ARM64: Introduce TempDoubleRegister as a lithium operand constraint.

src/lithium-allocator.cc

Index: src/lithium-allocator.cc
diff --git a/src/lithium-allocator.cc b/src/lithium-allocator.cc
index 7cbae0cdad712d8cebf650945edf53722619f0cd..c6e52ed824f12dcbf7d20cd5b75f428dd3b411e1 100644
--- a/src/lithium-allocator.cc
+++ b/src/lithium-allocator.cc
@@ -46,7 +46,8 @@ UsePosition::UsePosition(LifetimePosition pos,
       register_beneficial_(true) {
   if (operand_ != NULL && operand_->IsUnallocated()) {
     LUnallocated* unalloc = LUnallocated::cast(operand_);
-    requires_reg_ = unalloc->HasRegisterPolicy();
+    requires_reg_ = unalloc->HasRegisterPolicy() ||
+        unalloc->HasDoubleRegisterPolicy();
     register_beneficial_ = !unalloc->HasAnyPolicy();
   }
   ASSERT(pos_.IsValid());
@@ -1005,6 +1006,15 @@ void LAllocator::ProcessInstructions(HBasicBlock* block, BitVector* live) {
           }
           Use(block_start_position, curr_position.InstructionEnd(), temp, NULL);
           Define(curr_position, temp, NULL);
+
+          if (temp->IsUnallocated()) {
+            LUnallocated* temp_unalloc = LUnallocated::cast(temp);
+            if (temp_unalloc->HasDoubleRegisterPolicy()) {
+              double_artificial_registers_.Add(
+                  temp_unalloc->virtual_register() - first_artificial_register_,
+                  zone());
+            }
+          }
         }
       }
     }
@@ -1095,7 +1105,6 @@ bool LAllocator::Allocate(LChunk* chunk) {
 
 void LAllocator::MeetRegisterConstraints() {
   LAllocatorPhase phase("L_Register constraints", this);
-  first_artificial_register_ = next_virtual_register_;
   const ZoneList<HBasicBlock*>* blocks = graph_->blocks();
   for (int i = 0; i < blocks->length(); ++i) {
     HBasicBlock* block = blocks->at(i);