Index: lib/CodeGen/TargetInfo.cpp
===================================================================
--- lib/CodeGen/TargetInfo.cpp
+++ lib/CodeGen/TargetInfo.cpp
@@ -2717,7 +2717,8 @@
 
   uint64_t Size = getContext().getTypeSize(Ty);
 
-  if (const RecordType *RT = Ty->getAs<RecordType>()) {
+  const RecordType *RT = Ty->getAs<RecordType>();
+  if (RT) {
     if (IsReturnType) {
       if (isRecordReturnIndirect(RT, getCXXABI()))
         return ABIArgInfo::getIndirect(0, false);
@@ -2733,15 +2734,25 @@
     if (Size == 128 && getTarget().getTriple().isWindowsGNUEnvironment())
       return ABIArgInfo::getDirect(llvm::IntegerType::get(getVMContext(),
                                                           Size));
+  }
 
+  if (RT || (getTarget().getTriple().isWindowsMSVCEnvironment() &&
+             Ty->isMemberPointerType())) {
     // MS x64 ABI requirement: "Any argument that doesn't fit in 8 bytes, or is
     // not 1, 2, 4, or 8 bytes, must be passed by reference."
-    if (Size <= 64 &&
-        (Size & (Size - 1)) == 0)
-      return ABIArgInfo::getDirect(llvm::IntegerType::get(getVMContext(),
-                                                          Size));
+    if (Size > 64 || !llvm::isPowerOf2_64(Size))
+      return ABIArgInfo::getIndirect(0, /*ByVal=*/false);
 
-    return ABIArgInfo::getIndirect(0, /*ByVal=*/false);
+    // If it's a member pointer with a single field, use the field type.
+    if (const auto *MPT = Ty->getAs<MemberPointerType>()) {
+      const CXXRecordDecl *RD = MPT->getClass()->getAsCXXRecordDecl();
+      if (MSInheritanceAttr::hasOnlyOneField(MPT->isMemberFunctionPointer(),
+                                             RD->getMSInheritanceModel()))
+        return ABIArgInfo::getDirect();
+    }
+
+    // Otherwise, coerce it to a small integer.
+    return ABIArgInfo::getDirect(llvm::IntegerType::get(getVMContext(), Size));
   }
 
   if (Ty->isPromotableIntegerType())
Index: test/CodeGenCXX/microsoft-abi-member-pointers.cpp
===================================================================
--- test/CodeGenCXX/microsoft-abi-member-pointers.cpp
+++ test/CodeGenCXX/microsoft-abi-member-pointers.cpp
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -fno-rtti -emit-llvm %s -o - -triple=i386-pc-win32 | FileCheck %s
+// RUN: %clang_cc1 -fno-rtti -emit-llvm %s -o - -triple=x86_64-pc-win32 | FileCheck %s -check-prefix=X64
 // RUN: %clang_cc1 -fno-rtti -emit-llvm %s -o - -triple=i386-pc-win32 -DINCOMPLETE_VIRTUAL -fms-extensions -verify
 // RUN: %clang_cc1 -fno-rtti -emit-llvm %s -o - -triple=i386-pc-win32 -DINCOMPLETE_VIRTUAL -DMEMFUN -fms-extensions -verify
 // FIXME: Test x86_64 member pointers when codegen no longer asserts on records
@@ -235,6 +236,10 @@
 // CHECK:   %[[and1:.*]] = and i1 %[[and0]], %[[cmp2]]
 // CHECK:   ret i1 %[[and1]]
 // CHECK: }
+
+// Pass this large type indirectly.
+// X64-LABEL: define zeroext i1 @"\01?nullTestDataUnspecified@@
+// X64:             ({ i32, i32, i32 }*)
 }
 
 bool nullTestFunctionUnspecified(void (Unspecified::*mp)()) {
@@ -271,6 +276,11 @@
 // CHECK:   %[[v12:.*]] = load i32* %[[v11]]
 // CHECK:   ret i32 %[[v12]]
 // CHECK: }
+
+// A two-field data memptr on x64 gets coerced to i64 and is passed in a
+// register or memory.
+// X64-LABEL: define i32 @"\01?loadDataMemberPointerVirtual@@YAHPEAUVirtual@@PEQ1@H@Z"
+// X64:             (%struct.Virtual* %o, i64 %memptr.coerce)
 }
 
 int loadDataMemberPointerUnspecified(Unspecified *o, int Unspecified::*memptr) {
@@ -312,6 +322,11 @@
 // CHECK:   call x86_thiscallcc void %{{.*}}(%{{.*}} %{{.*}})
 // CHECK:   ret void
 // CHECK: }
+
+// X64-LABEL: define void @"\01?callMemberPointerSingle@@
+// X64:           (%struct.Single* %o, i8* %memptr)
+// X64:   bitcast i8* %{{[^ ]*}} to void (%struct.Single*)*
+// X64:   ret void
 }
 
 void callMemberPointerMultiple(Multiple *o, void (Multiple::*memptr)()) {
@@ -358,6 +373,9 @@
 // CHECK-NOT: icmp
 // CHECK:   ret i1 %[[r]]
 // CHECK: }
+
+// X64-LABEL: define zeroext i1 @"\01?compareSingleFunctionMemptr@@
+// X64:             (i8* %{{[^,]*}}, i8* %{{[^)]*}})
 }
 
 bool compareNeqSingleFunctionMemptr(void (Single::*l)(), void (Single::*r)()) {
@@ -393,6 +411,9 @@
 // CHECK:   %{{.*}} = and i1 %[[bits_or_null]], %[[cmp0]]
 // CHECK:   ret i1 %{{.*}}
 // CHECK: }
+
+// X64-LABEL: define zeroext i1 @"\01?unspecFuncMemptrEq@@
+// X64:             ({ i8*, i32, i32, i32 }*, { i8*, i32, i32, i32 }*)
 }
 
 bool unspecFuncMemptrNeq(void (Unspecified::*l)(), void (Unspecified::*r)()) {
@@ -435,6 +456,9 @@
 // CHECK:   and i1
 // CHECK:   ret i1
 // CHECK: }
+
+// X64-LABEL: define zeroext i1 @"\01?unspecDataMemptrEq@@
+// X64:             ({ i32, i32, i32 }*, { i32, i32, i32 }*)
 }
 
 void (Multiple::*convertB2FuncToMultiple(void (B2::*mp)()))() {