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

src/arm/lithium-arm.cc

Index: src/arm/lithium-arm.cc
diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index edc1120c5bb5665444b2117848ed632704de4186..ce8f7e09b5e8d03ec16c04fcaba49d3d3a0848d0 100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -1822,7 +1822,7 @@ 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);