From cc0f9f1a3b5df7fd308ff3d800fbbbbff805157d Mon Sep 17 00:00:00 2001
From: Fariborz Jahanian <fjahanian@apple.com>
Date: Tue, 3 May 2011 22:07:14 +0000
Subject: [PATCH] Only the first zero-length bitfield decides alignment of the
 followup data member in an ms_struct struct. // rdar:// 8823265

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@130795 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/AST/ASTContext.cpp              |  3 +-
 lib/AST/RecordLayoutBuilder.cpp     |  6 ++--
 test/CodeGen/ms_struct-bitfield-1.c | 46 +++++++++++++++++++++++++++++
 3 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index 8316ea68e9..287c8b2af6 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -546,7 +546,8 @@ bool ASTContext::ZeroBitfieldFollowsNonBitfield(const FieldDecl *FD,
 bool ASTContext::ZeroBitfieldFollowsBitfield(const FieldDecl *FD,
                                              const FieldDecl *LastFD) const {
   return (FD->isBitField() && LastFD && LastFD->isBitField() &&
-          FD->getBitWidth()-> EvaluateAsInt(*this).getZExtValue() == 0);
+          FD->getBitWidth()-> EvaluateAsInt(*this).getZExtValue() == 0 &&
+          LastFD->getBitWidth()-> EvaluateAsInt(*this).getZExtValue() != 0);
 
 }
 
diff --git a/lib/AST/RecordLayoutBuilder.cpp b/lib/AST/RecordLayoutBuilder.cpp
index 810f11b6e3..2203ed1324 100644
--- a/lib/AST/RecordLayoutBuilder.cpp
+++ b/lib/AST/RecordLayoutBuilder.cpp
@@ -1359,9 +1359,11 @@ void RecordLayoutBuilder::LayoutBitField(const FieldDecl *D) {
       std::pair<uint64_t, unsigned> FieldInfo = 
         Context.getTypeInfo(ZeroLengthBitfield->getType());
       unsigned ZeroLengthBitfieldAlignment = FieldInfo.second;
-      if (ZeroLengthBitfieldAlignment > FieldAlign)
+      // Ignore alignment of subsequent zero-length bitfields.
+      if ((ZeroLengthBitfieldAlignment > FieldAlign) || (FieldSize == 0))
         FieldAlign = ZeroLengthBitfieldAlignment;
-      ZeroLengthBitfield = 0;
+      if (FieldSize)
+        ZeroLengthBitfield = 0;
     }
   }
 
diff --git a/test/CodeGen/ms_struct-bitfield-1.c b/test/CodeGen/ms_struct-bitfield-1.c
index 10c6e2aed3..0b15a24f03 100644
--- a/test/CodeGen/ms_struct-bitfield-1.c
+++ b/test/CodeGen/ms_struct-bitfield-1.c
@@ -43,3 +43,49 @@ struct
 } ATTR t5;
 static int a5[(sizeof(t5) == 4) -1];
 
+struct
+{
+                   char foo : 4;
+                   short : 0;
+                   long  :0;
+                   char bar;
+} ATTR t6;
+static int a6[(sizeof(t6) == 4) -1];
+
+struct
+{
+                   char foo : 4;
+                   long  :0;
+                   short : 0;
+                   char bar;
+} ATTR t7;
+static int a7[(sizeof(t7) == 16) -1];
+
+struct
+{
+                   char foo : 4;
+                   short : 0;
+                   long  :0;
+                   char bar:7;
+} ATTR t8;
+static int a8[(sizeof(t8) == 4) -1];
+
+struct
+{
+                   char foo : 4;
+                   long  :0;
+                   short : 0;
+                   char bar: 8;
+} ATTR t9;
+static int a9[(sizeof(t9) == 16) -1];
+
+struct
+{
+                   char foo : 4;
+                   char : 0;
+                   short : 0;
+                   int : 0;
+                   long  :0;
+                   char bar;
+} ATTR t10;
+static int a10[(sizeof(t10) == 2) -1];
-- 
2.40.0