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Re: [PATCH] Fix pr57637


On 11 July 2013 18:31, Eric Botcazou <ebotcazou@adacore.com> wrote:
>> Shrink-wrap optimization sinks some instructions for more
>> opportunities. It uses DF_LR_BB_INFO (bb)->def to check whether BB
>> clobbers SRC. But for ARM, gcc might generate cond_exec insns before
>> shrink-wrapping. And DF_LR_BB_INFO (bb)->def does not include def info
>> from cond_exec insns. So the check in function
>> move_insn_for_shrink_wrap is not enough.
>
> Posting a testcase would be even better, but the analysis looks plausible.
> DF_REF_CONDITIONAL and DF_REF_PARTIAL defs aren't killing defs so they are not
> included in the def set for LR.
>
> As you pointed out, they are included in the gen set for LIVE if it exists, so
> I guess we should wonder if we really want to do the scanning if LIVE doesn't
> exist, i.e. at -O1, instead of simply giving up.  In any case, the scanning

Thanks.

The patch is updated based the comments: it will check GEN set of LIVE
if df_live exists. Otherwise, just give up.

And a testcase is included in the attached patch.

-Zhenqiang


> doesn't need to be redundant with the previous work, so:
>
>       if (!(DF_REF_FLAGS (def) & (DF_REF_PARTIAL | DF_REF_CONDITIONAL)))
>           continue;
>
> is missing in the patch.
>
> --
> Eric Botcazou

Attachment: pr57637-updated.patch
Description: Binary data


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