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290 lines
10 KiB
290 lines
10 KiB
4 months ago
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//=-- llvm/CodeGen/DwarfAccelTable.cpp - Dwarf Accelerator Tables -*- 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 file contains support for writing dwarf accelerator tables.
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//
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//===----------------------------------------------------------------------===//
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#include "DwarfAccelTable.h"
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#include "DwarfCompileUnit.h"
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#include "DwarfDebug.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/Twine.h"
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#include "llvm/CodeGen/AsmPrinter.h"
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#include "llvm/CodeGen/DIE.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCStreamer.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/Support/Debug.h"
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using namespace llvm;
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// The length of the header data is always going to be 4 + 4 + 4*NumAtoms.
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DwarfAccelTable::DwarfAccelTable(ArrayRef<DwarfAccelTable::Atom> atomList)
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: Header(8 + (atomList.size() * 4)), HeaderData(atomList),
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Entries(Allocator) {}
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void DwarfAccelTable::AddName(DwarfStringPoolEntryRef Name, const DIE *die,
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char Flags) {
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assert(Data.empty() && "Already finalized!");
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// If the string is in the list already then add this die to the list
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// otherwise add a new one.
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DataArray &DIEs = Entries[Name.getString()];
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assert(!DIEs.Name || DIEs.Name == Name);
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DIEs.Name = Name;
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DIEs.Values.push_back(new (Allocator) HashDataContents(die, Flags));
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}
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void DwarfAccelTable::ComputeBucketCount() {
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// First get the number of unique hashes.
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std::vector<uint32_t> uniques(Data.size());
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for (size_t i = 0, e = Data.size(); i < e; ++i)
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uniques[i] = Data[i]->HashValue;
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array_pod_sort(uniques.begin(), uniques.end());
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std::vector<uint32_t>::iterator p =
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std::unique(uniques.begin(), uniques.end());
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uint32_t num = std::distance(uniques.begin(), p);
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// Then compute the bucket size, minimum of 1 bucket.
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if (num > 1024)
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Header.bucket_count = num / 4;
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else if (num > 16)
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Header.bucket_count = num / 2;
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else
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Header.bucket_count = num > 0 ? num : 1;
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Header.hashes_count = num;
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}
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// compareDIEs - comparison predicate that sorts DIEs by their offset.
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static bool compareDIEs(const DwarfAccelTable::HashDataContents *A,
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const DwarfAccelTable::HashDataContents *B) {
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return A->Die->getOffset() < B->Die->getOffset();
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}
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void DwarfAccelTable::FinalizeTable(AsmPrinter *Asm, StringRef Prefix) {
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// Create the individual hash data outputs.
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Data.reserve(Entries.size());
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for (StringMap<DataArray>::iterator EI = Entries.begin(), EE = Entries.end();
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EI != EE; ++EI) {
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// Unique the entries.
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std::stable_sort(EI->second.Values.begin(), EI->second.Values.end(), compareDIEs);
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EI->second.Values.erase(
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std::unique(EI->second.Values.begin(), EI->second.Values.end()),
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EI->second.Values.end());
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HashData *Entry = new (Allocator) HashData(EI->getKey(), EI->second);
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Data.push_back(Entry);
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}
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// Figure out how many buckets we need, then compute the bucket
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// contents and the final ordering. We'll emit the hashes and offsets
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// by doing a walk during the emission phase. We add temporary
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// symbols to the data so that we can reference them during the offset
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// later, we'll emit them when we emit the data.
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ComputeBucketCount();
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// Compute bucket contents and final ordering.
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Buckets.resize(Header.bucket_count);
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for (size_t i = 0, e = Data.size(); i < e; ++i) {
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uint32_t bucket = Data[i]->HashValue % Header.bucket_count;
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Buckets[bucket].push_back(Data[i]);
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Data[i]->Sym = Asm->createTempSymbol(Prefix);
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}
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// Sort the contents of the buckets by hash value so that hash
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// collisions end up together. Stable sort makes testing easier and
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// doesn't cost much more.
