#include "llvm/ADT/SmallVector.h"
#include "llvm/Instructions.h"
#include "llvm/Support/Streams.h"
+#include "DominatorCalculation.h"
#include <algorithm>
using namespace llvm;
// DominatorTree Implementation
//===----------------------------------------------------------------------===//
//
-// DominatorTree construction - This pass constructs immediate dominator
-// information for a flow-graph based on the algorithm described in this
-// document:
-//
-// A Fast Algorithm for Finding Dominators in a Flowgraph
-// T. Lengauer & R. Tarjan, ACM TOPLAS July 1979, pgs 121-141.
-//
-// This implements both the O(n*ack(n)) and the O(n*log(n)) versions of EVAL and
-// LINK, but it turns out that the theoretically slower O(n*log(n))
-// implementation is actually faster than the "efficient" algorithm (even for
-// large CFGs) because the constant overheads are substantially smaller. The
-// lower-complexity version can be enabled with the following #define:
-//
-#define BALANCE_IDOM_TREE 0
+// Provide public access to DominatorTree information. Implementation details
+// can be found in DominatorCalculation.h.
//
//===----------------------------------------------------------------------===//
}
}
-unsigned DominatorTree::DFSPass(BasicBlock *V, unsigned N) {
- // This is more understandable as a recursive algorithm, but we can't use the
- // recursive algorithm due to stack depth issues. Keep it here for
- // documentation purposes.
-#if 0
- InfoRec &VInfo = Info[Roots[i]];
- VInfo.Semi = ++N;
- VInfo.Label = V;
-
- Vertex.push_back(V); // Vertex[n] = V;
- //Info[V].Ancestor = 0; // Ancestor[n] = 0
- //Info[V].Child = 0; // Child[v] = 0
- VInfo.Size = 1; // Size[v] = 1
-
- for (succ_iterator SI = succ_begin(V), E = succ_end(V); SI != E; ++SI) {
- InfoRec &SuccVInfo = Info[*SI];
- if (SuccVInfo.Semi == 0) {
- SuccVInfo.Parent = V;
- N = DFSPass(*SI, N);
- }
- }
-#else
- std::vector<std::pair<BasicBlock*, unsigned> > Worklist;
- Worklist.push_back(std::make_pair(V, 0U));
- while (!Worklist.empty()) {
- BasicBlock *BB = Worklist.back().first;
- unsigned NextSucc = Worklist.back().second;
-
- // First time we visited this BB?
- if (NextSucc == 0) {
- InfoRec &BBInfo = Info[BB];
- BBInfo.Semi = ++N;
- BBInfo.Label = BB;
-
- Vertex.push_back(BB); // Vertex[n] = V;
- //BBInfo[V].Ancestor = 0; // Ancestor[n] = 0
- //BBInfo[V].Child = 0; // Child[v] = 0
- BBInfo.Size = 1; // Size[v] = 1
- }
-
- // If we are done with this block, remove it from the worklist.
- if (NextSucc == BB->getTerminator()->getNumSuccessors()) {
- Worklist.pop_back();
- continue;
- }
-
- // Otherwise, increment the successor number for the next time we get to it.
- ++Worklist.back().second;
-
- // Visit the successor next, if it isn't already visited.
