/usr/lib/llvm-4.0/include/ is in libclang-common-4.0-dev 1:4.0.1-10~deb9u2.
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..
/usr/lib/llvm-4.0/include/polly/
/usr/lib/llvm-4.0/include/polly/Canonicalization.h
/usr/lib/llvm-4.0/include/polly/CodeGen/
/usr/lib/llvm-4.0/include/polly/CodeGen/BlockGenerators.h
/usr/lib/llvm-4.0/include/polly/CodeGen/CodeGeneration.h
/usr/lib/llvm-4.0/include/polly/CodeGen/CodegenCleanup.h
/usr/lib/llvm-4.0/include/polly/CodeGen/IRBuilder.h
/usr/lib/llvm-4.0/include/polly/CodeGen/IslAst.h
/usr/lib/llvm-4.0/include/polly/CodeGen/IslExprBuilder.h
/usr/lib/llvm-4.0/include/polly/CodeGen/IslNodeBuilder.h
/usr/lib/llvm-4.0/include/polly/CodeGen/LoopGenerators.h
/usr/lib/llvm-4.0/include/polly/CodeGen/RuntimeDebugBuilder.h
/usr/lib/llvm-4.0/include/polly/CodeGen/Utils.h
/usr/lib/llvm-4.0/include/polly/Config/
/usr/lib/llvm-4.0/include/polly/Config/config.h
/usr/lib/llvm-4.0/include/polly/DeLICM.h
/usr/lib/llvm-4.0/include/polly/DependenceInfo.h
/usr/lib/llvm-4.0/include/polly/FlattenAlgo.h
/usr/lib/llvm-4.0/include/polly/FlattenSchedule.h
/usr/lib/llvm-4.0/include/polly/LinkAllPasses.h
/usr/lib/llvm-4.0/include/polly/Options.h
/usr/lib/llvm-4.0/include/polly/PolyhedralInfo.h
/usr/lib/llvm-4.0/include/polly/RegisterPasses.h
/usr/lib/llvm-4.0/include/polly/ScheduleOptimizer.h
/usr/lib/llvm-4.0/include/polly/ScopBuilder.h
/usr/lib/llvm-4.0/include/polly/ScopDetection.h
/usr/lib/llvm-4.0/include/polly/ScopDetectionDiagnostic.h
/usr/lib/llvm-4.0/include/polly/ScopInfo.h
/usr/lib/llvm-4.0/include/polly/ScopPass.h
/usr/lib/llvm-4.0/include/polly/Support/
/usr/lib/llvm-4.0/include/polly/Support/GICHelper.h
/usr/lib/llvm-4.0/include/polly/Support/SCEVAffinator.h
/usr/lib/llvm-4.0/include/polly/Support/SCEVValidator.h
/usr/lib/llvm-4.0/include/polly/Support/ScopHelper.h
/usr/lib/llvm-4.0/include/polly/Support/ScopLocation.h