CGRecordLayoutBuilder.cpp revision 200583
1198092Srdivacky//===--- CGRecordLayoutBuilder.cpp - Record builder helper ------*- C++ -*-===// 2198092Srdivacky// 3198092Srdivacky// The LLVM Compiler Infrastructure 4198092Srdivacky// 5198092Srdivacky// This file is distributed under the University of Illinois Open Source 6198092Srdivacky// License. See LICENSE.TXT for details. 7198092Srdivacky// 8198092Srdivacky//===----------------------------------------------------------------------===// 9198092Srdivacky// 10198092Srdivacky// This is a helper class used to build CGRecordLayout objects and LLVM types. 11198092Srdivacky// 12198092Srdivacky//===----------------------------------------------------------------------===// 13198092Srdivacky 14198092Srdivacky#include "CGRecordLayoutBuilder.h" 15198092Srdivacky 16198092Srdivacky#include "clang/AST/ASTContext.h" 17198092Srdivacky#include "clang/AST/Attr.h" 18198092Srdivacky#include "clang/AST/DeclCXX.h" 19198092Srdivacky#include "clang/AST/Expr.h" 20198092Srdivacky#include "clang/AST/RecordLayout.h" 21198092Srdivacky#include "CodeGenTypes.h" 22198092Srdivacky#include "llvm/DerivedTypes.h" 23198092Srdivacky#include "llvm/Target/TargetData.h" 24198092Srdivacky 25198092Srdivacky 26198092Srdivackyusing namespace clang; 27198092Srdivackyusing namespace CodeGen; 28198092Srdivacky 29198092Srdivackyvoid CGRecordLayoutBuilder::Layout(const RecordDecl *D) { 30198092Srdivacky Alignment = Types.getContext().getASTRecordLayout(D).getAlignment() / 8; 31198092Srdivacky Packed = D->hasAttr<PackedAttr>(); 32198092Srdivacky 33198092Srdivacky if (D->isUnion()) { 34198092Srdivacky LayoutUnion(D); 35198092Srdivacky return; 36198092Srdivacky } 37198092Srdivacky 38198092Srdivacky if (LayoutFields(D)) 39198092Srdivacky return; 40198092Srdivacky 41198092Srdivacky // We weren't able to layout the struct. Try again with a packed struct 42198092Srdivacky Packed = true; 43198092Srdivacky AlignmentAsLLVMStruct = 1; 44198092Srdivacky NextFieldOffsetInBytes = 0; 45198092Srdivacky FieldTypes.clear(); 46198092Srdivacky LLVMFields.clear(); 47198092Srdivacky LLVMBitFields.clear(); 48198092Srdivacky 49198092Srdivacky LayoutFields(D); 50198092Srdivacky} 51198092Srdivacky 52198092Srdivackyvoid CGRecordLayoutBuilder::LayoutBitField(const FieldDecl *D, 53198092Srdivacky uint64_t FieldOffset) { 54198092Srdivacky uint64_t FieldSize = 55198092Srdivacky D->getBitWidth()->EvaluateAsInt(Types.getContext()).getZExtValue(); 56198092Srdivacky 57198092Srdivacky if (FieldSize == 0) 58198092Srdivacky return; 59198092Srdivacky 60198092Srdivacky uint64_t NextFieldOffset = NextFieldOffsetInBytes * 8; 61198092Srdivacky unsigned NumBytesToAppend; 62198092Srdivacky 63198092Srdivacky if (FieldOffset < NextFieldOffset) { 64198092Srdivacky assert(BitsAvailableInLastField && "Bitfield size mismatch!"); 65198092Srdivacky assert(NextFieldOffsetInBytes && "Must have laid out at least one byte!"); 66198092Srdivacky 67198092Srdivacky // The bitfield begins in the previous bit-field. 68198092Srdivacky NumBytesToAppend = 69198092Srdivacky llvm::RoundUpToAlignment(FieldSize - BitsAvailableInLastField, 8) / 8; 70198092Srdivacky } else { 71198092Srdivacky assert(FieldOffset % 8 == 0 && "Field offset not aligned correctly"); 72198092Srdivacky 73198092Srdivacky // Append padding if necessary. 