[WebAssembly] Avoid COMDAT hashmap lookup for each symbol. NFC

This reduces the number of lookups to one per COMDAT group, rather than
one per symbol in a COMDAT group.

Differential Revision: https://reviews.llvm.org/D44344

llvm-svn: 327523

7 files changed, 29 insertions, 15 deletions

diff --git a/lld/wasm/InputChunks.cpp b/lld/wasm/InputChunks.cpp
index ef3edb8b9ca..0cac19b3d4e 100644
--- a/lld/wasm/InputChunks.cpp
+++ b/lld/wasm/InputChunks.cpp
@@ -36,6 +36,13 @@ std::string lld::toString(const InputChunk *C) {
   return (toString(C->File) + ":(" + C->getName() + ")").str();
 }
 
+StringRef InputChunk::getComdatName() const {
+  uint32_t Index = getComdat();
+  if (Index == UINT32_MAX)
+    return StringRef();
+  return File->getWasmObj()->linkingData().Comdats[Index];
+}
+
 void InputChunk::copyRelocations(const WasmSection &Section) {
   if (Section.Relocations.empty())
     return;
diff --git a/lld/wasm/InputChunks.h b/lld/wasm/InputChunks.h
index f4e08ab4c25..3d6ea23680f 100644
--- a/lld/wasm/InputChunks.h
+++ b/lld/wasm/InputChunks.h
@@ -56,8 +56,9 @@ public:
 
   ArrayRef<WasmRelocation> getRelocations() const { return Relocations; }
 
-  virtual StringRef getComdat() const = 0;
   virtual StringRef getName() const = 0;
+  virtual uint32_t getComdat() const = 0;
+  StringRef getComdatName() const;
 
   size_t NumRelocations() const { return Relocations.size(); }
   void writeRelocations(llvm::raw_ostream &OS) const;
@@ -98,7 +99,7 @@ public:
 
   uint32_t getAlignment() const { return Segment.Data.Alignment; }
   StringRef getName() const override { return Segment.Data.Name; }
-  StringRef getComdat() const override { return Segment.Data.Comdat; }
+  uint32_t getComdat() const override { return Segment.Data.Comdat; }
 
   const OutputSegment *OutputSeg = nullptr;
   int32_t OutputSegmentOffset = 0;
@@ -125,7 +126,7 @@ public:
   }
 
   StringRef getName() const override { return Function->Name; }
-  StringRef getComdat() const override { return Function->Comdat; }
+  uint32_t getComdat() const override { return Function->Comdat; }
   uint32_t getFunctionIndex() const { return FunctionIndex.getValue(); }
   bool hasFunctionIndex() const { return FunctionIndex.hasValue(); }
   void setFunctionIndex(uint32_t Index);
@@ -161,7 +162,7 @@ public:
   }
 
   StringRef getName() const override { return Name; }
-  StringRef getComdat() const override { return StringRef(); }
+  uint32_t getComdat() const override { return UINT32_MAX; }
 
   void setBody(ArrayRef<uint8_t> Body_) { Body = Body_; }
 
diff --git a/lld/wasm/InputFiles.cpp b/lld/wasm/InputFiles.cpp
index 52be12ac51a..e7436863461 100644
--- a/lld/wasm/InputFiles.cpp
+++ b/lld/wasm/InputFiles.cpp
@@ -158,6 +158,11 @@ void ObjFile::parse() {
   TypeMap.resize(getWasmObj()->types().size());
   TypeIsUsed.resize(getWasmObj()->types().size(), false);
 
+  ArrayRef<StringRef> Comdats = WasmObj->linkingData().Comdats;
+  UsedComdats.resize(Comdats.size());
+  for (unsigned I = 0; I < Comdats.size(); ++I)
+    UsedComdats[I] = Symtab->addComdat(Comdats[I]);
+
   // Populate `Segments`.
   for (const WasmSegment &S : WasmObj->dataSegments()) {
     InputSegment *Seg = make<InputSegment>(S, this);
@@ -194,10 +199,10 @@ void ObjFile::parse() {
 }
 
 bool ObjFile::isExcludedByComdat(InputChunk *Chunk) const {
-  StringRef S = Chunk->getComdat();
-  if (S.empty())
+  uint32_t C = Chunk->getComdat();
+  if (C == UINT32_MAX)
     return false;
-  return !Symtab->addComdat(S, this);
+  return !UsedComdats[C];
 }
 
