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Add a new ASTRecordLayoutBuilder class. Not used yet. 

llvm-svn: 76330
This commit is contained in:
Anders Carlsson 2009-07-18 20:20:21 +00:00
parent d476720341
commit 7947433411
4 changed files with 231 additions and 4 deletions
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10
clang/clang.xcodeproj/project.pbxproj
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);
runOnlyForDeploymentPostprocessing = 0;
};

12
clang/include/clang/AST/RecordLayout.h
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@ -18,6 +18,7 @@
namespace clang {
class ASTContext;
class FieldDecl;
class RecordDecl;
/// ASTRecordLayout -
@ -34,6 +35,7 @@ class ASTRecordLayout {
unsigned Alignment; // Alignment of record in bits.
unsigned FieldCount; // Number of fields
friend class ASTContext;
friend class ASTRecordLayoutBuilder;
ASTRecordLayout(uint64_t S = 0, unsigned A = 8)
: Size(S), NextOffset(S), Alignment(A), FieldCount(0) {}
@ -41,6 +43,16 @@ class ASTRecordLayout {
delete [] FieldOffsets;
}
ASTRecordLayout(uint64_t Size, unsigned Alignment,
const uint64_t *fieldoffsets, unsigned fieldcount)
: Size(Size), FieldOffsets(0), Alignment(Alignment), FieldCount(fieldcount) {
if (FieldCount > 0) {
FieldOffsets = new uint64_t[FieldCount];
for (unsigned i = 0; i < FieldCount; ++i)
FieldOffsets[i] = fieldoffsets[i];
}
}
/// Initialize record layout. N is the number of fields in this record.
void InitializeLayout(unsigned N) {
FieldCount = N;

