[PATCH] [Review Request] Improve getVTList() in SelectionDAG

[Wan, Xiaofei]

  Change to use the existing data structure SmallDenseMap.

Hi resistor,

http://llvm-reviews.chandlerc.com/D1127

CHANGE SINCE LAST DIFF
  http://llvm-reviews.chandlerc.com/D1127?vs=2766&id=4756#toc

Files:
  include/llvm/CodeGen/SelectionDAG.h
  lib/CodeGen/SelectionDAG/SelectionDAG.cpp

Index: include/llvm/CodeGen/SelectionDAG.h
===================================================================
--- include/llvm/CodeGen/SelectionDAG.h
+++ include/llvm/CodeGen/SelectionDAG.h
@@ -58,6 +58,42 @@
   static void createNode(const SDNode &);
 };
 
+
+struct SDVTListInfo {
+  const EVT *pVTs;
+  unsigned int NumVTs;
+  
+  friend struct DenseMapInfo<SDVTListInfo>;
+
+  /// getEmptyKey() - A private constructor that returns an unknown that is
+  /// not equal to the tombstone key or SDVTListInfo().
+  static SDVTListInfo getEmptyKey() {
+    SDVTListInfo SDVTInfo;
+    SDVTInfo.NumVTs = 0;
+    return SDVTInfo;
+  }
+
+  /// getTombstoneKey() - A private constructor that returns an unknown that
+  /// is not equal to the empty key or SDVTListInfo().
+  static SDVTListInfo getTombstoneKey() {
+    SDVTListInfo SDVTInfo;
+    SDVTInfo.NumVTs = 0;
+    return SDVTInfo;
+  }
+
+  unsigned getHashValue() const;
+  bool operator==(const SDVTListInfo &SDVTInfo) const;
+  bool operator!=(const SDVTListInfo &SDVTInfo) const { return !(*this == SDVTInfo); }
+};
+
+template <>
+struct DenseMapInfo<SDVTListInfo> {
+  static SDVTListInfo getEmptyKey() { return SDVTListInfo::getEmptyKey(); }
+  static SDVTListInfo getTombstoneKey() { return SDVTListInfo::getTombstoneKey(); }
+  static bool isEqual(SDVTListInfo LHS, SDVTListInfo RHS) { return LHS == RHS; }
+  static unsigned getHashValue(const SDVTListInfo &Key) { return Key.getHashValue(); }
+};
+
 /// SDDbgInfo - Keeps track of dbg_value information through SDISel.  We do
 /// not build SDNodes for these so as not to perturb the generated code;
 /// instead the info is kept off to the side in this structure. Each SDNode may
@@ -1093,7 +1129,7 @@
   void allnodes_clear();
 
   /// VTList - List of non-single value types.
-  std::vector<SDVTList> VTList;
+  SmallDenseMap<SDVTListInfo, SDVTList, 256> VTListMap;
 
   /// CondCodeNodes - Maps to auto-CSE operations.
   std::vector<CondCodeSDNode*> CondCodeNodes;
Index: lib/CodeGen/SelectionDAG/SelectionDAG.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -52,6 +52,23 @@
 #include <cmath>
 using namespace llvm;
 
+unsigned SDVTListInfo::getHashValue() const {
+  unsigned hash = 0;
+  for (unsigned index = 0; index < NumVTs; ++index) {
+    hash = hash ^ pVTs[index].getRawBits();
+  }
+  hash = (hash << 2) ^ NumVTs; 
+  return hash;
+}
+
+bool SDVTListInfo::operator==(const SDVTListInfo &SDVTInfo) const {
+  if (NumVTs != SDVTInfo.NumVTs)
+    return false;
+  if (!std::equal(&pVTs[0], &pVTs[NumVTs], &SDVTInfo.pVTs[0]))
+    return false;
+  return true;
+}
+
 /// makeVTList - Return an instance of the SDVTList struct initialized with the
 /// specified members.
 static SDVTList makeVTList(const EVT *VTs, unsigned NumVTs) {
@@ -4891,75 +4908,31 @@
 }
 
