Index: lib/CodeGen/SwiftCallingConv.cpp
===================================================================
--- lib/CodeGen/SwiftCallingConv.cpp
+++ lib/CodeGen/SwiftCallingConv.cpp
@@ -57,6 +57,10 @@
   return CharUnits::fromQuantity(CGM.getDataLayout().getTypeStoreSize(type));
 }
 
+static CharUnits getTypeAllocSize(CodeGenModule &CGM, llvm::Type *type) {
+  return CharUnits::fromQuantity(CGM.getDataLayout().getTypeAllocSize(type));
+}
+
 void SwiftAggLowering::addTypedData(QualType type, CharUnits begin) {
   // Deal with various aggregate types as special cases:
 
@@ -542,7 +546,9 @@
       packed = true;
 
     elts.push_back(entry.Type);
-    lastEnd = entry.End;
+
+    lastEnd = entry.Begin + getTypeAllocSize(CGM, entry.Type);
+    assert(entry.End <= lastEnd);
   }
 
   // We don't need to adjust 'packed' to deal with possible tail padding
Index: test/CodeGen/64bit-swiftcall.c
===================================================================
--- test/CodeGen/64bit-swiftcall.c
+++ test/CodeGen/64bit-swiftcall.c
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -triple x86_64-apple-darwin10 -target-cpu core2 -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -target-cpu core2 -emit-llvm -o - %s | FileCheck %s --check-prefix=X86-64
 // RUN: %clang_cc1 -triple arm64-apple-ios9 -target-cpu cyclone -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -triple arm64-apple-ios9 -target-cpu cyclone -emit-llvm -o - %s | FileCheck %s --check-prefix=ARM64
 
@@ -1014,3 +1015,20 @@
 TEST(struct_v1f3)
 // ARM64-LABEL: define swiftcc { <2 x float>, float } @return_struct_v1f3()
 // ARM64-LABEL: define swiftcc void @take_struct_v1f3(<2 x float>, float)
+
+typedef struct {
+  int3 vect;
+  unsigned long long val;
+} __attribute__((packed)) padded_alloc_size_vector;
+TEST(padded_alloc_size_vector)
+// X86-64-LABEL: take_padded_alloc_size_vector(<3 x i32>, i64)
+// X86-64-NOT: [4 x i8]
+// x86-64: ret void
+
+typedef union {
+  float f1;
+  float3 fv2;
+} union_hom_fp_partial2;
+TEST(union_hom_fp_partial2)
+// X86-64-LABEL: take_union_hom_fp_partial2(i64, float)
+// ARM64-LABEL: take_union_hom_fp_partial2(i64, float)