diff --git a/llvm/include/llvm/CodeGen/SelectionDAGISel.h b/llvm/include/llvm/CodeGen/SelectionDAGISel.h
index f7dc327f3023..c204ce2be069 100644
--- a/llvm/include/llvm/CodeGen/SelectionDAGISel.h
+++ b/llvm/include/llvm/CodeGen/SelectionDAGISel.h
@@ -307,7 +307,7 @@ private:
   std::vector<unsigned> OpcodeOffset;
 
   void UpdateChains(SDNode *NodeToMatch, SDValue InputChain,
-                    const SmallVectorImpl<SDNode *> &ChainNodesMatched,
+                    SmallVectorImpl<SDNode *> &ChainNodesMatched,
                     bool isMorphNodeTo);
 };
 
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 508ba73315c7..d9d8d0c1fd10 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -2308,7 +2308,7 @@ GetVBR(uint64_t Val, const unsigned char *MatcherTable, unsigned &Idx) {
 /// to use the new results.
 void SelectionDAGISel::UpdateChains(
     SDNode *NodeToMatch, SDValue InputChain,
-    const SmallVectorImpl<SDNode *> &ChainNodesMatched, bool isMorphNodeTo) {
+    SmallVectorImpl<SDNode *> &ChainNodesMatched, bool isMorphNodeTo) {
   SmallVector<SDNode*, 4> NowDeadNodes;
 
   // Now that all the normal results are replaced, we replace the chain and
@@ -2320,6 +2320,11 @@ void SelectionDAGISel::UpdateChains(
     // Replace all the chain results with the final chain we ended up with.
     for (unsigned i = 0, e = ChainNodesMatched.size(); i != e; ++i) {
       SDNode *ChainNode = ChainNodesMatched[i];
+      // If ChainNode is null, it's because we replaced it on a previous
+      // iteration and we cleared it out of the map. Just skip it.
+      if (!ChainNode)
+        continue;
+
       assert(ChainNode->getOpcode() != ISD::DELETED_NODE &&
              "Deleted node left in chain");
 
@@ -2332,6 +2337,11 @@ void SelectionDAGISel::UpdateChains(
       if (ChainVal.getValueType() == MVT::Glue)
         ChainVal = ChainVal.getValue(ChainVal->getNumValues()-2);
       assert(ChainVal.getValueType() == MVT::Other && "Not a chain?");
+      SelectionDAG::DAGNodeDeletedListener NDL(
+          *CurDAG, [&](SDNode *N, SDNode *E) {
+            std::replace(ChainNodesMatched.begin(), ChainNodesMatched.end(), N,
+                         static_cast<SDNode *>(nullptr));
+          });
       CurDAG->ReplaceAllUsesOfValueWith(ChainVal, InputChain);
 
       // If the node became dead and we haven't already seen it, delete it.
diff --git a/llvm/test/CodeGen/SystemZ/pr31710.ll b/llvm/test/CodeGen/SystemZ/pr31710.ll
new file mode 100644
index 000000000000..1123827fd939
--- /dev/null
+++ b/llvm/test/CodeGen/SystemZ/pr31710.ll
@@ -0,0 +1,39 @@
+; RUN: llc < %s -mtriple=s390x-redhat-linux | FileCheck %s
+;
+; Triggers a path in SelectionDAG's UpdateChains where a node is
+; deleted but we try to read it later (pr31710), invoking UB in
+; release mode or hitting an assert if they're enabled.
+
+; CHECK: btldata:
+define void @btldata(i64* %u0, i32** %p0, i32** %p1, i32** %p3, i32** %p5, i32** %p7) {
+entry:
+  %x0 = load i32*, i32** %p0, align 8, !tbaa !0
+  store i64 0, i64* %u0, align 8, !tbaa !4
+  %x1 = load i32*, i32** %p1, align 8, !tbaa !0
+  %x2 = load i32, i32* %x1, align 4, !tbaa !6
+  %x2ext = sext i32 %x2 to i64
+  store i32 %x2, i32* %x1, align 4, !tbaa !6
+  %x3 = load i32*, i32** %p3, align 8, !tbaa !0
+  %ptr = getelementptr inbounds i32, i32* %x3, i64 %x2ext
+  %x4 = load i32, i32* %ptr, align 4, !tbaa !6
+  %x4inc = add nsw i32 %x4, 1
+  store i32 %x4inc, i32* %ptr, align 4, !tbaa !6
+  store i64 undef, i64* %u0, align 8, !tbaa !4
+  %x5 = load i32*, i32** %p5, align 8, !tbaa !0
+  %x6 = load i32, i32* %x5, align 4, !tbaa !6
+  store i32 %x6, i32* %x5, align 4, !tbaa !6
+  %x7 = load i32*, i32** %p7, align 8, !tbaa !0
+  %x8 = load i32, i32* %x7, align 4, !tbaa !6
+  %x8inc = add nsw i32 %x8, 1
+  store i32 %x8inc, i32* %x7, align 4, !tbaa !6
+  ret void
+}
+
+!0 = !{!1, !1, i64 0}
+!1 = !{!"any pointer", !2, i64 0}
+!2 = !{!"omnipotent char", !3, i64 0}
+!3 = !{!"Simple C/C++ TBAA"}
+!4 = !{!5, !5, i64 0}
+!5 = !{!"long", !2, i64 0}
+!6 = !{!7, !7, i64 0}
+!7 = !{!"int", !2, i64 0}