 SDVTList SelectionDAG::getVTList(EVT VT1, EVT VT2) {
-  for (std::vector<SDVTList>::reverse_iterator I = VTList.rbegin(),
-       E = VTList.rend(); I != E; ++I)
-    if (I->NumVTs == 2 && I->VTs[0] == VT1 && I->VTs[1] == VT2)
-      return *I;
-
-  EVT *Array = Allocator.Allocate<EVT>(2);
-  Array[0] = VT1;
-  Array[1] = VT2;
-  SDVTList Result = makeVTList(Array, 2);
-  VTList.push_back(Result);
-  return Result;
+  const EVT pVTs[2] = {VT1, VT2};
+  return getVTList(pVTs, 2);
 }
 
 SDVTList SelectionDAG::getVTList(EVT VT1, EVT VT2, EVT VT3) {
-  for (std::vector<SDVTList>::reverse_iterator I = VTList.rbegin(),
-       E = VTList.rend(); I != E; ++I)
-    if (I->NumVTs == 3 && I->VTs[0] == VT1 && I->VTs[1] == VT2 &&
-                          I->VTs[2] == VT3)
-      return *I;
-
-  EVT *Array = Allocator.Allocate<EVT>(3);
-  Array[0] = VT1;
-  Array[1] = VT2;
-  Array[2] = VT3;
-  SDVTList Result = makeVTList(Array, 3);
-  VTList.push_back(Result);
-  return Result;
+  const EVT pVTs[3] = {VT1, VT2, VT3};
+  return getVTList(pVTs, 3);
 }
 
 SDVTList SelectionDAG::getVTList(EVT VT1, EVT VT2, EVT VT3, EVT VT4) {
-  for (std::vector<SDVTList>::reverse_iterator I = VTList.rbegin(),
-       E = VTList.rend(); I != E; ++I)
-    if (I->NumVTs == 4 && I->VTs[0] == VT1 && I->VTs[1] == VT2 &&
-                          I->VTs[2] == VT3 && I->VTs[3] == VT4)
-      return *I;
-
-  EVT *Array = Allocator.Allocate<EVT>(4);
-  Array[0] = VT1;
-  Array[1] = VT2;
-  Array[2] = VT3;
-  Array[3] = VT4;
-  SDVTList Result = makeVTList(Array, 4);
-  VTList.push_back(Result);
-  return Result;
+  const EVT pVTs[4] = {VT1, VT2, VT3, VT4};
+  return getVTList(pVTs, 4);
 }
 
 SDVTList SelectionDAG::getVTList(const EVT *VTs, unsigned NumVTs) {
-  switch (NumVTs) {
-    case 0: llvm_unreachable("Cannot have nodes without results!");
-    case 1: return getVTList(VTs[0]);
-    case 2: return getVTList(VTs[0], VTs[1]);
-    case 3: return getVTList(VTs[0], VTs[1], VTs[2]);
-    case 4: return getVTList(VTs[0], VTs[1], VTs[2], VTs[3]);
-    default: break;
-  }
-
-  for (std::vector<SDVTList>::reverse_iterator I = VTList.rbegin(),
-       E = VTList.rend(); I != E; ++I) {
-    if (I->NumVTs != NumVTs || VTs[0] != I->VTs[0] || VTs[1] != I->VTs[1])
-      continue;
-
-    if (std::equal(&VTs[2], &VTs[NumVTs], &I->VTs[2]))
-      return *I;
-  }
-
+  SDVTListInfo Key = {VTs, NumVTs};
+  if (VTListMap.count(Key))
+    return VTListMap[Key];
+  
   EVT *Array = Allocator.Allocate<EVT>(NumVTs);
   std::copy(VTs, VTs+NumVTs, Array);
   SDVTList Result = makeVTList(Array, NumVTs);
-  VTList.push_back(Result);
+  Key.pVTs = Array;
+  VTListMap.insert(std::make_pair(Key, Result));
+
   return Result;
 }
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