search for: domin

Hi Tobias, 1) Daniel and Chandler have for a long time been talking about computing > dominance and post-dominance in one shot to reduce the cost of > post-dominance and make it (freely) available everywhere. Is this > covered by your current (or planned) work? I'm not sure what you exactly mean by one shot; I'll ask around tomorrow. I wanted to play a little bit with y...

>> all the zero paths from entry to %a pass by %b. > > > That is a graph-wise definition, sure. > So, this is an interesting definition, and maybe this is part of the source > of the problem. > > For SSA, at least GCC requires that both "definition block dominates use > block" (which would be true here), *and* > that "definition appears before use in block" (IE definition locally > dominates use). > > IE it has to pass both DT->dominates(block(%b), block(%a)) and > DT->dominates(%b, %a). > > LLVM special cases...

Hi Henrique, I have tried using -mergereturn and inserting a free into the predecessors of dominance frontier of malloc block and it caused double free. It is possible for multiple free's to be inserted on the path from malloc to an exit. For example, in the following CFG: BB10 (malloc) / \ BB11 BB12 ... / \ / \...

Try breaking the critical edges (-break-crit-edges). This way, a new block will be created between BB13 and BB11 (call this BB11.break) and BB15 and BB12 (call this BB12.break). The predecessors of the dominance frontier will, thus, be BB11.break, BB12.break, and BB14. When we enter through a block with a call to malloc(), we will end up in one of the blocks in the dominance frontier (kind of). These blocks must have multiple predecessors, else it would not be in the dominance frontier. If a predecess...

...VMAnalysis.a ../../lib/libLLVMObject.a ../../lib/libLLVMMCParser.a ../../lib/libLLVMMC.a ../../lib/libLLVMBitReader.a ../../lib/libLLVMProfileData.a ../../lib/libLLVMCore.a ../../lib/libLLVMBinaryFormat.a ../../lib/libLLVMSupport.a -lcurses -lz -lm ../../lib/libLLVMDemangle.a duplicate symbol llvm::DominatorTreeBase<llvm::BasicBlock, true>::releaseMemory() in: ../../lib/libLLVMAnalysis.a(PostDominators.cpp.o) ../../lib/libLLVMCore.a(Dominators.cpp.o) duplicate symbol llvm::DominatorTreeBase<llvm::BasicBlock, true>::verify() const in: ../../lib/libLLVMAnalysis.a(PostDomina...

Like I said, i'm nearly positive there is a much faster way, as the sets are mostly shared except in the cyclic case, and in all reducible cyclic cases, removal of back-arcs does not affect dominance (because in any reducible flowgraph, v dominates u whenever u,v is a back-arc) On Tue, Apr 25, 2017 at 7:38 PM, Hongbin Zheng <etherzhhb at gmail.com> wrote: > Hi Daniel, > > Thanks a lot for all these explanation, I will try it out. > > Hongbin > > On Tue, Apr 25...

...<dberlin at dberlin.org> >> wrote: >> >>> >>> >>> On Tue, Apr 25, 2017 at 6:17 PM, Hongbin Zheng <etherzhhb at gmail.com> >>> wrote: >>> >>>> Hi Daniel, >>>> >>>> I mean "*As a set*, B + C dominate D". >>>> >>>> On Tue, Apr 25, 2017 at 5:42 PM, Daniel Berlin <dberlin at dberlin.org> >>>> wrote: >>>> >>>>> When you say collectively, you mean "would dominate it if considered a >>>>> single block tog...

Many published analyses which build on post-dominance assume a canonical single-dominator-tree form induced by unifying all exits (and often adding a virtual edge from START to END). In contrast, it seems that the current LLVM post-dominator analysis only operates in a mode in which it generates a forest of post-dominator trees, with one rooted at...

When looking into https://llvm.org/bugs/show_bug.cgi?id=24866, I discovered that the root cause of the crash is that I was expecting every basic block to have a corresponding Node in the dominator tree. Apparently, the "while.end" basic block in the example does not have a Node in the Dominator Tree. Can anyone tell me if this is expected? If so, under what circumstances? Interestingly, the crash in question appears to be fairly recently introduced. A checkout from we...

