Re: [RS6000] Stack tie fix.

[Richard Guenther <richard.guenther@gmail.com>]

On Thu, Apr 12, 2012 at 5:34 PM, David Edelsohn <dje.gcc@gmail.com> wrote:
> On Thu, Apr 12, 2012 at 9:22 AM, Alan Modra <amodra@gmail.com> wrote:
>
>> I tried that.  It doesn't work without something else in the insn to
>> stop rtl-dce deleting it, so you may as well use SETs.  But thanks for
>> the prod in the right direction.  We do get slightly better results
>> when the regs are not hidden away in an UNSPEC, for instance
>> non-stack writes/reads are seen by the alias oracle to not conflict
>> with the epilogue frame deallocation.
>>
>> Bootstrapped etc. powerpc-linux.  OK to apply, David?
>>
>>        PR target/52828
>>        * config/rs6000/rs6000.c (rs6000_emit_stack_tie): Rewrite with
>>        tie regs on destination of sets.  Delete forward declaration.
>>        (rs6000_emit_stack_reset): Update rs6000_emit_stack_tie calls.
>>        (rs6000_emit_prologue): Likewise.
>>        (rs6000_emit_epilogue): Likewise.  Use in place of gen_frame_tie
>>        and gen_stack_tie.
>>        (is_mem_ref): Use tie_operand to recognise stack ties.
>>        * config/rs6000/predicates.md (tie_operand): New.
>>        * config/rs6000/rs6000.md (UNSPEC_TIE): Delete.
>>        (restore_stack_block): Generate new stack tie rtl.
>>        (restore_stack_nonlocal): Likewise.
>>        (stack_tie): Update.
>>        (frame_tie): Delete.
>
> This probably is getting close to the best we can do with GCC's RTL
> alias analysis infrastructure.
>
> This version is okay, but I also want to give Richi and Olivier an
> opportunity to comment if they still have any concerns.

It looks fine to me.

Richard.

> Thanks, David