Some improvements in register usage in lithium compilation of LoadKeyed/StoreKeyed operations.

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 a874a2400aa1a850eb924ceb83c0df8f02b03519..c6004e51b715d25b48dd0dbc0152ff0d66d8d4ae 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1844,16 +1844,15 @@ LInstruction* LChunkBuilder::DoLoadKeyed(HLoadKeyed* instr) {
   ASSERT(instr->key()->representation().IsInteger32() ||
          instr->key()->representation().IsTagged());
   ElementsKind elements_kind = instr->elements_kind();
-  bool clobbers_key = instr->key()->representation().IsTagged();
+  bool clobbers_key = ArrayOpClobbersKey<HLoadKeyed>(instr);
   LOperand* key = clobbers_key
       ? UseTempRegister(instr->key())
       : UseRegisterOrConstantAtStart(instr->key());
-  LLoadKeyed* result = NULL;
+  LOperand* elements = UseRegisterAtStart(instr->elements());
+  LLoadKeyed* result = new(zone()) LLoadKeyed(elements, key);
 
-  if (!instr->is_external()) {
-    LOperand* obj = UseRegisterAtStart(instr->elements());
-    result = new(zone()) LLoadKeyed(obj, key);
-  } else {
+#ifdef DEBUG
+  if (instr->is_external()) {
     ASSERT(
         (instr->representation().IsInteger32() &&
          (elements_kind != EXTERNAL_FLOAT_ELEMENTS) &&
@@ -1861,9 +1860,8 @@ 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);
   }
+#endif
 
   DefineAsRegister(result);
   bool can_deoptimize = instr->RequiresHoleCheck() ||
@@ -1884,33 +1882,21 @@ LInstruction* LChunkBuilder::DoLoadKeyedGeneric(HLoadKeyedGeneric* instr) {
 
 
 LInstruction* LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
-  ElementsKind elements_kind = instr->elements_kind();
   bool needs_write_barrier = instr->NeedsWriteBarrier();
-  bool clobbers_key = instr->key()->representation().IsTagged();
+  bool clobbers_key = ArrayOpClobbersKey<HStoreKeyed>(instr);
   LOperand* key = (clobbers_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 = (needs_write_barrier || val_is_temp_register)
+  LOperand* val = needs_write_barrier
       ? UseTempRegister(instr->value())
       : UseRegisterAtStart(instr->value());
-  LStoreKeyed* result = NULL;
+  LOperand* elements = UseRegisterAtStart(instr->elements());
 
+#ifdef DEBUG
   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) &&
@@ -1919,11 +1905,10 @@ 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;
 }