diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -4474,10 +4474,45 @@
 }
 
 bool MicrosoftCXXABI::isPermittedToBeHomogeneousAggregate(
-    const CXXRecordDecl *CXXRD) const {
-  // MSVC Windows on Arm64 considers a type not HFA if it is not an
-  // aggregate according to the C++14 spec. This is not consistent with the
-  // AAPCS64, but is defacto spec on that platform.
-  return !CGM.getTarget().getTriple().isAArch64() ||
-         isTrivialForAArch64MSVC(CXXRD);
+    const CXXRecordDecl *RD) const {
+  // All aggregates are permitted to be HFA on non-ARM platforms, which mostly
+  // affects vectorcall on x64/x86.
+  if (!CGM.getTarget().getTriple().isAArch64())
+    return true;
+  // MSVC Windows on Arm64 has its own rules for determining if a type is HFA
+  // that are inconsistent with the AAPCS64 ABI. The following are our best
+  // determination of those rules so far, based on observation of MSVC's
+  // behavior.
+  if (RD->isEmpty())
+    return false;
+  if (RD->isPolymorphic())
+    return false;
+  if (RD->hasNonTrivialCopyAssignment())
+    return false;
+  if (RD->hasNonTrivialDestructor())
+    return false;
+  if (RD->hasNonTrivialDefaultConstructor())
+    return false;
+  // These two are somewhat redundant given the caller
+  // (ABIInfo::isHomogeneousAggregate) checks the bases and fields, but that
+  // caller doesn't consider empty bases/fields to be non-homogenous, but it
+  // looks like Microsoft's AArch64 ABI does care about these empty types &
+  // anything containing/derived from one is non-homogeneous.
+  // Instead we could add another CXXABI entry point to query this property and
+  // have ABIInfo::isHomogeneousAggregate use that property.
+  // I don't think any other of the features listed above could be true of a
+  // base/field while not true of the outer struct. For example, if you have a
+  // base/field that has an non-trivial copy assignment/dtor/default ctor, then
+  // the outer struct's corresponding operation must be non-trivial.
+  for (const CXXBaseSpecifier &B : RD->bases()) {
+    if (const CXXRecordDecl *FRD = B.getType()->getAsCXXRecordDecl()) {
+      if (!isPermittedToBeHomogeneousAggregate(FRD))
+        return false;
+    }
+  }
+  // empty fields seem to be caught by the ABIInfo::isHomogeneousAggregate
+  // checking for padding - but maybe there are ways to end up with an empty
+  // field without padding? Not that I know of, so don't check fields here &
+  // rely on the padding check.
+  return true;
 }
diff --git a/clang/test/CodeGenCXX/homogeneous-aggregates.cpp b/clang/test/CodeGenCXX/homogeneous-aggregates.cpp
--- a/clang/test/CodeGenCXX/homogeneous-aggregates.cpp
+++ b/clang/test/CodeGenCXX/homogeneous-aggregates.cpp
@@ -92,7 +92,7 @@
 // ARM32: define{{.*}} arm_aapcs_vfpcc void @_Z15with_empty_base16HVAWithEmptyBase(%struct.HVAWithEmptyBase %a.coerce)
 void CC with_empty_base(HVAWithEmptyBase a) {}
 
-// FIXME: MSVC doesn't consider this an HVA because of the empty base.
+// WOA64: define dso_local void @"?with_empty_base@@YAXUHVAWithEmptyBase@@@Z"([2 x i64] %{{.*}})
 // X64: define dso_local x86_vectorcallcc void @"\01_Z15with_empty_base16HVAWithEmptyBase@@16"(%struct.HVAWithEmptyBase inreg %a.coerce)
 
