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Re: VIRT_ADDR_VARIES


From: Paul Eggert
Subject: Re: VIRT_ADDR_VARIES
Date: Thu, 10 Nov 2011 08:50:39 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0) Gecko/20110927 Thunderbird/7.0

On 11/10/11 08:43, Eli Zaretskii wrote:
> But why would someone do such a thing?

Performance.

Comparing against my_edata takes just one instruction.
Comparing against both the start and the end of 'pure'
takes two comparisons and some glue instructions and
typically includes a conditional branch.  The optimization
I've suggested in this thread prunes away most of this
underbrush, but it's still one more instruction
(a 'subtract') over the my_edata approach.



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