forked from OSchip/llvm-project
Fix PR681 by using the standard Lengauer and Tarjan algorithm for dominator
set construction, rather than intersecting various std::sets. This reduces the memory usage for the testcase in PR681 from 496 to 26MB of ram on my darwin system, and reduces the runtime from 32.8 to 0.8 seconds on a 2.5GHz G5. This also enables future code sharing between Dom and PostDom now that they share near-identical implementations. llvm-svn: 26707
This commit is contained in:
parent
69035f00e3
commit
d5811b965d
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@ -18,6 +18,42 @@
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namespace llvm {
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//===-------------------------------------
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/// ImmediatePostDominators Class - Concrete subclass of ImmediateDominatorsBase
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/// that is used to compute a normal immediate dominator set.
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///
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struct ImmediatePostDominators : public ImmediateDominatorsBase {
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ImmediatePostDominators() : ImmediateDominatorsBase(false) {}
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virtual bool runOnFunction(Function &F);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesAll();
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}
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private:
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struct InfoRec {
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unsigned Semi;
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unsigned Size;
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BasicBlock *Label, *Parent, *Child, *Ancestor;
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std::vector<BasicBlock*> Bucket;
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InfoRec() : Semi(0), Size(0), Label(0), Parent(0), Child(0), Ancestor(0){}
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};
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// Vertex - Map the DFS number to the BasicBlock*
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std::vector<BasicBlock*> Vertex;
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// Info - Collection of information used during the computation of idoms.
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std::map<BasicBlock*, InfoRec> Info;
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unsigned DFSPass(BasicBlock *V, InfoRec &VInfo, unsigned N);
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void Compress(BasicBlock *V, InfoRec &VInfo);
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BasicBlock *Eval(BasicBlock *v);
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void Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo);
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};
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/// PostDominatorSet Class - Concrete subclass of DominatorSetBase that is used
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/// to compute the post-dominator set. Because there can be multiple exit nodes
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/// in an LLVM function, we calculate post dominators with a special null block
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@ -27,40 +63,20 @@ namespace llvm {
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///
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struct PostDominatorSet : public DominatorSetBase {
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PostDominatorSet() : DominatorSetBase(true) {}
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virtual bool runOnFunction(Function &F);
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/// getAnalysisUsage - This pass does not modify the function at all.
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/// getAnalysisUsage - This simply provides a dominator set
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///
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<ImmediatePostDominators>();
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AU.setPreservesAll();
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}
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// stub - dummy function, just ignore it
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static void stub();
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};
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/// ImmediatePostDominators Class - Concrete subclass of ImmediateDominatorsBase
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/// that is used to compute the immediate post-dominators.
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///
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struct ImmediatePostDominators : public ImmediateDominatorsBase {
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ImmediatePostDominators() : ImmediateDominatorsBase(true) {}
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virtual bool runOnFunction(Function &F) {
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IDoms.clear(); // Reset from the last time we were run...
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PostDominatorSet &DS = getAnalysis<PostDominatorSet>();
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Roots = DS.getRoots();
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calcIDoms(DS);
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return false;
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}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesAll();
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AU.addRequired<PostDominatorSet>();
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}
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private:
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void calcIDoms(const DominatorSetBase &DS);
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};
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/// PostDominatorTree Class - Concrete subclass of DominatorTree that is used to
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/// compute the a post-dominator tree.
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///
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@ -69,18 +85,19 @@ struct PostDominatorTree : public DominatorTreeBase {
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virtual bool runOnFunction(Function &F) {
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reset(); // Reset from the last time we were run...