74198092Srdivacky AppendBytes((FieldOffset - NextFieldOffset) / 8); 75198092Srdivacky 76198092Srdivacky NumBytesToAppend = 77198092Srdivacky llvm::RoundUpToAlignment(FieldSize, 8) / 8; 78198092Srdivacky 79198092Srdivacky assert(NumBytesToAppend && "No bytes to append!"); 80198092Srdivacky } 81198092Srdivacky 82198092Srdivacky const llvm::Type *Ty = Types.ConvertTypeForMemRecursive(D->getType()); 83198092Srdivacky uint64_t TypeSizeInBits = getTypeSizeInBytes(Ty) * 8; 84198092Srdivacky 85198092Srdivacky LLVMBitFields.push_back(LLVMBitFieldInfo(D, FieldOffset / TypeSizeInBits, 86198092Srdivacky FieldOffset % TypeSizeInBits, 87198092Srdivacky FieldSize)); 88198092Srdivacky 89198092Srdivacky AppendBytes(NumBytesToAppend); 90198092Srdivacky 91198092Srdivacky BitsAvailableInLastField = 92198092Srdivacky NextFieldOffsetInBytes * 8 - (FieldOffset + FieldSize); 93198092Srdivacky} 94198092Srdivacky 95198092Srdivackybool CGRecordLayoutBuilder::LayoutField(const FieldDecl *D, 96198092Srdivacky uint64_t FieldOffset) { 97198092Srdivacky // If the field is packed, then we need a packed struct. 98198092Srdivacky if (!Packed && D->hasAttr<PackedAttr>()) 99198092Srdivacky return false; 100198092Srdivacky 101198092Srdivacky if (D->isBitField()) { 102198092Srdivacky // We must use packed structs for unnamed bit fields since they 103198092Srdivacky // don't affect the struct alignment. 104198092Srdivacky if (!Packed && !D->getDeclName()) 105198092Srdivacky return false; 106198092Srdivacky 107198092Srdivacky LayoutBitField(D, FieldOffset); 108198092Srdivacky return true; 109198092Srdivacky } 110198092Srdivacky 111198092Srdivacky assert(FieldOffset % 8 == 0 && "FieldOffset is not on a byte boundary!"); 112198092Srdivacky uint64_t FieldOffsetInBytes = FieldOffset / 8; 113198092Srdivacky 114198092Srdivacky const llvm::Type *Ty = Types.ConvertTypeForMemRecursive(D->getType()); 115198092Srdivacky unsigned TypeAlignment = getTypeAlignment(Ty); 116198092Srdivacky 117198092Srdivacky // If the type alignment is larger then the struct alignment, we must use 118198092Srdivacky // a packed struct. 119198092Srdivacky if (TypeAlignment > Alignment) { 120198092Srdivacky assert(!Packed && "Alignment is wrong even with packed struct!"); 121198092Srdivacky return false; 122198092Srdivacky } 123198092Srdivacky 124198092Srdivacky if (const RecordType *RT = D->getType()->getAs<RecordType>()) { 125198092Srdivacky const RecordDecl *RD = cast<RecordDecl>(RT->getDecl()); 126198092Srdivacky if (const PragmaPackAttr *PPA = RD->getAttr<PragmaPackAttr>()) { 127198092Srdivacky if (PPA->getAlignment() != TypeAlignment * 8 && !Packed) 128198092Srdivacky return false; 129198092Srdivacky } 130198092Srdivacky } 131198092Srdivacky 132198092Srdivacky // Round up the field offset to the alignment of the field type. 133198092Srdivacky uint64_t AlignedNextFieldOffsetInBytes = 134198092Srdivacky llvm::RoundUpToAlignment(NextFieldOffsetInBytes, TypeAlignment); 135198092Srdivacky 136198092Srdivacky if (FieldOffsetInBytes < AlignedNextFieldOffsetInBytes) { 137198092Srdivacky assert(!Packed && "Could not place field even with packed struct!"); 138198092Srdivacky return false; 139198092Srdivacky } 140198092Srdivacky 141198092Srdivacky if (AlignedNextFieldOffsetInBytes < FieldOffsetInBytes) { 142198092Srdivacky // Even with alignment, the field offset is not at the right place, 143198092Srdivacky // insert padding. 