[CodeView] Implement support for bitfields in LLVM

CodeView need to know the offset of the storage allocation for a
bitfield.  Encode this via the "extraData" field in DIDerivedType and
introduced a new flag, DIFlagBitField, to indicate whether or not a
member is a bitfield.

This fixes PR28162.

Differential Revision: http://reviews.llvm.org/D21782

llvm-svn: 274200

2 files changed, 33 insertions, 11 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
index e01ee0984ed..a6bcf9e848d 100644
--- a/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -20,6 +20,7 @@
 #include "llvm/DebugInfo/CodeView/TypeDumper.h"
 #include "llvm/DebugInfo/CodeView/TypeIndex.h"
 #include "llvm/DebugInfo/CodeView/TypeRecord.h"
+#include "llvm/IR/Constants.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCSectionCOFF.h"
 #include "llvm/MC/MCSymbol.h"
@@ -1500,23 +1501,32 @@ CodeViewDebug::lowerRecordFieldList(const DICompositeType *Ty) {
   for (ClassInfo::MemberInfo &MemberInfo : Info.Members) {
     const DIDerivedType *Member = MemberInfo.MemberTypeNode;
     TypeIndex MemberBaseType = getTypeIndex(Member->getBaseType());
+    StringRef MemberName = Member->getName();
+    MemberAccess Access =
+        translateAccessFlags(Ty->getTag(), Member->getFlags());
 
     if (Member->isStaticMember()) {
-      Fields.writeStaticDataMember(StaticDataMemberRecord(
-          translateAccessFlags(Ty->getTag(), Member->getFlags()),
-          MemberBaseType, Member->getName()));
+      Fields.writeStaticDataMember(
+          StaticDataMemberRecord(Access, MemberBaseType, MemberName));
       MemberCount++;
       continue;
     }
 
-    uint64_t OffsetInBytes = MemberInfo.BaseOffset;
-
-    // FIXME: Handle bitfield type memeber.
-    OffsetInBytes += Member->getOffsetInBits() / 8;
-
-    Fields.writeDataMember(
-        DataMemberRecord(translateAccessFlags(Ty->getTag(), Member->getFlags()),
-                         MemberBaseType, OffsetInBytes, Member->getName()));
+    // Data member.
+    uint64_t MemberOffsetInBits = Member->getOffsetInBits();
+    if (Member->isBitField()) {
+      uint64_t StartBitOffset = MemberOffsetInBits;
+      if (const auto *CI =
+              dyn_cast_or_null<ConstantInt>(Member->getStorageOffsetInBits())) {
+        MemberOffsetInBits = CI->getZExtValue();
+      }
+      StartBitOffset -= MemberOffsetInBits;
+      MemberBaseType = TypeTable.writeBitField(BitFieldRecord(
+          MemberBaseType, Member->getSizeInBits(), StartBitOffset));
+    }
+    uint64_t MemberOffsetInBytes = MemberOffsetInBits / 8;
+    Fields.writeDataMember(DataMemberRecord(Access, MemberBaseType,
+                                            MemberOffsetInBytes, MemberName));
     MemberCount++;
   }
 
diff --git a/llvm/lib/IR/DIBuilder.cpp b/llvm/lib/IR/DIBuilder.cpp
index ab03365d508..ce16fdd6894 100644
--- a/llvm/lib/IR/DIBuilder.cpp
+++ b/llvm/lib/IR/DIBuilder.cpp
@@ -308,6 +308,18 @@ static ConstantAsMetadata *getConstantOrNull(Constant *C) {
   return nullptr;
 }
 
+DIDerivedType *DIBuilder::createBitFieldMemberType(
+    DIScope *Scope, StringRef Name, DIFile *File, unsigned LineNumber,
+    uint64_t SizeInBits, uint64_t AlignInBits, uint64_t OffsetInBits,
+    uint64_t StorageOffsetInBits, unsigned Flags, DIType *Ty) {
+  Flags |= DINode::FlagBitField;
+  return DIDerivedType::get(
+      VMContext, dwarf::DW_TAG_member, Name, File, LineNumber,
+      getNonCompileUnitScope(Scope), Ty, SizeInBits, AlignInBits, OffsetInBits,
+      Flags, ConstantAsMetadata::get(ConstantInt::get(
+                 IntegerType::get(VMContext, 64), StorageOffsetInBits)));
+}
+
 DIDerivedType *DIBuilder::createStaticMemberType(DIScope *Scope, StringRef Name,
                                                  DIFile *File,
                                                  unsigned LineNumber,