A64: Synchronize with r17525.

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index 6262e7ede37719d537224d211569a945341ce68b..d90736a1673f3c35761ee81502455c9aec137035 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1757,13 +1757,10 @@ LInstruction* LChunkBuilder::DoDateField(HDateField* instr) {
 
 
 LInstruction* LChunkBuilder::DoSeqStringSetChar(HSeqStringSetChar* instr) {
-  LOperand* string = UseRegister(instr->string());
-  LOperand* index = UseRegister(instr->index());
-  ASSERT(rcx.is_byte_register());
-  LOperand* value = UseFixed(instr->value(), rcx);
-  LSeqStringSetChar* result =
-      new(zone()) LSeqStringSetChar(instr->encoding(), string, index, value);
-  return DefineSameAsFirst(result);
+  LOperand* string = UseRegisterAtStart(instr->string());
+  LOperand* index = UseRegisterOrConstantAtStart(instr->index());
+  LOperand* value = UseRegisterOrConstantAtStart(instr->value());
+  return new(zone()) LSeqStringSetChar(string, index, value);
 }