144198092Srdivacky uint64_t PaddingInBytes = FieldOffsetInBytes - NextFieldOffsetInBytes; 145198092Srdivacky 146198092Srdivacky AppendBytes(PaddingInBytes); 147198092Srdivacky } 148198092Srdivacky 149198092Srdivacky // Now append the field. 150198092Srdivacky LLVMFields.push_back(LLVMFieldInfo(D, FieldTypes.size())); 151198092Srdivacky AppendField(FieldOffsetInBytes, Ty); 152198092Srdivacky 153198092Srdivacky return true; 154198092Srdivacky} 155198092Srdivacky 156198092Srdivackyvoid CGRecordLayoutBuilder::LayoutUnion(const RecordDecl *D) { 157198092Srdivacky assert(D->isUnion() && "Can't call LayoutUnion on a non-union record!"); 158198092Srdivacky 159198092Srdivacky const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D); 160198092Srdivacky 161198092Srdivacky const llvm::Type *Ty = 0; 162198092Srdivacky uint64_t Size = 0; 163198092Srdivacky unsigned Align = 0; 164198092Srdivacky 165198092Srdivacky unsigned FieldNo = 0; 166198092Srdivacky for (RecordDecl::field_iterator Field = D->field_begin(), 167198092Srdivacky FieldEnd = D->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { 168198092Srdivacky assert(Layout.getFieldOffset(FieldNo) == 0 && 169198092Srdivacky "Union field offset did not start at the beginning of record!"); 170198092Srdivacky 171198092Srdivacky if (Field->isBitField()) { 172198092Srdivacky uint64_t FieldSize = 173198092Srdivacky Field->getBitWidth()->EvaluateAsInt(Types.getContext()).getZExtValue(); 174198092Srdivacky 175198092Srdivacky // Ignore zero sized bit fields. 176198092Srdivacky if (FieldSize == 0) 177198092Srdivacky continue; 178198092Srdivacky 179198092Srdivacky // Add the bit field info. 180198092Srdivacky Types.addBitFieldInfo(*Field, 0, 0, FieldSize); 181198092Srdivacky } else 182198092Srdivacky Types.addFieldInfo(*Field, 0); 183198092Srdivacky 184198092Srdivacky const llvm::Type *FieldTy = 185198092Srdivacky Types.ConvertTypeForMemRecursive(Field->getType()); 186198092Srdivacky unsigned FieldAlign = Types.getTargetData().getABITypeAlignment(FieldTy); 187198092Srdivacky uint64_t FieldSize = Types.getTargetData().getTypeAllocSize(FieldTy); 188198092Srdivacky 189198092Srdivacky if (FieldAlign < Align) 190198092Srdivacky continue; 191198092Srdivacky 192198092Srdivacky if (FieldAlign > Align || FieldSize > Size) { 193198092Srdivacky Ty = FieldTy; 194198092Srdivacky Align = FieldAlign; 195198092Srdivacky Size = FieldSize; 196198092Srdivacky } 197198092Srdivacky } 198198092Srdivacky 199198092Srdivacky // Now add our field. 200198092Srdivacky if (Ty) { 201198092Srdivacky AppendField(0, Ty); 202198092Srdivacky 203198092Srdivacky if (getTypeAlignment(Ty) > Layout.getAlignment() / 8) { 204198092Srdivacky // We need a packed struct. 205198092Srdivacky Packed = true; 206198092Srdivacky Align = 1; 207198092Srdivacky } 208198092Srdivacky } 209199482Srdivacky if (!Align) { 210199482Srdivacky assert((D->field_begin() == D->field_end()) && "LayoutUnion - Align 0"); 211199482Srdivacky Align = 1; 212199482Srdivacky } 213199482Srdivacky 214198092Srdivacky // Append tail padding. 