Re: [RFA][tree-optimization/90037] Cleanup const/copies between DOM and erroneous path isolation

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

On April 24, 2019 11:26:28 PM GMT+02:00, Jeff Law <law@redhat.com> wrote:
>On 4/24/19 4:44 AM, Richard Biener wrote:
>>> Given that we can use the lattice copy propagator by just adding the
>>> pass to passes.def whereas using the RPN VN actually requires a
>little
>>> bit of real code (to set up the entry/exits for the relevant SEME
>>> regions), I went with the lattice copy propagator.
>>>
>>> This change adds around .4% instruction executions to my testbed of
>.i
>>> files.  It has no significant impact on the resulting code -- I see
>>> different register allocation decisions in a lot of places which
>seem to
>>> primarily result in reversing arguments to comparisons.
>> 
>> Was there a need to have two copy-prop passes in the early
>> DOM/errorneous-path removal where we previously only had
>> a single phi-only-prop pass?  Is the testcase fixed also when
>> doing copy-prop only a single time?
>So if we replace phi-only cprop with the lattice propagator and move
>the
>pass which currently runs before erroneous path isolation so that it
>instead runs before erroneous path isolation we're in pretty good
>shape.
>
>isolate-2.c and isolate-4.c needed twiddling -- they need to look later
>in the pipeline for an expected simplification, but the simplification
>still occurs and it's not too much later than before.
>
>
>I've bootstrapped and regression tested on x86_64, but no other targets
>at this point.
>
>OK for the trunk now?

OK. 

Richard. 

>
>Jeff