Hi Matthew,

> -----Original Message-----
> From: Matthew Malcomson <matthew.malcom...@arm.com>
> Sent: 24 July 2020 17:03
> To: Kyrylo Tkachov <kyrylo.tkac...@arm.com>; gcc-patches@gcc.gnu.org
> Cc: Richard Earnshaw <richard.earns...@arm.com>; Ross Burton
> <ross.bur...@arm.com>; Richard Sandiford <richard.sandif...@arm.com>
> Subject: Re: SLS Mitigation patches backported for GCC9
> 
> On 24/07/2020 12:01, Kyrylo Tkachov wrote:
> > Hi Matthew,
> >
> >> -----Original Message-----
> >> From: Matthew Malcomson <matthew.malcom...@arm.com>
> >> Sent: 21 July 2020 16:16
> >> To: gcc-patches@gcc.gnu.org
> >> Cc: Richard Earnshaw <richard.earns...@arm.com>; Kyrylo Tkachov
> >> <kyrylo.tkac...@arm.com>; Ross Burton <ross.bur...@arm.com>
> >> Subject: SLS Mitigation patches backported for GCC9
> >>
> >> Hello,
> >>
> >> Eventually we will want to backport the SLS patches to older branches.
> >>
> >> When the GCC10 release is unfrozen we will work on getting the same
> >> patches
> >> already posted backported to that branch.  The patches already posted on
> >> the
> >> mailing list apply cleanly to the current releases/gcc-10 branch.
> >>
> >> I've heard interest in having the GCC 9 patches, so I'm posting the
> modified
> >> versions upstream sooner than otherwise.
> >
> > I'd say let's go ahead with the GCC 10 patches (assuming testing works out
> well on there).
> > For the GCC 9 patches it would be useful if you included a bit of text of 
> > how
> they differ from the GCC 10/11 patches.
> > This would speed up the technical review.
> > Thanks,
> > Kyrill
> >
> >>
> >> Cheers,
> >> Matthew
> >>
> >> Entire patch series attached to cover letter.
> 
> Below were the only two "interesting" hunks that failed to apply after
> `patch -p1`.
> 
> The differences causing these were:
> - in GCC-9 the `retab` instruction wasn't in the "do_return" pattern.
> - `simple_return` had "aarch64_use_simple_return_insn_p ()" as a
>     condition.
> 
> 

Thanks, the backports to GCC 10 and GCC 9 are okay, let's go ahead with them.
Kyrill

> 
> 
> --- gcc/config/aarch64/aarch64.md
> +++ gcc/config/aarch64/aarch64.md
> @@ -863,18 +882,23 @@
>     [(return)]
>     ""
>     {
> +    const char *ret = NULL;
>       if (aarch64_return_address_signing_enabled ()
>          && TARGET_ARMV8_3
>          && !crtl->calls_eh_return)
>         {
>          if (aarch64_ra_sign_key == AARCH64_KEY_B)
> -         return "retab";
> +         ret = "retab";
>          else
> -         return "retaa";
> +         ret = "retaa";
>         }
> -    return "ret";
> +    else
> +      ret = "ret";
> +    output_asm_insn (ret, operands);
> +    return aarch64_sls_barrier (aarch64_harden_sls_retbr_p ());
>     }
> -  [(set_attr "type" "branch")]
> +  [(set_attr "type" "branch")
> +   (set_attr "sls_length" "retbr")]
>   )
> 
>   (define_expand "return"
> @@ -886,8 +910,12 @@
>   (define_insn "simple_return"
>     [(simple_return)]
>     ""
> -  "ret"
> -  [(set_attr "type" "branch")]
> +  {
> +    output_asm_insn ("ret", operands);
> +    return aarch64_sls_barrier (aarch64_harden_sls_retbr_p ());
> +  }
> +  [(set_attr "type" "branch")
> +   (set_attr "sls_length" "retbr")]
>   )
> 
>   (define_insn "*cb<optab><mode>1"

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