Better constant fold identity checks. (100 bytes saved on swarm, yeah! :))

lib/compiler/implementation/ssa/optimize.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 interface OptimizationPhase {
   String get name();
   void visitGraph(HGraph graph);
 }
 
 class SsaOptimizerTask extends CompilerTask {
@@ skipping 275 matching lines @@
     }
 
     if (left.isNonPrimitive() && node.operation.isUserDefinable()) {
       SourceString methodName = Elements.constructOperatorName(
           const SourceString('operator'), node.operation.name);
       return fromInterceptorToDynamicInvocation(node, methodName);
     }
     return node;
   }
 
+  HInstruction handleIdentityCheck(HInvokeBinary node) {
+    HInstruction left = node.left;
+    HInstruction right = node.right;
+    HType leftType = left.propagatedType;
+    HType rightType = right.propagatedType;
+    assert(!leftType.isConflicting() && !rightType.isConflicting());
+
+    // We don't optimize on numbers to preserve the runtime semantics.
+    if (!(left.isNumber() && right.isNumber()) &&
+        leftType.intersection(rightType).isConflicting()) {
+      return graph.addConstantBool(false);
+    }
+
+    if (left.isConstantBoolean() && right.isBoolean()) {
+      HConstant constant = left;
+      if (constant.constant.isTrue()) {
+        return right;
+      } else {
+        return new HNot(right);
+      }
+    }
+
+    if (right.isConstantBoolean() && left.isBoolean()) {
+      HConstant constant = right;
+      if (constant.constant.isTrue()) {
+        return left;
+      } else {
+        return new HNot(left);
+      }
+    }
+
+    return null;
+  }
+
+  HInstruction visitIdentity(HIdentity node) {
+    HInstruction newInstruction = handleIdentityCheck(node);
+    return newInstruction === null ? super.visitIdentity(node) : newInstruction;
+  }
+
+  HInstruction foldBuiltinEqualsCheck(HEquals node) {
+    // TODO(floitsch): cache interceptors.
+    HInstruction newInstruction = handleIdentityCheck(node);
+    if (newInstruction === null) {
+      HStatic target = new HStatic(
+          compiler.builder.interceptors.getTripleEqualsInterceptor());
+      node.block.addBefore(node, target);
+      return new HIdentity(target, node.left, node.right);
+    } else {
+      return newInstruction;
+    }
+  }
+
   HInstruction visitEquals(HEquals node) {
     HInstruction left = node.left;
     HInstruction right = node.right;
 
+    if (node.builtin) {
+      return foldBuiltinEqualsCheck(node);
+    }
+
     if (left.isConstant() && right.isConstant()) {
       return visitInvokeBinary(node);
     }
 
     if (left.isNonPrimitive()) {
       HNonPrimitiveType type = left.propagatedType;
       Element element = type.lookupMember(Namer.OPERATOR_EQUALS);
       if (element !== null) {
         // If the left-hand side is guaranteed to be a non-primitive
         // type and and it defines operator==, we emit a call to that
         // operator.
         return visitInvokeBinary(node);
       } else if (right.isConstantNull()) {
         return graph.addConstantBool(false);
       } else {
         // We can just emit an identity check because the type does
         // not implement operator=.
-        // TODO(floitsch): cache interceptors.
-        HStatic target = new HStatic(
-            compiler.builder.interceptors.getTripleEqualsInterceptor());
-        node.block.addBefore(node, target);
-        return new HIdentity(target, left, right);
+        return foldBuiltinEqualsCheck(node);
       }
     }
 
-
     if (right.isConstantNull()) {
       if (left.propagatedType.isUseful()) {
         return graph.addConstantBool(false);
       } else {
         // TODO(floitsch): cache interceptors.
         HStatic target = new HStatic(
             compiler.builder.interceptors.getEqualsNullInterceptor());
         node.block.addBefore(node, target);
         return new HEquals(target, node.left, node.right);
       }
@@ skipping 529 matching lines @@
         }
       }
       if (!canBeMoved) continue;
 
       // This is safe because we are running after GVN.
       // TODO(ngeoffray): ensure GVN has been run.
       set_.add(current);
     }
   }
 }