Index: llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
===================================================================
--- llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
+++ llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
@@ -848,6 +848,37 @@
   return true;
 }
 
+static MDNode *GetLoopMetadata(MDNode *LoopID, StringRef Name) {
+  // First operand should refer to the loop id itself.
+  assert(LoopID->getNumOperands() > 0 && "requires at least one operand");
+  assert(LoopID->getOperand(0) == LoopID && "invalid loop id");
+
+  for (unsigned i = 1, e = LoopID->getNumOperands(); i < e; ++i) {
+    MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i));
+    if (!MD)
+      continue;
+
+    MDString *S = dyn_cast<MDString>(MD->getOperand(0));
+    if (!S)
+      continue;
+
+    if (Name.equals(S->getString()))
+      return MD;
+  }
+  return nullptr;
+}
+
+bool ContainsAnyPreventativeLoopMetadata(Loop *L) {
+  if (MDNode *LoopID = L->getLoopID()) {
+    if (GetLoopMetadata(LoopID, "llvm.loop.isvectorized"))
+      return true;
+  }
+  for (auto *SL : *L)
+    if (ContainsAnyPreventativeLoopMetadata(SL))
+      return true;
+  return false;
+}
+
 void ARMTTIImpl::getUnrollingPreferences(Loop *L, ScalarEvolution &SE,
                                          TTI::UnrollingPreferences &UP) {
   // Only currently enable these preferences for M-Class cores.
@@ -860,6 +891,9 @@
   if (L->getHeader()->getParent()->hasOptSize())
     return;
 
+  if (ContainsAnyPreventativeLoopMetadata(L))
+    return;
+
   // Only enable on Thumb-2 targets.
   if (!ST->isThumb2())
     return;
Index: llvm/test/Transforms/LoopUnroll/ARM/mve-nounroll.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/LoopUnroll/ARM/mve-nounroll.ll
@@ -0,0 +1,124 @@
+; RUN: opt -mtriple=thumbv8.1m.main -mattr=+mve.fp -loop-unroll -S < %s -o - | FileCheck %s
+
+; CHECK-LABEL: @loopfn
+; CHECK: vector.body:
+; CHECK:   br i1 %7, label %middle.block, label %vector.body, !llvm.loop !0
+; CHECK: middle.block:
+; CHECK:   br i1 %cmp.n, label %for.cond.cleanup, label %for.body.preheader13
+; CHECK: for.body:
+; CHECK:   br i1 %exitcond, label %for.cond.cleanup.loopexit, label %for.body, !llvm.loop !2
+
+define void @loopfn(float* %s1, float* %s2, float* %d, i32 %n) {
+entry:
+  %cmp10 = icmp sgt i32 %n, 0
+  br i1 %cmp10, label %for.body.preheader, label %for.cond.cleanup
+
+for.body.preheader:                               ; preds = %entry
+  %min.iters.check = icmp ult i32 %n, 4
+  br i1 %min.iters.check, label %for.body.preheader13, label %vector.ph
+
+for.body.preheader13:                             ; preds = %middle.block, %for.body.preheader
+  %i.011.ph = phi i32 [ 0, %for.body.preheader ], [ %n.vec, %middle.block ]
+  br label %for.body
+
+vector.ph:                                        ; preds = %for.body.preheader
+  %n.vec = and i32 %n, -4
+  br label %vector.body
+
+vector.body:                                      ; preds = %vector.body, %vector.ph
+  %index = phi i32 [ 0, %vector.ph ], [ %index.next, %vector.body ]
+  %0 = getelementptr inbounds float, float* %s1, i32 %index
+  %1 = bitcast float* %0 to <4 x float>*
+  %wide.load = load <4 x float>, <4 x float>* %1, align 4
+  %2 = getelementptr inbounds float, float* %s2, i32 %index
+  %3 = bitcast float* %2 to <4 x float>*
+  %wide.load12 = load <4 x float>, <4 x float>* %3, align 4
+  %4 = fadd fast <4 x float> %wide.load12, %wide.load
+  %5 = getelementptr inbounds float, float* %d, i32 %index
+  %6 = bitcast float* %5 to <4 x float>*
+  store <4 x float> %4, <4 x float>* %6, align 4
