[generators] Create the fixed array holding the registers only once.

src/code-stub-assembler.cc

Index: src/code-stub-assembler.cc
diff --git a/src/code-stub-assembler.cc b/src/code-stub-assembler.cc
index a88ac9aa0bae71d9839eafe4781160ed22835c23..09842db6ef73f2a26a0505b529845fcc0434b51a 100644
--- a/src/code-stub-assembler.cc
+++ b/src/code-stub-assembler.cc
@@ -46,6 +46,10 @@ Node* CodeStubAssembler::UndefinedConstant() {
   return LoadRoot(Heap::kUndefinedValueRootIndex);
 }
 
+Node* CodeStubAssembler::PlaceholderConstant() {
+  return LoadRoot(Heap::kPlaceholderRootIndex);
+}
+
 Node* CodeStubAssembler::Float64Round(Node* x) {
   Node* one = Float64Constant(1.0);
   Node* one_half = Float64Constant(0.5);