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Date: Mon, 18 Feb 2013 01:13:51 +0100
From: Jens Gustedt <>
Subject: Re: [PATCH 1/3] protect some clobbered variables with

Hello Rich,
AFAIR these both occurred when compiling with -flto. I would not trust
the static analysis of the compiler at 100 % either, but this is just
an argument to have the volatile in.

The compiler is telling us that here he thinks that an optimization
might hide a intermittent write, but that by the aliasing rules it
would be OK to save a read. So better be careful and trust the
compiler that he is willing to do bad things :)

Maybe LTO is broken, yet, in that it might do some optimizations that
it shouldn't. Or maybe this exposes possible problems that were
previously hidden because the write was in a different compilation
unit than the read. Who knows.

In any case, the performance hit should be limited, and my personal
preference would tend towards safety and calming down the compiler.


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