Re: [Minios-devel] [UNIKRAFT PATCHv5 22/46] arch/arm64: Avoid using the floating-point and Advanced SIMD registers

["Wei Chen (Arm Technology China)" <Wei.Chen@xxxxxxx>]

Hi Simon,

> -----Original Message-----
> From: Simon Kuenzer <simon.kuenzer@xxxxxxxxx>
> Sent: 2018年9月6日 23:35
> To: Wei Chen (Arm Technology China) <Wei.Chen@xxxxxxx>; minios-
> devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Kaly Xin (Arm Technology China) <Kaly.Xin@xxxxxxx>; nd <nd@xxxxxxx>
> Subject: Re: [Minios-devel] [UNIKRAFT PATCHv5 22/46] arch/arm64: Avoid using
> the floating-point and Advanced SIMD registers
> 
> Hi,
> 
> On 10.08.2018 09:08, Wei Chen wrote:
> > From: Wei Chen <Wei.Chen@xxxxxxx>
> >
> > On Arm64, sometimes, the GCC will use floating-point and Advanced
> > SIMD registers to pass parameters. For example, the va_list will
> > use the SIMD&FP registers (like q0, q1) to store parameters, no
> > matter you are using floating-point or not.
> >
> > So, we use the GCC -mgeneral-regs-only flag to force GCC to use
> > generic registers only util the floating-point and Advanced SIMD
> > registers are required actually.
> >
> > Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
> > ---
> >   arch/arm/arm64/Makefile.uk | 6 +++---
> >   1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/arm/arm64/Makefile.uk b/arch/arm/arm64/Makefile.uk
> > index d4ba7e3..82a159f 100644
> > --- a/arch/arm/arm64/Makefile.uk
> > +++ b/arch/arm/arm64/Makefile.uk
> > @@ -1,6 +1,6 @@
> > -ASFLAGS  += -D__ARM_64__
> > -CFLAGS   += -D__ARM_64__ -fms-extensions
> > -CXXFLAGS += -D__ARM_64__ -fms-extensions
> > +ASFLAGS  += -D__ARM_64__ -mgeneral-regs-only
> > +CFLAGS   += -D__ARM_64__ -fms-extensions -mgeneral-regs-only
> > +CXXFLAGS += -D__ARM_64__ -fms-extensions -mgeneral-regs-only
> 
> Could you maybe also add a short TODO comment and explain that we are
> using non-floating point for now.
> Other form this, this patch is fine ;-)
> 

No problem, I will add TODO comment in code comment and commit log : )

> >
> >   # GCC support -mcpu=native for arm64 from 6.0
> >   ifeq ($(CONFIG_MARCH_ARM64_NATIVE),y)
> >
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