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Re: RFA: Fix debug-insn sensitivity in RA


On Sat, Sep 7, 2013 at 11:14 AM, Richard Sandiford wrote:
> The problem seems to be split across IRA and LRA.  In IRA we have:
>
>   FOR_EACH_BB (bb)
>     FOR_BB_INSNS (bb, insn)
>       {
>         if (! INSN_P (insn))
>           continue;
>         for_each_rtx (&insn, set_paradoxical_subreg, (void *)pdx_subregs);
>       }
>
> which sets pdx_subregs[R] if R is used in a paradoxical subreg, followed by:
>
>           /* Don't set reg (if pdx_subregs[regno] == true) equivalent to a mem.  */
>           if (MEM_P (src) && pdx_subregs[regno])
>             {
>               note_stores (set, no_equiv, NULL);
>               continue;
>             }
>
> I think this should only happen when a paradoxical subreg is seen
> in a nondebug insn.

Agreed. Otherwise these debug insns would have influence on the
generated code and that's not supposed to happen.


> The patch below fixes the wide-int problem for me.  Bootstrapped &
> regression-tested on trunk for x86_64-linux-gnu.  OK to install?
>
> Thanks,
> Richard
>
>
> gcc/
>         * ira.c (update_equiv_regs): Only call set_paradoxical_subreg
>         for non-debug insns.
>         * lra.c (new_insn_reg): Take the containing insn as a parameter.
>         Only modify lra_reg_info[].biggest_mode if it's non-debug insn.
>         (collect_non_operand_hard_regs, add_regs_to_insn_regno_info): Update
>         accordingly.

I don't think this falls under "RTL optimizers", but the patch looks OK to me.

Can you please add a test case?

Ciao!
Steven


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