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Re: [PATCH] [RFC] loop index promotion pass

From: Richard Earnshaw <rearnsha at arm dot com>
To: Zdenek Dvorak <rakdver at kam dot mff dot cuni dot cz>
Cc: Richard Guenther <richard dot guenther at gmail dot com>, Mark Mitchell <mark at codesourcery dot com>, gcc-patches at gcc dot gnu dot org
Date: Wed, 20 May 2009 18:12:36 +0100
Subject: Re: [PATCH] [RFC] loop index promotion pass
References: <20090424184303.GZ22588@codesourcery.com> <84fc9c000904241250n6db93fbagc5c9e15fdf4d1c8f@mail.gmail.com> <4A133750.2090204@codesourcery.com> <84fc9c000905200151k309fb913u53fbdbd1234ff9c9@mail.gmail.com> <20090520133859.GH23911@codesourcery.com> <84fc9c000905200651r1ee6d7e0k6a476be62260f2ff@mail.gmail.com> <20090520142301.GI23911@codesourcery.com> <84fc9c000905200738h430f26c5v9dbbf16d25d43433@mail.gmail.com> <20090520151500.GJ23911@codesourcery.com> <84fc9c000905200845k8c9cf8cw7c384b998fc7c95a@mail.gmail.com> <20090520170347.GB4197@kam.mff.cuni.cz>

On Wed, 2009-05-20 at 19:03 +0200, Zdenek Dvorak wrote:

> However, the expression
> (i * w) + j could wrap (and in fact, it will, assuming 16-bit short int),

Only if the result is assigned to a 16-bit short int.  Otherwise it will
only wrap if the promoted version also wraps (arithmetic is done on
ints, not shorts).

References:
- Re: [PATCH] [RFC] loop index promotion pass
  - From: Mark Mitchell
- Re: [PATCH] [RFC] loop index promotion pass
  - From: Richard Guenther
- Re: [PATCH] [RFC] loop index promotion pass
  - From: Nathan Froyd
- Re: [PATCH] [RFC] loop index promotion pass
  - From: Richard Guenther
- Re: [PATCH] [RFC] loop index promotion pass
  - From: Nathan Froyd
- Re: [PATCH] [RFC] loop index promotion pass
  - From: Richard Guenther
- Re: [PATCH] [RFC] loop index promotion pass
  - From: Nathan Froyd
- Re: [PATCH] [RFC] loop index promotion pass
  - From: Richard Guenther
- Re: [PATCH] [RFC] loop index promotion pass
  - From: Zdenek Dvorak

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