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Re: [PATCH] Fix PR18754: add early loop pass

From: Andrew Pinski <pinskia at physics dot uc dot edu>
To: Richard Guenther <rguenth at tat dot physik dot uni-tuebingen dot de>
Cc: gcc-patches at gcc dot gnu dot org
Date: Thu, 20 Jan 2005 09:49:58 -0500
Subject: Re: [PATCH] Fix PR18754: add early loop pass
References: <Pine.LNX.4.44.0501201213470.16464-100000@alwazn.tat.physik.uni-tuebingen.de>

On Jan 20, 2005, at 6:57 AM, Richard Guenther wrote:

Hi!

This patch adds an early loop pass (just after ch) just
containing complete unrolling.  This allows the following
SRA pass to scalarize small arrays that were manipulated
in constant rolling loops, as it often happens in C++ code.

I did experiments with scheduling a second SRA pass after
loop optimization, but that doesn't help ivopts - we'd need
another loop pass after the second SRA this way.  I also
tried scheduling SRA inside loop, just after cunroll, but
SRA seems to not preserve some of the loop infrastructure,
so everyting breaks.


No because loop optimizations are slow.  The reason why SRA pass
after loop optimization does not help because we have a bug in the
loop unrolling pass, see PR 18755.

-- Pinski

References:
- [PATCH] Fix PR18754: add early loop pass
  - From: Richard Guenther

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