[flang-commits] [clang] [flang] [llvm] [mlir] [polly] [CMake][LLVM] Add PCH infrastructure and LLVMSupport PCH (PR #176420)

[Maksim Levental via flang-commits]

makslevental wrote:

@aengelke any idea about errors like this:

```
FAILED: [code=1] tools/mlir/lib/CAPI/Debug/CMakeFiles/obj.MLIRCAPIDebug.dir/Debug.cpp.o 
ccache /usr/bin/clang++ -DMLIR_CAPI_BUILDING_LIBRARY=1 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_EXTENSIVE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/Users/runner/work/eudsl/eudsl/llvm-build/tools/mlir/lib/CAPI/Debug -I/Users/runner/work/eudsl/eudsl/third_party/llvm-project/mlir/lib/CAPI/Debug -I/Users/runner/work/eudsl/eudsl/llvm-build/tools/mlir/include -I/Users/runner/work/eudsl/eudsl/third_party/llvm-project/mlir/include -I/Users/runner/work/eudsl/eudsl/llvm-build/include -I/Users/runner/work/eudsl/eudsl/third_party/llvm-project/llvm/include -fPIC -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wno-pass-failed -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -Xclang -fno-pch-timestamp -Wundef -Werror=mismatched-tags -O3 -DNDEBUG -std=c++17 -arch arm64 -mmacosx-version-min=11.0 -fvisibility=hidden -UNDEBUG -fno-exceptions -funwind-tables -Winvalid-pch -Xclang -include-pch -Xclang /Users/runner/work/eudsl/eudsl/llvm-build/lib/Support/CMakeFiles/LLVMSupport.dir/cmake_pch.hxx.pch -Xclang -include -Xclang /Users/runner/work/eudsl/eudsl/llvm-build/lib/Support/CMakeFiles/LLVMSupport.dir/cmake_pch.hxx -MD -MT tools/mlir/lib/CAPI/Debug/CMakeFiles/obj.MLIRCAPIDebug.dir/Debug.cpp.o -MF tools/mlir/lib/CAPI/Debug/CMakeFiles/obj.MLIRCAPIDebug.dir/Debug.cpp.o.d -o tools/mlir/lib/CAPI/Debug/CMakeFiles/obj.MLIRCAPIDebug.dir/Debug.cpp.o -c /Users/runner/work/eudsl/eudsl/third_party/llvm-project/mlir/lib/CAPI/Debug/Debug.cpp
error: default visibility for functions and variables [-fvisibility] differs in PCH file vs. current file
```

([here](https://github.com/llvm/eudsl/actions/runs/22268193848/job/64418143848#step:4:6291))

https://github.com/llvm/llvm-project/pull/176420