DominanceFrontier

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1

Hi Guys,
I saw in the API that DominanceFrontier has been deprecated. Is this for real?
I have read the computational issues but shouldn’t that be left to the users of llvm?
My concern is I am writing a Control Dependence module that uses Dominance-Frontier information.
Getting rid of Dominance Frontiers will put me in a tight spot.

George

2

Hi George,

   I saw in the API that DominanceFrontier has been deprecated. Is this for real?
I have read the computational issues but shouldn't that be left to the users of
llvm?
My concern is I am writing a Control Dependence module that uses
Dominance-Frontier information.
Getting rid of Dominance Frontiers will put me in a tight spot.

if the dominancefrontier code is deleted from LLVM you can always add a copy of
the last version of the code to your project for your own private use.

Ciao, Duncan.

3

That's right. It should be easy to maintain.

If you search the list archives I'm sure you'll find some motivation and alternatives.

My take on it is: checking the dominance frontier on-the-fly is easy, we want to discourage passes from precomputing all frontiers as a global analysis.

-Andy

4

George Baah <georgebaah@gmail.com> writes:

Hi Guys,

I saw in the API that DominanceFrontier has been deprecated. Is this
for real?
I have read the computational issues but shouldn't that be left to the
users of llvm?
My concern is I am writing a Control Dependence module that uses
Dominance-Frontier information.
Getting rid of Dominance Frontiers will put me in a tight spot.

George

Hi,

I had the same issue implementing a pass that build PDGs for an exam two
months ago.

As an alternative to the (post)-dominance frontier method I used the
algorithm described in [1], section 9.5 "Program Dependence Graph" where
you can find a method to build the CDG using only the post-dominator
tree.

Happy hacking,
Marco

[1] Advanced Compiler Design & Implementation by Steven S. Muchnick

5

The issue is that when I call the PostDominatorTree pass and I try to get the root of the tree, I get the seg fault. When I compile llvm in release mode everything works fine and dandy.

I removed the inline attribute from the functions in PostDominators.h and recompiled llvm in debug mode. Same problem!
The problems has to do with the PostDominators.h or PostDominatorTree. I am not even sure any longer.

–George