Hi, In browsing through the LLVM source, I don't currently see an implementation for a control dependence graph builder. Am I overlooking something? It doesn't look like LLVM currently provides a way to build the post-dominance frontier of the reverse CFG, either. Dominators.h mentions forward dominators, but I believe all this is referring to is dominators as opposed to post-dominators, not dominators on the CFG versus dominators on the reverse-CFG. I just wanted to make certain I'm not overlooking anything befo...

...la at gmail.com> wrote: >> >> > Maybe. >> > My view is the ideal is either no-unreachable code, or unreachable >> > blocks >> > only contain terminators. >> >> I am definitely happy with both. What worries me is introducing a >> special dominance rule for unreachable blocks. >> >> >> I don't think that rejecting >> >> >> >> %a = getelementptr inbounds i8* %a, i64 1 >> >> >> >> but accepting >> >> >> >> %a = getelementptr inbounds i8* %b, i6...

Btw, here is another interesting paper about post-dominators and control dependence: https://pdfs.semanticscholar.org/cbb2/9a0e4895025bd9df24f9263217df12f1ed1e.pdf I think a great outcome of your internship would be some precise documentation regarding the guarantees the LLVM dominators give -- possibly also considering classic and weak control depend...

Hi I run into an issue as part of splitting a critical edge during LICM. When a new basic block is created and needs to be added into the dominator tree, the block is already in the dominator tree. I print the dominator tree and I see it is added into the tree as child of node it is supposed to dominate. How do I debug to find out why/when its getting added into the tree. ? Tips/suggestions on how to debug to find out how the densemap inv...

There is PostDominatorTree for determining post-dominance. Even if A post-dominates B and B is executed, that doesn't guarantee that A will be executed. For example, there could be an infinite loop in-between. Strong post-dominance makes the stronger guarantee that there will be no infinite loop from B to A. Do w...

On Tue, Apr 25, 2017 at 6:32 PM, Daniel Berlin <dberlin at dberlin.org> wrote: > > > On Tue, Apr 25, 2017 at 6:17 PM, Hongbin Zheng <etherzhhb at gmail.com> > wrote: > >> Hi Daniel, >> >> I mean "*As a set*, B + C dominate D". >> >> On Tue, Apr 25, 2017 at 5:42 PM, Daniel Berlin <dberlin at dberlin.org> >> wrote: >> >>> When you say collectively, you mean "would dominate it if considered a >>> single block together? >>> >>> IE >>>...

...013 at 9:13 PM, Henrique Santos < henrique.nazare.santos at gmail.com> wrote: > PRE normally uses a latest placement algorithm to do something of the sort. > I don't know about GVN/PRE, but older version of PRE might have it. > Just placing the calls to free at the predecessors (dominated by BB12) of > the dominance frontier of BB12 seems to work, however. Is there anything > wrong with this? > It seems that placing the calls to free at the predecessors of dominance frontier is inadequate. It is possible that there are exit blocks that are dominated by BB12 (calls to ma...

> > It seems that placing the calls to free at the predecessors of dominance > frontier is inadequate. It is possible that there are exit blocks that are > dominated by BB12 (calls to malloc). I guess we can also insert calls to > free at these exit blocks too. That crossed my mind a few minutes later. : ) If you're interested, PRE.cpp existed last at r25...

Hi, Is there any way to quickly test if a set of basic block collectively dominate another basic block? Thanks Hongbin -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20170425/b9336a6d/attachment.html>

Hi folks, This summer I'm working on improving dominators during my internship at Google. Below is an RFC on switching to dynamic dominators, which you can also read as a Google Doc <https://docs.google.com/document/d/1wPYeWykeO51YDPLYQEg4KNTlDIGIdyF65OTfhSMaNHQ/edit?usp=sharing> if you prefer so. Please let us know what you think. ~Kuba ====...

On Aug 24, 2009, at 4:58 PM, Jonathan Ragan-Kelley wrote: > Many published analyses which build on post-dominance assume a > canonical single-dominator-tree form induced by unifying all exits > (and often adding a virtual edge from START to END). In contrast, it > seems that the current LLVM post-dominator analysis only operates in a > mode in which it generates a forest of post-dominator trees...