[flang][openmp] Build failure due to missing dependency

[VeeEM]

When building flang with openmp the build can fail like this:

CCACHE_CPP2=yes CCACHE_HASHDIR=yes CCACHE_SLOPPINESS=pch_defines,time_macros /usr/bin/ccache /usr/bin/c++ -DFLANG_INCLUDE_TESTS=1 -DGTEST_HAS_RTTI=0 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D_GLIBCXX_USE_CXX11_ABI=1 -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMI
T_MACROS -I/home/acc/llvm-stuff/build/tools/flang/lib/Support -I/home/acc/llvm-stuff/llvm-project/flang/lib/Support -I/home/acc/llvm-stuff/llvm-project/flang/include -I/home/acc/llvm-stuff/build/tools/flang/include -I/home/acc/llvm-stuff/build/include -I/home/acc/llvm-stuff/llvm-pr
oject/llvm/include -isystem /home/acc/llvm-stuff/llvm-project/flang/../mlir/include -isystem /home/acc/llvm-stuff/build/tools/mlir/include -isystem /home/acc/llvm-stuff/build/tools/clang/include -isystem /home/acc/llvm-stuff/llvm-project/llvm/../clang/include -fPIC -fno-semantic-in
terposition -fvisibility-inlines-hidden -Werror=date-time -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-maybe-uninitialized -Wno-nonnull -Wno-class-memaccess -Wno-dangling-referen
ce -Wno-redundant-move -Wno-pessimizing-move -Wno-array-bounds -Wno-stringop-overread -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wno-misleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -Wno-depre
cated-copy -Wno-ctad-maybe-unsupported -fno-semantic-interposition -fpch-preprocess -O3 -DNDEBUG -std=c++17  -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -MD -MT tools/flang/lib/Support/CMakeFiles/FortranSupport.dir/OpenMP-utils.cpp.o -MF tools/flang/lib/Support/CMakeFiles/Fo
rtranSupport.dir/OpenMP-utils.cpp.o.d -o tools/flang/lib/Support/CMakeFiles/FortranSupport.dir/OpenMP-utils.cpp.o -c /home/acc/llvm-stuff/llvm-project/flang/lib/Support/OpenMP-utils.cpp
In file included from /home/acc/llvm-stuff/llvm-project/flang/include/flang/Optimizer/HLFIR/HLFIROps.h:17,
                 from /home/acc/llvm-stuff/llvm-project/flang/include/flang/Optimizer/Builder/DirectivesCommon.h:25,
                 from /home/acc/llvm-stuff/llvm-project/flang/include/flang/Support/OpenMP-utils.h:12,
                 from /home/acc/llvm-stuff/llvm-project/flang/lib/Support/OpenMP-utils.cpp:9:
/home/acc/llvm-stuff/llvm-project/flang/include/flang/Optimizer/HLFIR/HLFIRDialect.h:28:10: fatal error: flang/Optimizer/HLFIR/HLFIRDialect.h.inc: No such file or directory
   28 | #include "flang/Optimizer/HLFIR/HLFIRDialect.h.inc"
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.

Adding HLFIROpsIncGen as a dependency in flang/lib/Support/CMakeLists.txt seems to fix this.

[schung-amd]

Hi @VeeEM, can you provide the steps to reproduce this? Seems similar to llvm#64268 but I guess you've found a build configuration that tries to build flang/lib/Support/OpenMP-utils.cpp before/without building Optimizer (and thereby generating the missing header).

[VeeEM]

I use the following build configuration:

cmake \
  -G Ninja \
  -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_INSTALL_PREFIX=$INSTALLDIR \
  -DCMAKE_CXX_STANDARD=17 \
  -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
  -DCMAKE_CXX_LINK_FLAGS="-Wl,-rpath,$LD_LIBRARY_PATH" \
  -DLLVM_ENABLE_ASSERTIONS=ON \
  -DLLVM_TARGETS_TO_BUILD='X86;AMDGPU' \
  -DLLVM_LIT_ARGS=-v \
  -DLLVM_ENABLE_PROJECTS='clang;mlir;flang;lld' \
  -DLLVM_ENABLE_RUNTIMES='compiler-rt;openmp;offload;flang-rt' \
  -DRUNTIMES_amdgcn-amd-amdhsa_LLVM_ENABLE_RUNTIMES='libc;openmp' \
  -DLLVM_RUNTIME_TARGETS='default;amdgcn-amd-amdhsa' \
  -DLLVM_CCACHE_BUILD=ON \
  -DCMAKE_VERBOSE_MAKEFILE=ON \
  -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON \
  /home/acc/llvm-stuff/llvm-project/llvm
cmake --build . -- -j12

I'm not sure if this is enough to reproduce the issue on any computer. These can be tricky to reproduce sometimes.

[schung-amd]

Not seeing this on my test system with the main branch of our fork or upstream. I'm running into other unrelated build issues with the amd-staging branch. Will try to work through those errors and continue trying to repro this.

[VeeEM]

Ah, yes, it's on amd-staging that I see this happen.

[schung-amd]

Thanks for the response. Personally still running into other build errors with amd-staging so I haven't reproduced it yet, but we think it might be a race condition that including the dependency would fix.

Adding HLFIROpsIncGen as a dependency in flang/lib/Support/CMakeLists.txt seems to fix this.

Do you have a diff for your workaround? Is it just adding

DEPENDS
HLFIROpsIncGen

to add_flang_library() in the CMakeLists?

[VeeEM]

Yep, that's the workaround.

diff --git a/flang/lib/Support/CMakeLists.txt b/flang/lib/Support/CMakeLists.txt
index 363f57ce97da..f13003d6921a 100644
--- a/flang/lib/Support/CMakeLists.txt
+++ b/flang/lib/Support/CMakeLists.txt
@@ -54,6 +54,9 @@ add_flang_library(FortranSupport
   Version.cpp
   ${version_inc}
 
+  DEPENDS
+  HLFIROpsIncGen
+
   LINK_COMPONENTS
   Support

It's not all the dependencies of the FortranSupport library, this can be checked by trying to build the FortranSupport target without building anything else. I don't know if building an internal library like that independently is even expected to work. It doesn't work on upstream either and I don't have a need for it to work, it's just something I came to think of that might help reproducing this issue.

In practice I have not seen the build fail with the configuration I posted after adding the HLFIROpsIncGen dependency.

[schung-amd]

Thanks for confirming. It makes sense that you see the issue building FortranSupport in isolation at the moment both upstream and with our fork, as there is a dependency on the generated HLFIR headers in flang/include/flang/Support/OpenMP-utils.h which is not satisfied by the CMakeLists as you point out.