llvm-project/clang/lib/CodeGen/CGRecordLayoutBuilder.cpp

387 lines
11 KiB
C++

//===--- CGRecordLayoutBuilder.cpp - Record builder helper ------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This is a helper class used to build CGRecordLayout objects and LLVM types.
//
//===----------------------------------------------------------------------===//
#include "CGRecordLayoutBuilder.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Attr.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/Expr.h"
#include "clang/AST/RecordLayout.h"
#include "CodeGenTypes.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Target/TargetData.h"
using namespace clang;
using namespace CodeGen;
void CGRecordLayoutBuilder::Layout(const RecordDecl *D) {
Alignment = Types.getContext().getASTRecordLayout(D).getAlignment() / 8;
Packed = D->hasAttr<PackedAttr>();
if (D->isUnion()) {
LayoutUnion(D);
return;
}
if (LayoutFields(D))
return;
// We weren't able to layout the struct. Try again with a packed struct
Packed = true;
AlignmentAsLLVMStruct = 1;
NextFieldOffsetInBytes = 0;
FieldTypes.clear();
LLVMFields.clear();
LLVMBitFields.clear();
LayoutFields(D);
}
void CGRecordLayoutBuilder::LayoutBitField(const FieldDecl *D,
uint64_t FieldOffset) {
uint64_t FieldSize =
D->getBitWidth()->EvaluateAsInt(Types.getContext()).getZExtValue();
if (FieldSize == 0)
return;
uint64_t NextFieldOffset = NextFieldOffsetInBytes * 8;
unsigned NumBytesToAppend;
if (FieldOffset < NextFieldOffset) {
assert(BitsAvailableInLastField && "Bitfield size mismatch!");
assert(NextFieldOffsetInBytes && "Must have laid out at least one byte!");
// The bitfield begins in the previous bit-field.
NumBytesToAppend =
llvm::RoundUpToAlignment(FieldSize - BitsAvailableInLastField, 8) / 8;
} else {
assert(FieldOffset % 8 == 0 && "Field offset not aligned correctly");
// Append padding if necessary.
AppendBytes((FieldOffset - NextFieldOffset) / 8);
NumBytesToAppend =
llvm::RoundUpToAlignment(FieldSize, 8) / 8;
assert(NumBytesToAppend && "No bytes to append!");
}
const llvm::Type *Ty = Types.ConvertTypeForMemRecursive(D->getType());
uint64_t TypeSizeInBits = getTypeSizeInBytes(Ty) * 8;
LLVMBitFields.push_back(LLVMBitFieldInfo(D, FieldOffset / TypeSizeInBits,
FieldOffset % TypeSizeInBits,
FieldSize));
AppendBytes(NumBytesToAppend);
AlignmentAsLLVMStruct = std::max(AlignmentAsLLVMStruct, getTypeAlignment(Ty));
BitsAvailableInLastField =
NextFieldOffsetInBytes * 8 - (FieldOffset + FieldSize);
}
bool CGRecordLayoutBuilder::LayoutField(const FieldDecl *D,
uint64_t FieldOffset) {
// If the field is packed, then we need a packed struct.
if (!Packed && D->hasAttr<PackedAttr>())
return false;
if (D->isBitField()) {
// We must use packed structs for unnamed bit fields since they
// don't affect the struct alignment.
if (!Packed && !D->getDeclName())
return false;
LayoutBitField(D, FieldOffset);
return true;
}
assert(FieldOffset % 8 == 0 && "FieldOffset is not on a byte boundary!");
uint64_t FieldOffsetInBytes = FieldOffset / 8;
const llvm::Type *Ty = Types.ConvertTypeForMemRecursive(D->getType());
unsigned TypeAlignment = getTypeAlignment(Ty);
// If the type alignment is larger then the struct alignment, we must use
// a packed struct.
if (TypeAlignment > Alignment) {
assert(!Packed && "Alignment is wrong even with packed struct!");
return false;
}
if (const RecordType *RT = D->getType()->getAs<RecordType>()) {
const RecordDecl *RD = cast<RecordDecl>(RT->getDecl());
if (const PragmaPackAttr *PPA = RD->getAttr<PragmaPackAttr>()) {
if (PPA->getAlignment() != TypeAlignment * 8 && !Packed)
return false;
}
}
// Round up the field offset to the alignment of the field type.
