On Mon, 2018-11-12 at 05:28:06 UTC, Joel Stanley wrote: > When building for ppc32 with clang these flags are unsupported: > > -ffixed-r2 and -mmultiple > > llvm's lib/Target/PowerPC/PPCRegisterInfo.cpp marks r2 as reserved on > when building for SVR4ABI and !ppc64: > > // The SVR4 ABI reserves r2 and r13 > if (Subtarget.isSVR4ABI()) { > // We only reserve r2 if we need to use the TOC pointer. If we have no > // explicit uses of the TOC pointer (meaning we're a leaf function with > // no constant-pool loads, etc.) and we have no potential uses inside an > // inline asm block, then we can treat r2 has an ordinary callee-saved > // register. > const PPCFunctionInfo *FuncInfo = MF.getInfo<PPCFunctionInfo>(); > if (!TM.isPPC64() || FuncInfo->usesTOCBasePtr() || MF.hasInlineAsm()) > markSuperRegs(Reserved, PPC::R2); // System-reserved register > markSuperRegs(Reserved, PPC::R13); // Small Data Area pointer register > } > > This means we can safely omit -ffixed-r2 when building for 32-bit > targets. > > The -mmultiple/-mno-multiple flags are not supported by clang, so > platforms that might support multiple miss out on using multiple word > instructions. > > We wrap these flags in cc-option so that when Clang gains support the > kernel will be able use these flags. > > Clang 8 can then build a ppc44x_defconfig which boots in Qemu: > > make CC=clang-8 ARCH=powerpc CROSS_COMPILE=powerpc-linux-gnu- > ppc44x_defconfig > ./scripts/config -e CONFIG_DEVTMPFS -d DEVTMPFS_MOUNT > make CC=clang-8 ARCH=powerpc CROSS_COMPILE=powerpc-linux-gnu- > > qemu-system-ppc -M bamboo \ > -kernel arch/powerpc/boot/zImage \ > -dtb arch/powerpc/boot/dts/bamboo.dtb \ > -initrd ~/ppc32-440-rootfs.cpio \ > -nographic -serial stdio -monitor pty -append "console=ttyS0" > > Link: https://github.com/ClangBuiltLinux/linux/issues/261 > Link: https://bugs.llvm.org/show_bug.cgi?id=39556 > Link: https://bugs.llvm.org/show_bug.cgi?id=39555 > Signed-off-by: Joel Stanley <j...@jms.id.au> > Reviewed-by: Nick Desaulniers <ndesaulni...@google.com>
Applied to powerpc next, thanks. https://git.kernel.org/powerpc/c/72e7bcc2cdf82bf03caaa5e6c9b013 cheers