diff --git a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
--- a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -2135,10 +2135,19 @@
     Value *ShadowPtr = nullptr, *OriginPtr = nullptr;
     const Align Alignment = I.getAlign();
     if (PropagateShadow) {
-      std::tie(ShadowPtr, OriginPtr) =
+      if (I.getMetadata(LLVMContext::MD_noundef)) {
+        IRBuilder<> IRB2(&I);
+        std::tie(ShadowPtr, OriginPtr) =
+          getShadowOriginPtr(Addr, IRB2, ShadowTy, Alignment, /*isStore*/ false);
+        insertShadowCheck(
+            IRB2.CreateAlignedLoad(ShadowTy, ShadowPtr, Alignment, "_msld"), OriginPtr, &I);
+        setShadow(&I, getCleanShadow(&I));
+      } else {
+        std::tie(ShadowPtr, OriginPtr) =
           getShadowOriginPtr(Addr, IRB, ShadowTy, Alignment, /*isStore*/ false);
-      setShadow(&I,
-                IRB.CreateAlignedLoad(ShadowTy, ShadowPtr, Alignment, "_msld"));
+        setShadow(
+            &I, IRB.CreateAlignedLoad(ShadowTy, ShadowPtr, Alignment, "_msld"));
+      }
     } else {
       setShadow(&I, getCleanShadow(&I));
     }