uint64_t AlignedNextFieldOffsetInBytes =
llvm::RoundUpToAlignment(NextFieldOffsetInBytes, TypeAlignment);
if (FieldOffsetInBytes < AlignedNextFieldOffsetInBytes) {
assert(!Packed && "Could not place field even with packed struct!");
return false;
}
if (AlignedNextFieldOffsetInBytes < FieldOffsetInBytes) {
// Even with alignment, the field offset is not at the right place,
// insert padding.
uint64_t PaddingInBytes = FieldOffsetInBytes - NextFieldOffsetInBytes;
AppendBytes(PaddingInBytes);
}
// Now append the field.
LLVMFields.push_back(LLVMFieldInfo(D, FieldTypes.size()));
AppendField(FieldOffsetInBytes, Ty);
return true;
}
void CGRecordLayoutBuilder::LayoutUnion(const RecordDecl *D) {
assert(D->isUnion() && "Can't call LayoutUnion on a non-union record!");
const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D);
const llvm::Type *Ty = 0;
uint64_t Size = 0;
unsigned Align = 0;
unsigned FieldNo = 0;
for (RecordDecl::field_iterator Field = D->field_begin(),
FieldEnd = D->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
assert(Layout.getFieldOffset(FieldNo) == 0 &&
"Union field offset did not start at the beginning of record!");
if (Field->isBitField()) {
uint64_t FieldSize =
Field->getBitWidth()->EvaluateAsInt(Types.getContext()).getZExtValue();
// Ignore zero sized bit fields.
if (FieldSize == 0)
continue;
// Add the bit field info.
Types.addBitFieldInfo(*Field, 0, 0, FieldSize);
} else
Types.addFieldInfo(*Field, 0);
const llvm::Type *FieldTy =
Types.ConvertTypeForMemRecursive(Field->getType());
unsigned FieldAlign = Types.getTargetData().getABITypeAlignment(FieldTy);
uint64_t FieldSize = Types.getTargetData().getTypeAllocSize(FieldTy);
if (FieldAlign < Align)
continue;
if (FieldAlign > Align || FieldSize > Size) {
Ty = FieldTy;
Align = FieldAlign;
Size = FieldSize;
}
}
// Now add our field.
if (Ty) {
AppendField(0, Ty);
if (getTypeAlignment(Ty) > Layout.getAlignment() / 8) {
// We need a packed struct.
Packed = true;
Align = 1;
}
}
// Append tail padding.
if (Layout.getSize() / 8 > Size)
AppendPadding(Layout.getSize() / 8, Align);
}
bool CGRecordLayoutBuilder::LayoutFields(const RecordDecl *D) {
assert(!D->isUnion() && "Can't call LayoutFields on a union!");
assert(Alignment && "Did not set alignment!");
const ASTRecordLayout &Layout = Types.getContext().getASTRecordLayout(D);
unsigned FieldNo = 0;
for (RecordDecl::field_iterator Field = D->field_begin(),
FieldEnd = D->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
if (!LayoutField(*Field, Layout.getFieldOffset(FieldNo))) {
assert(!Packed &&
"Could not layout fields even with a packed LLVM struct!");
return false;
}
}
// Append tail padding if necessary.
AppendTailPadding(Layout.getSize());
return true;
}
void CGRecordLayoutBuilder::AppendTailPadding(uint64_t RecordSize) {
assert(RecordSize % 8 == 0 && "Invalid record size!");
uint64_t RecordSizeInBytes = RecordSize / 8;
assert(NextFieldOffsetInBytes <= RecordSizeInBytes && "Size mismatch!");
unsigned NumPadBytes = RecordSizeInBytes - NextFieldOffsetInBytes;
AppendBytes(NumPadBytes);
}
void CGRecordLayoutBuilder::AppendField(uint64_t FieldOffsetInBytes,
const llvm::Type *FieldTy) {
AlignmentAsLLVMStruct = std::max(AlignmentAsLLVMStruct,
getTypeAlignment(FieldTy));
uint64_t FieldSizeInBytes = getTypeSizeInBytes(FieldTy);
FieldTypes.push_back(FieldTy);
NextFieldOffsetInBytes = FieldOffsetInBytes + FieldSizeInBytes;
BitsAvailableInLastField = 0;
}
void
CGRecordLayoutBuilder::AppendPadding(uint64_t FieldOffsetInBytes,
const llvm::Type *FieldTy) {
AppendPadding(FieldOffsetInBytes, getTypeAlignment(FieldTy));
}
void CGRecordLayoutBuilder::AppendPadding(uint64_t FieldOffsetInBytes,
unsigned FieldAlignment) {
assert(NextFieldOffsetInBytes <= FieldOffsetInBytes &&
"Incorrect field layout!");
// Round up the field offset to the alignment of the field type.
