[LLD] Remove global state in lld/COFF

This patch removes globals from the lldCOFF library, by moving globals
into a context class (COFFLinkingContext) and passing it around wherever
it's needed.

See https://lists.llvm.org/pipermail/llvm-dev/2021-June/151184.html for
context about removing globals from LLD.

I also haven't moved the `driver` or `config` variables yet.

Differential Revision: https://reviews.llvm.org/D109634

lld/COFF/CMakeLists.txt

@@ -5,6 +5,7 @@ add_public_tablegen_target(COFFOptionsTableGen)
 add_lld_library(lldCOFF
   CallGraphSort.cpp
   Chunks.cpp
+  COFFLinkerContext.cpp
   DebugTypes.cpp
   DLL.cpp
   Driver.cpp

lld/COFF/COFFLinkerContext.cpp

@@ -0,0 +1,53 @@
+//===- COFFContext.cpp ----------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Description
+//
+//===----------------------------------------------------------------------===//
+
+#include "COFFLinkerContext.h"
+#include "lld/Common/Memory.h"
+#include "llvm/DebugInfo/CodeView/TypeHashing.h"
+
+namespace lld {
+namespace coff {
+
+COFFLinkerContext::COFFLinkerContext()
+    : symtab(*this), rootTimer("Total Linking Time"),
+      inputFileTimer("Input File Reading", rootTimer),
+      ltoTimer("LTO", rootTimer), gcTimer("GC", rootTimer),
+      icfTimer("ICF", rootTimer), codeLayoutTimer("Code Layout", rootTimer),
+      outputCommitTimer("Commit Output File", rootTimer),
+      totalMapTimer("MAP Emission (Cumulative)", rootTimer),
+      symbolGatherTimer("Gather Symbols", totalMapTimer),
+      symbolStringsTimer("Build Symbol strings", totalMapTimer),
+      writeTimer("Write to File", totalMapTimer),
+      totalPdbLinkTimer("PDB Emission (Cumulative)", rootTimer),
+      addObjectsTimer("Add Objects", totalPdbLinkTimer),
+      symbolMergingTimer("Symbol Merging", addObjectsTimer),
+      typeMergingTimer("Type Merging", addObjectsTimer),
+      tpiStreamLayoutTimer("TPI Stream Layout", totalPdbLinkTimer),
+      publicsLayoutTimer("Publics Stream Layout", totalPdbLinkTimer),
+      diskCommitTimer("Commit to Disk", totalPdbLinkTimer),
+      loadGHashTimer("Global Type Hashing", addObjectsTimer),
+      mergeGHashTimer("GHash Type Merging", addObjectsTimer) {}
+
+COFFLinkerContext::~COFFLinkerContext() { clearGHashes(); }
+
+void COFFLinkerContext::clearGHashes() {
+  for (TpiSource *src : tpiSourceList) {
+    if (src->ownedGHashes)
+      delete[] src->ghashes.data();
+    src->ghashes = {};
+    src->isItemIndex.clear();
+    src->uniqueTypes.clear();
+  }
+}
+
+} // namespace coff
+} // namespace lld

