diff --git a/llvm/lib/Analysis/LoopNestAnalysis.cpp b/llvm/lib/Analysis/LoopNestAnalysis.cpp
--- a/llvm/lib/Analysis/LoopNestAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopNestAnalysis.cpp
@@ -228,6 +228,18 @@
       InnerLoop.getExitingBlock() != InnerLoopLatch || !InnerLoopExit)
     return false;
 
+  auto isLCSSABlock = [](const BasicBlock *B) {
+    if (!B)
+      return false;
+
+    return all_of(*B, [](const Instruction &I) {
+      if (dyn_cast<BranchInst>(&I))
+        return true;
+      auto *PN = dyn_cast<PHINode>(&I);
+      return PN && PN->getName().endswith(".lcssa");
+    });
+  };
+
   // Ensure the only branch that may exist between the loops is the inner loop
   // guard.
   if (OuterLoopHeader != InnerLoopPreHeader) {
@@ -244,6 +256,8 @@
         continue;
       if (Succ == OuterLoopLatch)
         continue;
+      if (isLCSSABlock(Succ) && Succ->getSingleSuccessor() == OuterLoopLatch)
+        continue;
 
       DEBUG_WITH_TYPE(VerboseDebug, {
         dbgs() << "Inner loop guard successor " << Succ->getName()
@@ -255,7 +269,10 @@
   }
 
