diff -upNr a/llvm-3.1.src/tools/clang/lib/Driver/ToolChains.cpp b/llvm-3.1.src/tools/clang/lib/Driver/ToolChains.cpp
--- a/llvm-3.1.src/tools/clang/lib/Driver/ToolChains.cpp	2012-05-24 03:32:31.593191000 -0400
+++ b/llvm-3.1.src/tools/clang/lib/Driver/ToolChains.cpp	2012-05-24 03:38:31.733163513 -0400
@@ -1145,6 +1145,25 @@ Generic_GCC::GCCInstallationDetector::GC
     Prefixes.push_back(D.InstalledDir + "/..");
   }
 
+  llvm::OwningPtr<llvm::MemoryBuffer> File;
+  for (unsigned k = 0, ke = CandidateTripleAliases.size(); k < ke; ++k) {
+    if (!llvm::MemoryBuffer::getFile(D.SysRoot + "/etc/env.d/gcc/config-" + CandidateTripleAliases[k].str(), File))
+    {
+      bool Exists;
+      const std::string VersionText = File.get()->getBuffer().rsplit('-').second.substr(0,5).str();
+      const std::string GentooPath = D.SysRoot + "/usr/lib/gcc/" + CandidateTripleAliases[k].str() + "/" + VersionText;
+      if (!llvm::sys::fs::exists(GentooPath + "/crtbegin.o", Exists) && Exists)
+      {
+        Version = GCCVersion::Parse(VersionText);
+        GCCInstallPath = GentooPath;
+        GCCParentLibPath = GCCInstallPath + "/../../..";
+        GCCTriple.setTriple(CandidateTripleAliases[k]);
+        IsValid = true;
+        return;
+      }
+    }
+  }
+
   // Loop over the various components which exist and select the best GCC
   // installation available. GCC installs are ranked by version number.
   Version = GCCVersion::Parse("0.0.0");