Instead of keeping two Value*->id# mappings, keep one Value->Value ma…

…pping and

one Value set. This is faster because we only need to use the set when there
isn't already an entry in the map. No functionality change!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126076 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/IPO/MergeFunctions.cpp

@@ -156,7 +156,7 @@ class FunctionComparator {
 public:
   FunctionComparator(const TargetData *TD, const Function *F1,
                      const Function *F2)
-    : F1(F1), F2(F2), TD(TD), IDMap1Count(0), IDMap2Count(0) {}
+    : F1(F1), F2(F2), TD(TD) {}
 
   /// Test whether the two functions have equivalent behaviour.
   bool compare();
@@ -191,9 +191,8 @@ class FunctionComparator {
 
   const TargetData *TD;
 
-  typedef DenseMap<const Value *, unsigned long> IDMap;
-  IDMap Map1, Map2;
-  unsigned long IDMap1Count, IDMap2Count;
+  DenseMap<const Value *, const Value *> id_map;
+  DenseSet<const Value *> seen_values;
 };
 
 }
@@ -397,15 +396,18 @@ bool FunctionComparator::enumerate(const Value *V1, const Value *V2) {
   if (isa<InlineAsm>(V1) || isa<InlineAsm>(V2))
     return V1 == V2;
 
-  unsigned long &ID1 = Map1[V1];
-  if (!ID1)
-    ID1 = ++IDMap1Count;
+  // Check that V1 maps to V2. If we find a value that V1 maps to then we simply
+  // check whether it's equal to V2. When there is no mapping then we need to
+  // ensure that V2 isn't already equivalent to something else. For this
+  // purpose, we track the V2 values in a set.
 
-  unsigned long &ID2 = Map2[V2];
-  if (!ID2)
-    ID2 = ++IDMap2Count;
-
-  return ID1 == ID2;
+  const Value *&map_elem = id_map[V1];
+  if (map_elem)
+    return map_elem == V2;
+  if (!seen_values.insert(V2).second)
+    return false;
+  map_elem = V2;
+  return true;
 }
 
 // Test whether two basic blocks have equivalent behaviour.