[lld] r248109 - COFF: Run InputFile::parse() in background using std::async().

[Rui Ueyama via llvm-commits]

Author: ruiu
Date: Sat Sep 19 22:11:16 2015
New Revision: 248109

URL: http://llvm.org/viewvc/llvm-project?rev=248109&view=rev
Log:
COFF: Run InputFile::parse() in background using std::async().

Previously, InputFile::parse() was run in batch. We construct a list
of all input files and call parse() on each file using parallel_for_each.
That means we cannot start parsing files until we get a complete list
of input files, although InputFile::parse() is safe to call from anywhere.

This patch makes it asynchronous. As soon as we add a file to the symbol
table, we now start parsing the file using std::async().

This change shortens self-hosting time (650 ms) by 28 ms. It's about 4%
improvement.

Modified:
    lld/trunk/COFF/SymbolTable.cpp
    lld/trunk/COFF/SymbolTable.h

Modified: lld/trunk/COFF/SymbolTable.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/SymbolTable.cpp?rev=248109&r1=248108&r2=248109&view=diff
==============================================================================
--- lld/trunk/COFF/SymbolTable.cpp (original)
+++ lld/trunk/COFF/SymbolTable.cpp Sat Sep 19 22:11:16 2015
@@ -27,10 +27,12 @@ void SymbolTable::addFile(std::unique_pt
   InputFile *File = FileP.get();
   Files.push_back(std::move(FileP));
   if (auto *F = dyn_cast<ArchiveFile>(File)) {
-    ArchiveQueue.push_back(F);
+    ArchiveQueue.push_back(
+        std::async(std::launch::async, [=]() { F->parse(); return F; }));
     return;
   }
-  ObjectQueue.push_back(File);
+  ObjectQueue.push_back(
+      std::async(std::launch::async, [=]() { File->parse(); return File; }));
   if (auto *F = dyn_cast<ObjectFile>(File)) {
     ObjectFiles.push_back(F);
   } else if (auto *F = dyn_cast<BitcodeFile>(File)) {
@@ -56,13 +58,11 @@ void SymbolTable::readArchives() {
   if (ArchiveQueue.empty())
     return;
 
-  parallel_for_each(ArchiveQueue.begin(), ArchiveQueue.end(),
-                    [](ArchiveFile *File) { File->parse(); });
-
   // Add lazy symbols to the symbol table. Lazy symbols that conflict
   // with existing undefined symbols are accumulated in LazySyms.
   std::vector<Symbol *> LazySyms;
-  for (ArchiveFile *File : ArchiveQueue) {
+  for (std::future<ArchiveFile *> &Future : ArchiveQueue) {
+    ArchiveFile *File = Future.get();
     if (Config->Verbose)
       llvm::outs() << "Reading " << File->getShortName() << "\n";
     for (Lazy &Sym : File->getLazySymbols())
@@ -82,25 +82,21 @@ void SymbolTable::readObjects() {
 
   // Add defined and undefined symbols to the symbol table.
   std::vector<StringRef> Directives;
-  for (size_t I = 0; I < ObjectQueue.size();) {
-    parallel_for_each(ObjectQueue.begin() + I, ObjectQueue.end(),
-                      [](InputFile *File) { File->parse(); });
-    for (size_t E = ObjectQueue.size(); I != E; ++I) {
-      InputFile *File = ObjectQueue[I];
+  for (size_t I = 0; I < ObjectQueue.size(); ++I) {
+    InputFile *File = ObjectQueue[I].get();
+    if (Config->Verbose)
+      llvm::outs() << "Reading " << File->getShortName() << "\n";
+    // Adding symbols may add more files to ObjectQueue
+    // (but not to ArchiveQueue).
+    for (SymbolBody *Sym : File->getSymbols())
+      if (Sym->isExternal())
+        addSymbol(Sym);
+    StringRef S = File->getDirectives();
+    if (!S.empty()) {
+      Directives.push_back(S);
       if (Config->Verbose)
-        llvm::outs() << "Reading " << File->getShortName() << "\n";
-      // Adding symbols may add more files to ObjectQueue
-      // (but not to ArchiveQueue).
-      for (SymbolBody *Sym : File->getSymbols())
-        if (Sym->isExternal())
-          addSymbol(Sym);
-      StringRef S = File->getDirectives();
-      if (!S.empty()) {
-        Directives.push_back(S);
-        if (Config->Verbose)
-          llvm::outs() << "Directives: " << File->getShortName()
-                       << ": " << S << "\n";
-      }
+        llvm::outs() << "Directives: " << File->getShortName()
+                     << ": " << S << "\n";
     }
   }
   ObjectQueue.clear();

Modified: lld/trunk/COFF/SymbolTable.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/SymbolTable.h?rev=248109&r1=248108&r2=248109&view=diff
==============================================================================
--- lld/trunk/COFF/SymbolTable.h (original)
+++ lld/trunk/COFF/SymbolTable.h Sat Sep 19 22:11:16 2015
@@ -16,6 +16,13 @@
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/raw_ostream.h"
 
+#ifdef _MSC_VER
+// <future> depends on <eh.h> for __uncaught_exception.
+#include <eh.h>
+#endif
+
+#include <future>
+
 namespace llvm {
 struct LTOCodeGenerator;
 }
@@ -104,8 +111,8 @@ private:
   llvm::DenseMap<StringRef, Symbol *> Symtab;
 
   std::vector<std::unique_ptr<InputFile>> Files;
-  std::vector<ArchiveFile *> ArchiveQueue;
-  std::vector<InputFile *> ObjectQueue;
+  std::vector<std::future<ArchiveFile *>> ArchiveQueue;
+  std::vector<std::future<InputFile *>> ObjectQueue;
 
   std::vector<BitcodeFile *> BitcodeFiles;
   std::vector<SmallVector<char, 0>> Objs;