[llvm-commits] Fold() function on TargetFolder class - removal of redundant constantexpr

[Jin Gu Kang]

replaceAllUsesWith() is an example. :)

I don't know all of passes which use inforamtion of Use.
so I would like to know whether this issue is trivial or not.

I think view of you and other llvm-commiters are right.

Thanks,
Jin-Gu Kang
________________________________________
From: Duncan Sands [baldrick at free.fr]
Sent: Tuesday, February 22, 2011 10:21 PM
To: Jin Gu Kang
Cc: llvm-commits at cs.uiuc.edu
Subject: Re: [llvm-commits] Fold() function on TargetFolder class - removal of redundant constantexpr

Hi Jin Gu Kang,

> If we makes useless ConstantExpr with previous Global variable,
> replaceAllUsesWith() function will change useless ConstantExpr's previous Global variable
> to new Global variable. I think it is inefficient.

as you discovered, avoiding this is much more subtle than it appears.  If a
trivial change could deal with it, then I would be happy to make that change.
But this is not the case, which then raises the question: is it worth spending
time working on if there is in fact no measurable compile time impact?  If you
want to speed up compilation there are much better places to start.

Ciao, Duncan.