Re: [Minios-devel] [UNIKRAFT PATCHv4 11/43] arch/arm64: Add processor optimization GCC flags for arm64

[Julien Grall <julien.grall@xxxxxxx>]

On 10/07/18 08:02, Wei Chen wrote:
> Hi Julien,
Hi Wei,

> > -----Original Message-----
> > From: Julien Grall <julien.grall@xxxxxxx>
> > Sent: 2018年7月9日 18:26
> > To: Wei Chen <Wei.Chen@xxxxxxx>; minios-devel@xxxxxxxxxxxxxxxxxxxx;
> > simon.kuenzer@xxxxxxxxx
> > Cc: Kaly Xin <Kaly.Xin@xxxxxxx>; nd <nd@xxxxxxx>
> > Subject: Re: [Minios-devel] [UNIKRAFT PATCHv4 11/43] arch/arm64: Add processor
> > optimization GCC flags for arm64
> >
> > On 09/07/18 10:17, Wei Chen wrote:
> > > Hi Julien,
> > Hi,
> >
> > > > -----Original Message-----
> > > > From: Julien Grall <julien.grall@xxxxxxx>
> > > > Sent: 2018年7月8日 5:59
> > > > To: Wei Chen <Wei.Chen@xxxxxxx>; minios-devel@xxxxxxxxxxxxxxxxxxxx;
> > > > simon.kuenzer@xxxxxxxxx
> > > > Cc: Kaly Xin <Kaly.Xin@xxxxxxx>; nd <nd@xxxxxxx>
> > > > Subject: Re: [Minios-devel] [UNIKRAFT PATCHv4 11/43] arch/arm64: Add
> > processor
> > > > optimization GCC flags for arm64
> > > >
> > > > Hi Wei,
> > > >
> > > > On 07/06/2018 10:03 AM, Wei Chen wrote:
> > > > > We added serval arm64 CPU models in support list. In this patch,
> > > > s/serval/several/
> > > Oh, thanks again!
> > >
> > > > Cheers,
> > > >
> > > > > we check the GCC version and add optimization GCC flags for
> > > > > selected processor.
> > > > >
> > > > > Current supported arm64 CPU models:
> > > > > native, generic, cortex-a53, cortex-a57, cortex-a72, cortex-a73,
> > > > > cortex-a55 and cortex-a75.
> > > > >
> > > > > Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
> > > > > ---
> > > > >     arch/arm/arm64/Compiler.uk |  6 ++++++
> > > > >     arch/arm/arm64/Makefile.uk | 43 ++++++++++++++++++++++++++++++++++++++
> > > > >     2 files changed, 49 insertions(+)
> > > > >     create mode 100644 arch/arm/arm64/Compiler.uk
> > > > >     create mode 100644 arch/arm/arm64/Makefile.uk
> > > > >
> > > > > diff --git a/arch/arm/arm64/Compiler.uk b/arch/arm/arm64/Compiler.uk
> > > > > new file mode 100644
> > > > > index 0000000..4572013
> > > > > --- /dev/null
> > > > > +++ b/arch/arm/arm64/Compiler.uk
> > > > > @@ -0,0 +1,6 @@
> > > > > +# set cross compile
> > > > > +ifeq ($(CONFIG_CROSS_COMPILE),)
> > > > > +ifneq ($(CONFIG_UK_ARCH),$(HOSTARCH))
> > > > > +       CONFIG_CROSS_COMPILE := aarch64-linux-gnu-
> > > > > +endif
> > > > > +endif
> > > > > diff --git a/arch/arm/arm64/Makefile.uk b/arch/arm/arm64/Makefile.uk
> > > > > new file mode 100644
> > > > > index 0000000..f6aeeac
> > > > > --- /dev/null
> > > > > +++ b/arch/arm/arm64/Makefile.uk
> > > > > @@ -0,0 +1,43 @@
> > > > > +ASFLAGS  += -D__ARM_64__
> > > > > +CFLAGS   += -D__ARM_64__ -fms-extensions
> > > > > +CXXFLAGS += -D__ARM_64__ -fms-extensions
> > > > I would rather avoid to define yet another macro and re-use __aarch64__
> > > > defined by the aarch64 compiler.
> > > It does make sense. But I am not sure if we keep __ARM_64__ here can improve
> > > the compatibility for other libraries. Because for internal libraries we can
> > > __aarch64__ uniformly. But for external libraries, we change them to
> > __aarch64__
> > > Easily.
> > If other libraries are using __ARM_64__, then I would say go an fix your
> > libraries :). But I would expect most of them to use what's the compiler
> > provide.
> Do you know from which version the GCC started to support __aarch64__ macro
> by default? Or if we don't use GCC, does other compiler like LLVM still
> provide __aarch64__ macro?
I don't know which GCC version that started to support __aarch64__, but 
I am ready to be this was there since the beginning as there are 
counterpart for other architectures [1].
Note that, we have been using that macro on Xen since that arm64 port 
was added (5 years ago).
For other compiler, while this is a GNU C extension, this is also at 
least defined by Clang. I would not be surprised if other supports that 
too as some headers will require to have different behavior depending on 
the architecture.
Cheers,

[1] https://sourceforge.net/p/predef/wiki/Architectures/

--
Julien Grall

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