Subject: Re: [PATCH v5 05/10] arm64: atomics: Remove atomic_ll_sc compilation unit

From: Will Deacon <[email-masked]>
Date: Thu, 29 Aug 2019 22:54:52 +0100

On Thu, Aug 29, 2019 at 01:07:04PM -0700, Tri Vo wrote:
> On Thu, Aug 29, 2019 at 10:47 AM Nick Desaulniers
> <[email-masked]> wrote:
> >
> > On Thu, Aug 29, 2019 at 8:48 AM Will Deacon <[email-masked]> wrote:
> > >
> > > From: Andrew Murray <[email-masked]>
> > >
> > > We no longer fall back to out-of-line atomics on systems with
> > > CONFIG_ARM64_LSE_ATOMICS where ARM64_HAS_LSE_ATOMICS is not set.
> > >
> > > Remove the unused compilation unit which provided these symbols.
> > >
> > > Signed-off-by: Andrew Murray <[email-masked]>
> > > Signed-off-by: Will Deacon <[email-masked]>
> > > ---
> > >  arch/arm64/lib/Makefile       | 19 -------------------
> > >  arch/arm64/lib/atomic_ll_sc.c |  3 ---
> > >  2 files changed, 22 deletions(-)
> > >  delete mode 100644 arch/arm64/lib/atomic_ll_sc.c
> > >
> > > diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile
> > > index 33c2a4abda04..f10809ef1690 100644
> > > --- a/arch/arm64/lib/Makefile
> > > +++ b/arch/arm64/lib/Makefile
> > > @@ -11,25 +11,6 @@ CFLAGS_REMOVE_xor-neon.o     += -mgeneral-regs-only
> > >  CFLAGS_xor-neon.o              += -ffreestanding
> > >  endif
> > >
> > > -# Tell the compiler to treat all general purpose registers (with the
> > > -# exception of the IP registers, which are already handled by the caller
> > > -# in case of a PLT) as callee-saved, which allows for efficient runtime
> > > -# patching of the bl instruction in the caller with an atomic instruction
> > > -# when supported by the CPU. Result and argument registers are handled
> > > -# correctly, based on the function prototype.
> > > -lib-$(CONFIG_ARM64_LSE_ATOMICS) += atomic_ll_sc.o
> > > -CFLAGS_atomic_ll_sc.o  := -ffixed-x1 -ffixed-x2                        \
> > > -                  -ffixed-x3 -ffixed-x4 -ffixed-x5 -ffixed-x6          \
> > > -                  -ffixed-x7 -fcall-saved-x8 -fcall-saved-x9           \
> > > -                  -fcall-saved-x10 -fcall-saved-x11 -fcall-saved-x12   \
> > > -                  -fcall-saved-x13 -fcall-saved-x14 -fcall-saved-x15   \
> > > -                  -fcall-saved-x18 -fomit-frame-pointer
> >
> > + Tri (who implemented support for -fcall-saved-x*, -ffixed-x* in
> > Clang).  I won't be sad to see the use of these flags go.
> 
> Nice! IMO these flags made the code hard to read.

Well, we didn't do it like that because it looked pretty ;)

Will

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