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for (size_t i = 0; i < Buckets.size(); ++i)
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std::stable_sort(Buckets[i].begin(), Buckets[i].end(),
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[] (HashData *LHS, HashData *RHS) {
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return LHS->HashValue < RHS->HashValue;
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});
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}
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// Emits the header for the table via the AsmPrinter.
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void DwarfAccelTable::EmitHeader(AsmPrinter *Asm) {
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Asm->OutStreamer->AddComment("Header Magic");
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Asm->EmitInt32(Header.magic);
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Asm->OutStreamer->AddComment("Header Version");
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Asm->EmitInt16(Header.version);
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Asm->OutStreamer->AddComment("Header Hash Function");
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Asm->EmitInt16(Header.hash_function);
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Asm->OutStreamer->AddComment("Header Bucket Count");
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Asm->EmitInt32(Header.bucket_count);
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Asm->OutStreamer->AddComment("Header Hash Count");
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Asm->EmitInt32(Header.hashes_count);
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Asm->OutStreamer->AddComment("Header Data Length");
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Asm->EmitInt32(Header.header_data_len);
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Asm->OutStreamer->AddComment("HeaderData Die Offset Base");
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Asm->EmitInt32(HeaderData.die_offset_base);
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Asm->OutStreamer->AddComment("HeaderData Atom Count");
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Asm->EmitInt32(HeaderData.Atoms.size());
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for (size_t i = 0; i < HeaderData.Atoms.size(); i++) {
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Atom A = HeaderData.Atoms[i];
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Asm->OutStreamer->AddComment(dwarf::AtomTypeString(A.type));
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Asm->EmitInt16(A.type);
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Asm->OutStreamer->AddComment(dwarf::FormEncodingString(A.form));
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Asm->EmitInt16(A.form);
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}
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}
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// Walk through and emit the buckets for the table. Each index is
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// an offset into the list of hashes.
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void DwarfAccelTable::EmitBuckets(AsmPrinter *Asm) {
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unsigned index = 0;
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for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
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Asm->OutStreamer->AddComment("Bucket " + Twine(i));
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if (Buckets[i].size() != 0)
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Asm->EmitInt32(index);
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else
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Asm->EmitInt32(UINT32_MAX);
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// Buckets point in the list of hashes, not to the data. Do not
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// increment the index multiple times in case of hash collisions.
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uint64_t PrevHash = UINT64_MAX;
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for (auto *HD : Buckets[i]) {
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uint32_t HashValue = HD->HashValue;
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if (PrevHash != HashValue)
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++index;
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PrevHash = HashValue;
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}
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}
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}
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// Walk through the buckets and emit the individual hashes for each
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// bucket.
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void DwarfAccelTable::EmitHashes(AsmPrinter *Asm) {
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uint64_t PrevHash = UINT64_MAX;
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for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
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for (HashList::const_iterator HI = Buckets[i].begin(),
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HE = Buckets[i].end();
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HI != HE; ++HI) {
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uint32_t HashValue = (*HI)->HashValue;
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if (PrevHash == HashValue)
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continue;
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Asm->OutStreamer->AddComment("Hash in Bucket " + Twine(i));
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Asm->EmitInt32(HashValue);
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PrevHash = HashValue;
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}
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}
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}
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// Walk through the buckets and emit the individual offsets for each
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// element in each bucket. This is done via a symbol subtraction from the
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// beginning of the section. The non-section symbol will be output later
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// when we emit the actual data.
