This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH 2/5] x86: Add -mindirect-branch-loop=
On 01/07/2018 03:59 PM, H.J. Lu wrote:
> Add -mindirect-branch-loop= option to control loop filler in call and
> return thunks generated by -mindirect-branch=. 'lfence' uses "lfence"
> as loop filler. 'pause' uses "pause" as loop filler. 'nop' uses "nop"
> as loop filler. The default is 'lfence'.
>
> gcc/
>
> * config/i386/i386-opts.h (indirect_branch_loop): New.
> * config/i386/i386.c (output_indirect_thunk): Support
> -mindirect-branch-loop=.
> * config/i386/i386.opt (mindirect-branch-loop=): New option.
> (indirect_branch_loop): New.
> (lfence): Likewise.
> (pause): Likewise.
> (nop): Likewise.
> * doc/invoke.texi: Document -mindirect-branch-loop= option.
>
> gcc/testsuite/
>
> * gcc.target/i386/indirect-thunk-loop-1.c: New test.
> * gcc.target/i386/indirect-thunk-loop-2.c: Likewise.
> * gcc.target/i386/indirect-thunk-loop-3.c: Likewise.
> * gcc.target/i386/indirect-thunk-loop-4.c: Likewise.
> * gcc.target/i386/indirect-thunk-loop-5.c: Likewise.
I think we should drop the ability to change the filler until such time
as we really need it. Just pick one and go with it. I think David
suggested that they wanted "pause". I'm obviously fine with that.
jeff