   // Ensure the inner loop exit block leads to the outer loop latch.
-  if (InnerLoopExit->getSingleSuccessor() != OuterLoopLatch) {
+  auto *SuccInner = InnerLoopExit->getSingleSuccessor();
+  if (!SuccInner || (SuccInner != OuterLoopLatch &&
+                     (!isLCSSABlock(SuccInner) ||
+                      SuccInner->getSingleSuccessor() != OuterLoopLatch))) {
     DEBUG_WITH_TYPE(
         VerboseDebug,
         dbgs() << "Inner loop exit block " << *InnerLoopExit
diff --git a/llvm/test/Analysis/LoopNestAnalysis/nests-with-lcssa.ll b/llvm/test/Analysis/LoopNestAnalysis/nests-with-lcssa.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Analysis/LoopNestAnalysis/nests-with-lcssa.ll
@@ -0,0 +1,201 @@
+; RUN: opt -S -passes='loop-rotate,print<loopnest>' < %s 2>&1 > /dev/null | FileCheck %s
+
+; int f(int N, int M) {
+;   int res = 0;
+;   for (int i = 0; i < N; ++i) {
+;     for (int j = 0; j < M; ++j) res += i * j;
+;   }
+;   return res;
+; }
+
+; Function Attrs: noinline nounwind optnone
+define i32 @f(i32 %N, i32 %M) #0 {
+; CHECK: IsPerfect=true, Depth=1, OutermostLoop: for.body3, Loops: ( for.body3 )
+; CHECK: IsPerfect=true, Depth=2, OutermostLoop: for.body, Loops: ( for.body for.body3 )
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.inc4, %entry
+  %res.0 = phi i32 [ 0, %entry ], [ %res.1, %for.inc4 ]
+  %i.0 = phi i32 [ 0, %entry ], [ %inc5, %for.inc4 ]
+  %cmp = icmp slt i32 %i.0, %N
+  br i1 %cmp, label %for.body, label %for.end6
+
+for.body:                                         ; preds = %for.cond
+  br label %for.cond1
+
+for.cond1:                                        ; preds = %for.inc, %for.body
+  %res.1 = phi i32 [ %res.0, %for.body ], [ %add, %for.inc ]
+  %j.0 = phi i32 [ 0, %for.body ], [ %inc, %for.inc ]
+  %cmp2 = icmp slt i32 %j.0, %M
+  br i1 %cmp2, label %for.body3, label %for.end
+
+for.body3:                                        ; preds = %for.cond1
+  %mul = mul nsw i32 %i.0, %j.0
+  %add = add nsw i32 %res.1, %mul
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body3
+  %inc = add nsw i32 %j.0, 1
+  br label %for.cond1
+
+for.end:                                          ; preds = %for.cond1
+  br label %for.inc4
+
+for.inc4:                                         ; preds = %for.end
+  %inc5 = add nsw i32 %i.0, 1
+  br label %for.cond
+
+for.end6:                                         ; preds = %for.cond
+  ret i32 %res.0
+}
+
+; int g(int N, int M, int K) {
+;   int sum = 0, prod = 1;
+;   for (int i = 0; i < N; ++i) {
+;     for (int j = 0; j < M; ++j) {
+;       for (int k = 0; k < K; ++k) {
+;         sum += i * j * k;
+;       }
+;       prod *= (i + j);
+;     }
+;   }
+;   return sum + prod;
+; }
+
+; Function Attrs: noinline nounwind optnone
+define i32 @g(i32 %N, i32 %M, i32 %K) #0 {
+; CHECK: IsPerfect=true, Depth=1, OutermostLoop: for.body6, Loops: ( for.body6 )
+; CHECK: IsPerfect=false, Depth=2, OutermostLoop: for.body3, Loops: ( for.body3 for.body6 )
+; CHECK: IsPerfect=false, Depth=3, OutermostLoop: for.body, Loops: ( for.body for.body3 for.body6 )
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.inc13, %entry
+  %prod.0 = phi i32 [ 1, %entry ], [ %prod.1, %for.inc13 ]
+  %sum.0 = phi i32 [ 0, %entry ], [ %sum.1, %for.inc13 ]
+  %i.0 = phi i32 [ 0, %entry ], [ %inc14, %for.inc13 ]
+  %cmp = icmp slt i32 %i.0, %N
+  br i1 %cmp, label %for.body, label %for.end15
+
+for.body:                                         ; preds = %for.cond
+  br label %for.cond1
+
+for.cond1:                                        ; preds = %for.inc10, %for.body
+  %prod.1 = phi i32 [ %prod.0, %for.body ], [ %mul9, %for.inc10 ]
+  %sum.1 = phi i32 [ %sum.0, %for.body ], [ %sum.2, %for.inc10 ]
+  %j.0 = phi i32 [ 0, %for.body ], [ %inc11, %for.inc10 ]
+  %cmp2 = icmp slt i32 %j.0, %M
+  br i1 %cmp2, label %for.body3, label %for.end12
+
+for.body3:                                        ; preds = %for.cond1
+  br label %for.cond4
+
+for.cond4:                                        ; preds = %for.inc, %for.body3
+  %sum.2 = phi i32 [ %sum.1, %for.body3 ], [ %add, %for.inc ]
+  %k.0 = phi i32 [ 0, %for.body3 ], [ %inc, %for.inc ]
+  %cmp5 = icmp slt i32 %k.0, %K
+  br i1 %cmp5, label %for.body6, label %for.end
+
+for.body6:                                        ; preds = %for.cond4
+  %mul = mul nsw i32 %i.0, %j.0
+  %mul7 = mul nsw i32 %mul, %k.0
+  %add = add nsw i32 %sum.2, %mul7
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body6
+  %inc = add nsw i32 %k.0, 1
+  br label %for.cond4
+
+for.end:                                          ; preds = %for.cond4
+  %add8 = add nsw i32 %i.0, %j.0
+  %mul9 = mul nsw i32 %prod.1, %add8
+  br label %for.inc10
+
+for.inc10:                                        ; preds = %for.end
+  %inc11 = add nsw i32 %j.0, 1
+  br label %for.cond1
+
+for.end12:                                        ; preds = %for.cond1
+  br label %for.inc13
+
+for.inc13:                                        ; preds = %for.end12
+  %inc14 = add nsw i32 %i.0, 1
+  br label %for.cond
+
+for.end15:                                        ; preds = %for.cond
+  %add16 = add nsw i32 %sum.0, %prod.0
+  ret i32 %add16
+}
+
+; int h(int N, int M, int K) {
+;   int sum = 0;
+;   for (int i = 0; i < N; ++i) {
+;     for (int j = 0; j < M; ++j) {
+;       for (int k = 0; k < K; ++k) {
+;         sum += i * j * k;
+;       }
+;     }
+;   }
+;   return sum;
+; }
+
+; Function Attrs: noinline nounwind optnone
+define i32 @h(i32 %N, i32 %M, i32 %K) #0 {
+; CHECK: IsPerfect=true, Depth=1, OutermostLoop: for.body6, Loops: ( for.body6 )
+; CHECK: IsPerfect=true, Depth=2, OutermostLoop: for.body3, Loops: ( for.body3 for.body6 )
+; CHECK: IsPerfect=true, Depth=3, OutermostLoop: for.body, Loops: ( for.body for.body3 for.body6 )
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.inc11, %entry
+  %sum.0 = phi i32 [ 0, %entry ], [ %sum.1, %for.inc11 ]
+  %i.0 = phi i32 [ 0, %entry ], [ %inc12, %for.inc11 ]
+  %cmp = icmp slt i32 %i.0, %N
+  br i1 %cmp, label %for.body, label %for.end13
+
+for.body:                                         ; preds = %for.cond
+  br label %for.cond1
+
+for.cond1:                                        ; preds = %for.inc8, %for.body
+  %sum.1 = phi i32 [ %sum.0, %for.body ], [ %sum.2, %for.inc8 ]
+  %j.0 = phi i32 [ 0, %for.body ], [ %inc9, %for.inc8 ]
+  %cmp2 = icmp slt i32 %j.0, %M
+  br i1 %cmp2, label %for.body3, label %for.end10
+
+for.body3:                                        ; preds = %for.cond1
+  br label %for.cond4
+
+for.cond4:                                        ; preds = %for.inc, %for.body3
+  %sum.2 = phi i32 [ %sum.1, %for.body3 ], [ %add, %for.inc ]
+  %k.0 = phi i32 [ 0, %for.body3 ], [ %inc, %for.inc ]
+  %cmp5 = icmp slt i32 %k.0, %K
+  br i1 %cmp5, label %for.body6, label %for.end
+
+for.body6:                                        ; preds = %for.cond4
+  %mul = mul nsw i32 %i.0, %j.0
+  %mul7 = mul nsw i32 %mul, %k.0
+  %add = add nsw i32 %sum.2, %mul7
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body6
+  %inc = add nsw i32 %k.0, 1
+  br label %for.cond4
+
+for.end:                                          ; preds = %for.cond4
+  br label %for.inc8
+
+for.inc8:                                         ; preds = %for.end
+  %inc9 = add nsw i32 %j.0, 1
+  br label %for.cond1
+
+for.end10:                                        ; preds = %for.cond1
+  br label %for.inc11
+
+for.inc11:                                        ; preds = %for.end10
+  %inc12 = add nsw i32 %i.0, 1
+  br label %for.cond
+
+for.end13:                                        ; preds = %for.cond
+  ret i32 %sum.0
+}