diff --git a/llvm/lib/Analysis/MemoryLocation.cpp b/llvm/lib/Analysis/MemoryLocation.cpp
--- a/llvm/lib/Analysis/MemoryLocation.cpp
+++ b/llvm/lib/Analysis/MemoryLocation.cpp
@@ -271,10 +271,18 @@
       return MemoryLocation(Arg, Size, AATags);
     }
     case LibFunc_memset_pattern16:
+    case LibFunc_memset_pattern4:
+    case LibFunc_memset_pattern8:
       assert((ArgIdx == 0 || ArgIdx == 1) &&
              "Invalid argument index for memset_pattern16");
-      if (ArgIdx == 1)
-        return MemoryLocation(Arg, LocationSize::precise(16), AATags);
+      if (ArgIdx == 1) {
+        unsigned Size = 16;
+        if (F == LibFunc_memset_pattern4)
+          Size = 4;
+        else if (F == LibFunc_memset_pattern8)
+          Size = 8;
+        return MemoryLocation(Arg, LocationSize::precise(Size), AATags);
+      }
       if (const ConstantInt *LenCI =
               dyn_cast<ConstantInt>(Call->getArgOperand(2)))
         return MemoryLocation(Arg, LocationSize::precise(LenCI->getZExtValue()),
@@ -309,7 +317,6 @@
       break;
     };
   }
-  // FIXME: Handle memset_pattern4 and memset_pattern8 also.
 
   return MemoryLocation::getBeforeOrAfter(Call->getArgOperand(ArgIdx), AATags);
 }
diff --git a/llvm/test/Analysis/BasicAA/libfuncs-darwin.ll b/llvm/test/Analysis/BasicAA/libfuncs-darwin.ll
--- a/llvm/test/Analysis/BasicAA/libfuncs-darwin.ll
+++ b/llvm/test/Analysis/BasicAA/libfuncs-darwin.ll
@@ -9,9 +9,9 @@
 ; CHECK:       Just Mod:  Ptr: i8* %a	<->  call void @memset_pattern4(i8* %a, i8* %pattern, i64 17)
 ; CHECK-NEXT:  Just Ref:  Ptr: i8* %pattern	<->  call void @memset_pattern4(i8* %a, i8* %pattern, i64 17)
 ; CHECK-NEXT:  Just Mod:  Ptr: i8* %a.gep.1	<->  call void @memset_pattern4(i8* %a, i8* %pattern, i64 17)
-; CHECK-NEXT:  Just Mod:  Ptr: i8* %a.gep.17	<->  call void @memset_pattern4(i8* %a, i8* %pattern, i64 17)
+; CHECK-NEXT:  NoModRef:  Ptr: i8* %a.gep.17	<->  call void @memset_pattern4(i8* %a, i8* %pattern, i64 17)
 ; CHECK-NEXT:  Just Ref:  Ptr: i8* %pattern.gep.3	<->  call void @memset_pattern4(i8* %a, i8* %pattern, i64 17)
-; CHECK-NEXT:  Just Ref:  Ptr: i8* %pattern.gep.4	<->  call void @memset_pattern4(i8* %a, i8* %pattern, i64 17)
+; CHECK-NEXT:  NoModRef:  Ptr: i8* %pattern.gep.4	<->  call void @memset_pattern4(i8* %a, i8* %pattern, i64 17)
 ;
 entry:
   call void @memset_pattern4(i8* %a, i8* %pattern, i64 17)
@@ -48,9 +48,9 @@
 ; CHECK:       Just Mod:  Ptr: i8* %a	<->  call void @memset_pattern8(i8* %a, i8* %pattern, i64 17)
 ; CHECK-NEXT:  Just Ref:  Ptr: i8* %pattern	<->  call void @memset_pattern8(i8* %a, i8* %pattern, i64 17)
 ; CHECK-NEXT:  Just Mod:  Ptr: i8* %a.gep.1	<->  call void @memset_pattern8(i8* %a, i8* %pattern, i64 17)
-; CHECK-NEXT:  Just Mod:  Ptr: i8* %a.gep.17	<->  call void @memset_pattern8(i8* %a, i8* %pattern, i64 17)
+; CHECK-NEXT:  NoModRef:  Ptr: i8* %a.gep.17	<->  call void @memset_pattern8(i8* %a, i8* %pattern, i64 17)
 ; CHECK-NEXT:  Just Ref:  Ptr: i8* %pattern.gep.7	<->  call void @memset_pattern8(i8* %a, i8* %pattern, i64 17)
-; CHECK-NEXT:  Just Ref:  Ptr: i8* %pattern.gep.8	<->  call void @memset_pattern8(i8* %a, i8* %pattern, i64 17)
+; CHECK-NEXT:  NoModRef:  Ptr: i8* %pattern.gep.8	<->  call void @memset_pattern8(i8* %a, i8* %pattern, i64 17)
 ;
 entry:
   call void @memset_pattern8(i8* %a, i8* %pattern, i64 17)