A64: Relax the register constraints for LSeqStringGetChar.

src/a64/lithium-a64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
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 //
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@@ skipping 1996 matching lines @@
   LOperand* context = info()->IsStub()
       ? UseFixed(instr->context(), cp)
       : NULL;
   LOperand* parameter_count = UseRegisterOrConstant(instr->parameter_count());
   return new(zone()) LReturn(UseFixed(instr->value(), x0), context,
                              parameter_count);
 }
 
 
 LInstruction* LChunkBuilder::DoSeqStringGetChar(HSeqStringGetChar* instr) {
-  // TODO(all): Use UseRegisterAtStart and UseRegisterOrConstantAtStart here.
-  // We cannot do it now because the debug code in the implementation changes
-  // temp.
-  LOperand* string = UseRegister(instr->string());
-  LOperand* index = UseRegisterOrConstant(instr->index());
+  LOperand* string = UseRegisterAtStart(instr->string());
+  LOperand* index = UseRegisterOrConstantAtStart(instr->index());
   LOperand* temp = TempRegister();
   LSeqStringGetChar* result =
       new(zone()) LSeqStringGetChar(string, index, temp);
   return DefineAsRegister(result);
 }
 
 
 LInstruction* LChunkBuilder::DoSeqStringSetChar(HSeqStringSetChar* instr) {
   LOperand* string = UseRegister(instr->string());
   LOperand* index = FLAG_debug_code
@@ skipping 531 matching lines @@
 
 LInstruction* LChunkBuilder::DoWrapReceiver(HWrapReceiver* instr) {
   LOperand* receiver = UseRegister(instr->receiver());
   LOperand* function = UseRegister(instr->function());
   LWrapReceiver* result = new(zone()) LWrapReceiver(receiver, function);
   return AssignEnvironment(DefineAsRegister(result));
 }
 
 
 } }  // namespace v8::internal