lld/COFF/COFFLinkerContext.h

@@ -0,0 +1,88 @@
+//===- COFFLinkerContext.h --------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLD_COFF_COFFLinkerContext_H
+#define LLD_COFF_COFFLinkerContext_H
+
+#include "Chunks.h"
+#include "Config.h"
+#include "DebugTypes.h"
+#include "InputFiles.h"
+#include "SymbolTable.h"
+#include "Writer.h"
+#include "lld/Common/Timer.h"
+
+namespace lld {
+namespace coff {
+
+class COFFLinkerContext {
+public:
+  COFFLinkerContext();
+  COFFLinkerContext(const COFFLinkerContext &) = delete;
+  COFFLinkerContext &operator=(const COFFLinkerContext &) = delete;
+  ~COFFLinkerContext();
+
+  void addTpiSource(TpiSource *tpi) { tpiSourceList.push_back(tpi); }
+
+  /// Free heap allocated ghashes.
+  void clearGHashes();
+
+  SymbolTable symtab;
+
+  std::vector<ObjFile *> objFileInstances;
+  std::map<std::string, PDBInputFile *> pdbInputFileInstances;
+  std::vector<ImportFile *> importFileInstances;
+  std::vector<BitcodeFile *> bitcodeFileInstances;
+
+  MergeChunk *mergeChunkInstances[Log2MaxSectionAlignment + 1] = {};
+
+  /// All sources of type information in the program.
+  std::vector<TpiSource *> tpiSourceList;
+
+  std::map<llvm::codeview::GUID, TpiSource *> typeServerSourceMappings;
+  std::map<uint32_t, TpiSource *> precompSourceMappings;
+
+  /// List of all output sections. After output sections are finalized, this
+  /// can be indexed by getOutputSection.
+  std::vector<OutputSection *> outputSections;
+
+  OutputSection *getOutputSection(const Chunk *c) const {
+    return c->osidx == 0 ? nullptr : outputSections[c->osidx - 1];
+  }
+
+  // All timers used in the COFF linker.
+  Timer rootTimer;
+  Timer inputFileTimer;
+  Timer ltoTimer;
+  Timer gcTimer;
+  Timer icfTimer;
+
+  // Writer timers.
+  Timer codeLayoutTimer;
+  Timer outputCommitTimer;
+  Timer totalMapTimer;
+  Timer symbolGatherTimer;
+  Timer symbolStringsTimer;
+  Timer writeTimer;
+
+  // PDB timers.
+  Timer totalPdbLinkTimer;
+  Timer addObjectsTimer;
+  Timer symbolMergingTimer;
+  Timer typeMergingTimer;
+  Timer tpiStreamLayoutTimer;
+  Timer publicsLayoutTimer;
+  Timer diskCommitTimer;
+  Timer loadGHashTimer;
+  Timer mergeGHashTimer;
+};
+
+} // namespace coff
+} // namespace lld
+
+#endif

lld/COFF/CallGraphSort.cpp

@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "CallGraphSort.h"
+#include "COFFLinkerContext.h"
 #include "InputFiles.h"
 #include "SymbolTable.h"
 #include "Symbols.h"
@@ -48,7 +49,7 @@ struct Cluster {
 
 class CallGraphSort {
 public:
-  CallGraphSort();
+  CallGraphSort(const COFFLinkerContext &ctx);
 
   DenseMap<const SectionChunk *, int> run();
 
@@ -70,7 +71,7 @@ using SectionPair = std::pair<const SectionChunk *, const SectionChunk *>;
 // Take the edge list in Config->CallGraphProfile, resolve symbol names to
 // Symbols, and generate a graph between InputSections with the provided
 // weights.
-CallGraphSort::CallGraphSort() {
+CallGraphSort::CallGraphSort(const COFFLinkerContext &ctx) {
   MapVector<SectionPair, uint64_t> &profile = config->callGraphProfile;
   DenseMap<const SectionChunk *, int> secToCluster;
 
@@ -95,7 +96,7 @@ CallGraphSort::CallGraphSort() {
     // output.  This messes with the cluster size and density calculations.  We
     // would also end up moving input sections in other output sections without
     // moving them closer to what calls them.
-    if (fromSec->getOutputSection() != toSec->getOutputSection())
+    if (ctx.getOutputSection(fromSec) != ctx.getOutputSection(toSec))
       continue;
 
     int from = getOrCreateNode(fromSec);
@@ -240,6 +241,7 @@ DenseMap<const SectionChunk *, int> CallGraphSort::run() {
 // This first builds a call graph based on the profile data then merges sections
 // according to the C³ heuristic. All clusters are then sorted by a density
 // metric to further improve locality.
-DenseMap<const SectionChunk *, int> coff::computeCallGraphProfileOrder() {
-  return CallGraphSort().run();
+DenseMap<const SectionChunk *, int>
+coff::computeCallGraphProfileOrder(const COFFLinkerContext &ctx) {
+  return CallGraphSort(ctx).run();
 }

lld/COFF/CallGraphSort.h

@@ -14,8 +14,10 @@
 namespace lld {
 namespace coff {
 class SectionChunk;
+class COFFLinkerContext;
 
-llvm::DenseMap<const SectionChunk *, int> computeCallGraphProfileOrder();
+llvm::DenseMap<const SectionChunk *, int>
+computeCallGraphProfileOrder(const COFFLinkerContext &ctx);
 } // namespace coff
 } // namespace lld
 

lld/COFF/Chunks.cpp

@@ -7,10 +7,11 @@
 //===----------------------------------------------------------------------===//
 
 #include "Chunks.h"
+#include "COFFLinkerContext.h"
 #include "InputFiles.h"
+#include "SymbolTable.h"
 #include "Symbols.h"
 #include "Writer.h"
-#include "SymbolTable.h"
 #include "lld/Common/ErrorHandler.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/BinaryFormat/COFF.h"
@@ -385,7 +386,7 @@ void SectionChunk::applyRelocation(uint8_t *off,
   // section is needed to compute SECREL and SECTION relocations used in debug
   // info.
   Chunk *c = sym ? sym->getChunk() : nullptr;
-  OutputSection *os = c ? c->getOutputSection() : nullptr;
+  OutputSection *os = c ? file->ctx.getOutputSection(c) : nullptr;
 
