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sdk/lib/_internal/compiler/implementation/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.
 
 part of ssa;
 
 /**
  * Instead of emitting each SSA instruction with a temporary variable
  * mark instructions that can be emitted at their use-site.
  * For example, in:
@@ skipping 246 matching lines @@
     return false;
   }
 
   bool isSafeToGenerateAtUseSite(HInstruction user, HInstruction input) {
     // A [HForeign] instruction uses operators and if we generate
     // [input] at use site, the precedence might be wrong.
     if (user is HForeign) return false;
     // A [HCheck] instruction with control flow uses its input
     // multiple times, so we avoid generating it at use site.
     if (user is HCheck && user.isControlFlow()) return false;
-    // A [HIs] instruction uses its input multiple times, so we
-    // avoid generating it at use site.
-    if (user is HIs) return false;
     return true;
   }
 
   void visitBasicBlock(HBasicBlock block) {
     if (block.last is !HIf) return;
     HIf startIf = block.last;
     HBasicBlock end = startIf.joinBlock;
 
     // We check that the structure is the following:
     //         If
@@ skipping 87 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);
     }
   }
 }