Reapply "Avoid "=== true" inside code by calling a function that does this for us."

lib/compiler/implementation/ssa/optimize.dart

Index: lib/compiler/implementation/ssa/optimize.dart
diff --git a/lib/compiler/implementation/ssa/optimize.dart b/lib/compiler/implementation/ssa/optimize.dart
index b4eee8611116d9f37a58f8dfd44cc719220d12ab..b93e18428ca2f76741f98a1cf5f652773166576e 100644
--- a/lib/compiler/implementation/ssa/optimize.dart
+++ b/lib/compiler/implementation/ssa/optimize.dart
@@ -293,6 +293,43 @@ class SsaConstantFolder extends HBaseVisitor implements OptimizationPhase {
     return node;
   }
 
+  bool allUsersAreBoolifies(HInstruction instruction) {
+    List<HInstruction> users = instruction.usedBy;
+    int length = users.length;
+    for (int i = 0; i < length; i++) {
+      if (users[i] is! HBoolify) return false;
+    }
+    return true;
+  }
+
+  HInstruction visitRelational(HRelational node) {
+    if (allUsersAreBoolifies(node)) {
+      Interceptors interceptors = compiler.builder.interceptors;
+      HStatic oldTarget = node.target;
+      Element boolifiedInterceptor =
+          interceptors.getBoolifiedVersionOf(oldTarget.element);
+      if (boolifiedInterceptor !== null) {
+        HStatic boolifiedTarget = new HStatic(boolifiedInterceptor);
+        // We don't remove the [oldTarget] in case it is used by other
+        // instructions. If it is unused it will be treated as dead code and
+        // discarded.
+        oldTarget.block.addAfter(oldTarget, boolifiedTarget);
+        // Remove us as user from the [oldTarget].
+        HBasicBlock.removeUser(oldTarget, node);
+        // Replace old target with boolified target.
+        assert(node.target == node.inputs[0]);
+        node.inputs[0] = boolifiedTarget;
+        boolifiedTarget.usedBy.add(node);
+        node.usesBoolifiedInterceptor = true;
+        node.propagatedType = HType.BOOLEAN;
+      }
+      // This node stays the same, but the Boolify node will go away.
+    }
+    // Note that we still have to call [super] to make sure that we end up
+    // in the remaining optimizations.
+    return super.visitRelational(node);
+  }
+
   HInstruction handleIdentityCheck(HInvokeBinary node) {
     HInstruction left = node.left;
     HInstruction right = node.right;
@@ -354,7 +391,7 @@ class SsaConstantFolder extends HBaseVisitor implements OptimizationPhase {
     }
 
     if (left.isConstant() && right.isConstant()) {
-      return visitInvokeBinary(node);
+      return super.visitEquals(node);
     }
 
     if (left.isNonPrimitive()) {
@@ -364,7 +401,7 @@ class SsaConstantFolder extends HBaseVisitor implements OptimizationPhase {
         // 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);
+        return super.visitEquals(node);
       } else if (right.isConstantNull()) {
         return graph.addConstantBool(false);
       } else {
@@ -379,15 +416,27 @@ class SsaConstantFolder extends HBaseVisitor implements OptimizationPhase {
         return graph.addConstantBool(false);
       } else {
         // TODO(floitsch): cache interceptors.
-        HStatic target = new HStatic(
-            compiler.builder.interceptors.getEqualsNullInterceptor());
+        Interceptors interceptors = compiler.builder.interceptors;
+        Element targetElement = interceptors.getEqualsNullInterceptor();
+        bool onlyUsedInBoolify = allUsersAreBoolifies(node);
+        if (onlyUsedInBoolify) {
+          targetElement = interceptors.getBoolifiedVersionOf(targetElement);
+        }
+        HStatic target = new HStatic(targetElement);
         node.block.addBefore(node, target);
-        return new HEquals(target, node.left, node.right);
+        HEquals result = new HEquals(target, node.left, node.right);
+        if (onlyUsedInBoolify) {
+          result.usesBoolifiedInterceptor = true;
+          result.propagatedType = HType.BOOLEAN;
+        }
+        return result;
       }
     }
 
-    // All other cases are dealt with by the [visitInvokeBinary].
-    return visitInvokeBinary(node);
+    // All other cases are dealt with by the [visitRelational] and
+    // [visitInvokeBinary], which are visited by invoking the [super]'s
+    // visit method.
+    return super.visitEquals(node);
   }
 
   HInstruction visitTypeGuard(HTypeGuard node) {