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Re: [Qemu-devel] [PATCH 0/3] tci rewrite

From: Peter Maydell
Subject: Re: [Qemu-devel] [PATCH 0/3] tci rewrite
Date: Tue, 13 May 2014 22:49:09 +0100

On 13 May 2014 22:22, Richard Henderson <address@hidden> wrote:
> There are a number of problems with the current interpreter:
>   (1) It uses direct unaligned accesses as part of the bytecode stream.
>       This fails with SIGBUS for strict alignment hosts.  This could of
>       course be fixed to use "proper" unaligned accesses, but this would
>       just be slow.
>   (2) The method by which it implements calls is non-portable, and really
>       only works for x86.
>   (3) The code is full of ifdefs and TODOs that never got completed.
>   (4) The "registers" are in a global "tci_reg" array that implies that
>       if threads are ever used, we'll immediately get corruption.  Fixing
>       this is complicated by the structure of the interpreter.
>   (5) It hasn't been updated to the "new" ldst opcodes.
> To me, all of this adds up to a complete rewrite.

Does the TCG interpreter actually have any interesting uses
to merit our carrying it around, maintaining it and (in this case)
rewriting it? Mostly I just see it when people accidentally configure
it and I have to say "don't do that, you really want the native TCG

-- PMM

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