Revert "fix compile-time issue in spec2017 527.cam4_r"

This reverts commit 05d8a51.

Author: c-rhodes

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -5077,9 +5077,6 @@ InstCombinerImpl::pushFreezeToPreventPoisonFromPropagating(FreezeInst &OrigFI) {
       if (U == OrigUse)
         return nullptr;
 
-      if (isa<PoisonValue>(V))
-        continue;
-
       auto *UserI = cast<Instruction>(U->getUser());
       if (auto *PN = dyn_cast<PHINode>(UserI))
         Builder.SetInsertPoint(PN->getIncomingBlock(*U)->getTerminator());