[LoopVersioning] Don't modify the list that we iterate over in addPHINodes
Summary:
In LoopVersioning::addPHINodes we need to iterate over all
users for a value "Inst", and if the user is outside of the
VersionedLoop we should replace the use of "Inst" by using
the value "PN" instead.
Replacing the use of "Inst" for a user of "Inst" also means
that Inst->users() is modified. So it is not safe to do the
replace while iterating over Inst->users() as we used to do.
This patch splits the task into two steps. First we iterate
over Inst->users() to find all users that should be updated.
Those users are saved into a local data structure on the stack.
And then, in the second step, we do the actual updates. This
time iterating over the local data structure.
Reviewers: mzolotukhin, anemet
Reviewed By: mzolotukhin
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D47134
llvm-svn: 332958
diff --git a/llvm/lib/Transforms/Utils/LoopVersioning.cpp b/llvm/lib/Transforms/Utils/LoopVersioning.cpp
index 95e9a186..abbcd5f 100644
--- a/llvm/lib/Transforms/Utils/LoopVersioning.cpp
+++ b/llvm/lib/Transforms/Utils/LoopVersioning.cpp
@@ -140,9 +140,12 @@
if (!PN) {
PN = PHINode::Create(Inst->getType(), 2, Inst->getName() + ".lver",
&PHIBlock->front());
- for (auto *User : Inst->users())
- if (!VersionedLoop->contains(cast<Instruction>(User)->getParent()))
- User->replaceUsesOfWith(Inst, PN);
+ SmallVector<User*, 8> UsersToUpdate;
+ for (User *U : Inst->users())
+ if (!VersionedLoop->contains(cast<Instruction>(U)->getParent()))
+ UsersToUpdate.push_back(U);
+ for (User *U : UsersToUpdate)
+ U->replaceUsesOfWith(Inst, PN);
PN->addIncoming(Inst, VersionedLoop->getExitingBlock());
}
}