diff --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
index ea1fbc9..e8ce3f9 100644
--- a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
@@ -842,6 +842,12 @@
                      B.getInt8PtrTy(), castToCStr(Ptr, B), B, TLI);
 }
 
+Value *llvm::emitStrDup(Value *Ptr, IRBuilder<> &B,
+                        const TargetLibraryInfo *TLI) {
+  return emitLibCall(LibFunc_strdup, B.getInt8PtrTy(), B.getInt8PtrTy(),
+                     castToCStr(Ptr, B), B, TLI);
+}
+
 Value *llvm::emitStrChr(Value *Ptr, char C, IRBuilder<> &B,
                         const TargetLibraryInfo *TLI) {
   Type *I8Ptr = B.getInt8PtrTy();
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index b003a72..813816e 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -531,6 +531,19 @@
   return nullptr;
 }
 
+Value *LibCallSimplifier::optimizeStrNDup(CallInst *CI, IRBuilder<> &B) {
+  Value *Src = CI->getArgOperand(0);
+  ConstantInt *Size = dyn_cast<ConstantInt>(CI->getArgOperand(1));
+  uint64_t SrcLen = GetStringLength(Src);
+  if (SrcLen && Size) {
+    annotateDereferenceableBytes(CI, 0, SrcLen);
+    if (SrcLen <= Size->getZExtValue() + 1)
+      return emitStrDup(Src, B, TLI);
+  }
+
+  return nullptr;
+}
+
 Value *LibCallSimplifier::optimizeStrCpy(CallInst *CI, IRBuilder<> &B) {
   Value *Dst = CI->getArgOperand(0), *Src = CI->getArgOperand(1);
   if (Dst == Src) // strcpy(x,x)  -> x
@@ -2713,6 +2726,8 @@
       return optimizeStrLen(CI, Builder);
     case LibFunc_strpbrk:
       return optimizeStrPBrk(CI, Builder);
+    case LibFunc_strndup:
+      return optimizeStrNDup(CI, Builder);
     case LibFunc_strtol:
     case LibFunc_strtod:
     case LibFunc_strtof: