Simplify ArraySpec::widenToBespoke

Summary: None of these branches are needed. The first one is unnecessary because if the vanilla bit is unset, masking it off is a no-op. The second one is unnecessary because ArraySpec::Top has integer value 0 (it's ArraySpec::Bottom that has a special non-zero integer value).

Reviewed By: ricklavoie

Differential Revision: D20379283

fbshipit-source-id: d6e01b2107eb9a9e848d21edf8e69384ea8bc385

Author: skishore

hphp/runtime/vm/jit/type-specialization-inl.h

@@ -202,10 +202,8 @@ inline ArraySpec ArraySpec::narrowToVanilla() const {
 }
 
 inline ArraySpec ArraySpec::widenToBespoke() const {
-  if (!(m_sort & IsVanilla)) return *this;
   auto result = *this;
   result.m_sort &= ~IsVanilla;
-  if (!result.m_sort) return Top();
   assertx(result.checkInvariants());
   return result;
 }