[CodeView] Implement support for bitfields in Clang

[majnemer]

Summary

Emit the underlying storage offset in addition to the starting bit
position of the field.

[aaboud]

Looks good, one minor comments below.

lib/CodeGen/CGDebugInfo.h

243

You have a mismatch between definition and this declaration, definition does not take SourceLocation parameter!

[majnemer]

• Address review comments

[aaboud]

LGTM.
Please update PR28162.

[rnk]

lgtm

Cute, preserves debug info compatibility at the cost of some complexity.

lib/CodeGen/CGDebugInfo.h

#include "clang/Basic/OpenCLImageTypes.def"
 
   /// A helper function to collect debug info for template
   /// parameters.
   llvm::DINodeArray
   CollectCXXTemplateParams(const ClassTemplateSpecializationDecl *TS,
                            llvm::DIFile *F);
 
   llvm::DIType *createFieldType(StringRef name, QualType type,
-                                uint64_t sizeInBitsOverride, SourceLocation loc,
-                                AccessSpecifier AS, uint64_t offsetInBits,
-                                llvm::DIFile *tunit, llvm::DIScope *scope,
+                                SourceLocation loc, AccessSpecifier AS,
+                                uint64_t offsetInBits, llvm::DIFile *tunit,
+                                llvm::DIScope *scope,
                                 const RecordDecl *RD = nullptr);
 
+  /// Create new bit field member.
+  llvm::DIType *createBitFieldType(const FieldDecl *BitFieldDecl,
+                                   llvm::DIScope *RecordTy,
+                                   const RecordDecl *RD);
+
   /// Helpers for collecting fields of a record.
   /// @{
   void CollectRecordLambdaFields(const CXXRecordDecl *CXXDecl,
                                  SmallVectorImpl<llvm::Metadata *> &E,
                                  llvm::DIType *RecordTy);
   llvm::DIDerivedType *CreateRecordStaticField(const VarDecl *Var,
                                                llvm::DIType *RecordTy,
                                                const RecordDecl *RD);

lib/CodeGen/CGDebugInfo.cpp

 //===--- CGDebugInfo.cpp - Emit Debug Information for a Module ------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This coordinates the debug information generation while generating code.
 //
 //===----------------------------------------------------------------------===//
 
 #include "CGDebugInfo.h"
 #include "CGBlocks.h"
+#include "CGRecordLayout.h"
 #include "CGCXXABI.h"
 #include "CGObjCRuntime.h"
 #include "CodeGenFunction.h"
 #include "CodeGenModule.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclFriend.h"
 #include "clang/AST/DeclObjC.h"
 #include "clang/AST/DeclTemplate.h"
static unsigned getAccessFlag(AccessSpecifier Access, const RecordDecl *RD) {
   case clang::AS_public:
     return llvm::DINode::FlagPublic;
   case clang::AS_none:
     return 0;
   }
   llvm_unreachable("unexpected access enumerator");
 }
 
-llvm::DIType *CGDebugInfo::createFieldType(
-    StringRef name, QualType type, uint64_t sizeInBitsOverride,
-    SourceLocation loc, AccessSpecifier AS, uint64_t offsetInBits,
-    llvm::DIFile *tunit, llvm::DIScope *scope, const RecordDecl *RD) {
+llvm::DIType *CGDebugInfo::createBitFieldType(const FieldDecl *BitFieldDecl,
+                                              llvm::DIScope *RecordTy,
+                                              const RecordDecl *RD) {
+  StringRef Name = BitFieldDecl->getName();
+  QualType Ty = BitFieldDecl->getType();
+  SourceLocation Loc = BitFieldDecl->getLocation();
+  llvm::DIFile *VUnit = getOrCreateFile(Loc);
+  llvm::DIType *DebugType = getOrCreateType(Ty, VUnit);
+
+  // Get the location for the field.
+  llvm::DIFile *File = getOrCreateFile(Loc);
+  unsigned Line = getLineNumber(Loc);
+
+  const CGBitFieldInfo &BitFieldInfo =
+      CGM.getTypes().getCGRecordLayout(RD).getBitFieldInfo(BitFieldDecl);
+  uint64_t SizeInBits = BitFieldInfo.Size;
+  assert(SizeInBits > 0 && "found named 0-width bitfield");
+  unsigned AlignInBits = CGM.getContext().getTypeAlign(Ty);
+  uint64_t StorageOffsetInBits =
+      CGM.getContext().toBits(BitFieldInfo.StorageOffset);
+  uint64_t OffsetInBits = StorageOffsetInBits + BitFieldInfo.Offset;
+  unsigned Flags = getAccessFlag(BitFieldDecl->getAccess(), RD);
+  return DBuilder.createBitFieldMemberType(
+      RecordTy, Name, File, Line, SizeInBits, AlignInBits, OffsetInBits,
+      StorageOffsetInBits, Flags, DebugType);
+}
+
+llvm::DIType *
+CGDebugInfo::createFieldType(StringRef name, QualType type, SourceLocation loc,
+                             AccessSpecifier AS, uint64_t offsetInBits,
+                             llvm::DIFile *tunit, llvm::DIScope *scope,
+                             const RecordDecl *RD) {
   llvm::DIType *debugType = getOrCreateType(type, tunit);
 
