1 files changed, 26 insertions, 3 deletions
diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp
index e5866b4718da..66608ec631f6 100644
--- a/lib/Transforms/Scalar/SCCP.cpp
+++ b/lib/Transforms/Scalar/SCCP.cpp
@@ -1929,9 +1929,32 @@ static bool runIPSCCP(Module &M, const DataLayout &DL,
         if (!I) continue;
 
         bool Folded = ConstantFoldTerminator(I->getParent());
-        assert(Folded &&
-              "Expect TermInst on constantint or blockaddress to be folded");
-        (void) Folded;
+        if (!Folded) {
+          // The constant folder may not have been able to fold the terminator
+          // if this is a branch or switch on undef.  Fold it manually as a
+          // branch to the first successor.
+#ifndef NDEBUG
+          if (auto *BI = dyn_cast<BranchInst>(I)) {
+            assert(BI->isConditional() && isa<UndefValue>(BI->getCondition()) &&
+                   "Branch should be foldable!");
+          } else if (auto *SI = dyn_cast<SwitchInst>(I)) {
+            assert(isa<UndefValue>(SI->getCondition()) && "Switch should fold");
+          } else {
+            llvm_unreachable("Didn't fold away reference to block!");
+          }
+#endif
+
+          // Make this an uncond branch to the first successor.
+          TerminatorInst *TI = I->getParent()->getTerminator();
+          BranchInst::Create(TI->getSuccessor(0), TI);
+
+          // Remove entries in successor phi nodes to remove edges.
+          for (unsigned i = 1, e = TI->getNumSuccessors(); i != e; ++i)
+            TI->getSuccessor(i)->removePredecessor(TI->getParent());
+
+          // Remove the old terminator.
+          TI->eraseFromParent();
+        }
       }
 
       // Finally, delete the basic block.