215198092Srdivacky if (Layout.getSize() / 8 > Size) 216198092Srdivacky AppendPadding(Layout.getSize() / 8, Align); 217198092Srdivacky} 218198092Srdivacky 219198092Srdivackybool CGRecordLayoutBuilder::LayoutFields(const RecordDecl *D) { 220198092Srdivacky assert(!D->isUnion() && "Can't call LayoutFields on a union!"); 221198092Srdivacky assert(Alignment && "Did not set alignment!"); 222198092Srdivacky 223198092Srdivacky const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D); 224198092Srdivacky 225198092Srdivacky unsigned FieldNo = 0; 226198092Srdivacky 227198092Srdivacky for (RecordDecl::field_iterator Field = D->field_begin(), 228198092Srdivacky FieldEnd = D->field_end(); Field != FieldEnd; ++Field, ++FieldNo) { 229198092Srdivacky if (!LayoutField(*Field, Layout.getFieldOffset(FieldNo))) { 230198092Srdivacky assert(!Packed && 231198092Srdivacky "Could not layout fields even with a packed LLVM struct!"); 232198092Srdivacky return false; 233198092Srdivacky } 234198092Srdivacky } 235198092Srdivacky 236198092Srdivacky // Append tail padding if necessary. 237198092Srdivacky AppendTailPadding(Layout.getSize()); 238198092Srdivacky 239198092Srdivacky return true; 240198092Srdivacky} 241198092Srdivacky 242198092Srdivackyvoid CGRecordLayoutBuilder::AppendTailPadding(uint64_t RecordSize) { 243198092Srdivacky assert(RecordSize % 8 == 0 && "Invalid record size!"); 244198092Srdivacky 245198092Srdivacky uint64_t RecordSizeInBytes = RecordSize / 8; 246198092Srdivacky assert(NextFieldOffsetInBytes <= RecordSizeInBytes && "Size mismatch!"); 247198092Srdivacky 248200583Srdivacky uint64_t AlignedNextFieldOffset = 249200583Srdivacky llvm::RoundUpToAlignment(NextFieldOffsetInBytes, AlignmentAsLLVMStruct); 250200583Srdivacky 251200583Srdivacky if (AlignedNextFieldOffset == RecordSizeInBytes) { 252200583Srdivacky // We don't need any padding. 253200583Srdivacky return; 254200583Srdivacky } 255200583Srdivacky 256198092Srdivacky unsigned NumPadBytes = RecordSizeInBytes - NextFieldOffsetInBytes; 257198092Srdivacky AppendBytes(NumPadBytes); 258198092Srdivacky} 259198092Srdivacky 260198092Srdivackyvoid CGRecordLayoutBuilder::AppendField(uint64_t FieldOffsetInBytes, 261198092Srdivacky const llvm::Type *FieldTy) { 262198092Srdivacky AlignmentAsLLVMStruct = std::max(AlignmentAsLLVMStruct, 263198092Srdivacky getTypeAlignment(FieldTy)); 264198092Srdivacky 265198092Srdivacky uint64_t FieldSizeInBytes = getTypeSizeInBytes(FieldTy); 266198092Srdivacky 267198092Srdivacky FieldTypes.push_back(FieldTy); 268198092Srdivacky 269198092Srdivacky NextFieldOffsetInBytes = FieldOffsetInBytes + FieldSizeInBytes; 270198092Srdivacky BitsAvailableInLastField = 0; 271198092Srdivacky} 272198092Srdivacky 273198092Srdivackyvoid 274198092SrdivackyCGRecordLayoutBuilder::AppendPadding(uint64_t FieldOffsetInBytes, 275198092Srdivacky const llvm::Type *FieldTy) { 276198092Srdivacky AppendPadding(FieldOffsetInBytes, getTypeAlignment(FieldTy)); 277198092Srdivacky} 278198092Srdivacky 279198092Srdivackyvoid CGRecordLayoutBuilder::AppendPadding(uint64_t FieldOffsetInBytes, 280198092Srdivacky unsigned FieldAlignment) { 281198092Srdivacky assert(NextFieldOffsetInBytes <= FieldOffsetInBytes && 282198092Srdivacky "Incorrect field layout!"); 283198092Srdivacky 284198092Srdivacky // Round up the field offset to the alignment of the field type. 285198092Srdivacky uint64_t AlignedNextFieldOffsetInBytes = 286198092Srdivacky llvm::RoundUpToAlignment(NextFieldOffsetInBytes, FieldAlignment); 287198092Srdivacky 288198092Srdivacky if (AlignedNextFieldOffsetInBytes < FieldOffsetInBytes) { 289198092Srdivacky // Even with alignment, the field offset is not at the right place, 290198092Srdivacky // insert padding. 