uint64_t AlignedNextFieldOffsetInBytes =
llvm::RoundUpToAlignment(NextFieldOffsetInBytes, FieldAlignment);
if (AlignedNextFieldOffsetInBytes < FieldOffsetInBytes) {
// Even with alignment, the field offset is not at the right place,
// insert padding.
uint64_t PaddingInBytes = FieldOffsetInBytes - NextFieldOffsetInBytes;
AppendBytes(PaddingInBytes);
}
}
void CGRecordLayoutBuilder::AppendBytes(uint64_t NumBytes) {
if (NumBytes == 0)
return;
const llvm::Type *Ty = llvm::Type::getInt8Ty(Types.getLLVMContext());
if (NumBytes > 1)
Ty = llvm::ArrayType::get(Ty, NumBytes);
// Append the padding field
AppendField(NextFieldOffsetInBytes, Ty);
}
unsigned CGRecordLayoutBuilder::getTypeAlignment(const llvm::Type *Ty) const {
if (Packed)
return 1;
return Types.getTargetData().getABITypeAlignment(Ty);
}
uint64_t CGRecordLayoutBuilder::getTypeSizeInBytes(const llvm::Type *Ty) const {
return Types.getTargetData().getTypeAllocSize(Ty);
}
void CGRecordLayoutBuilder::CheckForMemberPointer(const FieldDecl *FD) {
// This record already contains a member pointer.
if (ContainsMemberPointer)
return;
// Can only have member pointers if we're compiling C++.
if (!Types.getContext().getLangOptions().CPlusPlus)
return;
QualType Ty = FD->getType();
if (Ty->isMemberPointerType()) {
// We have a member pointer!
ContainsMemberPointer = true;
return;
}
}
static const CXXMethodDecl *GetKeyFunction(const RecordDecl *D) {
const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D);
if (!RD || !RD->isDynamicClass())
return 0;
for (CXXRecordDecl::method_iterator I = RD->method_begin(),
E = RD->method_end(); I != E; ++I) {
const CXXMethodDecl *MD = *I;
if (!MD->isVirtual())
continue;
if (MD->isPure())
continue;
if (MD->getBody())
continue;
// We found it.
return MD;
}
return 0;
}
CGRecordLayout *
CGRecordLayoutBuilder::ComputeLayout(CodeGenTypes &Types,
const RecordDecl *D) {
CGRecordLayoutBuilder Builder(Types);
Builder.Layout(D);
const llvm::Type *Ty = llvm::StructType::get(Types.getLLVMContext(),
Builder.FieldTypes,
Builder.Packed);
assert(Types.getContext().getASTRecordLayout(D).getSize() / 8 ==
Types.getTargetData().getTypeAllocSize(Ty) &&
"Type size mismatch!");
// Add all the field numbers.
for (unsigned i = 0, e = Builder.LLVMFields.size(); i != e; ++i) {
const FieldDecl *FD = Builder.LLVMFields[i].first;
unsigned FieldNo = Builder.LLVMFields[i].second;
Types.addFieldInfo(FD, FieldNo);
}
// Add bitfield info.
for (unsigned i = 0, e = Builder.LLVMBitFields.size(); i != e; ++i) {
const LLVMBitFieldInfo &Info = Builder.LLVMBitFields[i];
Types.addBitFieldInfo(Info.FD, Info.FieldNo, Info.Start, Info.Size);
}
const CXXMethodDecl *KeyFunction = GetKeyFunction(D);
return new CGRecordLayout(Ty, Builder.ContainsMemberPointer, KeyFunction);
}