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RE: Jump threading in tree dom pass prevents if-conversion & following vectorization
- From: "Bingfeng Mei" <bmei at broadcom dot com>
- To: "Jeff Law" <law at redhat dot com>, "Andrew Pinski" <pinskia at gmail dot com>, "Richard Biener" <richard dot guenther at gmail dot com>
- Cc: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
- Date: Fri, 22 Nov 2013 17:13:52 +0000
- Subject: RE: Jump threading in tree dom pass prevents if-conversion & following vectorization
- Authentication-results: sourceware.org; auth=none
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So if we are about to fix this in if-conversion, we need to do both in tree & rtl as both ifcvt & ce passes cannot handle it.
I am still not convinced jump threading is good for target with predicated execution (assuming no fix for if-conversion). I am doing benchmarking on our target now.
Bingfeng
-----Original Message-----
From: Jeff Law [mailto:law@redhat.com]
Sent: 22 November 2013 16:58
To: Bingfeng Mei; Andrew Pinski
Cc: gcc@gcc.gnu.org
Subject: Re: Jump threading in tree dom pass prevents if-conversion & following vectorization
On 11/22/13 04:03, Bingfeng Mei wrote:
> Well, in your modified example, it is still due to jump threading that produce
> code of bad control flow that cannot be if-converted and vectorized, though in
> tree-vrp pass this time.
>
> Try this
> ~/install-4.8/bin/gcc vect-ifconv-2.c -O2 -fdump-tree-ifcvt-details -ftree-vectorize -save-temps -fno-tree-vrp
>
> The code can be vectorized.
>
> Grep "threading" in gcc, it seems that dom and vrp passes are two places that apply
> jump threading. Any other place? I think we need an target hook to control it.
No no. The right thing to do is fix if-conversion.
jeff