291198092Srdivacky uint64_t PaddingInBytes = FieldOffsetInBytes - NextFieldOffsetInBytes; 292198092Srdivacky 293198092Srdivacky AppendBytes(PaddingInBytes); 294198092Srdivacky } 295198092Srdivacky} 296198092Srdivacky 297198092Srdivackyvoid CGRecordLayoutBuilder::AppendBytes(uint64_t NumBytes) { 298198092Srdivacky if (NumBytes == 0) 299198092Srdivacky return; 300198092Srdivacky 301198092Srdivacky const llvm::Type *Ty = llvm::Type::getInt8Ty(Types.getLLVMContext()); 302198092Srdivacky if (NumBytes > 1) 303198092Srdivacky Ty = llvm::ArrayType::get(Ty, NumBytes); 304198092Srdivacky 305198092Srdivacky // Append the padding field 306198092Srdivacky AppendField(NextFieldOffsetInBytes, Ty); 307198092Srdivacky} 308198092Srdivacky 309198092Srdivackyunsigned CGRecordLayoutBuilder::getTypeAlignment(const llvm::Type *Ty) const { 310198092Srdivacky if (Packed) 311198092Srdivacky return 1; 312198092Srdivacky 313198092Srdivacky return Types.getTargetData().getABITypeAlignment(Ty); 314198092Srdivacky} 315198092Srdivacky 316198092Srdivackyuint64_t CGRecordLayoutBuilder::getTypeSizeInBytes(const llvm::Type *Ty) const { 317198092Srdivacky return Types.getTargetData().getTypeAllocSize(Ty); 318198092Srdivacky} 319198092Srdivacky 320198092Srdivackyvoid CGRecordLayoutBuilder::CheckForMemberPointer(const FieldDecl *FD) { 321198092Srdivacky // This record already contains a member pointer. 322198092Srdivacky if (ContainsMemberPointer) 323198092Srdivacky return; 324198092Srdivacky 325198092Srdivacky // Can only have member pointers if we're compiling C++. 326198092Srdivacky if (!Types.getContext().getLangOptions().CPlusPlus) 327198092Srdivacky return; 328198092Srdivacky 329198092Srdivacky QualType Ty = FD->getType(); 330198092Srdivacky 331198092Srdivacky if (Ty->isMemberPointerType()) { 332198092Srdivacky // We have a member pointer! 333198092Srdivacky ContainsMemberPointer = true; 334198092Srdivacky return; 335198092Srdivacky } 336198092Srdivacky 337198092Srdivacky} 338198092Srdivacky 339198092SrdivackyCGRecordLayout * 340198092SrdivackyCGRecordLayoutBuilder::ComputeLayout(CodeGenTypes &Types, 341198092Srdivacky const RecordDecl *D) { 342198092Srdivacky CGRecordLayoutBuilder Builder(Types); 343198092Srdivacky 344198092Srdivacky Builder.Layout(D); 345198092Srdivacky 346198092Srdivacky const llvm::Type *Ty = llvm::StructType::get(Types.getLLVMContext(), 347198092Srdivacky Builder.FieldTypes, 348198092Srdivacky Builder.Packed); 349198092Srdivacky assert(Types.getContext().getASTRecordLayout(D).getSize() / 8 == 350198092Srdivacky Types.getTargetData().getTypeAllocSize(Ty) && 351198092Srdivacky "Type size mismatch!"); 352198092Srdivacky 353198092Srdivacky // Add all the field numbers. 354198092Srdivacky for (unsigned i = 0, e = Builder.LLVMFields.size(); i != e; ++i) { 355198092Srdivacky const FieldDecl *FD = Builder.LLVMFields[i].first; 356198092Srdivacky unsigned FieldNo = Builder.LLVMFields[i].second; 357198092Srdivacky 358198092Srdivacky Types.addFieldInfo(FD, FieldNo); 359198092Srdivacky } 360198092Srdivacky 361198092Srdivacky // Add bitfield info. 362198092Srdivacky for (unsigned i = 0, e = Builder.LLVMBitFields.size(); i != e; ++i) { 363198092Srdivacky const LLVMBitFieldInfo &Info = Builder.LLVMBitFields[i]; 364198092Srdivacky 365198092Srdivacky Types.addBitFieldInfo(Info.FD, Info.FieldNo, Info.Start, Info.Size); 366198092Srdivacky } 367198092Srdivacky 368199990Srdivacky return new CGRecordLayout(Ty, Builder.ContainsMemberPointer); 369198092Srdivacky} 370