Streamline NewTuple and NewArray helpers

Rearrange the code so when we allocate an array from JIT code,
we call one helper where most of the code is inline.

Differential Revision: D917956

hphp/runtime/vm/bytecode.cpp

@@ -3424,18 +3424,17 @@ inline void OPTBLD_INLINE VMExecutionContext::iopArray(PC& pc) {
 
 inline void OPTBLD_INLINE VMExecutionContext::iopNewArray(PC& pc) {
   NEXT();
-  // Clever sizing avoids extra work in HphpArray construction.
-  auto arr = ArrayData::Make(size_t(3U) << (HphpArray::MinLgTableSize-2));
-  m_stack.pushArray(arr);
+  auto arr = ArrayData::MakeReserve(HphpArray::SmallSize);
+  m_stack.pushArrayNoRc(arr);
 }
 
 inline void OPTBLD_INLINE VMExecutionContext::iopNewTuple(PC& pc) {
   NEXT();
   DECODE_IVA(n);
   // This constructor moves values, no inc/decref is necessary.
-  HphpArray* arr = ArrayData::Make(n, m_stack.topC());
+  auto* a = HphpArray::MakeTuple(n, m_stack.topC());
   m_stack.ndiscard(n);
-  m_stack.pushArray(arr);
+  m_stack.pushArrayNoRc(a);
 }
 
 inline void OPTBLD_INLINE VMExecutionContext::iopAddElemC(PC& pc) {