Re: [Qemu-devel] patch for qemu with newer gcc-3.4.x (support repz retq optimization for amd processors correctly)

[Jim C. Brown]

On Thu, Nov 10, 2005 at 01:44:04AM +0000, Jamie Lokier wrote:
> > 
> > The use of gcc to generate the back end in QEMU's early days was a 
> > clever way to get the project up and running quickly.  But surely
> > now it would be better to transition to a handwritten backend, so
> 
> It should be trivial to take the _currently_ generated GCC code for
> all the architectures QEMU is commonly built on, and just distribute
> that code with the QEMU source.
> 

You mean convert the code with gcc 3 into asm, and then distribute that?

I'm no expert, but I would imagine such a solution would be quite brittle.
That's assuming one can make gcc 3 assembly code work with gcc 4 (5?) code
to form a single object file.

> Then it would be independent of future changes to GCC.

Well, someone would still need to maintain all those assembly files.

Or else keep an old copy of gcc 3 around to regenerate them whenever needed.

> 
> I understand a handwritten backend is already being written.  But
> until a proper one is done, wouldn't that serve as a useful stopgap?
> 

I believe the current version works - but it doesn't implement every possible
op yet. For now, it relies on dyngen to produce the missing ops (until they are
replaced with the hand coded version).

> -- Jamie
> 

-- 
Infinite complexity begets infinite beauty.
Infinite precision begets infinite perfection.