[MLIR] Build broken on Windows with GNU tools.

[carlo-bramini]

I tried to build mlir on Windows, but I got many errors on undefined references when linking mlir-tblgen.exe:

If you look the attached screenshot, you can see that I have highlighted lib/libMLIRTableGen.a.
This is a static library and it is the cause of the problem, because it has not its dependencies satisfied.
By looking into the generated build.ninja file, I have found this line, which provides the above libraries when linking:

LINK_LIBRARIES = lib/libLLVMCodeGenTypes.dll.a  lib/libMLIRTblgenLib.a  lib/libLLVMTableGen.dll.a  lib/libLLVMSupport.dll.a  lib/libLLVMDemangle.dll.a  lib/libMLIRTableGen.a

I just did a quick hack to this file, by changing the above line to:

LINK_LIBRARIES = lib/libMLIRTblgenLib.a  lib/libMLIRTableGen.a lib/libLLVMCodeGenTypes.dll.a  lib/libLLVMTableGen.dll.a  lib/libLLVMSupport.dll.a  lib/libLLVMDemangle.dll.a

After that, mlir-tblgen.exe has been linked successfully.
Actually, the libraries should respect some order when linking, something like:

static_lib1.a import_deps_for_lib1.dll.a   static_lib2.a import_deps_for_lib2.dll.a ...etc

or all static libraries and then all import libraries if you prefer.
It is interesting to notice that lib/libMLIRTblgenLib.a and lib/libMLIRTableGen.a cannot be swapped, lib/libMLIRTblgenLib.a must be written before lib/libMLIRTableGen.a, otherwise you will got lot of undefined references again.
Evidently, one static library is also a dependency for the other one.
MSVC does not seem to suffer about this behaviour on libraries at link time.

I configured the sources according to the guidelines, by using this command line:

cmake ../a/llvm-project/llvm -G Ninja -DCMAKE_BUILD_TYPE=Release -Wno-dev -DBUILD_SHARED_LIBS=ON -DLLVM_ENABLE_PROJECTS="lld;clang;clang-tools-extra;bolt;cross-project-tests;polly;libclc;mlir"

This effect happens with GCC for CYGWIN and MinGW-w64 cross compiler.
I'm using -DBUILD_SHARED_LIBS=ON on the command line since this is the only way to bypass issue #60659 for me.

EDIT: unfortunately, I was not able to find the right point for fixing this issue, if somebody could give me some suggestions about the fixes to do, I could test them and provide a patch at https://reviews.llvm.org/.

I'm using the development sources from head, 4f30746.

[llvmbot]

@llvm/issue-subscribers-mlir

[carlo-bramini]

Actually, building mlir-pdll.exe shows the same identical problem, but when the issue on mlir-tblgen.exe will be solved, probably mlir-pdll.exe will be solved too.