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PostDominatorSet &DS = getAnalysis<PostDominatorSet>();
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Roots = DS.getRoots();
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calculate(DS);
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ImmediatePostDominators &IPD = getAnalysis<ImmediatePostDominators>();
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Roots = IPD.getRoots();
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calculate(IPD);
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return false;
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}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesAll();
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AU.addRequired<PostDominatorSet>();
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AU.addRequired<ImmediatePostDominators>();
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}
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private:
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void calculate(const PostDominatorSet &DS);
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void calculate(const ImmediatePostDominators &IPD);
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Node *getNodeForBlock(BasicBlock *BB);
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};
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@ -16,8 +16,131 @@
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#include "llvm/Support/CFG.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/SetOperations.h"
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#include <iostream>
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using namespace llvm;
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//===----------------------------------------------------------------------===//
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// ImmediatePostDominators Implementation
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//===----------------------------------------------------------------------===//
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static RegisterAnalysis<ImmediatePostDominators>
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D("postidom", "Immediate Post-Dominators Construction", true);
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unsigned ImmediatePostDominators::DFSPass(BasicBlock *V, InfoRec &VInfo,
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unsigned N) {
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VInfo.Semi = ++N;
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VInfo.Label = V;
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Vertex.push_back(V); // Vertex[n] = V;
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//Info[V].Ancestor = 0; // Ancestor[n] = 0
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//Child[V] = 0; // Child[v] = 0
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VInfo.Size = 1; // Size[v] = 1
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// For PostDominators, we want to walk predecessors rather than successors
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// as we do in forward Dominators.
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for (pred_iterator PI = pred_begin(V), PE = pred_end(V); PI != PE; ++PI) {
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InfoRec &SuccVInfo = Info[*PI];
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if (SuccVInfo.Semi == 0) {
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SuccVInfo.Parent = V;
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N = DFSPass(*PI, SuccVInfo, N);
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}
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}
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return N;
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}
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void ImmediatePostDominators::Compress(BasicBlock *V, InfoRec &VInfo) {
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BasicBlock *VAncestor = VInfo.Ancestor;
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InfoRec &VAInfo = Info[VAncestor];
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if (VAInfo.Ancestor == 0)
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return;
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Compress(VAncestor, VAInfo);
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BasicBlock *VAncestorLabel = VAInfo.Label;
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BasicBlock *VLabel = VInfo.Label;
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if (Info[VAncestorLabel].Semi < Info[VLabel].Semi)
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VInfo.Label = VAncestorLabel;
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VInfo.Ancestor = VAInfo.Ancestor;
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}
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BasicBlock *ImmediatePostDominators::Eval(BasicBlock *V) {
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InfoRec &VInfo = Info[V];
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// Higher-complexity but faster implementation
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if (VInfo.Ancestor == 0)
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return V;
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Compress(V, VInfo);
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return VInfo.Label;
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}
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void ImmediatePostDominators::Link(BasicBlock *V, BasicBlock *W,
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InfoRec &WInfo) {
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// Higher-complexity but faster implementation
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WInfo.Ancestor = V;
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}
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bool ImmediatePostDominators::runOnFunction(Function &F) {
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IDoms.clear(); // Reset from the last time we were run...
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Roots.clear();
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// Step #0: Scan the function looking for the root nodes of the post-dominance
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// relationships. These blocks, which have no successors, end with return and
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// unwind instructions.
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for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
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if (succ_begin(I) == succ_end(I))
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Roots.push_back(I);
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Vertex.push_back(0);
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// Step #1: Number blocks in depth-first order and initialize variables used
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// in later stages of the algorithm.
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unsigned N = 0;
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for (unsigned i = 0, e = Roots.size(); i != e; ++i)
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N = DFSPass(Roots[i], Info[Roots[i]], N);
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for (unsigned i = N; i >= 2; --i) {
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BasicBlock *W = Vertex[i];
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InfoRec &WInfo = Info[W];
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// Step #2: Calculate the semidominators of all vertices
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for (succ_iterator SI = succ_begin(W), SE = succ_end(W); SI != SE; ++SI)
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if (Info.count(*SI)) { // Only if this predecessor is reachable!
