On Mon, Jul 27, 2015 at 5:40 PM, Ingo Molnar <[email protected]> wrote: > > * Uros Bizjak <[email protected]> wrote: > >> From: Uros Bizjak <[email protected]> >> >> This patch introduces GCC ASM flags to bitops. Instead of e.g. >> >> 136d7: 48 0f a3 3d 00 00 00 bt %rdi,0x0(%rip) >> 136de: 00 >> 136df: 19 ff sbb %edi,%edi >> 136e1: 85 ff test %edi,%edi >> 136e3: 0f 95 c0 setne %al >> >> following code is generated: >> >> 13767: 48 0f a3 3d 00 00 00 bt %rdi,0x0(%rip) >> 1376e: 00 >> 1376f: 0f 92 c0 setb %al >> >> Similar improvement can be seen in following code: >> >> 7a6c: 48 0f a3 11 bt %rdx,(%rcx) >> 7a70: 19 d2 sbb %edx,%edx >> 7a72: 85 d2 test %edx,%edx >> 7a74: 74 eb je 7a61 >> >> which becomes: >> >> 7a8c: 48 0f a3 11 bt %rdx,(%rcx) >> 7a90: 73 ef jae 7a81 >> >> Signed-off-by: Uros Bizjak <[email protected]> >> --- >> arch/x86/include/asm/bitops.h | 26 ++++++++++++++++++++++++-- >> arch/x86/include/asm/percpu.h | 18 +++++++++++++++++- >> arch/x86/include/asm/signal.h | 6 ++++++ >> arch/x86/include/asm/sync_bitops.h | 18 ++++++++++++++++++ >> 4 files changed, 65 insertions(+), 3 deletions(-) > > Nothing in your patch seems to be setting __GCC_ASM_FLAG_OUTPUTS__, and the > patch > does not seem to be mailed as part of a larger series ... > > So how is this supposed to work?
GCC version 6+ will automatically define __GCC_ASM_FLAG_OUTPUTS__ when this feature is supported. Please see [1] for RFC GCC patch series and [2] for final committed patch. [1] https://gcc.gnu.org/ml/gcc-patches/2015-05/msg00594.html [2] https://gcc.gnu.org/ml/gcc-patches/2015-06/msg02087.html Uros. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
