[Openmp-commits] [PATCH] D111987: [libomptarget][nfc]Generalise DeviceRTL cmake to allow building for amdgpu

Jon Chesterfield via Phabricator via Openmp-commits openmp-commits at lists.llvm.org
Tue Oct 26 12:43:18 PDT 2021

JonChesterfield added inline comments.

Comment at: openmp/libomptarget/DeviceRTL/CMakeLists.txt:217
   # Copy library to destination.
+  # Note: This is acting on the llvm-link'ed library, not the opt'ed one
   add_custom_command(TARGET ${bclib_target_name} POST_BUILD
Meinersbur wrote:
> JonChesterfield wrote:
> > Meinersbur wrote:
> > > [not related to this patch] There seems to be a serious mistake:
> > > ```
> > >   add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/${bclib_name}_opt
> > >       COMMAND ${OPT_TOOL} ${link_opt_flags} ${CMAKE_CURRENT_BINARY_DIR}/${bclib_name}
> > >                       -o ${CMAKE_CURRENT_BINARY_DIR}/${bclib_name}
> > > ```
> > > Says it would generate the `${bclib_name}_opt` file, but the `-o` parameter points to `${bclib_name}`, overwriting the input file.
> > Maybe? Install copies bclib_name, which was overwritten in place, so perhaps the OUTPUT statement doesn't need to match the file created.
> > 
> > It would certainly be clearer if we created ${bclib_name}_link.bc or similar as an intermediate file and fed that to opt to get ${bc_lib} which was then installed.
> Commands should never overwrite in-place, it breaks the entire dependency system. 
> To run two commands without anoter intermediate file, use two COMMAND in the same rule:
> ```
>   add_custom_command(OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/${bclib_name}
>       COMMAND ${LINK_TOOL} -o ${CMAKE_CURRENT_BINARY_DIR}/${bclib_name} ${bc_files}
>       COMMAND ${OPT_TOOL} ${link_opt_flags} ${CMAKE_CURRENT_BINARY_DIR}/${bclib_name} -o ${CMAKE_CURRENT_BINARY_DIR}/${bclib_name}
>       DEPENDS ${bc_files}
>       COMMENT "Linking LLVM bitcode ${bclib_name}"
>   )
> ```
this patch now has the halfway fix of patching up DEPENDS/OUTPUT for consistency, but doesn't attempt to merge the two custom commands together

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