   // Get the location for the field.
   llvm::DIFile *file = getOrCreateFile(loc);
   unsigned line = getLineNumber(loc);
 
   uint64_t SizeInBits = 0;
   unsigned AlignInBits = 0;
   if (!type->isIncompleteArrayType()) {
     TypeInfo TI = CGM.getContext().getTypeInfo(type);
     SizeInBits = TI.Width;
     AlignInBits = TI.Align;
-
-    if (sizeInBitsOverride)
-      SizeInBits = sizeInBitsOverride;
   }
 
   unsigned flags = getAccessFlag(AS, RD);
   return DBuilder.createMemberType(scope, name, file, line, SizeInBits,
                                    AlignInBits, offsetInBits, flags, debugType);
 }
 
 void CGDebugInfo::CollectRecordLambdaFields(
     const CXXRecordDecl *CXXDecl, SmallVectorImpl<llvm::Metadata *> &elements,
     llvm::DIType *RecordTy) {
   // For C++11 Lambdas a Field will be the same as a Capture, but the Capture
   // has the name and the location of the variable so we should iterate over
   // both concurrently.
   const ASTRecordLayout &layout = CGM.getContext().getASTRecordLayout(CXXDecl);
   RecordDecl::field_iterator Field = CXXDecl->field_begin();
   unsigned fieldno = 0;
   for (CXXRecordDecl::capture_const_iterator I = CXXDecl->captures_begin(),
                                              E = CXXDecl->captures_end();
        I != E; ++I, ++Field, ++fieldno) {
     const LambdaCapture &C = *I;
     if (C.capturesVariable()) {
+      SourceLocation Loc = C.getLocation();
+      assert(!Field->isBitField() && "lambdas don't have bitfield members!");
       VarDecl *V = C.getCapturedVar();
-      llvm::DIFile *VUnit = getOrCreateFile(C.getLocation());
       StringRef VName = V->getName();
-      uint64_t SizeInBitsOverride = 0;
-      if (Field->isBitField()) {
-        SizeInBitsOverride = Field->getBitWidthValue(CGM.getContext());
-        assert(SizeInBitsOverride && "found named 0-width bitfield");
-      }
-      llvm::DIType *fieldType = createFieldType(
-          VName, Field->getType(), SizeInBitsOverride, C.getLocation(),
-          Field->getAccess(), layout.getFieldOffset(fieldno), VUnit, RecordTy,
-          CXXDecl);
-      elements.push_back(fieldType);
+      llvm::DIFile *VUnit = getOrCreateFile(Loc);
+      llvm::DIType *FieldType = createFieldType(
+          VName, Field->getType(), Loc, Field->getAccess(),
+          layout.getFieldOffset(fieldno), VUnit, RecordTy, CXXDecl);
+      elements.push_back(FieldType);
     } else if (C.capturesThis()) {
       // TODO: Need to handle 'this' in some way by probably renaming the
       // this of the lambda class and having a field member of 'this' or
       // by using AT_object_pointer for the function and having that be
       // used as 'this' for semantic references.
       FieldDecl *f = *Field;
       llvm::DIFile *VUnit = getOrCreateFile(f->getLocation());
       QualType type = f->getType();
       llvm::DIType *fieldType = createFieldType(
-          "this", type, 0, f->getLocation(), f->getAccess(),
+          "this", type, f->getLocation(), f->getAccess(),
           layout.getFieldOffset(fieldno), VUnit, RecordTy, CXXDecl);
 
       elements.push_back(fieldType);
     }
   }
 }
 
 llvm::DIDerivedType *
void CGDebugInfo::CollectRecordNormalField(
     const RecordDecl *RD) {
   StringRef name = field->getName();
   QualType type = field->getType();
 
   // Ignore unnamed fields unless they're anonymous structs/unions.
   if (name.empty() && !type->isRecordType())
     return;
 
