as it causes a layering violation/dependency cycle: llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp -> llvm/DebugInfo/DWARF/DWARFExpression.h llvm/include/llvm/DebugInfo/DWARF/DWARFOptimizer.h -> llvm/CodeGen/NonRelocatableStringpool.h This reverts commit abc7f6800df8a1f40e1e2c9ccce826abb0208284.