- BasicBlock *Succ = BB->getTerminator()->getSuccessor(NextSucc);
-
- InfoRec &SuccVInfo = Info[Succ];
- if (SuccVInfo.Semi == 0) {
- SuccVInfo.Parent = BB;
- Worklist.push_back(std::make_pair(Succ, 0U));
- }
- }
-#endif
- return N;
-}
-
-void DominatorTree::Compress(BasicBlock *VIn) {
-
- std::vector<BasicBlock *> Work;
- SmallPtrSet<BasicBlock *, 32> Visited;
- BasicBlock *VInAncestor = Info[VIn].Ancestor;
- InfoRec &VInVAInfo = Info[VInAncestor];
-
- if (VInVAInfo.Ancestor != 0)
- Work.push_back(VIn);
-
- while (!Work.empty()) {
- BasicBlock *V = Work.back();
- InfoRec &VInfo = Info[V];
- BasicBlock *VAncestor = VInfo.Ancestor;
- InfoRec &VAInfo = Info[VAncestor];
-
- // Process Ancestor first
- if (Visited.insert(VAncestor) &&
- VAInfo.Ancestor != 0) {
- Work.push_back(VAncestor);
- continue;
- }
- Work.pop_back();
-
- // Update VInfo based on Ancestor info
- if (VAInfo.Ancestor == 0)
- continue;
- BasicBlock *VAncestorLabel = VAInfo.Label;
- BasicBlock *VLabel = VInfo.Label;
- if (Info[VAncestorLabel].Semi < Info[VLabel].Semi)
- VInfo.Label = VAncestorLabel;
- VInfo.Ancestor = VAInfo.Ancestor;
- }
-}
-
-BasicBlock *DominatorTree::Eval(BasicBlock *V) {
- InfoRec &VInfo = Info[V];
-#if !BALANCE_IDOM_TREE
- // Higher-complexity but faster implementation
- if (VInfo.Ancestor == 0)
- return V;
- Compress(V);
- return VInfo.Label;
-#else
- // Lower-complexity but slower implementation
- if (VInfo.Ancestor == 0)
- return VInfo.Label;
- Compress(V);
- BasicBlock *VLabel = VInfo.Label;
-
- BasicBlock *VAncestorLabel = Info[VInfo.Ancestor].Label;
- if (Info[VAncestorLabel].Semi >= Info[VLabel].Semi)
- return VLabel;
- else
- return VAncestorLabel;
-#endif
-}
-
-void DominatorTree::Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo){
-#if !BALANCE_IDOM_TREE
- // Higher-complexity but faster implementation
- WInfo.Ancestor = V;
-#else
- // Lower-complexity but slower implementation
- BasicBlock *WLabel = WInfo.Label;
- unsigned WLabelSemi = Info[WLabel].Semi;
- BasicBlock *S = W;
- InfoRec *SInfo = &Info[S];
-
- BasicBlock *SChild = SInfo->Child;
- InfoRec *SChildInfo = &Info[SChild];
-
- while (WLabelSemi < Info[SChildInfo->Label].Semi) {
- BasicBlock *SChildChild = SChildInfo->Child;
- if (SInfo->Size+Info[SChildChild].Size >= 2*SChildInfo->Size) {
- SChildInfo->Ancestor = S;
- SInfo->Child = SChild = SChildChild;
- SChildInfo = &Info[SChild];
- } else {
- SChildInfo->Size = SInfo->Size;
- S = SInfo->Ancestor = SChild;
- SInfo = SChildInfo;
- SChild = SChildChild;
- SChildInfo = &Info[SChild];
- }
- }
-
- InfoRec &VInfo = Info[V];
- SInfo->Label = WLabel;
-
- assert(V != W && "The optimization here will not work in this case!");
- unsigned WSize = WInfo.Size;
- unsigned VSize = (VInfo.Size += WSize);
-
- if (VSize < 2*WSize)
- std::swap(S, VInfo.Child);
-
- while (S) {
- SInfo = &Info[S];
- SInfo->Ancestor = V;
- S = SInfo->Child;
- }
-#endif
-}
-
-void DominatorTree::calculate(Function &F) {
- BasicBlock* Root = Roots[0];
-
- // Add a node for the root...
- DomTreeNodes[Root] = RootNode = new DomTreeNode(Root, 0);
-
- Vertex.push_back(0);
-
- // Step #1: Number blocks in depth-first order and initialize variables used
- // in later stages of the algorithm.
- unsigned N = DFSPass(Root, 0);
-
- for (unsigned i = N; i >= 2; --i) {
- BasicBlock *W = Vertex[i];
- InfoRec &WInfo = Info[W];
-
- // Step #2: Calculate the semidominators of all vertices
- for (pred_iterator PI = pred_begin(W), E = pred_end(W); PI != E; ++PI)
- if (Info.count(*PI)) { // Only if this predecessor is reachable!
