mati865 added inline comments.
================
Comment at: llvm/cmake/modules/HandleLLVMOptions.cmake:967
CMAKE_EXE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
- elseif(LINKER_IS_LLD_LINK)
+ elseif(LINKER_IS_LLD_LINK AND NOT MINGW)
append("/lldltocache:${PROJECT_BINARY_DIR}/lto.cache"
----------------
mstorsjo wrote:
> mati865 wrote:
> > mstorsjo wrote:
> > > mati865 wrote:
> > > > thieta wrote:
> > > > > mstorsjo wrote:
> > > > > > Do you happen to know why `LINKER_IS_LLD_LINK` gets set in this
> > > > > > case? `ld.lld` (the ELF linker interface, which then the MinGW
> > > > > > driver remaps onto the COFF backend with the `lld-link` interface)
> > > > > > certainly doesn't take `lld-link` style options. I believe (without
> > > > > > diving further into it) that we shouldn't be setting this flag in
> > > > > > this combination, but with the option implemented, we should fit it
> > > > > > into the case further above, `elseif((UNIX OR MINGW) AND
> > > > > > LLVM_USE_LINKER STREQUAL "lld")`
> > > > > Yeah I bet that variable is set because I pass `LLVM_USE_LINKER=lld`
> > > > > but I haven't digged to deeply. I can rework the if statement here
> > > > > when we have the lld option in there.
> > > > > Yeah I bet that variable is set because I pass LLVM_USE_LINKER=lld
> > > > > but I haven't digged to deeply.
> > > >
> > > > It does use `lld-link` when you use `LLVM_USE_LINKER=lld`.
> > > >
> > > > The problem lies in this line:
> > > > ```
> > > > append("/lldltocache:${PROJECT_BINARY_DIR}/lto.cache"
> > > > ```
> > > > For MinGW that should read:
> > > > ```
> > > > append("-Wl,/lldltocache:${PROJECT_BINARY_DIR}/lto.cache"
> > > > ```
> > > > That's because you are passing this flag to GCC/Clang.
> > > > For MinGW that should read:
> > > >
> > > > append("-Wl,/lldltocache:${PROJECT_BINARY_DIR}/lto.cache"
> > >
> > > We're adding this option properly in the mingw frontend, so we shouldn't
> > > do the hacky way of passing lld-link options via the mingw frontend by
> > > passing them as `/option`.
> > >
> > > And the reason `LINKER_IS_LLD_LINK` is set seems to be this:
> > >
> > > ```
> > > if(CMAKE_LINKER MATCHES "lld-link" OR (WIN32 AND LLVM_USE_LINKER STREQUAL
> > > "lld") OR LLVM_ENABLE_LLD)
> > > ```
> > >
> > > Perhaps that should be changed into
> > >
> > > ```
> > > if(CMAKE_LINKER MATCHES "lld-link" OR (WIN32 AND LLVM_USE_LINKER STREQUAL
> > > "lld" AND NOT MINGW) OR LLVM_ENABLE_LLD)
> > > ```
> > >
> > > We're adding this option properly in the mingw frontend, so we shouldn't
> > > do the hacky way of passing lld-link options via the mingw frontend by
> > > passing them as /option.
> >
> > I was about to add that and one more LTO related option but thought "what
> > if LLVM should link with lld-link on MinGW?" and eventually forgot about it.
> >
> >
> >
> > > And the reason LINKER_IS_LLD_LINK is set seems to be this:
> > > ```
> > > if(CMAKE_LINKER MATCHES "lld-link" OR (WIN32 AND LLVM_USE_LINKER STREQUAL
> > > "lld") OR LLVM_ENABLE_LLD)
> > > ```
> > > Perhaps that should be changed into
> > > ```
> > > if(CMAKE_LINKER MATCHES "lld-link" OR (WIN32 AND LLVM_USE_LINKER STREQUAL
> > > "lld" AND NOT MINGW) OR LLVM_ENABLE_LLD)
> > > ```
> >
> > It won't work if somebody uses `LLVM_ENABLE_LLD=ON` instead of
> > `LLVM_USE_LINKER=lld` which is supposed to be equivalent.
> > That raises question how `LLVM_ENABLE_LLD=ON` does even work on UNIX
> > platforms.
> >
> > IMO this would be better:
> > ```
> > if(CMAKE_LINKER MATCHES "lld-link" OR MSVC AND (LLVM_USE_LINKER STREQUAL
> > "lld" OR LLVM_ENABLE_LLD))
> > ```
> > I was about to add that and one more LTO related option but thought "what
> > if LLVM should link with lld-link on MinGW?" and eventually forgot about it.
>
> I don't think that really is a supposedly supported setup - lld-link wouldn't
> find any libs to link against etc, as the compiler driver is supposed to pass
> those as `-L` options in mingw/unix style tools.
>
> > It won't work if somebody uses LLVM_ENABLE_LLD=ON instead of
> > LLVM_USE_LINKER=lld which is supposed to be equivalent.
> > That raises question how LLVM_ENABLE_LLD=ON does even work on UNIX
> > platforms.
>
> Either it doesn't work and nobody actually use it that way, or the effects of
> `LINKER_IS_LLD_LINK` are mostly harmless.
>
> > IMO this would be better:
> >
> > `if(CMAKE_LINKER MATCHES "lld-link" OR MSVC AND (LLVM_USE_LINKER STREQUAL
> > "lld" OR LLVM_ENABLE_LLD))`
>
> Yeah, that looks sensible.
> I don't think that really is a supposedly supported setup - lld-link wouldn't
> find any libs to link against etc, as the compiler driver is supposed to pass
> those as -L options in mingw/unix style tools.
Well, it worked both ways (`lld-link` and `ld.lld`) with slight changes to
CMake files when using your toolchain ;)
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D80425/new/
https://reviews.llvm.org/D80425
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