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Re: [Qemu-devel] Use Clang to compile Qemu?

From: 陳韋任
Subject: Re: [Qemu-devel] Use Clang to compile Qemu?
Date: Sat, 24 Dec 2011 09:48:18 +0800
User-agent: Mutt/1.5.21 (2010-09-15)

On Fri, Dec 23, 2011 at 02:07:53PM +0100, David Turner wrote:
> Some parts of QEMU (the JIT) require the use of a global register variable
> to point to the "env" CPU state variable.
> This feature is not supported by Clang (which is not very surprising given
> that it uses LLVM as its backend, and LLVM explicitely doesn't support this)
> Until the JIT is modified to not require this anymore, it is very unlikely
> that Clang will be able to build QEMU.
> There were previous discussions about such a change on this mailing list,
> but I believe nobody started working on that change because many feared it
> was a lot of work that would have a negative impact on performance (though
> I think it was all conjecture, i.e. no one really tried it and got any real
> data).

  You're right. Here is the discussion,

  Since TCI (Tiny Code Interpreter) doesn't need AREG0, I configure QEMU to use
TCI and try it out. Here's my flow.

# apply patches under /usr/ports/emulators/qemu-devel/files/ first
$ ../configure --prefix=$INSTALL --target-list=i386-bsd-user \
  --enable-tcg-interpreter \
$ gmake install

  So far so good (perhaps freebsd guys should upstream those patches?). But I am
stuck at the error below,

$ qemu-i386 -bsd freebsd hello
Unable to load interpreter

  Any thoughts? Thanks! :)


Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj

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