Weddington, Eric wrote:
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From:
avr-libc-dev-bounces+eweddington=cso.atmel....@nongnu.org
[mailto:avr-libc-dev-bounces+eweddington=cso.atmel....@nongnu.
org] On Behalf Of David Brown
Sent: Tuesday, March 17, 2009 4:19 PM
To: avr-libc-dev@nongnu.org
Subject: [avr-libc-dev] Re: Inline assembler and compiler optimization
Googling for "gcc memory_barrier" suggests that it is a name
used in the
RTL patterns.
Hmm. Need to look more into the machine description then.
The linux kernel uses names such as mb(), rmb() and wmb(), which are a
bit too short. On the architectures I looked at, these are defined to
be "barrier()", which for gcc is in turn defined as a volatile memory
clobber and for the intel compiler it is defined as the
__memory_barrier() builtin.
Well that's certainly one route. We could perhaps add it as a gcc builtin.
Thanks for doing this research, David. :-)
Thank Google :-)
I would imagine that a builtin involves more work than just #defining
__memory_barrier() as a memory clobber. It would be better, however, if
gcc could have a consistent set of memory barrier builtins (including
the read and write barriers used by Linux) that could be used across all
targets. I don't know how much influence you have in the gcc world at
large...
Either way, a "#define memory_barrier() __memory_barrier()" in one of
the headers would be useful to give a slightly more friendly name to users.
mvh.,
David
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