llvm-6502/lib/Analysis/PostDominators.cpp
Devang Patel 4d42dea253 Break DominatorTree from ETNode.
Remove unused PostETForest.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37551 91177308-0d34-0410-b5e6-96231b3b80d8
2007-06-12 00:54:38 +00:00

263 lines
8.8 KiB
C++

//===- PostDominators.cpp - Post-Dominator Calculation --------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the post-dominator construction algorithms.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/PostDominators.h"
#include "llvm/Instructions.h"
#include "llvm/Support/CFG.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/SetOperations.h"
using namespace llvm;
//===----------------------------------------------------------------------===//
// PostDominatorTree Implementation
//===----------------------------------------------------------------------===//
char PostDominatorTree::ID = 0;
char PostDominanceFrontier::ID = 0;
static RegisterPass<PostDominatorTree>
F("postdomtree", "Post-Dominator Tree Construction", true);
unsigned PostDominatorTree::DFSPass(BasicBlock *V, InfoRec &VInfo,
unsigned N) {
std::vector<std::pair<BasicBlock *, InfoRec *> > workStack;
std::set<BasicBlock *> visited;
workStack.push_back(std::make_pair(V, &VInfo));
do {
BasicBlock *currentBB = workStack.back().first;
InfoRec *currentVInfo = workStack.back().second;
// Visit each block only once.
if (visited.count(currentBB) == 0) {
visited.insert(currentBB);
currentVInfo->Semi = ++N;
currentVInfo->Label = currentBB;
Vertex.push_back(currentBB); // Vertex[n] = current;
// Info[currentBB].Ancestor = 0;
// Ancestor[n] = 0
// Child[currentBB] = 0;
currentVInfo->Size = 1; // Size[currentBB] = 1
}
// Visit children
bool visitChild = false;
for (pred_iterator PI = pred_begin(currentBB), PE = pred_end(currentBB);
PI != PE && !visitChild; ++PI) {
InfoRec &SuccVInfo = Info[*PI];
if (SuccVInfo.Semi == 0) {
SuccVInfo.Parent = currentBB;
if (visited.count (*PI) == 0) {
workStack.push_back(std::make_pair(*PI, &SuccVInfo));
visitChild = true;
}
}
}
// If all children are visited or if this block has no child then pop this
// block out of workStack.
if (!visitChild)
workStack.pop_back();
} while (!workStack.empty());
return N;
}
void PostDominatorTree::Compress(BasicBlock *V, InfoRec &VInfo) {
BasicBlock *VAncestor = VInfo.Ancestor;
InfoRec &VAInfo = Info[VAncestor];
if (VAInfo.Ancestor == 0)
return;
Compress(VAncestor, VAInfo);
BasicBlock *VAncestorLabel = VAInfo.Label;
BasicBlock *VLabel = VInfo.Label;
if (Info[VAncestorLabel].Semi < Info[VLabel].Semi)
VInfo.Label = VAncestorLabel;
VInfo.Ancestor = VAInfo.Ancestor;
}
BasicBlock *PostDominatorTree::Eval(BasicBlock *V) {
InfoRec &VInfo = Info[V];
// Higher-complexity but faster implementation
if (VInfo.Ancestor == 0)
return V;
Compress(V, VInfo);
return VInfo.Label;
}
void PostDominatorTree::Link(BasicBlock *V, BasicBlock *W,
InfoRec &WInfo) {
// Higher-complexity but faster implementation
WInfo.Ancestor = V;
}
void PostDominatorTree::calculate(Function &F) {
// Step #0: Scan the function looking for the root nodes of the post-dominance
// relationships. These blocks, which have no successors, end with return and
// unwind instructions.
for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
if (succ_begin(I) == succ_end(I))
Roots.push_back(I);
Vertex.push_back(0);
// Step #1: Number blocks in depth-first order and initialize variables used
// in later stages of the algorithm.
unsigned N = 0;
for (unsigned i = 0, e = Roots.size(); i != e; ++i)
N = DFSPass(Roots[i], Info[Roots[i]], N);
for (unsigned i = N; i >= 2; --i) {
BasicBlock *W = Vertex[i];
InfoRec &WInfo = Info[W];
// Step #2: Calculate the semidominators of all vertices
for (succ_iterator SI = succ_begin(W), SE = succ_end(W); SI != SE; ++SI)
if (Info.count(*SI)) { // Only if this predecessor is reachable!
unsigned SemiU = Info[Eval(*SI)].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];
}
if (Roots.empty()) return;
// Add a node for the root. This node might be the actual root, if there is
// one exit block, or it may be the virtual exit (denoted by (BasicBlock *)0)
// which postdominates all real exits if there are multiple exit blocks.
