/usr/lib/llvm-6.0/include/polly/CodeGen/ is in libclang-common-6.0-dev 1:6.0-1ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/llvm-6.0/include/polly/CodeGen/BlockGenerators.h
/usr/lib/llvm-6.0/include/polly/CodeGen/CodeGeneration.h
/usr/lib/llvm-6.0/include/polly/CodeGen/CodegenCleanup.h
/usr/lib/llvm-6.0/include/polly/CodeGen/IRBuilder.h
/usr/lib/llvm-6.0/include/polly/CodeGen/IslAst.h
/usr/lib/llvm-6.0/include/polly/CodeGen/IslExprBuilder.h
/usr/lib/llvm-6.0/include/polly/CodeGen/IslNodeBuilder.h
/usr/lib/llvm-6.0/include/polly/CodeGen/LoopGenerators.h
/usr/lib/llvm-6.0/include/polly/CodeGen/PPCGCodeGeneration.h
/usr/lib/llvm-6.0/include/polly/CodeGen/PerfMonitor.h
/usr/lib/llvm-6.0/include/polly/CodeGen/RuntimeDebugBuilder.h
/usr/lib/llvm-6.0/include/polly/CodeGen/Utils.h