Add support for IncrementCounter in Hydrogen.

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 9c6efed3d2f57ea37a8a1ed37aaeb5be97c8918c..4153417473e24e4dfc2d915799b294dc3c4413d5 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1997,6 +1997,8 @@ LInstruction* LChunkBuilder::DoConstant(HConstant* instr) {
   } else if (r.IsDouble()) {
     LOperand* temp = TempRegister();
     return DefineAsRegister(new(zone()) LConstantD(temp));
+  } else if (r.IsExternal()) {
+    return DefineAsRegister(new(zone()) LConstantE);
   } else if (r.IsTagged()) {
     return DefineAsRegister(new(zone()) LConstantT);
   } else {
@@ -2074,6 +2076,10 @@ LInstruction* LChunkBuilder::DoStoreContextSlot(HStoreContextSlot* instr) {
 
 
 LInstruction* LChunkBuilder::DoLoadNamedField(HLoadNamedField* instr) {
+  if (instr->access().IsExternalMemory() && instr->access().offset() == 0) {
+    LOperand* obj = UseRegisterOrConstantAtStart(instr->object());
+    return DefineFixed(new(zone()) LLoadNamedField(obj), rax);
+  }
   LOperand* obj = UseRegisterAtStart(instr->object());
   return DefineAsRegister(new(zone()) LLoadNamedField(obj));
 }
@@ -2249,6 +2255,8 @@ LInstruction* LChunkBuilder::DoTrapAllocationMemento(
 
 LInstruction* LChunkBuilder::DoStoreNamedField(HStoreNamedField* instr) {
   bool is_in_object = instr->access().IsInobject();
+  bool is_external_location = instr->access().IsExternalMemory() &&
+      instr->access().offset() == 0;
   bool needs_write_barrier = instr->NeedsWriteBarrier();
   bool needs_write_barrier_for_map = !instr->transition().is_null() &&
       instr->NeedsWriteBarrierForMap();
@@ -2258,6 +2266,11 @@ LInstruction* LChunkBuilder::DoStoreNamedField(HStoreNamedField* instr) {
     obj = is_in_object
         ? UseRegister(instr->object())
         : UseTempRegister(instr->object());
+  } else if (is_external_location) {
+    ASSERT(!is_in_object);
+    ASSERT(!needs_write_barrier);
+    ASSERT(!needs_write_barrier_for_map);
+    obj = UseRegisterOrConstant(instr->object());
   } else {
     obj = needs_write_barrier_for_map
         ? UseRegister(instr->object())
@@ -2271,6 +2284,8 @@ LInstruction* LChunkBuilder::DoStoreNamedField(HStoreNamedField* instr) {
   LOperand* val;
   if (needs_write_barrier) {
     val = UseTempRegister(instr->value());
+  } else if (is_external_location) {
+    val = UseFixed(instr->value(), rax);
   } else if (can_be_constant) {
     val = UseRegisterOrConstant(instr->value());
   } else if (FLAG_track_fields && instr->field_representation().IsSmi()) {