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Date:   Mon, 26 Feb 2018 20:05:20 +0000
From:   "Maciej W. Rozycki" <macro@mips.com>
To:     Matt Redfearn <matt.redfearn@mips.com>
CC:     James Hogan <jhogan@kernel.org>,
        Ralf Baechle <ralf@linux-mips.org>,
        <linux-mips@linux-mips.org>, Paul Burton <paul.burton@mips.com>,
        <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/4] MIPS: Introduce isa-rev.h to define MIPS_ISA_REV
In-Reply-To: <1519664565-10955-2-git-send-email-matt.redfearn@mips.com>
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References: <1519664565-10955-1-git-send-email-matt.redfearn@mips.com> <1519664565-10955-2-git-send-email-matt.redfearn@mips.com>
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On Mon, 26 Feb 2018, Matt Redfearn wrote:

> +/* If the compiler has defined __mips_isa_rev, believe it. */
> +#ifdef __mips_isa_rev
> +#define MIPS_ISA_REV __mips_isa_rev
> +#else
> +/* The compiler hasn't defined the isa rev so assume it's MIPS I - V (0) */
> +#define MIPS_ISA_REV 0
> +#endif

 FYI, GCC has this:

/* The ISA revision level.  This is 0 for MIPS I to V and N for
   MIPS{32,64}rN.  */
int mips_isa_rev;

and this:

      if (mips_isa < 32)
	mips_isa_rev = 0;
      else
	mips_isa_rev = (mips_isa & 31) + 1;

and then:

      if (mips_isa_rev > 0)						\
	builtin_define_with_int_value ("__mips_isa_rev",		\
				       mips_isa_rev);			\

so your proposal looks like the right approach to me.  I think we should 
have the various target macros documented in the GCC manual.

Reviewed-by: Maciej W. Rozycki <macro@mips.com>

  Maciej