[tree-ssa] Removal of gotos from cfg based ir
law@redhat.com
law@redhat.com
Fri Nov 14 19:53:00 GMT 2003
In message <Pine.LNX.4.44.0311142014440.13268-100000@wotan.suse.de>, Michael Ma
tz writes:
>Hi,
>
>On Fri, 14 Nov 2003 law@redhat.com wrote:
>
>> In message <1068818613.2305.29.camel@p4>, Andrew MacLeod writes:
>> >I simply dont see a significant win for this kind of representation. I
>> >can't beleive that changing GOTO's and labels are that much of a
>> >headache when you want to change program flow. That seems like fairly
>> >minor work.
>> I don't see it as a huge win either.
>
>Let's state it this way: If Honza and Zdenek (as ones who wrote a massive
>amount of the CFG manipulating functions) say it will be simpler with that
>separation, I trust them. Even if I wouldn't trust them, I still would be
>convinced, because IMHO it's a very straight forward idea, and the
>advantages are clear to me (mostly no problematic redundancy between insn
>stream and CFG, which together make up the IL).
>
>OTOH: what advantages do you see in creating ugly hacks inside the stream,
>like proposed in this thread, in order to not make the above separation?
I see the benefits, particularly in CFG manipulation. Hell, myself and
others have pondered similar ideas for RTL and tree-ssa in the past, but
we never were able to say that it's actually a significant improvement.
But more importantly in my mind is the design implications -- namely that
the IL no longer represents the function. The function's representation
is the IL + the CFG in Zdenek's scheme. That's a fundamental design
change and that's what we need to sort out -- is it a good design change
or not. Details about duality of manipulations, the -O0 argument are
secondary.
And for me at least, a fundamental design change needs to have large benefits,
not minor ones.
Jeff
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