[lld] r289915 - COFF: Cache the result of library searches.

[Peter Collingbourne via llvm-commits]

Author: pcc
Date: Thu Dec 15 21:45:59 2016
New Revision: 289915

URL: http://llvm.org/viewvc/llvm-project?rev=289915&view=rev
Log:
COFF: Cache the result of library searches.

File system operations were still dominating the profile on Windows. In this
case we were spending a significant amount of our time repeatedly searching
for libraries as a result of processing linker directives. Address this
by caching whether we have already found a library with a given name. For
chrome_child.dll:

Before: 10.53s
After: 6.88s

Differential Revision: https://reviews.llvm.org/D27840

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

Modified: lld/trunk/COFF/Driver.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Driver.cpp?rev=289915&r1=289914&r2=289915&view=diff
==============================================================================
--- lld/trunk/COFF/Driver.cpp (original)
+++ lld/trunk/COFF/Driver.cpp Thu Dec 15 21:45:59 2016
@@ -280,11 +280,12 @@ StringRef LinkerDriver::doFindLib(String
 Optional<StringRef> LinkerDriver::findLib(StringRef Filename) {
   if (Config->NoDefaultLibAll)
     return None;
+  if (!VisitedLibs.insert(Filename.lower()).second)
+    return None;
   StringRef Path = doFindLib(Filename);
   if (Config->NoDefaultLibs.count(Path))
     return None;
-  bool Seen = !VisitedFiles.insert(Path.lower()).second;
-  if (Seen)
+  if (!VisitedFiles.insert(Path.lower()).second)
     return None;
   return Path;
 }

Modified: lld/trunk/COFF/Driver.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/COFF/Driver.h?rev=289915&r1=289914&r2=289915&view=diff
==============================================================================
--- lld/trunk/COFF/Driver.h (original)
+++ lld/trunk/COFF/Driver.h Thu Dec 15 21:45:59 2016
@@ -91,6 +91,7 @@ private:
   // Library search path. The first element is always "" (current directory).
   std::vector<StringRef> SearchPaths;
   std::set<std::string> VisitedFiles;
+  std::set<std::string> VisitedLibs;
 
   SymbolBody *addUndefined(StringRef Sym);
   StringRef mangle(StringRef Sym);