Index: llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp
+++ llvm/trunk/lib/Transforms/Utils/LoopUnrollPeel.cpp
@@ -583,6 +583,18 @@
   SmallVector<std::pair<BasicBlock *, BasicBlock *>, 4> ExitEdges;
   L->getExitEdges(ExitEdges);
 
+  DenseMap<BasicBlock *, BasicBlock *> ExitIDom;
+  if (DT) {
+    assert(L->hasDedicatedExits() && "No dedicated exits?");
+    for (auto Edge : ExitEdges) {
+      if (ExitIDom.count(Edge.second))
+        continue;
+      BasicBlock *BB = DT->getNode(Edge.second)->getIDom()->getBlock();
+      assert(L->contains(BB) && "IDom is not in a loop");
+      ExitIDom[Edge.second] = BB;
+    }
+  }
+
   Function *F = Header->getParent();
 
   // Set up all the necessary basic blocks. It is convenient to split the
@@ -675,9 +687,9 @@
       // latter is the first cloned loop body, as original PreHeader dominates
       // the original loop body.
       if (Iter == 0)
-        for (auto Edge : ExitEdges)
-          DT->changeImmediateDominator(Edge.second,
-                                       cast<BasicBlock>(LVMap[Edge.first]));
+        for (auto Exit : ExitIDom)
+          DT->changeImmediateDominator(Exit.first,
+                                       cast<BasicBlock>(LVMap[Exit.second]));
 #ifdef EXPENSIVE_CHECKS
       assert(DT->verify(DominatorTree::VerificationLevel::Fast));
 #endif
@@ -719,6 +731,9 @@
   // We modified the loop, update SE.
   SE->forgetTopmostLoop(L);
 
+  // Finally DomtTree must be correct.
+  assert(DT->verify(DominatorTree::VerificationLevel::Fast));
+
   // FIXME: Incrementally update loop-simplify
   simplifyLoop(L, DT, LI, SE, AC, nullptr, PreserveLCSSA);
 
Index: llvm/trunk/test/Transforms/LoopUnroll/peel-loop-pgo-deopt-idom.ll
===================================================================
--- llvm/trunk/test/Transforms/LoopUnroll/peel-loop-pgo-deopt-idom.ll
+++ llvm/trunk/test/Transforms/LoopUnroll/peel-loop-pgo-deopt-idom.ll
@@ -0,0 +1,55 @@
+; REQUIRES: asserts
+; RUN: opt < %s -S -debug-only=loop-unroll -loop-unroll -unroll-runtime -unroll-peel-multi-deopt-exit 2>&1 | FileCheck %s
+; RUN: opt < %s -S -debug-only=loop-unroll -unroll-peel-multi-deopt-exit -passes='require<profile-summary>,function(require<opt-remark-emit>,unroll)' 2>&1 | FileCheck %s
+
+; Regression test for setting the correct idom for exit blocks.
+
+; CHECK: Loop Unroll: F[basic]
+; CHECK: PEELING loop %for.body with iteration count 1!
+
+define i32 @basic(i32* %p, i32 %k, i1 %c1, i1 %c2) #0 !prof !3 {
+entry:
+  %cmp3 = icmp slt i32 0, %k
+  br i1 %cmp3, label %for.body.lr.ph, label %for.end
+
+for.body.lr.ph:                                   ; preds = %entry
+  br label %for.body
+
+for.body:                                         ; preds = %for.body.lr.ph, %for.body
+  %i.05 = phi i32 [ 0, %for.body.lr.ph ], [ %inc, %latch ]
+  %p.addr.04 = phi i32* [ %p, %for.body.lr.ph ], [ %incdec.ptr, %latch ]
+  %incdec.ptr = getelementptr inbounds i32, i32* %p.addr.04, i32 1
+  store i32 %i.05, i32* %p.addr.04, align 4
+  %inc = add nsw i32 %i.05, 1
+  %cmp = icmp slt i32 %inc, %k
+  br i1 %c1, label %continue, label %to_side_exit
+
+continue:
+  br i1 %c2, label %latch, label %side_exit, !prof !2
+
+latch:
+  br i1 %cmp, label %for.body, label %for.cond.for.end_crit_edge, !prof !1
+
+for.cond.for.end_crit_edge:                       ; preds = %for.body
+  br label %for.end
+
+to_side_exit:
+  br i1 %c2, label %continue, label %side_exit, !prof !2
+
+
+for.end:                                          ; preds = %for.cond.for.end_crit_edge, %entry
+  %res = phi i32 [ 0, %entry ], [ %inc, %for.cond.for.end_crit_edge ]
+  ret i32 %res
+
+side_exit:
+  %rval = call i32(...) @llvm.experimental.deoptimize.i32() [ "deopt"(i32 %inc) ]
+  ret i32 %rval
+}
+
+declare i32 @llvm.experimental.deoptimize.i32(...)
+
+attributes #0 = { nounwind }
+
+!1 = !{!"branch_weights", i32 1, i32 1}
+!2 = !{!"branch_weights", i32 1, i32 0}
+!3 = !{!"function_entry_count", i64 1}