Revert change r12912 due to x64 perf issue

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 17f3325b754c3449f682425313062cf438c8d581..ff6da03bb5811260b4add49b34bc8dff5bb838c6 100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -1881,7 +1881,6 @@ LInstruction* LChunkBuilder::DoLoadKeyed(HLoadKeyed* instr) {
         (instr->representation().IsDouble() &&
          ((elements_kind == EXTERNAL_FLOAT_ELEMENTS) ||
           (elements_kind == EXTERNAL_DOUBLE_ELEMENTS))));
-
     LOperand* external_pointer = UseRegister(instr->elements());
     result = new(zone()) LLoadKeyed(external_pointer, key);
   }
@@ -1906,22 +1905,32 @@ LInstruction* LChunkBuilder::DoLoadKeyedGeneric(HLoadKeyedGeneric* instr) {
 
 
 LInstruction* LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
-  LOperand* elements = UseRegisterAtStart(instr->elements());
-  LOperand* key;
-  LOperand* val;
-  if (instr->NeedsWriteBarrier()) {
-    key = UseTempRegister(instr->key());
-    val = UseTempRegister(instr->value());
-  } else {
-    key = UseRegisterOrConstantAtStart(instr->key());
-    val = UseRegisterAtStart(instr->value());
-  }
+  ElementsKind elements_kind = instr->elements_kind();
+  bool needs_write_barrier = instr->NeedsWriteBarrier();
+  LOperand* key = needs_write_barrier
+      ? UseTempRegister(instr->key())
+      : UseRegisterOrConstantAtStart(instr->key());
+  bool val_is_temp_register =
+      elements_kind == EXTERNAL_PIXEL_ELEMENTS ||
+      elements_kind == EXTERNAL_FLOAT_ELEMENTS;
+  LOperand* val = val_is_temp_register || needs_write_barrier
+      ? UseTempRegister(instr->value())
+      : UseRegister(instr->value());
 
-#ifdef DEBUG
+  LStoreKeyed* result = NULL;
   if (!instr->is_external()) {
     ASSERT(instr->elements()->representation().IsTagged());
+
+    LOperand* object = NULL;
+    if (instr->value()->representation().IsDouble()) {
+      object = UseRegisterAtStart(instr->elements());
+    } else {
+      ASSERT(instr->value()->representation().IsTagged());
+      object = UseTempRegister(instr->elements());
+    }
+
+    result = new(zone()) LStoreKeyed(object, key, val);
   } else {
-    ElementsKind elements_kind = instr->elements_kind();
     ASSERT(
         (instr->value()->representation().IsInteger32() &&
          (elements_kind != EXTERNAL_FLOAT_ELEMENTS) &&
@@ -1930,10 +1939,11 @@ LInstruction* LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
          ((elements_kind == EXTERNAL_FLOAT_ELEMENTS) ||
           (elements_kind == EXTERNAL_DOUBLE_ELEMENTS))));
     ASSERT(instr->elements()->representation().IsExternal());
+
+    LOperand* external_pointer = UseRegister(instr->elements());
+    result = new(zone()) LStoreKeyed(external_pointer, key, val);
   }
-#endif
 
-  LStoreKeyed* result = new(zone()) LStoreKeyed(elements, key, val);
   ASSERT(result != NULL);
   return result;
 }