162
clang/lib/AST/RecordLayoutBuilder.cpp Normal file
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@ -0,0 +1,162 @@
//=== ASTRecordLayoutBuilder.cpp - Helper class for building record layouts ==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "RecordLayoutBuilder.h"
#include "clang/AST/Attr.h"
#include "clang/AST/Decl.h"
#include "clang/AST/Expr.h"
#include "clang/AST/RecordLayout.h"
#include "clang/Basic/TargetInfo.h"
#include <llvm/Support/MathExtras.h>
using namespace clang;
ASTRecordLayoutBuilder::ASTRecordLayoutBuilder(ASTContext &Ctx)
: Ctx(Ctx), Size(0), Alignment(8), StructPacking(0), NextOffset(0),
IsUnion(false) {}
void ASTRecordLayoutBuilder::Layout(const RecordDecl *D) {
IsUnion = D->isUnion();
if (const PackedAttr* PA = D->getAttr<PackedAttr>())
StructPacking = PA->getAlignment();
if (const AlignedAttr *AA = D->getAttr<AlignedAttr>())
UpdateAlignment(AA->getAlignment());
// Layout each field, for now, just sequentially, respecting alignment. In
// the future, this will need to be tweakable by targets.
for (RecordDecl::field_iterator Field = D->field_begin(),
FieldEnd = D->field_end(); Field != FieldEnd; ++Field)
LayoutField(*Field);
// Finally, round the size of the total struct up to the alignment of the
// struct itself.
FinishLayout();
}
void ASTRecordLayoutBuilder::LayoutField(const FieldDecl *D) {
unsigned FieldPacking = StructPacking;
uint64_t FieldOffset = IsUnion ? 0 : Size;
uint64_t FieldSize;
unsigned FieldAlign;
// FIXME: Should this override struct packing? Probably we want to
// take the minimum?
if (const PackedAttr *PA = D->getAttr<PackedAttr>())
FieldPacking = PA->getAlignment();
if (const Expr *BitWidthExpr = D->getBitWidth()) {
// TODO: Need to check this algorithm on other targets!
// (tested on Linux-X86)
FieldSize = BitWidthExpr->EvaluateAsInt(Ctx).getZExtValue();
std::pair<uint64_t, unsigned> FieldInfo = Ctx.getTypeInfo(D->getType());
uint64_t TypeSize = FieldInfo.first;
// Determine the alignment of this bitfield. The packing
// attributes define a maximum and the alignment attribute defines
// a minimum.
// FIXME: What is the right behavior when the specified alignment
// is smaller than the specified packing?
FieldAlign = FieldInfo.second;
if (FieldPacking)
FieldAlign = std::min(FieldAlign, FieldPacking);
if (const AlignedAttr *AA = D->getAttr<AlignedAttr>())
FieldAlign = std::max(FieldAlign, AA->getAlignment());
// Check if we need to add padding to give the field the correct
// alignment.
if (FieldSize == 0 || (FieldOffset & (FieldAlign-1)) + FieldSize > TypeSize)
FieldOffset = (FieldOffset + (FieldAlign-1)) & ~(FieldAlign-1);
// Padding members don't affect overall alignment
if (!D->getIdentifier())
FieldAlign = 1;
} else {
if (D->getType()->isIncompleteArrayType()) {
// This is a flexible array member; we can't directly
// query getTypeInfo about these, so we figure it out here.
// Flexible array members don't have any size, but they
// have to be aligned appropriately for their element type.
FieldSize = 0;
const ArrayType* ATy = Ctx.getAsArrayType(D->getType());
FieldAlign = Ctx.getTypeAlign(ATy->getElementType());
} else if (const ReferenceType *RT = D->getType()->getAsReferenceType()) {
unsigned AS = RT->getPointeeType().getAddressSpace();
FieldSize = Ctx.Target.getPointerWidth(AS);
FieldAlign = Ctx.Target.getPointerAlign(AS);
} else {
std::pair<uint64_t, unsigned> FieldInfo = Ctx.getTypeInfo(D->getType());
FieldSize = FieldInfo.first;
FieldAlign = FieldInfo.second;
}
// Determine the alignment of this bitfield. The packing
// attributes define a maximum and the alignment attribute defines
// a minimum. Additionally, the packing alignment must be at least
// a byte for non-bitfields.
//
// FIXME: What is the right behavior when the specified alignment
// is smaller than the specified packing?
if (FieldPacking)
FieldAlign = std::min(FieldAlign, std::max(8U, FieldPacking));
if (const AlignedAttr *AA = D->getAttr<AlignedAttr>())
FieldAlign = std::max(FieldAlign, AA->getAlignment());
// Round up the current record size to the field's alignment boundary.
FieldOffset = (FieldOffset + (FieldAlign-1)) & ~(FieldAlign-1);
}
// Place this field at the current location.
FieldOffsets.push_back(FieldOffset);
// Reserve space for this field.
if (IsUnion)
Size = std::max(Size, FieldSize);
else
Size = FieldOffset + FieldSize;
// Remember the next available offset.
NextOffset = Size;
// Remember max struct/class alignment.
UpdateAlignment(FieldAlign);
}
void ASTRecordLayoutBuilder::FinishLayout() {
// In C++, records cannot be of size 0.
if (Ctx.getLangOptions().CPlusPlus && Size == 0)
Size = 8;
// Finally, round the size of the record up to the alignment of the
// record itself.
Size = (Size + (Alignment-1)) & ~(Alignment-1);
}
void ASTRecordLayoutBuilder::UpdateAlignment(unsigned NewAlignment) {
if (NewAlignment <= Alignment)
return;
assert(llvm::isPowerOf2_32(NewAlignment && "Alignment not a power of 2"));
Alignment = NewAlignment;
}
const ASTRecordLayout *
ASTRecordLayoutBuilder::ComputeLayout(ASTContext &Ctx,
const RecordDecl *D) {
ASTRecordLayoutBuilder Builder(Ctx);
Builder.Layout(D);
return new ASTRecordLayout(Builder.Size, Builder.Alignment,
Builder.FieldOffsets.data(),
Builder.FieldOffsets.size());
}

51
clang/lib/AST/RecordLayoutBuilder.h Normal file
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@ -0,0 +1,51 @@
//===- ASTRecordLayoutBuilder.h - Helper class for building record layouts ===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_AST_RECORDLAYOUTBUILDER_H
#define LLVM_CLANG_AST_RECORDLAYOUTBUILDER_H
#include "llvm/ADT/SmallVector.h"
namespace clang {
class ASTContext;
class ASTRecordLayout;
class FieldDecl;
class RecordDecl;
class ASTRecordLayoutBuilder {
ASTContext &Ctx;
uint64_t Size;
uint64_t Alignment;
llvm::SmallVector<uint64_t, 16> FieldOffsets;
unsigned StructPacking;
unsigned NextOffset;
bool IsUnion;
ASTRecordLayoutBuilder(ASTContext &Ctx);
void Layout(const RecordDecl *D);
void LayoutField(const FieldDecl *D);
void FinishLayout();
void UpdateAlignment(unsigned NewAlignment);
ASTRecordLayoutBuilder(const ASTRecordLayoutBuilder&); // DO NOT IMPLEMENT
void operator=(const ASTRecordLayoutBuilder&); // DO NOT IMPLEMENT
public:
static const ASTRecordLayout *ComputeLayout(ASTContext &Ctx,
const RecordDecl *RD);
};
} // end namespace clang
#endif