Clear GEPChainInfoMap after visiting a function

It is possible for GEPOperator* to overlap between function visits, so
we have to clear the map or else there could be stale data leftover that
causes GEPs to be incorrectly generated or skipped over.

Author: Icohedron

llvm/lib/Target/DirectX/DXILFlattenArrays.cpp

@@ -92,6 +92,7 @@ class DXILFlattenArraysVisitor
 } // namespace
 
 bool DXILFlattenArraysVisitor::finish() {
+  GEPChainInfoMap.clear();
   RecursivelyDeleteTriviallyDeadInstructionsPermissive(PotentiallyDeadInstrs);
   return true;
 }