r200031 - Fixing PR18510 by checking whether the non-virtual base of the derived class

[Yunzhong Gao]

Author: ygao
Date: Fri Jan 24 13:28:24 2014
New Revision: 200031

URL: http://llvm.org/viewvc/llvm-project?rev=200031&view=rev
Log:
Fixing PR18510 by checking whether the non-virtual base of the derived class
might have a smaller size as compared to the stand-alone type of the base class.
This is possible when the derived class is packed and hence might have smaller
alignment requirement than the base class.

Differential Revision: http://llvm-reviews.chandlerc.com/D2599


Added:
    cfe/trunk/test/CodeGenCXX/pragma-pack-3.cpp
Modified:
    cfe/trunk/lib/CodeGen/CGRecordLayoutBuilder.cpp

Modified: cfe/trunk/lib/CodeGen/CGRecordLayoutBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGRecordLayoutBuilder.cpp?rev=200031&r1=200030&r2=200031&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGRecordLayoutBuilder.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGRecordLayoutBuilder.cpp Fri Jan 24 13:28:24 2014
@@ -558,7 +558,12 @@ bool CGRecordLayoutBuilder::LayoutBase(c
   if (getTypeAlignment(subobjectType) > Alignment)
     return false;
 
-  AppendField(baseOffset, subobjectType);
+  if (LastLaidOutBase.NonVirtualSize < CharUnits::fromQuantity(
+      Types.getDataLayout().getStructLayout(subobjectType)->getSizeInBytes()))
+    AppendBytes(LastLaidOutBase.NonVirtualSize);
+  else
+    AppendField(baseOffset, subobjectType);
+
   return true;
 }
 

Added: cfe/trunk/test/CodeGenCXX/pragma-pack-3.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/pragma-pack-3.cpp?rev=200031&view=auto
==============================================================================
--- cfe/trunk/test/CodeGenCXX/pragma-pack-3.cpp (added)
+++ cfe/trunk/test/CodeGenCXX/pragma-pack-3.cpp Fri Jan 24 13:28:24 2014
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 %s -triple=i686-apple-darwin10 -emit-llvm -o - | FileCheck %s
+
+struct Base {
+  char a;
+};
+
+struct Derived_1 : virtual Base
+{
+  char b;
+};
+
+#pragma pack(1)
+struct Derived_2 : Derived_1 {
+  // CHECK: %struct.Derived_2 = type <{ [5 x i8], %struct.Base }>
+};
+
+Derived_2 x;