-  uint64_t SizeInBitsOverride = 0;
+  llvm::DIType *FieldType;
   if (field->isBitField()) {
-    SizeInBitsOverride = field->getBitWidthValue(CGM.getContext());
-    assert(SizeInBitsOverride && "found named 0-width bitfield");
+    FieldType = createBitFieldType(field, RecordTy, RD);
+  } else {
+    FieldType =
+        createFieldType(name, type, field->getLocation(), field->getAccess(),
+                        OffsetInBits, tunit, RecordTy, RD);
   }
 
-  llvm::DIType *fieldType =
-      createFieldType(name, type, SizeInBitsOverride, field->getLocation(),
-                      field->getAccess(), OffsetInBits, tunit, RecordTy, RD);
-
-  elements.push_back(fieldType);
+  elements.push_back(FieldType);
 }
 
 void CGDebugInfo::CollectRecordFields(
     const RecordDecl *record, llvm::DIFile *tunit,
     SmallVectorImpl<llvm::Metadata *> &elements,
     llvm::DICompositeType *RecordTy) {
   const CXXRecordDecl *CXXDecl = dyn_cast<CXXRecordDecl>(record);
 
void CGDebugInfo::EmitDeclareOfBlockLiteralArgVariable(const CGBlockInfo &block,
 
   // Build the debug-info type for the block literal.
   getDeclContextDescriptor(blockDecl);
 
   const llvm::StructLayout *blockLayout =
       CGM.getDataLayout().getStructLayout(block.StructureType);
 
   SmallVector<llvm::Metadata *, 16> fields;
-  fields.push_back(createFieldType("__isa", C.VoidPtrTy, 0, loc, AS_public,
+  fields.push_back(createFieldType("__isa", C.VoidPtrTy, loc, AS_public,
                                    blockLayout->getElementOffsetInBits(0),
                                    tunit, tunit));
-  fields.push_back(createFieldType("__flags", C.IntTy, 0, loc, AS_public,
+  fields.push_back(createFieldType("__flags", C.IntTy, loc, AS_public,
                                    blockLayout->getElementOffsetInBits(1),
                                    tunit, tunit));
-  fields.push_back(createFieldType("__reserved", C.IntTy, 0, loc, AS_public,
+  fields.push_back(createFieldType("__reserved", C.IntTy, loc, AS_public,
                                    blockLayout->getElementOffsetInBits(2),
                                    tunit, tunit));
   auto *FnTy = block.getBlockExpr()->getFunctionType();
   auto FnPtrType = CGM.getContext().getPointerType(FnTy->desugar());
-  fields.push_back(createFieldType("__FuncPtr", FnPtrType, 0, loc, AS_public,
+  fields.push_back(createFieldType("__FuncPtr", FnPtrType, loc, AS_public,
                                    blockLayout->getElementOffsetInBits(3),
                                    tunit, tunit));
   fields.push_back(createFieldType(
       "__descriptor", C.getPointerType(block.NeedsCopyDispose
                                            ? C.getBlockDescriptorExtendedType()
                                            : C.getBlockDescriptorType()),
-      0, loc, AS_public, blockLayout->getElementOffsetInBits(4), tunit, tunit));
+      loc, AS_public, blockLayout->getElementOffsetInBits(4), tunit, tunit));
 
   // We want to sort the captures by offset, not because DWARF
   // requires this, but because we're paranoid about debuggers.
   SmallVector<BlockLayoutChunk, 8> chunks;
 
   // 'this' capture.
   if (blockDecl->capturesCXXThis()) {
     BlockLayoutChunk chunk;
if (!capture) {
       if (auto *Method =
               cast_or_null<CXXMethodDecl>(blockDecl->getNonClosureContext()))
         type = Method->getThisType(C);
       else if (auto *RDecl = dyn_cast<CXXRecordDecl>(blockDecl->getParent()))
         type = QualType(RDecl->getTypeForDecl(), 0);
       else
         llvm_unreachable("unexpected block declcontext");
 
-      fields.push_back(createFieldType("this", type, 0, loc, AS_public,
+      fields.push_back(createFieldType("this", type, loc, AS_public,
                                        offsetInBits, tunit, tunit));
       continue;
     }
 
     const VarDecl *variable = capture->getVariable();
     StringRef name = variable->getName();
 
     llvm::DIType *fieldType;
     if (capture->isByRef()) {
       TypeInfo PtrInfo = C.getTypeInfo(C.VoidPtrTy);
 
       // FIXME: this creates a second copy of this type!
       uint64_t xoffset;
       fieldType = EmitTypeForVarWithBlocksAttr(variable, &xoffset);
       fieldType = DBuilder.createPointerType(fieldType, PtrInfo.Width);
       fieldType =
           DBuilder.createMemberType(tunit, name, tunit, line, PtrInfo.Width,
                                     PtrInfo.Align, offsetInBits, 0, fieldType);
     } else {
-      fieldType = createFieldType(name, variable->getType(), 0, loc, AS_public,
+      fieldType = createFieldType(name, variable->getType(), loc, AS_public,
                                   offsetInBits, tunit, tunit);
     }
     fields.push_back(fieldType);
   }
 
