Fully unwrap a HCheck instruction to a real non-checked instruction. In case the check does not hav…

dart/lib/compiler/implementation/ssa/codegen.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.
 
 class SsaCodeGeneratorTask extends CompilerTask {
   final JavaScriptBackend backend;
   SsaCodeGeneratorTask(JavaScriptBackend backend)
       : this.backend = backend,
         super(backend.compiler);
   String get name() => 'SSA code generator';
@@ skipping 2269 matching lines @@
     if (!graph.entry.hasGuards()) return;
     indent--; // Close original case.
     indent--;
     addIndented('}\n');  // Close 'switch'.
     setup.add('  }\n');
   }
 
   // For instructions that reference a guard or a check, we change that
   // reference to the instruction they guard against. Therefore, we must
   // use that instruction when restoring the environment.
-  HInstruction unwrap(HInstruction argument) {
-    if (argument is HIntegerCheck) {
-      HIntegerCheck instruction = argument;
-      return unwrap(instruction.value);
-    } else if (argument is HBoundsCheck) {
-      HBoundsCheck instruction = argument;
-      return unwrap(instruction.index);
-    } else if (argument is HTypeGuard) {
-      HTypeGuard instruction = argument;
-      return unwrap(instruction.guarded);
-    } else {
-      return argument;
-    }
+  HInstruction unwrap(argument) {
+    while (argument is HCheck) argument = argument.checkedInput;
+    return argument;
   }
 
   bool visitAndOrInfo(HAndOrBlockInformation info) => false;
   bool visitIfInfo(HIfBlockInformation info) => false;
   bool visitLoopInfo(HLoopBlockInformation info) => false;
   bool visitTryInfo(HTryBlockInformation info) => false;
   bool visitSequenceInfo(HStatementSequenceInformation info) => false;
 
   void visitTypeGuard(HTypeGuard node) {
     indent--;
@@ skipping 157 matching lines @@
       startBailoutSwitch();
     }
   }
 
   void endLabeledBlock(HLabeledBlockInformation labeledBlockInfo) {
     if (labeledBlockInfo.body.start.hasGuards()) {
       endBailoutSwitch();
     }
   }
 }