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void DwarfAccelTable::emitOffsets(AsmPrinter *Asm, const MCSymbol *SecBegin) {
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uint64_t PrevHash = UINT64_MAX;
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for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
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for (HashList::const_iterator HI = Buckets[i].begin(),
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HE = Buckets[i].end();
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HI != HE; ++HI) {
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uint32_t HashValue = (*HI)->HashValue;
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if (PrevHash == HashValue)
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continue;
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PrevHash = HashValue;
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Asm->OutStreamer->AddComment("Offset in Bucket " + Twine(i));
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MCContext &Context = Asm->OutStreamer->getContext();
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const MCExpr *Sub = MCBinaryExpr::createSub(
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MCSymbolRefExpr::create((*HI)->Sym, Context),
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MCSymbolRefExpr::create(SecBegin, Context), Context);
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Asm->OutStreamer->EmitValue(Sub, sizeof(uint32_t));
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}
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}
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}
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// Walk through the buckets and emit the full data for each element in
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// the bucket. For the string case emit the dies and the various offsets.
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// Terminate each HashData bucket with 0.
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void DwarfAccelTable::EmitData(AsmPrinter *Asm, DwarfDebug *D) {
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for (size_t i = 0, e = Buckets.size(); i < e; ++i) {
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uint64_t PrevHash = UINT64_MAX;
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for (HashList::const_iterator HI = Buckets[i].begin(),
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HE = Buckets[i].end();
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HI != HE; ++HI) {
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// Terminate the previous entry if there is no hash collision
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// with the current one.
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if (PrevHash != UINT64_MAX && PrevHash != (*HI)->HashValue)
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Asm->EmitInt32(0);
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// Remember to emit the label for our offset.
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Asm->OutStreamer->EmitLabel((*HI)->Sym);
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Asm->OutStreamer->AddComment((*HI)->Str);
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Asm->emitDwarfStringOffset((*HI)->Data.Name);
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Asm->OutStreamer->AddComment("Num DIEs");
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Asm->EmitInt32((*HI)->Data.Values.size());
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for (HashDataContents *HD : (*HI)->Data.Values) {
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// Emit the DIE offset
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DwarfCompileUnit *CU = D->lookupUnit(HD->Die->getUnit());
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assert(CU && "Accelerated DIE should belong to a CU.");
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Asm->EmitInt32(HD->Die->getOffset() + CU->getDebugInfoOffset());
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// If we have multiple Atoms emit that info too.
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// FIXME: A bit of a hack, we either emit only one atom or all info.
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if (HeaderData.Atoms.size() > 1) {
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Asm->EmitInt16(HD->Die->getTag());
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Asm->EmitInt8(HD->Flags);
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}
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}
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PrevHash = (*HI)->HashValue;
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}
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// Emit the final end marker for the bucket.
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if (!Buckets[i].empty())
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Asm->EmitInt32(0);
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}
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}
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// Emit the entire data structure to the output file.
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void DwarfAccelTable::emit(AsmPrinter *Asm, const MCSymbol *SecBegin,
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DwarfDebug *D) {
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// Emit the header.
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EmitHeader(Asm);
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// Emit the buckets.
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EmitBuckets(Asm);
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// Emit the hashes.
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EmitHashes(Asm);
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// Emit the offsets.
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emitOffsets(Asm, SecBegin);
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// Emit the hash data.
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EmitData(Asm, D);
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}
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#ifndef NDEBUG
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void DwarfAccelTable::print(raw_ostream &O) {
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Header.print(O);
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HeaderData.print(O);
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O << "Entries: \n";
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for (StringMap<DataArray>::const_iterator EI = Entries.begin(),
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EE = Entries.end();
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EI != EE; ++EI) {
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O << "Name: " << EI->getKeyData() << "\n";
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for (HashDataContents *HD : EI->second.Values)
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HD->print(O);
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}
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O << "Buckets and Hashes: \n";
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for (size_t i = 0, e = Buckets.size(); i < e; ++i)
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for (HashList::const_iterator HI = Buckets[i].begin(),
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HE = Buckets[i].end();
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HI != HE; ++HI)
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(*HI)->print(O);
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O << "Data: \n";
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for (std::vector<HashData *>::const_iterator DI = Data.begin(),
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DE = Data.end();
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DI != DE; ++DI)
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(*DI)->print(O);
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}
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#endif
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