary->isRelational();
+    }
+    return false;
+  }
+
+  static bool isSymmetric(Binary* binary) {
+    switch (binary->op) {
+      case AddInt32:
+      case MulInt32: 
+      case AndInt32:
+      case OrInt32:
+      case XorInt32:
+      case EqInt32:
+      case NeInt32:
+
+      case AddInt64:
+      case MulInt64: 
+      case AndInt64:
+      case OrInt64:
+      case XorInt64:
+      case EqInt64:
+      case NeInt64: return true;
+
+      default: return false;
+    }
+  }
+};
+
+} // wasm
+
+#endif // wams_ast_properties_h
+
diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
index 7f1483371..a5c665458 100644
--- a/src/passes/OptimizeInstructions.cpp
+++ b/src/passes/OptimizeInstructions.cpp
@@ -25,6 +25,7 @@
 #include <wasm-s-parser.h>
 #include <support/threads.h>
 #include <ast_utils.h>
+#include <ast/properties.h>
 
 namespace wasm {
 
@@ -197,6 +198,12 @@ struct OptimizeInstructions : public WalkerPass<PostWalker<OptimizeInstructions,
   // Optimizations that don't yet fit in the pattern DSL, but could be eventually maybe
   Expression* handOptimize(Expression* curr) {
     if (auto* binary = curr->dynCast<Binary>()) {
+      if (Properties::isSymmetric(binary)) {
+        // canonicalize a const to the second position
+        if (binary->left->is<Const>() && !binary->right->is<Const>()) {
+          std::swap(binary->left, binary->right);
+        }
+      }
       // pattern match a load of 8 bits and a sign extend using a shl of 24 then shr_s of 24 as well, etc.
       if (binary->op == BinaryOp::ShrSInt32 && binary->right->is<Const>()) {
         auto shifts = binary->right->cast<Const>()->value.geti32();
@@ -238,6 +245,9 @@ struct OptimizeInstructions : public WalkerPass<PostWalker<OptimizeInstructions,
                 load->signed_ = false;
                 return load;
               }
+            } else if (mask == 1 && Properties::emitsBoolean(binary->left)) {
+              // (bool) & 1 does not need the outer mask
+              return binary->left;
             }
           }
         }