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Re: [PATCH] Add soft frame pointer pseudo on ppc{32,64} and prepare for (optional) FRAME_GROWS_DOWNWARD


On Tue, Jun 28, 2005 at 12:39:32PM -0400, David Edelsohn wrote:
> Okay.

Thanks.

> 	I would appreciate if you would wait to apply the patch until
> PowerPC is able to bootstrap again.

It is not bootstrappable?  I admit I haven't tried that today yet,
but there is a recent testresults:
http://gcc.gnu.org/ml/gcc-testresults/2005-06/msg01660.html

> 	Is the manipulation and elimination of the soft frame pointer
> expensive in terms of compile time?  It seems unfortunate that it needs to
> be used even when stack guard is not enabled.

I think it is very cheap.  Perhaps with some generic changes we could allow
FRAME_POINTER_REGNUM to be sometimes HARD_FRAME_POINTER_REGNUM and sometimes
not.  ATM there is a lot of code that uses
#if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
...
#endif
which wouldn't work if either HARD_FRAME_POINTER_REGNUM or
FRAME_POINTER_REGNUM weren't compile time constants.

	Jakub


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