[PATCH] [ScalarEvolution] Change data structure to memorize computed result

[Wan, Xiaofei]

  Hashing on a pointer pair

Hi atrick,

http://llvm-reviews.chandlerc.com/D2117

CHANGE SINCE LAST DIFF
  http://llvm-reviews.chandlerc.com/D2117?vs=5393&id=5443#toc

Files:
  include/llvm/Analysis/ScalarEvolution.h
  lib/Analysis/ScalarEvolution.cpp

Index: include/llvm/Analysis/ScalarEvolution.h
===================================================================
--- include/llvm/Analysis/ScalarEvolution.h
+++ include/llvm/Analysis/ScalarEvolution.h
@@ -360,19 +360,16 @@
     /// ValuesAtScopes - This map contains entries for all the expressions
     /// that we attempt to compute getSCEVAtScope information for, which can
     /// be expensive in extreme cases.
-    DenseMap<const SCEV *,
-             std::map<const Loop *, const SCEV *> > ValuesAtScopes;
+    DenseMap<std::pair<const SCEV *, const Loop *>, const SCEV *> ValuesAtScopes;
 
     /// LoopDispositions - Memoized computeLoopDisposition results.
-    DenseMap<const SCEV *,
-             std::map<const Loop *, LoopDisposition> > LoopDispositions;
+    DenseMap<std::pair<const SCEV *, const Loop *>, LoopDisposition> LoopDispositions;
 
     /// computeLoopDisposition - Compute a LoopDisposition value.
     LoopDisposition computeLoopDisposition(const SCEV *S, const Loop *L);
 
     /// BlockDispositions - Memoized computeBlockDisposition results.
-    DenseMap<const SCEV *,
-             std::map<const BasicBlock *, BlockDisposition> > BlockDispositions;
+    DenseMap<std::pair<const SCEV *, const BasicBlock *>, BlockDisposition> BlockDispositions;
 
     /// computeBlockDisposition - Compute a BlockDisposition value.
     BlockDisposition computeBlockDisposition(const SCEV *S, const BasicBlock *BB);
Index: lib/Analysis/ScalarEvolution.cpp
===================================================================
--- lib/Analysis/ScalarEvolution.cpp
+++ lib/Analysis/ScalarEvolution.cpp
@@ -5059,15 +5059,13 @@
 /// original value V is returned.
 const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
   // Check to see if we've folded this expression at this loop before.
-  std::map<const Loop *, const SCEV *> &Values = ValuesAtScopes[V];
-  std::pair<std::map<const Loop *, const SCEV *>::iterator, bool> Pair =
-    Values.insert(std::make_pair(L, static_cast<const SCEV *>(0)));
-  if (!Pair.second)
-    return Pair.first->second ? Pair.first->second : V;
+  DenseMap<std::pair<const SCEV *, const Loop *>, const SCEV *>::iterator Pair = ValuesAtScopes.find(std::make_pair(V, L));
+  if (Pair != ValuesAtScopes.end())
+    return Pair->second ? Pair->second : V;
 
   // Otherwise compute it.
   const SCEV *C = computeSCEVAtScope(V, L);
-  ValuesAtScopes[V][L] = C;
+  ValuesAtScopes[std::make_pair(V, L)] = C;
   return C;
 }
 
@@ -6727,7 +6725,7 @@
 //===----------------------------------------------------------------------===//
 
 ScalarEvolution::ScalarEvolution()
-  : FunctionPass(ID), FirstUnknown(0) {
+  : FunctionPass(ID), ValuesAtScopes(64), LoopDispositions(128), BlockDispositions(128), FirstUnknown(0) {
   initializeScalarEvolutionPass(*PassRegistry::getPassRegistry());
 }
 
@@ -6865,14 +6863,12 @@
 
 ScalarEvolution::LoopDisposition
 ScalarEvolution::getLoopDisposition(const SCEV *S, const Loop *L) {
-  std::map<const Loop *, LoopDisposition> &Values = LoopDispositions[S];
-  std::pair<std::map<const Loop *, LoopDisposition>::iterator, bool> Pair =
-    Values.insert(std::make_pair(L, LoopVariant));
-  if (!Pair.second)
-    return Pair.first->second;
+  DenseMap<std::pair<const SCEV *, const Loop *>, LoopDisposition>::iterator Pair = LoopDispositions.find(std::make_pair(S, L));
+  if (Pair != LoopDispositions.end())
+    return Pair->second;
 
   LoopDisposition D = computeLoopDisposition(S, L);
-  return LoopDispositions[S][L] = D;
+  return LoopDispositions[std::make_pair(S, L)] = D;
 }
 
 ScalarEvolution::LoopDisposition
@@ -6964,14 +6960,12 @@
 
 ScalarEvolution::BlockDisposition
 ScalarEvolution::getBlockDisposition(const SCEV *S, const BasicBlock *BB) {
-  std::map<const BasicBlock *, BlockDisposition> &Values = BlockDispositions[S];
-  std::pair<std::map<const BasicBlock *, BlockDisposition>::iterator, bool>
-    Pair = Values.insert(std::make_pair(BB, DoesNotDominateBlock));
-  if (!Pair.second)
-    return Pair.first->second;
+  DenseMap<std::pair<const SCEV *, const BasicBlock *>, BlockDisposition>::iterator Pair = BlockDispositions.find(std::make_pair(S, BB));
+  if (Pair != BlockDispositions.end())
+    return Pair->second;
 
   BlockDisposition D = computeBlockDisposition(S, BB);
-  return BlockDispositions[S][BB] = D;
+  return BlockDispositions[std::make_pair(S, BB)] = D;
 }
 
 ScalarEvolution::BlockDisposition
@@ -7070,9 +7064,6 @@
 }
 
 void ScalarEvolution::forgetMemoizedResults(const SCEV *S) {
-  ValuesAtScopes.erase(S);
-  LoopDispositions.erase(S);
-  BlockDispositions.erase(S);
   UnsignedRanges.erase(S);
   SignedRanges.erase(S);
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