llvm dev - Jul 2012 - [LLVMdev] Does the pass -postdomfrontier exist?

On 07/13/2012 04:30 PM, Duncan Sands wrote:
> Hi,
>
>> I found the -postdomfrontier pass in *llvm*.org/docs/Passes.html, but
>> 'opt' does not accept it. I could not find the relevant codes
in
>> PostDominance.cpp in SVN trunk, but I found some relevant codes  here
>>
http://opensource.apple.com/source/clang/clang-137/src/lib/Analysis/PostDominators.cpp.
>>
>>
>> I am wondering why this pass is removed and what should I do if I want
>> the post dominance frontier information?
> there was some discussion of this on the mailing list already, so I suggest
you
> search the archives.
>
> Ciao, Duncan.
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I searched the archives and found
http://llvm.1065342.n5.nabble.com/post-dominance-frontier-fix-td10221.html
http://llvm.1065342.n5.nabble.com/Is-there-a-control-dependence-graph-builder-td35919.html#a35921
http://llvm.1065342.n5.nabble.com/post-dominance-frontier-td6783.html

It seems none of them are relevant.  Could you give me more hints about 
this topic? Thanks!

Hi shadowkernel,
> I searched the archives and found
> http://llvm.1065342.n5.nabble.com/post-dominance-frontier-fix-td10221.html
>
http://llvm.1065342.n5.nabble.com/Is-there-a-control-dependence-graph-builder-td35919.html#a35921
> http://llvm.1065342.n5.nabble.com/post-dominance-frontier-td6783.html
>
> It seems none of them are relevant.  Could you give me more hints about
> this topic? Thanks!
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
I'm not sure this is what I had in mind, but it does explain the issues with
dominance frontiers in general:

http://lists.cs.uiuc.edu/pipermail/llvmdev/2012-January/046638.html

Ciao, Duncan.

On Fri, Jul 13, 2012 at 5:35 AM, Duncan Sands <baldrick at free.fr>
wrote:
> Hi shadowkernel,
>
>> I searched the archives and found
>>
http://llvm.1065342.n5.nabble.com/post-dominance-frontier-fix-td10221.html
>>
http://llvm.1065342.n5.nabble.com/Is-there-a-control-dependence-graph-builder-td35919.html#a35921
>> http://llvm.1065342.n5.nabble.com/post-dominance-frontier-td6783.html
>>
>> It seems none of them are relevant.  Could you give me more hints about
>> this topic? Thanks!
>
> I'm not sure this is what I had in mind, but it does explain the issues
with
> dominance frontiers in general:
>
> http://lists.cs.uiuc.edu/pipermail/llvmdev/2012-January/046638.html
Also, PostDominators is broken in various ways in a number of edge
cases (nick llewycky had emailed me some), so in all likelihood there
are edge cases where post dominance frontiers are broken as well.

In any case, as Duncan's quoted emails point out, computing
post-dominance frontiers for the entire function is expensive but not
really useful.