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unsigned SemiU = Info[Eval(*SI)].Semi;
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if (SemiU < WInfo.Semi)
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WInfo.Semi = SemiU;
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}
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Info[Vertex[WInfo.Semi]].Bucket.push_back(W);
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BasicBlock *WParent = WInfo.Parent;
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Link(WParent, W, WInfo);
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// Step #3: Implicitly define the immediate dominator of vertices
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std::vector<BasicBlock*> &WParentBucket = Info[WParent].Bucket;
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while (!WParentBucket.empty()) {
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BasicBlock *V = WParentBucket.back();
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WParentBucket.pop_back();
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BasicBlock *U = Eval(V);
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IDoms[V] = Info[U].Semi < Info[V].Semi ? U : WParent;
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}
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}
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// Step #4: Explicitly define the immediate dominator of each vertex
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for (unsigned i = 2; i <= N; ++i) {
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BasicBlock *W = Vertex[i];
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BasicBlock *&WIDom = IDoms[W];
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if (WIDom != Vertex[Info[W].Semi])
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WIDom = IDoms[WIDom];
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}
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// Free temporary memory used to construct idom's
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Info.clear();
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std::vector<BasicBlock*>().swap(Vertex);
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return false;
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}
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//===----------------------------------------------------------------------===//
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// PostDominatorSet Implementation
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//===----------------------------------------------------------------------===//
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// sets for the function.
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//
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bool PostDominatorSet::runOnFunction(Function &F) {
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Doms.clear(); // Reset from the last time we were run...
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// Scan the function looking for the root nodes of the post-dominance
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// relationships. These blocks end with return and unwind instructions.
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// While we are iterating over the function, we also initialize all of the
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// domsets to empty.
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Roots.clear();
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for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
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Doms[I]; // Initialize to empty
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for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
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if (succ_begin(I) == succ_end(I))
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Roots.push_back(I);
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}
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// If there are no exit nodes for the function, postdomsets are all empty.
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// This can happen if the function just contains an infinite loop, for
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// example.
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ImmediatePostDominators &IPD = getAnalysis<ImmediatePostDominators>();
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Doms.clear(); // Reset from the last time we were run...
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if (Roots.empty()) return false;
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// If we have more than one root, we insert an artificial "null" exit, which
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// has "virtual edges" to each of the real exit nodes.
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if (Roots.size() > 1)
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Doms[0].insert(0);
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//if (Roots.size() > 1)
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// Doms[0].insert(0);
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bool Changed;
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do {
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Changed = false;
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// Root nodes only dominate themselves.
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for (unsigned i = 0, e = Roots.size(); i != e; ++i)
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Doms[Roots[i]].insert(Roots[i]);
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// Loop over all of the blocks in the function, calculating dominator sets for
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// each function.
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for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
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if (BasicBlock *IPDom = IPD[I]) { // Get idom if block is reachable
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DomSetType &DS = Doms[I];
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assert(DS.empty() && "PostDomset already filled in for this block?");
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DS.insert(I); // Blocks always dominate themselves
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std::set<BasicBlock*> Visited;
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DomSetType WorkingSet;
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for (unsigned i = 0, e = Roots.size(); i != e; ++i)
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for (idf_ext_iterator<BasicBlock*> It = idf_ext_begin(Roots[i], Visited),
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E = idf_ext_end(Roots[i], Visited); It != E; ++It) {
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BasicBlock *BB = *It;
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succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
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if (SI != SE) { // Is there SOME successor?
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// Loop until we get to a successor that has had it's dom set filled
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// in at least once. We are guaranteed to have this because we are
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// traversing the graph in DFO and have handled start nodes specially.
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//
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while (Doms[*SI].size() == 0) ++SI;
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WorkingSet = Doms[*SI];
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for (++SI; SI != SE; ++SI) { // Intersect all of the successor sets
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DomSetType &SuccSet = Doms[*SI];
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if (SuccSet.size())
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set_intersect(WorkingSet, SuccSet);
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}
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// Insert all dominators into the set...
