[Openmp-commits] [PATCH] D101509: An attempt to abandon omptarget out-of-tree builds.

[Vyacheslav Zakharin via Phabricator via Openmp-commits]

vzakhari added inline comments.


================
Comment at: openmp/libomptarget/deviceRTLs/amdgcn/CMakeLists.txt:27
+  # Builds that use pre-installed LLVM have LLVM_DIR set.
+  find_program(CLANG_TOOL clang PATHS ${LLVM_TOOLS_BINARY_DIR} NO_DEFAULT_PATH)
+  find_program(LINK_TOOL llvm-link PATHS ${LLVM_TOOLS_BINARY_DIR}
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tianshilei1992 wrote:
> tianshilei1992 wrote:
> > vzakhari wrote:
> > > tianshilei1992 wrote:
> > > > This line of code is problematic. If I build OpenMP standalone and set `CMAKE_C_COMPILER` to the right `clang`, and the right `clang` is not in `$PATH`, it still finds the one in `$PATH`.
> > > I am not sure I understand the problem.  These `find_program` invocations explicitly look the tools (including `clang`) in `${LLVM_TOOLS_BINARY_DIR}`, which is supposed to be set up by `find_package` (which also sets `LLVM_DIR` the causes cmake to hit this clause).  Is it the case that in your build you get valid `LLVM_DIR` and invalid `LLVM_TOOLS_BINARY_DIR`?  Is it possible that your pre-installed LLVM package is corrupted?
> > > 
> > > Can you please insert `libomptarget_say("Using: ${LLVM_DIR}; using ${LLVM_TOOLS_BINARY_DIR}")` here and tell me what it is printing?
> > Okay. I see the problem here. This patch was trying to abandon out-of-tree build of `libomptarget`, which exactly what I'm using. So the root cause is, I have multiple version of LLVM installed in my system. `find_package(LLVM)` can return one of them, but not the one I want to use (I cannot control the system so I cannot remove those LLVMs in my system). As a result, `LLVM_TOOLS_BINARY_DIR` is set to the wrong place, therefore the `clang` detected is also wrong, no matter what compiler I set for CMake. So in order to let CMake pick up the one I want, `LLVM_ROOT` needs to be set when invoking CMake.
> So actually, even with `find_package(LLVM)`, CMake can still pick up a wrong version. That's why I guard it with a version in https://reviews.llvm.org/D102587.
Thank you for the explanation.  Can you please clarify what you mean by "a wrong version"?  Is there any code in `libomptarget` or `plugins` that requires some minimal `LLVM` version?  In other words, what kind of a breakage you get in your build?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D101509/new/

https://reviews.llvm.org/D101509