[StructurizeCFG] Refactor OrderNodes.

Justin Lebar · Justin Lebar · commit 6c0f25aec605 · 2016-11-22T23:14:11.000Z
Summary: No need to copy the RPOT vector before using it. Switch from std::map to SmallDenseMap. Get rid of an unused variable (TempVisited). Get rid of a typedef, RNVector, which is now used only once. Differential Revision: https://reviews.llvm.org/D26997 llvm-svn: 287721
diff --git a/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp b/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
@@ -175,7 +175,7 @@ class StructurizeCFG : public RegionPass {
   DominatorTree *DT;
   LoopInfo *LI;
 
-  RNVector Order;
+  SmallVector<RegionNode *, 8> Order;
   BBSet Visited;
 
   BBPhiMap DeletedPhis;
@@ -288,26 +288,21 @@ bool StructurizeCFG::doInitialization(Region *R, RGPassManager &RGM) {
 
 /// \brief Build up the general order of nodes
 void StructurizeCFG::orderNodes() {
-  RNVector TempOrder;
   ReversePostOrderTraversal<Region*> RPOT(ParentRegion);
-  TempOrder.append(RPOT.begin(), RPOT.end());
-
-  std::map<Loop*, unsigned> LoopBlocks;
-
+  SmallDenseMap<Loop*, unsigned, 8> LoopBlocks;
 
   // The reverse post-order traversal of the list gives us an ordering close
   // to what we want.  The only problem with it is that sometimes backedges
   // for outer loops will be visited before backedges for inner loops.
-  for (RegionNode *RN : TempOrder) {
+  for (RegionNode *RN : RPOT) {
     BasicBlock *BB = RN->getEntry();
     Loop *Loop = LI->getLoopFor(BB);
     ++LoopBlocks[Loop];
   }
 
   unsigned CurrentLoopDepth = 0;
   Loop *CurrentLoop = nullptr;
-  BBSet TempVisited;
-  for (RNVector::iterator I = TempOrder.begin(), E = TempOrder.end(); I != E; ++I) {
+  for (auto I = RPOT.begin(), E = RPOT.end(); I != E; ++I) {
     BasicBlock *BB = (*I)->getEntry();
     unsigned LoopDepth = LI->getLoopDepth(BB);
 
@@ -318,7 +313,7 @@ void StructurizeCFG::orderNodes() {
       // Make sure we have visited all blocks in this loop before moving back to
       // the outer loop.
 
-      RNVector::iterator LoopI = I;
+      auto LoopI = I;
       while (unsigned &BlockCount = LoopBlocks[CurrentLoop]) {
         LoopI++;
         BasicBlock *LoopBB = (*LoopI)->getEntry();
@@ -330,9 +325,8 @@ void StructurizeCFG::orderNodes() {
     }
 
     CurrentLoop = LI->getLoopFor(BB);
-    if (CurrentLoop) {
+    if (CurrentLoop)
       LoopBlocks[CurrentLoop]--;
-    }
 
     CurrentLoopDepth = LoopDepth;
     Order.push_back(*I);