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while (IPDom) {
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// If we have already computed the dominator sets for our immediate post
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// dominator, just use it instead of walking all the way up to the root.
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DomSetType &IPDS = Doms[IPDom];
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if (!IPDS.empty()) {
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DS.insert(IPDS.begin(), IPDS.end());
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break;
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} else {
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// If this node has no successors, it must be one of the root nodes.
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// We will already take care of the notion that the node
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// post-dominates itself. The only thing we have to add is that if
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// there are multiple root nodes, we want to insert a special "null"
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// exit node which dominates the roots as well.
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if (Roots.size() > 1)
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WorkingSet.insert(0);
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DS.insert(IPDom);
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IPDom = IPD[IPDom];
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}
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WorkingSet.insert(BB); // A block always dominates itself
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DomSetType &BBSet = Doms[BB];
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if (BBSet != WorkingSet) {
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BBSet.swap(WorkingSet); // Constant time operation!
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Changed = true; // The sets changed.
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}
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WorkingSet.clear(); // Clear out the set for next iteration
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}
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} while (Changed);
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return false;
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}
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//===----------------------------------------------------------------------===//
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// ImmediatePostDominators Implementation
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//===----------------------------------------------------------------------===//
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static RegisterAnalysis<ImmediatePostDominators>
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D("postidom", "Immediate Post-Dominators Construction", true);
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// calcIDoms - Calculate the immediate dominator mapping, given a set of
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// dominators for every basic block.
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void ImmediatePostDominators::calcIDoms(const DominatorSetBase &DS) {
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// Loop over all of the nodes that have dominators... figuring out the IDOM
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// for each node...
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//
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for (DominatorSet::const_iterator DI = DS.begin(), DEnd = DS.end();
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DI != DEnd; ++DI) {
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BasicBlock *BB = DI->first;
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const DominatorSet::DomSetType &Dominators = DI->second;
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unsigned DomSetSize = Dominators.size();
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if (DomSetSize == 1) continue; // Root node... IDom = null
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// Loop over all dominators of this node. This corresponds to looping over
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// nodes in the dominator chain, looking for a node whose dominator set is
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// equal to the current nodes, except that the current node does not exist
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// in it. This means that it is one level higher in the dom chain than the
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// current node, and it is our idom!
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//
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DominatorSet::DomSetType::const_iterator I = Dominators.begin();
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DominatorSet::DomSetType::const_iterator End = Dominators.end();
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for (; I != End; ++I) { // Iterate over dominators...
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// All of our dominators should form a chain, where the number of elements
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// in the dominator set indicates what level the node is at in the chain.
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// We want the node immediately above us, so it will have an identical
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// dominator set, except that BB will not dominate it... therefore it's
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// dominator set size will be one less than BB's...
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//
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if (DS.getDominators(*I).size() == DomSetSize - 1) {
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IDoms[BB] = *I;
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break;
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}
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} else {
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// Ensure that every basic block has at least an empty set of nodes. This
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// is important for the case when there is unreachable blocks.
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Doms[I];
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}
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}
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return false;
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}
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//===----------------------------------------------------------------------===//
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@ -152,59 +215,45 @@ void ImmediatePostDominators::calcIDoms(const DominatorSetBase &DS) {
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static RegisterAnalysis<PostDominatorTree>
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F("postdomtree", "Post-Dominator Tree Construction", true);
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void PostDominatorTree::calculate(const PostDominatorSet &DS) {
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DominatorTreeBase::Node *PostDominatorTree::getNodeForBlock(BasicBlock *BB) {
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Node *&BBNode = Nodes[BB];
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if (BBNode) return BBNode;
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// Haven't calculated this node yet? Get or calculate the node for the
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// immediate postdominator.
