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