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Re: PR 23551: why should we coalesce inlined variables?

On Jul  9, 2007, Jan Hubicka <> wrote:

>> On Jul  9, 2007, "Richard Guenther" <> 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
FSF Latin America Board Member
Red Hat Compiler Engineer   aoliva@{,}
Free Software Evangelist  oliva@{,}

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