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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. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26707 91177308-0d34-0410-b5e6-96231b3b80d8
366 lines
13 KiB
C++
366 lines
13 KiB
C++
//===- PostDominators.cpp - Post-Dominator Calculation --------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the post-dominator construction algorithms.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/PostDominators.h"
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#include "llvm/Instructions.h"
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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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static RegisterAnalysis<PostDominatorSet>
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B("postdomset", "Post-Dominator Set Construction", true);
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// Postdominator set construction. This converts the specified function to only
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// have a single exit node (return stmt), then calculates the post dominance
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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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// 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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if (succ_begin(I) == succ_end(I))
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Roots.push_back(I);
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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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// 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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// 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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DS.insert(IPDom);
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IPDom = IPD[IPDom];
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}
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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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return false;
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}
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//===----------------------------------------------------------------------===//
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// PostDominatorTree Implementation
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//===----------------------------------------------------------------------===//
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static RegisterAnalysis<PostDominatorTree>
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F("postdomtree", "Post-Dominator Tree Construction", true);
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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);
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Function *F = Roots[0]->getParent();
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// Loop over all of the reachable blocks in the function...
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for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I)
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if (BasicBlock *ImmPostDom = IPD.get(I)) { // Reachable block.
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Node *&BBNode = Nodes[I];
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if (!BBNode) { // Haven't calculated this node yet?
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// Get or calculate the node for the immediate dominator
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Node *IPDomNode = getNodeForBlock(ImmPostDom);
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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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BBNode = IPDomNode->addChild(new Node(I, IPDomNode));
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}
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}
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}
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//===----------------------------------------------------------------------===//
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// PostETForest Implementation
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//===----------------------------------------------------------------------===//
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static RegisterAnalysis<PostETForest>
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G("postetforest", "Post-ET-Forest Construction", true);
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ETNode *PostETForest::getNodeForBlock(BasicBlock *BB) {
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ETNode *&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 dominator.
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BasicBlock *IDom = getAnalysis<ImmediatePostDominators>()[BB];
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// If we are unreachable, we may not have an immediate dominator.
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if (!IDom)
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return BBNode = new ETNode(BB);
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else {
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ETNode *IDomNode = getNodeForBlock(IDom);
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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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BBNode = new ETNode(BB);
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BBNode->setFather(IDomNode);
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return BBNode;
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}
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}
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void PostETForest::calculate(const ImmediatePostDominators &ID) {
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for (unsigned i = 0, e = Roots.size(); i != e; ++i)
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Nodes[Roots[i]] = new ETNode(Roots[i]); // Add a node for the root
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// Iterate over all nodes in inverse 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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ETNode *&BBNode = Nodes[BB];
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if (!BBNode) {
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ETNode *IDomNode = NULL;
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if (ID.get(BB))
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IDomNode = getNodeForBlock(ID.get(BB));
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// Add a new ETNode for this BasicBlock, and set it's parent
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// to it's immediate dominator.
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BBNode = new ETNode(BB);
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if (IDomNode)
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BBNode->setFather(IDomNode);
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}
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}
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int dfsnum = 0;
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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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if (!getNodeForBlock(*I)->hasFather())
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getNodeForBlock(*I)->assignDFSNumber(dfsnum);
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}
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DFSInfoValid = true;
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}
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//===----------------------------------------------------------------------===//
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// PostDominanceFrontier Implementation
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//===----------------------------------------------------------------------===//
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static RegisterAnalysis<PostDominanceFrontier>
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H("postdomfrontier", "Post-Dominance Frontier Construction", true);
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const DominanceFrontier::DomSetType &
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PostDominanceFrontier::calculate(const PostDominatorTree &DT,
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const DominatorTree::Node *Node) {
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// Loop over CFG successors to calculate DFlocal[Node]
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BasicBlock *BB = Node->getBlock();
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DomSetType &S = Frontiers[BB]; // The new set to fill in...
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if (getRoots().empty()) return S;
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if (BB)
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for (pred_iterator SI = pred_begin(BB), SE = pred_end(BB);
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SI != SE; ++SI)
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// Does Node immediately dominate this predecessor?
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if (DT[*SI]->getIDom() != Node)
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S.insert(*SI);
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// At this point, S is DFlocal. Now we union in DFup's of our children...
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// Loop through and visit the nodes that Node immediately dominates (Node's
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// children in the IDomTree)
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//
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for (PostDominatorTree::Node::const_iterator
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NI = Node->begin(), NE = Node->end(); NI != NE; ++NI) {
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DominatorTree::Node *IDominee = *NI;
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const DomSetType &ChildDF = calculate(DT, IDominee);
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DomSetType::const_iterator CDFI = ChildDF.begin(), CDFE = ChildDF.end();
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for (; CDFI != CDFE; ++CDFI) {
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if (!Node->properlyDominates(DT[*CDFI]))
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S.insert(*CDFI);
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}
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}
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return S;
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}
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// stub - a dummy function to make linking work ok.
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void PostDominanceFrontier::stub() {
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}
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