BasicBlock *Root = Roots.size() == 1 ? Roots[0] : 0;
DomTreeNodes[Root] = RootNode = new DomTreeNode(Root, 0);
// Loop over all of the reachable blocks in the function...
for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
if (BasicBlock *ImmPostDom = getIDom(I)) { // Reachable block.
DomTreeNode *&BBNode = DomTreeNodes[I];
if (!BBNode) { // Haven't calculated this node yet?
// Get or calculate the node for the immediate dominator
DomTreeNode *IPDomNode = getNodeForBlock(ImmPostDom);
// Add a new tree node for this BasicBlock, and link it as a child of
// IDomNode
DomTreeNode *C = new DomTreeNode(I, IPDomNode);
DomTreeNodes[I] = C;
BBNode = IPDomNode->addChild(C);
}
}
// Free temporary memory used to construct idom's
IDoms.clear();
Info.clear();
std::vector<BasicBlock*>().swap(Vertex);
int dfsnum = 0;
// Iterate over all nodes in depth first order...
for (unsigned i = 0, e = Roots.size(); i != e; ++i)
for (idf_iterator<BasicBlock*> I = idf_begin(Roots[i]),
E = idf_end(Roots[i]); I != E; ++I) {
if (!getNodeForBlock(*I)->getIDom())
getNodeForBlock(*I)->assignDFSNumber(dfsnum);
}
DFSInfoValid = true;
}
DomTreeNode *PostDominatorTree::getNodeForBlock(BasicBlock *BB) {
DomTreeNode *&BBNode = DomTreeNodes[BB];
if (BBNode) return BBNode;
// Haven't calculated this node yet? Get or calculate the node for the
// immediate postdominator.
BasicBlock *IPDom = getIDom(BB);
DomTreeNode *IPDomNode = getNodeForBlock(IPDom);
// Add a new tree node for this BasicBlock, and link it as a child of
// IDomNode
DomTreeNode *C = new DomTreeNode(BB, IPDomNode);
DomTreeNodes[BB] = C;
return BBNode = IPDomNode->addChild(C);
}
//===----------------------------------------------------------------------===//
// PostDominanceFrontier Implementation
//===----------------------------------------------------------------------===//
static RegisterPass<PostDominanceFrontier>
H("postdomfrontier", "Post-Dominance Frontier Construction", true);
const DominanceFrontier::DomSetType &
PostDominanceFrontier::calculate(const PostDominatorTree &DT,
const DomTreeNode *Node) {
// Loop over CFG successors to calculate DFlocal[Node]
BasicBlock *BB = Node->getBlock();
DomSetType &S = Frontiers[BB]; // The new set to fill in...
if (getRoots().empty()) return S;
if (BB)
for (pred_iterator SI = pred_begin(BB), SE = pred_end(BB);
SI != SE; ++SI) {
// Does Node immediately dominate this predecessor?
DomTreeNode *SINode = DT[*SI];
if (SINode && SINode->getIDom() != Node)
S.insert(*SI);
}
// At this point, S is DFlocal. Now we union in DFup's of our children...
// Loop through and visit the nodes that Node immediately dominates (Node's
// children in the IDomTree)
//
for (DomTreeNode::const_iterator
NI = Node->begin(), NE = Node->end(); NI != NE; ++NI) {
DomTreeNode *IDominee = *NI;
const DomSetType &ChildDF = calculate(DT, IDominee);
DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
for (; CDFI != CDFE; ++CDFI) {
if (!DT.properlyDominates(Node, DT[*CDFI]))
S.insert(*CDFI);
}
}
return S;
}
// Ensure that this .cpp file gets linked when PostDominators.h is used.
DEFINING_FILE_FOR(PostDominanceFrontier)