   // Skip the relocation if it refers to a discarded section, and diagnose it
   // as an error if appropriate. If a symbol was discarded early, it may be
@@ -938,18 +939,16 @@ uint8_t Baserel::getDefaultType() {
   }
 }
 
-MergeChunk *MergeChunk::instances[Log2MaxSectionAlignment + 1] = {};
-
 MergeChunk::MergeChunk(uint32_t alignment)
     : builder(StringTableBuilder::RAW, alignment) {
   setAlignment(alignment);
 }
 
-void MergeChunk::addSection(SectionChunk *c) {
+void MergeChunk::addSection(COFFLinkerContext &ctx, SectionChunk *c) {
   assert(isPowerOf2_32(c->getAlignment()));
   uint8_t p2Align = llvm::Log2_32(c->getAlignment());
-  assert(p2Align < array_lengthof(instances));
-  auto *&mc = instances[p2Align];
+  assert(p2Align < array_lengthof(ctx.mergeChunkInstances));
+  auto *&mc = ctx.mergeChunkInstances[p2Align];
   if (!mc)
     mc = make<MergeChunk>(c->getAlignment());
   mc->sections.push_back(c);

lld/COFF/Chunks.h

@@ -101,7 +101,6 @@ class Chunk {
   // chunk has a back pointer to an output section.
   void setOutputSectionIdx(uint16_t o) { osidx = o; }
   uint16_t getOutputSectionIdx() const { return osidx; }
-  OutputSection *getOutputSection() const;
 
   // Windows-specific.
   // Collect all locations that contain absolute addresses for base relocations.
@@ -415,7 +414,7 @@ inline StringRef Chunk::getDebugName() const {
 class MergeChunk : public NonSectionChunk {
 public:
   MergeChunk(uint32_t alignment);
-  static void addSection(SectionChunk *c);
+  static void addSection(COFFLinkerContext &ctx, SectionChunk *c);
   void finalizeContents();
   void assignSubsectionRVAs();
 
@@ -424,7 +423,6 @@ class MergeChunk : public NonSectionChunk {
   size_t getSize() const override;
   void writeTo(uint8_t *buf) const override;
 
-  static MergeChunk *instances[Log2MaxSectionAlignment + 1];
   std::vector<SectionChunk *> sections;
 
 private:

lld/COFF/DLL.cpp

@@ -18,6 +18,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "DLL.h"
+#include "COFFLinkerContext.h"
 #include "Chunks.h"
 #include "SymbolTable.h"
 #include "llvm/Object/COFF.h"
@@ -631,7 +632,7 @@ uint64_t DelayLoadContents::getDirSize() {
   return dirs.size() * sizeof(delay_import_directory_table_entry);
 }
 
-void DelayLoadContents::create(Defined *h) {
+void DelayLoadContents::create(COFFLinkerContext &ctx, Defined *h) {
   helper = h;
   std::vector<std::vector<DefinedImportData *>> v = binImports(imports);
 
@@ -660,13 +661,13 @@ void DelayLoadContents::create(Defined *h) {
         // call targets for Control Flow Guard.
         StringRef symName = saver.save("__imp_load_" + extName);
         s->loadThunkSym =
-            cast<DefinedSynthetic>(symtab->addSynthetic(symName, t));
+            cast<DefinedSynthetic>(ctx.symtab.addSynthetic(symName, t));
       }
     }
     thunks.push_back(tm);
     StringRef tmName =
         saver.save("__tailMerge_" + syms[0]->getDLLName().lower());
-    symtab->addSynthetic(tmName, tm);
+    ctx.symtab.addSynthetic(tmName, tm);
     // Terminate with null values.
     addresses.push_back(make<NullChunk>(8));
     names.push_back(make<NullChunk>(8));

lld/COFF/DLL.h

@@ -40,7 +40,7 @@ class DelayLoadContents {
 public:
   void add(DefinedImportData *sym) { imports.push_back(sym); }
   bool empty() { return imports.empty(); }
-  void create(Defined *helper);
+  void create(COFFLinkerContext &ctx, Defined *helper);
   std::vector<Chunk *> getChunks();
   std::vector<Chunk *> getDataChunks();
   ArrayRef<Chunk *> getCodeChunks() { return thunks; }