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Re: g++ 4.3, troubles with C++ indexing idioms

From: Paolo Bonzini <bonzini at gnu dot org>
To: Richard Guenther <richard dot guenther at gmail dot com>
Cc: tbp <tbptbp at gmail dot com>, Dave Korn <dave dot korn at artimi dot com>, gcc at gcc dot gnu dot org
Date: Wed, 25 Jul 2007 08:28:58 +0200
Subject: Re: g++ 4.3, troubles with C++ indexing idioms
References: <4fc48eb10707190607x2e58e275m7cb4148b804be460@mail.gmail.com> <84fc9c000707190933k181d8cb4s8f59707102b3fe46@mail.gmail.com> <4fc48eb10707191131m6ee4dfcfo74c9951de4df756@mail.gmail.com> <84fc9c000707191215i53380452t958527a119981eee@mail.gmail.com> <4fc48eb10707210633m6a68060x520ebcdd77a0cce5@mail.gmail.com> <84fc9c000707240534u4b837b1csd1dbf1b782b8f400@mail.gmail.com>

For performance small arrays should be the same as individual members
(I can see the annoying fact that initialization is a headache - this has
annoyed me as well).  For larger arrays (>4 members), aliasing will
make a difference possibly, making the array variant slower.  Any union
variant is expected to be slower for aliasing reasons (we do not do
field-sensitive aliasing for unions).

I wonder if the fabled "union as VIEW_CONVERT_EXPR" patch would help... Richi, do you know?

Paolo

Follow-Ups:
- Re: g++ 4.3, troubles with C++ indexing idioms
  - From: Richard Guenther

References:
- g++ 4.3, troubles with C++ indexing idioms
  - From: tbp
- Re: g++ 4.3, troubles with C++ indexing idioms
  - From: Richard Guenther
- Re: g++ 4.3, troubles with C++ indexing idioms
  - From: tbp
- Re: g++ 4.3, troubles with C++ indexing idioms
  - From: Richard Guenther
- Re: g++ 4.3, troubles with C++ indexing idioms
  - From: tbp
- Re: g++ 4.3, troubles with C++ indexing idioms
  - From: Richard Guenther

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