+  %index.next = add i32 %index, 4
+  %7 = icmp eq i32 %index.next, %n.vec
+  br i1 %7, label %middle.block, label %vector.body, !llvm.loop !0
+
+middle.block:                                     ; preds = %vector.body
+  %cmp.n = icmp eq i32 %n.vec, %n
+  br i1 %cmp.n, label %for.cond.cleanup, label %for.body.preheader13
+
+for.cond.cleanup.loopexit:                        ; preds = %for.body
+  br label %for.cond.cleanup
+
+for.cond.cleanup:                                 ; preds = %for.cond.cleanup.loopexit, %middle.block, %entry
+  ret void
+
+for.body:                                         ; preds = %for.body.preheader13, %for.body
+  %i.011 = phi i32 [ %add3, %for.body ], [ %i.011.ph, %for.body.preheader13 ]
+  %arrayidx = getelementptr inbounds float, float* %s1, i32 %i.011
+  %8 = load float, float* %arrayidx, align 4
+  %arrayidx1 = getelementptr inbounds float, float* %s2, i32 %i.011
+  %9 = load float, float* %arrayidx1, align 4
+  %add = fadd fast float %9, %8
+  %arrayidx2 = getelementptr inbounds float, float* %d, i32 %i.011
+  store float %add, float* %arrayidx2, align 4
+  %add3 = add nuw nsw i32 %i.011, 1
+  %exitcond = icmp eq i32 %add3, %n
+  br i1 %exitcond, label %for.cond.cleanup.loopexit, label %for.body, !llvm.loop !2
+}
+
+
+
+; CHECK-LABEL: @nested
+; CHECK: for.outer:
+; CHECK:   br label %vector.body
+; CHECK: vector.body:
+; CHECK:   br i1 %8, label %for.latch, label %vector.body, !llvm.loop !0
+; CHECK: for.latch:
+; CHECK:   br i1 %exitcond34, label %for.cond.cleanup, label %for.outer
+
+define void @nested(float* %s1, float* %s2, float* %d, i32 %n) {
+entry:
+  %cmp31 = icmp eq i32 %n, 0
+  br i1 %cmp31, label %for.cond.cleanup, label %for.outer.preheader
+
+for.outer.preheader:                 ; preds = %entry
+  %min.iters.check = icmp ult i32 %n, 4
+  %n.vec = and i32 %n, -4
+  %cmp.n = icmp eq i32 %n.vec, %n
+  br label %for.outer
+
+for.outer:                           ; preds = %for.outer.preheader, %for.cond1.for.cond.cleanup3_crit_edge.us
+  %j.032.us = phi i32 [ %inc.us, %for.latch ], [ 0, %for.outer.preheader ]
+  %mul.us = mul i32 %j.032.us, %n
+  br label %vector.body
+
+vector.body:                                      ; preds = %for.outer, %vector.body
+  %index = phi i32 [ %index.next, %vector.body ], [ 0, %for.outer ]
+  %0 = add i32 %index, %mul.us
+  %1 = getelementptr inbounds float, float* %s1, i32 %0
+  %2 = bitcast float* %1 to <4 x float>*
+  %wide.load = load <4 x float>, <4 x float>* %2, align 4
+  %3 = getelementptr inbounds float, float* %s2, i32 %0
+  %4 = bitcast float* %3 to <4 x float>*
+  %wide.load35 = load <4 x float>, <4 x float>* %4, align 4
+  %5 = fadd fast <4 x float> %wide.load35, %wide.load
+  %6 = getelementptr inbounds float, float* %d, i32 %0
+  %7 = bitcast float* %6 to <4 x float>*
+  store <4 x float> %5, <4 x float>* %7, align 4
+  %index.next = add i32 %index, 4
+  %8 = icmp eq i32 %index.next, %n.vec
+  br i1 %8, label %for.latch, label %vector.body, !llvm.loop !0
+
+for.latch:                           ; preds = %vector.body, %for.outer
+  %i.030.us.ph = phi i32 [ %n.vec, %vector.body ]
+  %inc.us = add nuw i32 %j.032.us, 1
+  %exitcond34 = icmp eq i32 %inc.us, %n
+  br i1 %exitcond34, label %for.cond.cleanup, label %for.outer
+
+for.cond.cleanup:                                 ; preds = %for.cond1.for.cond.cleanup3_crit_edge.us, %entry
+  ret void
+}
+
+!0 = distinct !{!0, !1}
+!1 = !{!"llvm.loop.isvectorized", i32 1}
+!2 = distinct !{!2, !3, !1}
+!3 = !{!"llvm.loop.unroll.runtime.disable"}
\ No newline at end of file