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Re: i * i is nonnegative

From: Jeff Law <law at redhat dot com>
To: Marc Glisse <marc dot glisse at inria dot fr>
Cc: gcc-patches at gcc dot gnu dot org
Date: Tue, 19 Mar 2013 10:21:42 -0600
Subject: Re: i * i is nonnegative
References: <alpine dot DEB dot 2 dot 02 dot 1303191659110 dot 4515 at stedding dot saclay dot inria dot fr>

On 03/19/2013 10:08 AM, Marc Glisse wrote:

Hello,

this patch extends the property that x*x is non-negative, which was
already known for floats, to integers with undefined overflow.

2013-03-19  Marc Glisse  <marc.glisse@inria.fr>

     PR tree-optimization/56355
gcc/
     * fold-const.c (tree_binary_nonnegative_warnv_p) <MULT_EXPR>:
     Also handle integers with undefined overflow.

gcc/testsuite/
     * gcc.dg/pr56355-1.c: New file.

Fine for the trunk. Though I would suggest waiting for http service &web archives to return before committing.

BTW, did you check if VRP creates a non-negative range for this case aswell?


jeff

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