 FunctionSymbol *ObjFile::getFunctionSymbol(uint32_t Index) const {
diff --git a/lld/wasm/InputFiles.h b/lld/wasm/InputFiles.h
index 1239e5bcabd..f0fd267d910 100644
--- a/lld/wasm/InputFiles.h
+++ b/lld/wasm/InputFiles.h
@@ -104,6 +104,7 @@ public:
   std::vector<bool> TypeIsUsed;
   // Maps function indices to table indices
   std::vector<uint32_t> TableEntries;
+  std::vector<bool> UsedComdats;
   std::vector<InputSegment *> Segments;
   std::vector<InputFunction *> Functions;
   std::vector<InputGlobal *> Globals;
diff --git a/lld/wasm/SymbolTable.cpp b/lld/wasm/SymbolTable.cpp
index a722472c291..153b507f89d 100644
--- a/lld/wasm/SymbolTable.cpp
+++ b/lld/wasm/SymbolTable.cpp
@@ -304,6 +304,6 @@ void SymbolTable::addLazy(ArchiveFile *File, const Archive::Symbol *Sym) {
   }
 }
 
-bool SymbolTable::addComdat(StringRef Name, const ObjFile *File) {
-  return Comdats.insert({Name, File}).first->second == File;
+bool SymbolTable::addComdat(StringRef Name) {
+  return Comdats.insert(CachedHashStringRef(Name)).second;
 }
diff --git a/lld/wasm/SymbolTable.h b/lld/wasm/SymbolTable.h
index 17c5a3bb699..6fb5c15782d 100644
--- a/lld/wasm/SymbolTable.h
+++ b/lld/wasm/SymbolTable.h
@@ -13,7 +13,7 @@
 #include "InputFiles.h"
 #include "Symbols.h"
 #include "llvm/ADT/CachedHashString.h"
-#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseSet.h"
 #include "llvm/Support/raw_ostream.h"
 
 using llvm::wasm::WasmGlobalType;
@@ -65,7 +65,7 @@ public:
 
   void addLazy(ArchiveFile *F, const Archive::Symbol *Sym);
 
-  bool addComdat(StringRef Name, const ObjFile *File);
+  bool addComdat(StringRef Name);
 
   DefinedData *addSyntheticDataSymbol(StringRef Name, uint32_t Flags);
   DefinedGlobal *addSyntheticGlobal(StringRef Name, uint32_t Flags,
@@ -79,7 +79,7 @@ private:
   llvm::DenseMap<llvm::CachedHashStringRef, Symbol *> SymMap;
   std::vector<Symbol *> SymVector;
 
-  llvm::DenseMap<StringRef, const ObjFile *> Comdats;
+  llvm::DenseSet<llvm::CachedHashStringRef> Comdats;
 };
 
 extern SymbolTable *Symtab;
diff --git a/lld/wasm/Writer.cpp b/lld/wasm/Writer.cpp
index b6ffd1ef983..3c6a90bf1bb 100644
--- a/lld/wasm/Writer.cpp
+++ b/lld/wasm/Writer.cpp
@@ -477,7 +477,7 @@ void Writer::createLinkingSection() {
   std::map<StringRef, std::vector<ComdatEntry>> Comdats;
 
   for (const InputFunction *F : InputFunctions) {
-    StringRef Comdat = F->getComdat();
+    StringRef Comdat = F->getComdatName();
     if (!Comdat.empty())
       Comdats[Comdat].emplace_back(
           ComdatEntry{WASM_COMDAT_FUNCTION, F->getFunctionIndex()});
@@ -486,10 +486,10 @@ void Writer::createLinkingSection() {
     const auto &InputSegments = Segments[I]->InputSegments;
     if (InputSegments.empty())
       continue;
-    StringRef Comdat = InputSegments[0]->getComdat();
+    StringRef Comdat = InputSegments[0]->getComdatName();
 #ifndef NDEBUG
     for (const InputSegment *IS : InputSegments)
-      assert(IS->getComdat() == Comdat);
+      assert(IS->getComdatName() == Comdat);
 #endif
     if (!Comdat.empty())
       Comdats[Comdat].emplace_back(ComdatEntry{WASM_COMDAT_DATA, I});