Index: include/llvm/IR/Function.h
===================================================================
--- include/llvm/IR/Function.h
+++ include/llvm/IR/Function.h
@@ -149,6 +149,10 @@
   /// from Value::setName() whenever the name of this function changes.
   void recalculateIntrinsicID();
 
+  /// Returns the intrinsic ID from its name, or Intrinsic::not_intrinsic if the
+  /// name does not match any intrinsic.
+  static Intrinsic::ID lookupIntrinsicID(StringRef ValName);
+
   /// getCallingConv()/setCallingConv(CC) - These method get and set the
   /// calling convention of this function.  The enum values for the known
   /// calling conventions are defined in CallingConv.h.
Index: lib/IR/Function.cpp
===================================================================
--- lib/IR/Function.cpp
+++ lib/IR/Function.cpp
@@ -416,9 +416,7 @@
 
 /// \brief This does the actual lookup of an intrinsic ID which
 /// matches the given function name.
-static Intrinsic::ID lookupIntrinsicID(const ValueName *ValName) {
-  StringRef Name = ValName->getKey();
-
+Intrinsic::ID Function::lookupIntrinsicID(StringRef Name) {
   ArrayRef<const char *> NameTable(&IntrinsicNameTable[1],
                                    std::end(IntrinsicNameTable));
   int Idx = Intrinsic::lookupLLVMIntrinsicByName(NameTable, Name);
@@ -438,7 +436,7 @@
     IntID = Intrinsic::not_intrinsic;
     return;
   }
-  IntID = lookupIntrinsicID(ValName);
+  IntID = lookupIntrinsicID(ValName->getKey());
 }
 
 /// Returns a stable mangling for the type specified for use in the name
Index: lib/Transforms/Scalar/LoopIdiomRecognize.cpp
===================================================================
--- lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -50,6 +50,7 @@
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
@@ -769,6 +770,10 @@
     Value *MSP =
         M->getOrInsertFunction("memset_pattern16", Builder.getVoidTy(),
                                Int8PtrTy, Int8PtrTy, IntPtr, (void *)nullptr);
+    // memset_pattern is not an intrinsic, so it won't automatically gets the
+    // right set of attributes. Let's manually pulled the same ones as memset
+    cast<Function>(MSP)->setAttributes(Intrinsic::getAttributes(
+        M->getContext(), Function::lookupIntrinsicID("llvm.memset.")));
 
     // Otherwise we should form a memset_pattern16.  PatternValue is known to be
     // an constant array of 16-bytes.  Plop the value into a mergable global.
Index: test/Transforms/LoopIdiom/basic.ll
===================================================================
--- test/Transforms/LoopIdiom/basic.ll
+++ test/Transforms/LoopIdiom/basic.ll
@@ -564,3 +564,8 @@
 ; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* %X, i8 0, i64 10000, i32 1, i1 false)
 ; CHECK: ret void
 }
+
+
+; Validate that "memset_pattern" has inherited attributed from memset
+; CHECK-LABEL: declare void @memset_pattern16(i8* nocapture, i8*, i64) #
+