On 2024-10-29 15:49, Koakuma via B4 Relay wrote: > Hello~ > > This changes the CFLAGS for building the SPARC kernel so that it can be > built with clang, as a follow up from the discussion in this thread: > > https://lore.kernel.org/lkml/JAYB7uS-EdLABTR4iWZdtFOVa5MvlKosIrD_cKTzgeozCOGRM7lhxeLigFB1g3exX445I_W5VKB-tAzl2_G1zCVJRQjp67ODfsSqiZWOZ9o=@protonmail.com/T/#u > > The changes are removal of various `-fcall-used-*` flags, and adding > clang target flags for SPARC: > > - `-fcall-used-*` flags is gated behind cc-option as it is > not supported in clang. It should be safe; clang won't use the registers > specified as temporaries, but it is a safe change wrt. the ABI. > Assembly code can still use those registers as needed. > A cursory look at the assembly generated by GCC 13.2 shows that > the compiler was able to reallocate uses of those registers into > other temporary registers without adding extra spills, so there > should be no change in performance. > > - More trivial is to add CLANG_TARGET_FLAGS for SPARC target. > > Building with these changes still result in a working kernel, > at least for Sun T5120, Oracle T4-1, and qemu virtual machines. > > On the LLVM side, the effort for building Linux/SPARC is tracked here: > https://github.com/llvm/llvm-project/issues/40792 > > Signed-off-by: Koakuma <koachan@xxxxxxxxxxxxxx> > --- > Changes in v3: > - Use cc-option to allow GCC to still use -fcall-used-* flags. > - Add documentation on building on SPARC, along with required LLVM version. > - Link to v2: https://lore.kernel.org/r/20240717-sparc-cflags-v2-0-259407e6eb5f@xxxxxxxxxxxxxx > > Changes in v2: > - Remove the -mv8plus change; it will be handled on clang side: > https://github.com/llvm/llvm-project/pull/98713 > - Add CLANG_TARGET_FLAGS as suggested in v1 review. > - Link to v1: https://lore.kernel.org/r/20240620-sparc-cflags-v1-1-bba7d0ff7d42@xxxxxxxxxxxxxx > > --- > Koakuma (2): > sparc/build: Put usage of -fcall-used* flags behind cc-option > sparc/build: Add SPARC target flags for compiling with clang > > Documentation/kbuild/llvm.rst | 3 +++ > arch/sparc/Makefile | 4 ++-- > arch/sparc/vdso/Makefile | 2 +- > scripts/Makefile.clang | 1 + > 4 files changed, 7 insertions(+), 3 deletions(-) > --- > base-commit: c2ee9f594da826bea183ed14f2cc029c719bf4da > change-id: 20240620-sparc-cflags-e7f2dbbd4b9d Reviewed-by: Andreas Larsson <andreas@xxxxxxxxxxx> I see no pressing need for a v4. Picking the series up to my for-next. Thanks, Andreas
