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Re: Loop optimizer issues
Hello.
> On Wed, 2 Jul 2003, David Edelsohn wrote:
>
> > I'm sorry, I'm still confused. If you are writing an RTL-based
> > loop optimizer, you cannot avoid supporting LIBCALLs.
>
> I think the confusion arises because Zdenek wasn't very clear about what
> he exactly means with dropping support for libcalls.
>
> There _will_ be libcall constructs in the RTL the loop optimizer sees
> (except if we somewhen really can remove them alltogether from the
> compiler, but I don't see that), and hence it obviously has to evalutate
> their data flow effects at least.
>
> I guess (and only guess) that Zdenek meant to drop actually moving of
> libcalls. Zdenek, could you clarify?
Exactly.
> Btw. I would agree that most of those constructs resulting in libcalls
> should already have been optimized by tree-ssa, but OTOH I have
> difficulties understanding why removing supporting libcalls would be so
> much easier to implement. libcalls for REG_NO_CONFLICT blocks are simply
> funny multi-pattern statements, and libcalls with just calls, are well,
> simply calls. Why is it so much easier to not handle them?
It is not somehow terribly difficult (a hundred or two of lines of code,
I guess); but IMO it would be nice to get rid of this feature with
tree-ssa completely.
Zdenek