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

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 4207410cdf28c4dbc5c9c779da85436c7ac0a32f..ba9c97eba215922c87fc43ba459d75527452c364 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -1933,17 +1933,14 @@ LInstruction* LChunkBuilder::DoLoadKeyed(HLoadKeyed* instr) {
   ASSERT(instr->key()->representation().IsInteger32() ||
          instr->key()->representation().IsTagged());
   ElementsKind elements_kind = instr->elements_kind();
-  bool clobbers_key = ExternalArrayOpRequiresTemp(
-      instr->key()->representation(), elements_kind);
-  LOperand* key = clobbers_key
+  LOperand* elements = UseRegisterAtStart(instr->elements());
+  LOperand* key = instr->is_external() &&
+    ExternalArrayOpRequiresTemp<HLoadKeyed>(instr)
       ? UseTempRegister(instr->key())
       : UseRegisterOrConstantAtStart(instr->key());
-  LLoadKeyed* result = NULL;
 
-  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) &&
@@ -1951,10 +1948,10 @@ 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
 
+  LLoadKeyed* result = new(zone()) LLoadKeyed(elements, key);
   DefineAsRegister(result);
   bool can_deoptimize = instr->RequiresHoleCheck() ||
       (elements_kind == EXTERNAL_UNSIGNED_INT_ELEMENTS);
@@ -1976,34 +1973,27 @@ LInstruction* LChunkBuilder::DoLoadKeyedGeneric(HLoadKeyedGeneric* instr) {
 
 
 LInstruction* LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
-  LStoreKeyed* result = NULL;
+  ElementsKind elements_kind = instr->elements_kind();
+  LOperand* elements;
+  LOperand* val;
+  LOperand* key;
 
   if (!instr->is_external()) {
     ASSERT(instr->elements()->representation().IsTagged());
     ASSERT(instr->key()->representation().IsInteger32() ||
            instr->key()->representation().IsTagged());
 
-    if (instr->value()->representation().IsDouble()) {
-      LOperand* object = UseRegisterAtStart(instr->elements());
-      LOperand* val = UseTempRegister(instr->value());
-      LOperand* key = UseRegisterOrConstantAtStart(instr->key());
-
-      result = new(zone()) LStoreKeyed(object, key, val);
+    if (instr->NeedsWriteBarrier() &&
+        !IsFastDoubleElementsKind(elements_kind)) {
+      val = UseTempRegister(instr->value());
+      key = UseTempRegister(instr->key());
+      elements = UseRegister(instr->elements());
     } else {
-      ASSERT(instr->value()->representation().IsTagged());
-      bool needs_write_barrier = instr->NeedsWriteBarrier();
-
-      LOperand* obj = UseRegister(instr->elements());
-      LOperand* val = needs_write_barrier
-          ? UseTempRegister(instr->value())
-          : UseRegisterAtStart(instr->value());
-      LOperand* key = needs_write_barrier
-          ? UseTempRegister(instr->key())
-          : UseRegisterOrConstantAtStart(instr->key());
-      result = new(zone()) LStoreKeyed(obj, key, val);
+      val = UseRegisterAtStart(instr->value());
+      key = UseRegisterOrConstantAtStart(instr->key());
+      elements = UseRegisterAtStart(instr->elements());
     }
   } else {
-    ElementsKind elements_kind = instr->elements_kind();
     ASSERT(
         (instr->value()->representation().IsInteger32() &&
          (elements_kind != EXTERNAL_FLOAT_ELEMENTS) &&
@@ -2013,26 +2003,25 @@ LInstruction* LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
           (elements_kind == EXTERNAL_DOUBLE_ELEMENTS))));
     ASSERT(instr->elements()->representation().IsExternal());
 
-    LOperand* external_pointer = UseRegister(instr->elements());
+    if (ExternalArrayOpRequiresTemp<HStoreKeyed>(instr)) {
+      key = UseTempRegister(instr->key());
+      elements = UseRegister(instr->elements());
+    } else {
+      key = UseRegisterOrConstantAtStart(instr->key());
+      elements = UseRegisterAtStart(instr->elements());
+    }
+
     // Determine if we need a byte register in this case for the value.
     bool val_is_fixed_register =
         elements_kind == EXTERNAL_BYTE_ELEMENTS ||
         elements_kind == EXTERNAL_UNSIGNED_BYTE_ELEMENTS ||
         elements_kind == EXTERNAL_PIXEL_ELEMENTS;
-
-    LOperand* val = val_is_fixed_register
+    val = val_is_fixed_register
         ? UseFixed(instr->value(), eax)
         : UseRegister(instr->value());
-    bool clobbers_key = ExternalArrayOpRequiresTemp(
-        instr->key()->representation(), elements_kind);
-    LOperand* key = clobbers_key
-        ? UseTempRegister(instr->key())
-        : UseRegisterOrConstantAtStart(instr->key());
-    result = new(zone()) LStoreKeyed(external_pointer,
-                                     key,
-                                     val);
   }
 
+  LStoreKeyed* result = new(zone()) LStoreKeyed(elements, key, val);
   ASSERT(result != NULL);
   return result;
 }