[opt] Inline a trivial lookup function into the header.

[chandlerc]

Summary

This function is actually *very* hot. It is hard to see currently
because the call graph is very recursive, but I'm working to remove that
and when I do this function becomes significantly higher on the profile
(up to 5%!) and so worth avoiding the call overhead.

No specific perf gain I can measure yet (below the noise), but likely to
have more impact as we stop cluttering the call graph.

[ruiu]

LGTM.

lld/trunk/COFF/InputFiles.h

public:
   explicit ObjectFile(MemoryBufferRef M) : InputFile(ObjectKind, M) {}
   static bool classof(const InputFile *F) { return F->kind() == ObjectKind; }
   std::error_code parse() override;
   std::vector<Chunk *> &getChunks() { return Chunks; }
   std::vector<SymbolBody *> &getSymbols() override { return SymbolBodies; }
 
   // Returns a SymbolBody object for the SymbolIndex'th symbol in the
   // underlying object file.
-  SymbolBody *getSymbolBody(uint32_t SymbolIndex);
+  SymbolBody *getSymbolBody(uint32_t SymbolIndex) {
+    return SparseSymbolBodies[SymbolIndex]->getReplacement();
+  }
 
   // Returns the underying COFF file.
   COFFObjectFile *getCOFFObj() { return COFFObj.get(); }
 
 private:
   std::error_code initializeChunks();
   std::error_code initializeSymbols();
 

lld/trunk/COFF/InputFiles.cpp

std::error_code ObjectFile::parse() {
   }
 
   // Read section and symbol tables.
   if (auto EC = initializeChunks())
     return EC;
   return initializeSymbols();
 }
 
-SymbolBody *ObjectFile::getSymbolBody(uint32_t SymbolIndex) {
-  return SparseSymbolBodies[SymbolIndex]->getReplacement();
-}
-
 std::error_code ObjectFile::initializeChunks() {
   uint32_t NumSections = COFFObj->getNumberOfSections();
   Chunks.reserve(NumSections);
   SparseChunks.resize(NumSections + 1);
   for (uint32_t I = 1; I < NumSections + 1; ++I) {
     const coff_section *Sec;
     StringRef Name;
     if (auto EC = COFFObj->getSection(I, Sec)) {