Messages in this thread | | | From | Nick Desaulniers <> | Date | Mon, 9 Nov 2020 17:55:41 -0800 | Subject | Re: [PATCH v2] Make iwmmxt.S support Clang's integrated assembler |
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On Sat, Nov 7, 2020 at 12:29 AM Ard Biesheuvel <ardb@kernel.org> wrote: > > On Sat, 7 Nov 2020 at 01:11, Jian Cai <jiancai@google.com> wrote: > > > > This patch replaces 6 IWMMXT instructions Clang's integrated assembler > > does not support in iwmmxt.S using macros, while making sure GNU > > assembler still emit the same instructions. This should be easier than > > providing full IWMMXT support in Clang. > > > > "Intel Wireless MMX Technology - Developer Guide - August, 2002" should > > be referenced for the encoding schemes of these extensions. > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/975 > > > > Suggested-by: Nick Desaulniers <ndesaulniers@google.com> > > Suggested-by: Ard Biesheuvel <ardb@kernel.org> > > Signed-off-by: Jian Cai <jiancai@google.com> > > Please make sure you test this carefully on BE32, as the instruction > byte order used by .inst is LE IIRC
Unless that was a recent-ish change in GAS, it looks like I get the same disassembly/encodings before/after this patch for CONFIG_BIG_ENDIAN with GNU as.
$ ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- make CC=clang -j71 defconfig $ ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- make CC=clang -j71 menuconfig <enable CPU_BIG_ENDIAN> $ grep BIG_ENDIAN .config CONFIG_CPU_BIG_ENDIAN=y CONFIG_ARCH_SUPPORTS_BIG_ENDIAN=y $ ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- make CC=clang -j71 arch/arm/kernel/iwmmxt.o $ arm-linux-gnueabi-objdump -dr arch/arm/kernel/iwmmxt.o > gas_before.txt $ b4 am https://lore.kernel.org/lkml/20201107001056.225807-1-jiancai@google.com/ -o - | git am $ ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- make CC=clang -j71 arch/arm/kernel/iwmmxt.o $ arm-linux-gnueabi-objdump -dr arch/arm/kernel/iwmmxt.o > gas_after.txt $ diff -u gas_before.txt gas_after.txt $ echo $? 0
(Orthogonal, it looks like llvm-objdump has issues decoding elf32-bigarm that we'll need to fix.)
Either way the patch LGTM for IWMMXT, thanks Jian for the patch and Ard for the suggestions.
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Tested-by: Nick Desaulniers <ndesaulniers@google.com> -- Thanks, ~Nick Desaulniers
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