Lithium: avoid registers for constants when possible.

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 6707455efb7b2f66e6b9e9ea141bf5cc5320876a..5a9a65394db0b0c87032b72b82150655db700801 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -557,6 +557,11 @@ LOperand* LChunkBuilder::UseRegisterOrConstantAtStart(HValue* value) {
 }
 
 
+LOperand* LChunkBuilder::UseConstant(HValue* value) {
+  return chunk_->DefineConstantOperand(HConstant::cast(value));
+}
+
+
 LOperand* LChunkBuilder::UseAny(HValue* value) {
   return value->IsConstant()
       ? chunk_->DefineConstantOperand(HConstant::cast(value))
@@ -2115,19 +2120,6 @@ LInstruction* LChunkBuilder::DoLoadKeyedGeneric(HLoadKeyedGeneric* instr) {
 }
 
 
-// DoStoreKeyed and DoStoreNamedField have special considerations for allowing
-// use of a constant instead of a register.
-static bool StoreConstantValueAllowed(HValue* value) {
-  if (value->IsConstant()) {
-    HConstant* constant_value = HConstant::cast(value);
-    return constant_value->HasSmiValue()
-        || constant_value->HasDoubleValue()
-        || constant_value->ImmortalImmovable();
-  }
-  return false;
-}
-
-
 LInstruction* LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
   ElementsKind elements_kind = instr->elements_kind();
   bool clobbers_key = instr->key()->representation().IsTagged();
@@ -2151,18 +2143,12 @@ LInstruction* LChunkBuilder::DoStoreKeyed(HStoreKeyed* instr) {
         val = UseTempRegister(instr->value());
         key = UseTempRegister(instr->key());
       } else {
-        if (StoreConstantValueAllowed(instr->value())) {
-          val = UseRegisterOrConstantAtStart(instr->value());
-        } else {
-          val = UseRegisterAtStart(instr->value());
-        }
+        val = UseRegisterOrConstantAtStart(instr->value());
 
         if (clobbers_key) {
           key = UseTempRegister(instr->key());
-        } else if (StoreConstantValueAllowed(instr->key())) {
-          key = UseRegisterOrConstantAtStart(instr->key());
         } else {
-          key = UseRegisterAtStart(instr->key());
+          key = UseRegisterOrConstantAtStart(instr->key());
         }
       }
     }
@@ -2258,10 +2244,13 @@ LInstruction* LChunkBuilder::DoStoreNamedField(HStoreNamedField* instr) {
         : UseRegisterAtStart(instr->object());
   }
 
+  bool can_be_constant = instr->value()->IsConstant() &&
+      !HConstant::cast(instr->value())->InNewSpace();
+
   LOperand* val;
   if (needs_write_barrier) {
     val = UseTempRegister(instr->value());
-  } else if (StoreConstantValueAllowed(instr->value())) {
+  } else if (can_be_constant) {
     val = UseRegisterOrConstant(instr->value());
   } else {
     val = UseRegister(instr->value());
@@ -2323,7 +2312,9 @@ LInstruction* LChunkBuilder::DoAllocateObject(HAllocateObject* instr) {
 
 LInstruction* LChunkBuilder::DoAllocate(HAllocate* instr) {
   info()->MarkAsDeferredCalling();
-  LOperand* size = UseTempRegister(instr->size());
+  LOperand* size = instr->size()->IsConstant()
+      ? UseConstant(instr->size())
+      : UseTempRegister(instr->size());
   LOperand* temp = TempRegister();
   LAllocate* result = new(zone()) LAllocate(size, temp);
   return AssignPointerMap(DefineAsRegister(result));