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From: | Vincent Lefevre |
Subject: | Re: [Tinycc-devel] [PATCH] tccgen.c: Optimise 0<<x, 0>>x, -1>>x, x&0, x*0, x|-1, x%1. |
Date: | Fri, 6 Mar 2015 08:29:06 +0100 |
User-agent: | Mutt/1.5.23-6424-vl-r76280 (2015-02-19) |
On 2015-03-05 22:09:22 +0000, Edmund Grimley Evans wrote: > Do not optimise (0 / x) and (0 % x) here as x might be zero, though > for an architecture that does not generate an exception for division > by zero the back end might choose to optimise those. When x is 0, this is undefined behavior, so that you are free to optimize them, even if the architecture generates an exception for division by 0. Contrary to IEEE 754, there isn't any requirement to generate an exception for integer operations. -- Vincent Lefèvre <address@hidden> - Web: <https://www.vinc17.net/> 100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/> Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
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