[PATCH] D97537: [Codegenprepare] Use IV increment instead of IV if we can prove it is not a poisoned value

[Sanjay Patel via Phabricator via llvm-commits]

spatel added subscribers: nikic, aqjune, lebedev.ri.
spatel added inline comments.


================
Comment at: llvm/lib/CodeGen/CodeGenPrepare.cpp:3874
+          ICmpInst::Predicate Pred;
+          if (match(BB->getTerminator(),
+                    m_Br(m_ICmp(Pred, m_Specific(IVInc), m_Value()),
----------------
reames wrote:
> Detail on the proof here -- the fact the branch is a loop exit is definitely irrelevant.
> 
> It's not clear to me whether branching on poison is immediate UB.  LangRef seems to say "yes", but the code in ValueTracking seems to say "no".  We need to draw in the experts here.  (Juneyoung)
cc @aqjune @lebedev.ri @nikic for branch-on-poison question.


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https://reviews.llvm.org/D97537