[PATCH] Makefile: Add option to use toolchain default ABI and ISA string

[Anup Patel]

> -----Original Message-----
> From: Anup Patel
> Sent: 02 November 2020 09:04
> To: Jessica Clarke <jrtc27 at jrtc27.com>; Alistair Francis
> <Alistair.Francis at wdc.com>
> Cc: Atish Patra <Atish.Patra at wdc.com>; anup at brainfault.org;
> opensbi at lists.infradead.org
> Subject: RE: [PATCH] Makefile: Add option to use toolchain default ABI and
> ISA string
> 
> 
> 
> > -----Original Message-----
> > From: Jessica Clarke <jrtc27 at jrtc27.com>
> > Sent: 30 October 2020 03:28
> > To: Alistair Francis <Alistair.Francis at wdc.com>
> > Cc: Atish Patra <Atish.Patra at wdc.com>; Anup Patel
> > <Anup.Patel at wdc.com>; anup at brainfault.org;
> opensbi at lists.infradead.org
> > Subject: Re: [PATCH] Makefile: Add option to use toolchain default ABI
> > and ISA string
> >
> > On 29 Oct 2020, at 17:08, Alistair Francis <Alistair.Francis at wdc.com> wrote:
> > >
> > > On Thu, 2020-10-29 at 14:28 +0530, Anup Patel wrote:
> > >> When PLATFORM_RISCV_ABI and PLATFORM_RISCV_ISA are not
> > specified, we
> > >> force "-mabi=lp64 -march=rv64gc" for RV64 and force "-mabi=ilp32
> > >> -march=rv32gc" for RV32. This can prevent users from using the
> > >> toolchain default "-mabi" and "-march" options.
> > >>
> > >> To allow using toolchain defaults, we add compile-time option
> > >> PLATFORM_RISCV_TOOLCHAIN_DEFAULT which when enabled forces
> the
> > >> top-level makefile to use toolchain default ABI and ISA string.
> > >>
> > >> To enable the option, pass
> "PLATFORM_RISCV_TOOLCHAIN_DEFAULT=1"
> > >> to top-level make.
> > >>
> > >> Reported-by: Alistair Francis <alistair.francis at wdc.com>
> > >> Signed-off-by: Anup Patel <anup.patel at wdc.com>
> > >
> > > Thanks!
> > >
> > > Reviewed-by: Alistair Francis <alistair.francis at wdc.com>
> >
> > FYI, --with-arch/--with-abi are GCC-specific configure flags. Clang
> > doesn't have such a notion, and even if it did it's using CMake so
> > those would be differently-named. Though I don't understand why we
> > need to probe to see what they are; if you want the default, just don't
> specify -march/-mabi?
> > Seems a bit unnecessary to go and ask what the default is only to then
> > explicitly give it to the tool you just asked.
> 
> Okay, sounds good to me. Let's just skip specifying "-mabi/-march" when
> "PLATFORM_RISCV_TOOLCHAIN_DEFAULT=1"

I tried this approach but it breaks "make install" because OpenSBI installs
Library and firmware in a sub-directory named based on PLATFORM_RISCV_ABI

Let's stay with current approach of guessing default ABI and ISA from GCC
configure flags. For Clang, we will extend OPENSBI_CC_xyz guess work
to first test which compiler it is GCC/Clang and then based on that
guess OPENSBI_CC_xyz accordingly.

Regards,
Anup