- unsigned SemiU = Info[Eval(*PI)].Semi;
- if (SemiU < WInfo.Semi)
- WInfo.Semi = SemiU;
- }
-
- Info[Vertex[WInfo.Semi]].Bucket.push_back(W);
-
- BasicBlock *WParent = WInfo.Parent;
- Link(WParent, W, WInfo);
-
- // Step #3: Implicitly define the immediate dominator of vertices
- std::vector<BasicBlock*> &WParentBucket = Info[WParent].Bucket;
- while (!WParentBucket.empty()) {
- BasicBlock *V = WParentBucket.back();
- WParentBucket.pop_back();
- BasicBlock *U = Eval(V);
- IDoms[V] = Info[U].Semi < Info[V].Semi ? U : WParent;
- }
- }
-
- // Step #4: Explicitly define the immediate dominator of each vertex
- for (unsigned i = 2; i <= N; ++i) {
- BasicBlock *W = Vertex[i];
- BasicBlock *&WIDom = IDoms[W];
- if (WIDom != Vertex[Info[W].Semi])
- WIDom = IDoms[WIDom];
- }
-
- // Loop over all of the reachable blocks in the function...
- for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
- if (BasicBlock *ImmDom = getIDom(I)) { // Reachable block.
- DomTreeNode *BBNode = DomTreeNodes[I];
- if (BBNode) continue; // Haven't calculated this node yet?
-
- // Get or calculate the node for the immediate dominator
- DomTreeNode *IDomNode = getNodeForBlock(ImmDom);
-
- // Add a new tree node for this BasicBlock, and link it as a child of
- // IDomNode
- DomTreeNode *C = new DomTreeNode(I, IDomNode);
- DomTreeNodes[I] = IDomNode->addChild(C);
- }
-
- // Free temporary memory used to construct idom's
- Info.clear();
- IDoms.clear();
- std::vector<BasicBlock*>().swap(Vertex);
-
- updateDFSNumbers();
-}
-
void DominatorTreeBase::updateDFSNumbers() {
unsigned DFSNum = 0;
RootNode = 0;
}
+DomTreeNode *DominatorTreeBase::getNodeForBlock(BasicBlock *BB) {
+ if (DomTreeNode *BBNode = DomTreeNodes[BB])
+ return BBNode;
+
+ // Haven't calculated this node yet? Get or calculate the node for the
+ // immediate dominator.
+ BasicBlock *IDom = getIDom(BB);
+ DomTreeNode *IDomNode = getNodeForBlock(IDom);
+
+ // Add a new tree node for this BasicBlock, and link it as a child of
+ // IDomNode
+ DomTreeNode *C = new DomTreeNode(BB, IDomNode);
+ return DomTreeNodes[BB] = IDomNode->addChild(C);
+}
+
/// findNearestCommonDominator - Find nearest common dominator basic block
/// for basic block A and B. If there is no such block then return NULL.
BasicBlock *DominatorTreeBase::findNearestCommonDominator(BasicBlock *A,
}
}
-DomTreeNode *DominatorTree::getNodeForBlock(BasicBlock *BB) {
- if (DomTreeNode *BBNode = DomTreeNodes[BB])
- return BBNode;
-
- // Haven't calculated this node yet? Get or calculate the node for the
- // immediate dominator.
- BasicBlock *IDom = getIDom(BB);
- DomTreeNode *IDomNode = getNodeForBlock(IDom);
-
- // Add a new tree node for this BasicBlock, and link it as a child of
- // IDomNode
- DomTreeNode *C = new DomTreeNode(BB, IDomNode);
- return DomTreeNodes[BB] = IDomNode->addChild(C);
-}
-
static std::ostream &operator<<(std::ostream &o, const DomTreeNode *Node) {
if (Node->getBlock())
WriteAsOperand(o, Node->getBlock(), false);
void DominatorTreeBase::eraseNode(BasicBlock *BB) {
DomTreeNode *Node = getNode(BB);
assert (Node && "Removing node that isn't in dominator tree.");
-
+ assert (Node->getChildren().empty() && "Node is not a leaf node.");
+
// Remove node from immediate dominator's children list.
DomTreeNode *IDom = Node->getIDom();
if (IDom) {
IDom->Children.erase(I);
}
- assert (Node->getChildren().empty() && "Children list is not empty");
-
DomTreeNodes.erase(BB);
delete Node;
}
bool DominatorTree::runOnFunction(Function &F) {
reset(); // Reset from the last time we were run...
Roots.push_back(&F.getEntryBlock());
- calculate(F);
+ DTcalculate(*this, F);
return false;
}
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