   SmallString<36> typeName;
   llvm::raw_svector_ostream(typeName) << "__block_literal_"
                                       << CGM.getUniqueBlockCount();

test/CodeGen/debug-info-packed-struct.c

struct layout0 {
   char l0_ofs0;
   struct size8 l0_ofs8;
   int l0_ofs16 : 1;
 };
 // CHECK: l0_ofs0
 // CHECK: !DIDerivedType(tag: DW_TAG_member, name: "l0_ofs8",
 // CHECK-SAME:     {{.*}}size: 64, align: 64, offset: 64)
 // CHECK: !DIDerivedType(tag: DW_TAG_member, name: "l0_ofs16",
-// CHECK-SAME:     {{.*}}size: 1, align: 32, offset: 128)
+// CHECK-SAME:     {{.*}}size: 1, align: 32, offset: 128, flags: DIFlagBitField, extraData: i64 128)
 
 
 // ---------------------------------------------------------------------
 // Implicitly packed.
 // ---------------------------------------------------------------------
 struct size8_anon {
   int : 4;
   long long : 60;
 };
 struct layout1 {
   char l1_ofs0;
   struct size8_anon l1_ofs1;
   int l1_ofs9 : 1;
 };
 // CHECK: l1_ofs0
 // CHECK: !DIDerivedType(tag: DW_TAG_member, name: "l1_ofs1",
 // CHECK-SAME:     {{.*}}size: 64, align: 8, offset: 8)
 // CHECK: !DIDerivedType(tag: DW_TAG_member, name: "l1_ofs9",
-// CHECK-SAME:     {{.*}}size: 1, align: 32, offset: 72)
+// CHECK-SAME:     {{.*}}size: 1, align: 32, offset: 72, flags: DIFlagBitField, extraData: i64 72)
 
 
 // ---------------------------------------------------------------------
 // Explicitly packed.
 // ---------------------------------------------------------------------
 #pragma pack(1)
 struct size8_pack1 {
   int i : 4;
   long long l : 60;
 };
 struct layout2 {
   char l2_ofs0;
   struct size8_pack1 l2_ofs1;
   int l2_ofs9 : 1;
 };
 #pragma pack()
 // CHECK: l2_ofs0
 // CHECK: !DIDerivedType(tag: DW_TAG_member, name: "l2_ofs1",
 // CHECK-SAME:     {{.*}}size: 64, align: 8, offset: 8)
 // CHECK: !DIDerivedType(tag: DW_TAG_member, name: "l2_ofs9",
-// CHECK-SAME:     {{.*}}size: 1, align: 32, offset: 72)
+// CHECK-SAME:     {{.*}}size: 1, align: 32, offset: 72, flags: DIFlagBitField, extraData: i64 72)
 
 
 
 // ---------------------------------------------------------------------
 // Explicitly packed with different alignment.
 // ---------------------------------------------------------------------
 #pragma pack(4)
 struct size8_pack4 {
   int i : 4;
   long long l : 60;
 };
 struct layout3 {
   char l3_ofs0;
   struct size8_pack4 l3_ofs4;
   int l3_ofs12 : 1;
 };
 #pragma pack()
 // CHECK: l3_ofs0
 // CHECK: !DIDerivedType(tag: DW_TAG_member, name: "l3_ofs4",
 // CHECK-SAME:     {{.*}}size: 64, align: 32, offset: 32)
 // CHECK: !DIDerivedType(tag: DW_TAG_member, name: "l3_ofs12",
-// CHECK-SAME:     {{.*}}size: 1, align: 32, offset: 96)
+// CHECK-SAME:     {{.*}}size: 1, align: 32, offset: 96, flags: DIFlagBitField, extraData: i64 96)
 
 struct layout0 l0;
 struct layout1 l1;
 struct layout2 l2;
 struct layout3 l3;

test/CodeGenCXX/debug-info-ms-bitfields.cpp

+// RUN: %clang_cc1 -triple x86_64-pc-win32 -debug-info-kind=limited -gcodeview %s -emit-llvm -o - | FileCheck %s
+
+#pragma pack(1)
+struct S {
+  char : 8;
+  short   : 8;
+  short x : 8;
+} s;
+
+// CHECK: !DIDerivedType(tag: DW_TAG_member, name: "x", {{.*}}, size: 8, align: 16, offset: 16, flags: DIFlagBitField, extraData: i64 8)