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Re: A doubt about constraint modifiers

From: Ian Lance Taylor <iant at google dot com>
To: "Mohamed Shafi" <shafitvm at gmail dot com>
Cc: gcc at gcc dot gnu dot org
Date: Fri, 11 Apr 2008 00:11:58 -0700
Subject: Re: A doubt about constraint modifiers
References: <ba0bd44d0804102258n3c2ccae7v8a0f9a28b253893e@mail.gmail.com>

"Mohamed Shafi" <shafitvm@gmail.com> writes:

> I have noticed that when strict_low_part is used in a patten we need
> to use '+' as the constraint modifier if any constraints are used in
> the patterns.
> Why is this so?

Using strict_low_part implies that the register or memory location is
neither a pure input nor a pure output.  It is both an input and an
output.  Therefore a '+' constraint is appropriate.

Ian

Follow-Ups:
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  - From: Mohamed Shafi

References:
- A doubt about constraint modifiers
  - From: Mohamed Shafi

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