From ac3a79c4d88e7e73d274a73eb11c5fac8ea89c3c Mon Sep 17 00:00:00 2001
From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Sat, 17 May 2014 02:21:47 +0000
Subject: [PATCH] Switch to a more efficient expression of this check.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@209055 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaOverload.cpp | 44 +++++++++++++++++++++------------------
 1 file changed, 24 insertions(+), 20 deletions(-)

diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index bc8eb2cf6a..8d03404e7a 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -8309,37 +8309,41 @@ isBetterOverloadCandidate(Sema &S,
     // specific_attr_iterator<EnableIfAttr> but going in declaration order,
     // instead of reverse order which is how they're stored in the AST.
     AttrVec Cand1Attrs;
-    AttrVec::iterator Cand1E = Cand1Attrs.end();
     if (Cand1.Function->hasAttrs()) {
       Cand1Attrs = Cand1.Function->getAttrs();
-      Cand1E = std::remove_if(Cand1Attrs.begin(), Cand1Attrs.end(),
-                              IsNotEnableIfAttr);
-      std::reverse(Cand1Attrs.begin(), Cand1E);
+      Cand1Attrs.erase(std::remove_if(Cand1Attrs.begin(), Cand1Attrs.end(),
+                                      IsNotEnableIfAttr),
+                       Cand1Attrs.end());
+      std::reverse(Cand1Attrs.begin(), Cand1Attrs.end());
     }
 
     AttrVec Cand2Attrs;
-    AttrVec::iterator Cand2E = Cand2Attrs.end();
     if (Cand2.Function->hasAttrs()) {
       Cand2Attrs = Cand2.Function->getAttrs();
-      Cand2E = std::remove_if(Cand2Attrs.begin(), Cand2Attrs.end(),
-                              IsNotEnableIfAttr);
-      std::reverse(Cand2Attrs.begin(), Cand2E);
-    }
-    for (AttrVec::iterator
-         Cand1I = Cand1Attrs.begin(), Cand2I = Cand2Attrs.begin();
-         Cand1I != Cand1E || Cand2I != Cand2E; ++Cand1I, ++Cand2I) {
-      if (Cand1I == Cand1E)
-        return false;
-      if (Cand2I == Cand2E)
-        return true;
+      Cand2Attrs.erase(std::remove_if(Cand2Attrs.begin(), Cand2Attrs.end(),
+                                      IsNotEnableIfAttr),
+                       Cand2Attrs.end());
+      std::reverse(Cand2Attrs.begin(), Cand2Attrs.end());
+    }
+
+    // Candidate 1 is better if it has strictly more attributes and
+    // the common sequence is identical.
+    if (Cand1Attrs.size() <= Cand2Attrs.size())
+      return false;
+
+    auto Cand1I = Cand1Attrs.begin();
+    for (auto &Cand2A : Cand2Attrs) {
+      auto &Cand1A = *Cand1I++;
       llvm::FoldingSetNodeID Cand1ID, Cand2ID;
-      cast<EnableIfAttr>(*Cand1I)->getCond()->Profile(Cand1ID,
-                                                      S.getASTContext(), true);
-      cast<EnableIfAttr>(*Cand2I)->getCond()->Profile(Cand2ID,
-                                                      S.getASTContext(), true);
+      cast<EnableIfAttr>(Cand1A)->getCond()->Profile(Cand1ID,
+                                                     S.getASTContext(), true);
+      cast<EnableIfAttr>(Cand2A)->getCond()->Profile(Cand2ID,
+                                                     S.getASTContext(), true);
       if (Cand1ID != Cand2ID)
         return false;
     }
+
+    return true;
   }
 
   return false;
-- 
2.40.0