[PATCH] D104063: [SimplifyCFG] avoid crash on degenerate loop

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added inline comments.


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Comment at: llvm/lib/Transforms/Utils/SimplifyCFG.cpp:2710
   BasicBlock *IfTrue, *IfFalse;
   Value *IfCond = GetIfCondition(BB, IfTrue, IfFalse);
   if (!IfCond ||
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(1) If you change `IfCond`'s type to `AssertingVH<Value>` ...


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Comment at: llvm/lib/Transforms/Utils/SimplifyCFG.cpp:2843
 
     Value *Sel = Builder.CreateSelect(IfCond, TrueVal, FalseVal, "", InsertPt);
     PN->replaceAllUsesWith(Sel);
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(3) ... so here on the second loop iteration `IfCond` is use-after-free.


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Comment at: llvm/lib/Transforms/Utils/SimplifyCFG.cpp:2846
     Sel->takeName(PN);
     PN->eraseFromParent();
   }
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(2) ... the backtrace will tell you that the handle goes bad here ...


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https://reviews.llvm.org/D104063