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BasicBlock *IPDom = getAnalysis<ImmediatePostDominators>()[BB];
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Node *IPDomNode = getNodeForBlock(IPDom);
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// Add a new tree node for this BasicBlock, and link it as a child of
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// IDomNode
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return BBNode = IPDomNode->addChild(new Node(BB, IPDomNode));
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}
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void PostDominatorTree::calculate(const ImmediatePostDominators &IPD) {
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if (Roots.empty()) return;
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// Add a node for the root. This node might be the actual root, if there is
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// one exit block, or it may be the virtual exit (denoted by (BasicBlock *)0)
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// which postdominates all real exits if there are multiple exit blocks.
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BasicBlock *Root = Roots.size() == 1 ? Roots[0] : 0;
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Nodes[Root] = RootNode = new Node(Root, 0); // Add a node for the root...
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// Iterate over all nodes in depth first order...
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for (unsigned i = 0, e = Roots.size(); i != e; ++i)
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for (idf_iterator<BasicBlock*> I = idf_begin(Roots[i]),
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E = idf_end(Roots[i]); I != E; ++I) {
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BasicBlock *BB = *I;
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const DominatorSet::DomSetType &Dominators = DS.getDominators(BB);
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unsigned DomSetSize = Dominators.size();
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if (DomSetSize == 1) continue; // Root node... IDom = null
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// If we have already computed the immediate dominator for this node,
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// don't revisit. This can happen due to nodes reachable from multiple
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// roots, but which the idf_iterator doesn't know about.
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if (Nodes.find(BB) != Nodes.end()) continue;
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|
||||
// Loop over all dominators of this node. This corresponds to looping
|
||||
// over nodes in the dominator chain, looking for a node whose dominator
|
||||
// set is equal to the current nodes, except that the current node does
|
||||
// not exist in it. This means that it is one level higher in the dom
|
||||
// chain than the current node, and it is our idom! We know that we have
|
||||
// already added a DominatorTree node for our idom, because the idom must
|
||||
// be a predecessor in the depth first order that we are iterating through
|
||||
// the function.
|
||||
//
|
||||
for (DominatorSet::DomSetType::const_iterator I = Dominators.begin(),
|
||||
E = Dominators.end(); I != E; ++I) { // Iterate over dominators.
|
||||
// All of our dominators should form a chain, where the number
|
||||
// of elements in the dominator set indicates what level the
|
||||
// node is at in the chain. We want the node immediately
|
||||
// above us, so it will have an identical dominator set,
|
||||
// except that BB will not dominate it... therefore it's
|
||||
// dominator set size will be one less than BB's...
|
||||
//
|
||||
if (DS.getDominators(*I).size() == DomSetSize - 1) {
|
||||
// We know that the immediate dominator should already have a node,
|
||||
// because we are traversing the CFG in depth first order!
|
||||
//
|
||||
Node *IDomNode = Nodes[*I];
|
||||
assert(IDomNode && "No node for IDOM?");
|
||||
|
||||
// Add a new tree node for this BasicBlock, and link it as a child of
|
||||
// IDomNode
|
||||
Nodes[BB] = IDomNode->addChild(new Node(BB, IDomNode));
|
||||
break;
|
||||
}
|
||||
Nodes[Root] = RootNode = new Node(Root, 0);
|
||||
|
||||
Function *F = Roots[0]->getParent();
|
||||
// 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 = IPD.get(I)) { // Reachable block.
|
||||
Node *&BBNode = Nodes[I];
|
||||
if (!BBNode) { // Haven't calculated this node yet?
|
||||
// Get or calculate the node for the immediate dominator
|
||||
Node *IPDomNode = getNodeForBlock(ImmPostDom);
|
||||
|
||||
// Add a new tree node for this BasicBlock, and link it as a child of
|
||||
// IDomNode
|
||||
BBNode = IPDomNode->addChild(new Node(I, IPDomNode));
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
//===----------------------------------------------------------------------===//
|
||||
// PostETForest Implementation
|
||||
//===----------------------------------------------------------------------===//
|
||||
|
|
Loading…
Reference in New Issue