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Subject: Re: svn commit: r253802 - head/contrib/llvm/tools/clang/lib/Headers
From: David Chisnall <theraven@FreeBSD.org>
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To: John Baldwin <jhb@FreeBSD.org>
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Cc: Matthew Fleming <mdf@FreeBSD.org>,
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On 14 Aug 2013, at 13:21, John Baldwin <jhb@freebsd.org> wrote:

> On Wednesday, August 14, 2013 4:23:11 am David Chisnall wrote:
>> On 13 Aug 2013, at 21:57, Jilles Tjoelker <jilles@stack.nl> wrote:
>> 
>>> Given that JIT is for performance and larger addresses increase code
>>> size and register pressure, the mmap() flag is probably useful.
>>> Alternatively, all the JITted code could be placed in one block and use
>>> relative addressing.
>> 
>> This would be a good thing to have in for 10.0, as the LLVM 3.4 JIT will
>> require it unless someone wants to contribute support for the large code
>> model...
> 
> So you just need a flag to cap the virtual address at 2GB?  Do you think we
> need an arbitrary address flag for this, or is a hardcoded 2GB flag ok?
> 
> Linux has a MAP_32BIT that does what you want I think.

Yes, MAP_32BIT is used on Linux to solve this.

David