Fix code gen bug on arm and mips; SeqStringSetChar overwrites a register; Add better default PrintD…

src/mips/lithium-mips.cc

Index: src/mips/lithium-mips.cc
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index 21963255899796d932daf8a6437ac75389b8c285..5ca8cd9b96c69fef24d28a699391eb7c267061d5 100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -1699,7 +1699,7 @@ LInstruction* LChunkBuilder::DoDateField(HDateField* instr) {
 LInstruction* LChunkBuilder::DoSeqStringSetChar(HSeqStringSetChar* instr) {
   LOperand* string = UseRegister(instr->string());
   LOperand* index = UseRegister(instr->index());
-  LOperand* value = UseRegister(instr->value());
+  LOperand* value = UseTempRegister(instr->value());
   LSeqStringSetChar* result =
       new(zone()) LSeqStringSetChar(instr->encoding(), string, index, value);
   return DefineAsRegister(result);