 struct HVAWithEmptyBitField : Float1, Float2 {
@@ -172,4 +172,117 @@
   // WOA64-LABEL: define dso_local void @"?call_copy_haspodbase@pr47611@@YAXPEAUHasPodBase@1@@Z"
   // WOA64: call void @"?copy@pr47611@@YA?AUHasPodBase@1@PEAU21@@Z"(%"struct.pr47611::HasPodBase"* inreg sret(%"struct.pr47611::HasPodBase") align 8 %{{.*}}, %"struct.pr47611::HasPodBase"* noundef %{{.*}})
 }
-}; // namespace pr47611
+} // namespace pr47611
+
+namespace protected_member {
+struct HFA {
+  double x;
+  double y;
+protected:
+  double z;
+};
+double foo(HFA v) { return v.x + v.y; }
+// WOA64: define dso_local noundef double @"?foo@protected_member@@YANUHFA@1@@Z"([3 x double] %{{.*}})
+}
+namespace private_member {
+struct HFA {
+  double x;
+  double y;
+private:
+  double z;
+};
+double foo(HFA v) { return v.x + v.y; }
+// WOA64: define dso_local noundef double @"?foo@private_member@@YANUHFA@1@@Z"([3 x double] %{{.*}})
+}
+namespace polymorphic {
+struct NonHFA {
+  double x;
+  double y;
+  double z;
+  virtual void f1();
+};
+double foo(NonHFA v) { return v.x + v.y; }
+// WOA64: define dso_local noundef double @"?foo@polymorphic@@YANUNonHFA@1@@Z"(%"struct.polymorphic::NonHFA"* noundef %{{.*}})
+}
+namespace trivial_copy_assignment {
+struct HFA {
+  double x;
+  double y;
+  double z;
+  HFA &operator=(const HFA&) = default;
+};
+double foo(HFA v) { return v.x + v.y; }
+// WOA64: define dso_local noundef double @"?foo@trivial_copy_assignment@@YANUHFA@1@@Z"([3 x double] %{{.*}})
+}
+namespace non_trivial_copy_assignment {
+struct NonHFA {
+  double x;
+  double y;
+  double z;
+  NonHFA &operator=(const NonHFA&);
+};
+double foo(NonHFA v) { return v.x + v.y; }
+// WOA64: define dso_local noundef double @"?foo@non_trivial_copy_assignment@@YANUNonHFA@1@@Z"(%"struct.non_trivial_copy_assignment::NonHFA"* noundef %{{.*}})
+}
+namespace user_provided_ctor {
+struct HFA {
+  double x;
+  double y;
+  double z;
+  HFA(int);
+};
+double foo(HFA v) { return v.x + v.y; }
+// WOA64: define dso_local noundef double @"?foo@user_provided_ctor@@YANUHFA@1@@Z"([3 x double] %{{.*}})
+}
+namespace trivial_dtor {
+struct HFA {
+  double x;
+  double y;
+  double z;
+  ~HFA() = default;
+};
+double foo(HFA v) { return v.x + v.y; }
+// WOA64: define dso_local noundef double @"?foo@trivial_dtor@@YANUHFA@1@@Z"([3 x double] %{{.*}})
+}
+namespace non_trivial_dtor {
+struct NonHFA {
+  double x;
+  double y;
+  double z;
+  ~NonHFA();
+};
+double foo(NonHFA v) { return v.x + v.y; }
+// WOA64: define dso_local noundef double @"?foo@non_trivial_dtor@@YANUNonHFA@1@@Z"(%"struct.non_trivial_dtor::NonHFA"* noundef %{{.*}})
+}
+namespace non_empty_base {
+struct non_empty_base { double d; };
+struct HFA : non_empty_base {
+  double x;
+  double y;
+  double z;
+};
+double foo(HFA v) { return v.x + v.y; }
+// WOA64: define dso_local noundef double @"?foo@non_empty_base@@YANUHFA@1@@Z"([4 x double] %{{.*}})
+}
+namespace empty_field {
+struct empty { };
+struct NonHFA {
+  double x;
+  double y;
+  double z;
+  empty e;
+};
+double foo(NonHFA v) { return v.x + v.y; }
+// WOA64: define dso_local noundef double @"?foo@empty_field@@YANUNonHFA@1@@Z"(%"struct.empty_field::NonHFA"* noundef %{{.*}})
+}
+namespace non_empty_field {
+struct non_empty { double d; };
+struct HFA {
+  double x;
+  double y;
+  double z;
+  non_empty e;
+};
+double foo(HFA v) { return v.x + v.y; }
+// WOA64: define dso_local noundef double @"?foo@non_empty_field@@YANUHFA@1@@Z"([4 x double] %{{.*}})
+}