Use ASTContext::getDeclAlign(<Field Decl>) to get the alignment of the first

field to be memcpy'd, rather instead of ASTContext::getTypeAlign(<Field Type>).
For packed structs the alignment of a field may be less than the alignment of
the field's type.

<rdar://problem/13338585>

llvm-svn: 176512

2 files changed, 21 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CGClass.cpp b/clang/lib/CodeGen/CGClass.cpp
index ac2dada0834..4319e43b91b 100644
--- a/clang/lib/CodeGen/CGClass.cpp
+++ b/clang/lib/CodeGen/CGClass.cpp
@@ -794,9 +794,7 @@ namespace {
         const CGBitFieldInfo &BFInfo = RL.getBitFieldInfo(FirstField);
         Alignment = CharUnits::fromQuantity(BFInfo.StorageAlignment);
       } else {
-        unsigned AlignBits =
-          CGF.getContext().getTypeAlign(FirstField->getType());
-        Alignment = CGF.getContext().toCharUnitsFromBits(AlignBits);
+        Alignment = CGF.getContext().getDeclAlign(FirstField);
       }
 
       assert((CGF.getContext().toCharUnitsFromBits(FirstFieldOffset) %
diff --git a/clang/test/CodeGenCXX/pod-member-memcpys.cpp b/clang/test/CodeGenCXX/pod-member-memcpys.cpp
index 1e76c08899a..534d5d19e99 100644
--- a/clang/test/CodeGenCXX/pod-member-memcpys.cpp
+++ b/clang/test/CodeGenCXX/pod-member-memcpys.cpp
@@ -86,6 +86,12 @@ struct ReferenceMember {
   int &d;
 };
 
+struct __attribute__((packed)) PackedMembers {
+  char c;
+  NonPOD np;
+  int w, x, y, z;
+};
+
 // COPY-ASSIGNMENT OPERATORS:
 
 // Assignment operators are output in the order they're encountered.
@@ -99,6 +105,7 @@ CALL_AO(ArrayMember)
 CALL_AO(VolatileMember)
 CALL_AO(BitfieldMember)
 CALL_AO(InnerClassMember)
+CALL_AO(PackedMembers)
 
 // Basic copy-assignment:
 // CHECK: define linkonce_odr %struct.Basic* @_ZN5BasicaSERKS_(%struct.Basic* %this, %struct.Basic*)
@@ -151,6 +158,12 @@ CALL_AO(InnerClassMember)
 // CHECK: tail call void @llvm.memcpy.p0i8.p0i8.i64({{.*}}i64 16, i32 4{{.*}})
 // CHECK: ret %struct.InnerClassMember* %this
 
+// PackedMembers copy-assignment:
+// CHECK: define linkonce_odr %struct.PackedMembers* @_ZN13PackedMembersaSERKS_(%struct.PackedMembers* %this, %struct.PackedMembers*)
+// CHECK: tail call %struct.NonPOD* @_ZN6NonPODaSERKS_
+// CHECK: tail call void @llvm.memcpy.p0i8.p0i8.i64({{.*}}i64 16, i32 1{{.*}})
+// CHECK: ret %struct.PackedMembers* %this
+
 // COPY-CONSTRUCTORS:
 
 // Clang outputs copy-constructors in the reverse of the order that
@@ -159,6 +172,7 @@ CALL_AO(InnerClassMember)
 
 #define CALL_CC(T) T callCC##T(const T& b) { return b; }
 
+CALL_CC(PackedMembers)
 CALL_CC(BitfieldMember2)
 CALL_CC(ReferenceMember)
 CALL_CC(InnerClassMember)
@@ -234,3 +248,9 @@ CALL_CC(Basic)
 // CHECK-2: call void @llvm.memcpy.p0i8.p0i8.i64({{.*}}i64 16, i32 4, i1 false)
 // CHECK-2: call void @_ZN6NonPODC1ERKS_
 // CHECK-2: ret void
+
+// PackedMembers copy-assignment:
+// CHECK: define linkonce_odr void @_ZN13PackedMembersC2ERKS_(%struct.PackedMembers* %this, %struct.PackedMembers*)
+// CHECK: tail call void @_ZN6NonPODC1ERKS_
+// CHECK: tail call void @llvm.memcpy.p0i8.p0i8.i64({{.*}}i64 16, i32 1{{.*}})
+// CHECK: ret void