Fix generateAtUseSite for complex HIs checks

pkg/compiler/lib/src/ssa/codegen_helpers.dart

 // Copyright (c) 2012, 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.
 
 import '../compiler.dart' show Compiler;
 import '../constants/values.dart';
 import '../elements/elements.dart';
 import '../js_backend/js_backend.dart';
 import '../types/types.dart';
 import '../universe/selector.dart' show Selector;
@@ skipping 422 matching lines @@
     // to be generated at use site, and only analyze all other arguments.
     if (!backend.canUseAliasedSuperMember(superMethod, selector)) {
       analyzeInputs(instruction, 1);
     } else {
       super.visitInvokeSuper(instruction);
     }
   }
 
   void visitIs(HIs instruction) {
     // In the general case the input might be used multple multiple times, so it
-    // must not be set generate at use site.  If the code will generate
-    // 'instanceof' then we can generate at use site.
+    // must not be set generate at use site.
+
+    // If the code will generate 'instanceof' then we can generate at use site.
     if (instruction.useInstanceOf) {
       analyzeInputs(instruction, 0);
     }
+
+    // Compound and variable checks use a separate instruction to compute the
+    // result.
+    if (instruction.isCompoundCheck || instruction.isVariableCheck) {
+      analyzeInputs(instruction, 0);
+    }
   }
 
   // A bounds check method must not have its first input generated at use site,
   // because it's using it twice.
   void visitBoundsCheck(HBoundsCheck instruction) {
     analyzeInputs(instruction, 1);
   }
 
   // An identity operation must only have its inputs generated at use site if
   // does not require an expression with multiple uses (because of null /
@@ skipping 330 matching lines @@
     }
 
     // If [thenInput] is defined in the first predecessor, then it is only used
     // by [phi] and can be generated at use site.
     if (identical(thenInput.block, end.predecessors[0])) {
       assert(thenInput.usedBy.length == 1);
       markAsGenerateAtUseSite(thenInput);
     }
   }
 }