Use the correct inputs when checking if inverse operator can be used.

lib/compiler/implementation/ssa/codegen.dart

Index: lib/compiler/implementation/ssa/codegen.dart
diff --git a/lib/compiler/implementation/ssa/codegen.dart b/lib/compiler/implementation/ssa/codegen.dart
index db2c5005505abe97003b41478f0f41ecaa7b6768..16081b16dc27b91592582710d33730c1e5bf7cfe 100644
--- a/lib/compiler/implementation/ssa/codegen.dart
+++ b/lib/compiler/implementation/ssa/codegen.dart
@@ -1789,23 +1789,23 @@ abstract class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
 
 
   void generateNot(HInstruction input) {
-    bool isBuiltinRelational(HInstruction instruction) {
+    bool canGenerateOptimizedComparison(HInstruction instruction) {
       if (instruction is !HRelational) return false;
       HRelational relational = instruction;
-      return relational.isBuiltin(types);
+      HInstruction left = relational.left;
+      HInstruction right = relational.right;
+      // This optimization doesn't work for NaN, so we only do it if the
+      // type is known to be an integer.
+      return relational.isBuiltin(types)
+          && types[left].isUseful() && left.isInteger(types)
+          && types[right].isUseful() && right.isInteger(types);
     }
 
     if (input is HBoolify && isGenerateAtUseSite(input)) {
       use(input.inputs[0]);
       push(new js.Binary("!==", pop(), new js.LiteralBool(true)), input);
-    } else if (isBuiltinRelational(input) &&
-               isGenerateAtUseSite(input) &&
-               types[input.inputs[0]].isUseful() &&
-               !input.inputs[0].isDouble(types) &&
-               types[input.inputs[1]].isUseful() &&
-               !input.inputs[1].isDouble(types)) {
-      // This optimization doesn't work for NaN, so we only do it if the
-      // type is known to be non-Double.
+    } else if (canGenerateOptimizedComparison(input) &&
+               isGenerateAtUseSite(input)) {
       Map<String, String> inverseOperator = const <String, String>{
         "==" : "!=",
         "!=" : "==",
@@ -1817,9 +1817,8 @@ abstract class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
         ">=" : "<"
       };
       HRelational relational = input;
-      
-      visitInvokeBinary(input,
-                        inverseOperator[relational.operation.name.stringValue]);
+      BinaryOperation operation = relational.operation(backend.constantSystem);
+      visitInvokeBinary(input, inverseOperator[operation.name.stringValue]);
     } else {
       use(input);
       push(new js.Prefix("!", pop()));