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Re: PR 23551: why should we coalesce inlined variables?
On Jul 9, 2007, Jan Hubicka <hubicka@ucw.cz> wrote:
>> On Jul 9, 2007, "Richard Guenther" <richard.guenther@gmail.com> wrote:
>>
>> > It shoulnd't be too hard to get this working to the point that it is as good
>> > as with your patch disabling coalescing (which you say doesn't help anyway
>> > as optimization passes do this coalescing by propagation anyway).
>>
>> That's the thing, I don't see how it's going to be accomplished if we
>> just throw that assignment away. And if we don't, whether we coalesce
>> or not is irrelevant, we have to keep an annotation at that point to
>> indicate the state of some user variable changed at that point. And
> If we end up having arbitrary copy instructions to represent this, we
> will lose quality of code for heavy C++ inlining.
Annotations won't generate copies. There's a reason why I'm
representing them as comments.
> It still seems to me that we should just record list of variables
> belonging to given SSA name
This loses information. I've heard a lot from heavy users of debug
information that wrong debug information is worse that no debug
information. So this would be a step backward.
--
Alexandre Oliva http://www.lsd.ic.unicamp.br/~oliva/
FSF Latin America Board Member http://www.fsfla.org/
Red Hat Compiler Engineer aoliva@{redhat.com, gcc.gnu.org}
Free Software Evangelist oliva@{lsd.ic.unicamp.br, gnu.org}