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https://github.com/c64scene-ar/llvm-6502.git
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91bd25d9df
Naveen Neelakantam, thanks! git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21543 91177308-0d34-0410-b5e6-96231b3b80d8
474 lines
15 KiB
C++
474 lines
15 KiB
C++
//===- Dominators.cpp - 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 simple dominator construction algorithms for finding
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// forward dominators. Postdominators are available in libanalysis, but are not
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// included in libvmcore, because it's not needed. Forward dominators are
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// needed to support the Verifier pass.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Assembly/Writer.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/SetOperations.h"
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#include <algorithm>
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using namespace llvm;
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//===----------------------------------------------------------------------===//
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// ImmediateDominators Implementation
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//===----------------------------------------------------------------------===//
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//
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// Immediate Dominators construction - This pass constructs immediate dominator
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// information for a flow-graph based on the algorithm described in this
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// document:
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//
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// A Fast Algorithm for Finding Dominators in a Flowgraph
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// T. Lengauer & R. Tarjan, ACM TOPLAS July 1979, pgs 121-141.
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//
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// This implements both the O(n*ack(n)) and the O(n*log(n)) versions of EVAL and
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// LINK, but it turns out that the theoretically slower O(n*log(n))
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// implementation is actually faster than the "efficient" algorithm (even for
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// large CFGs) because the constant overheads are substantially smaller. The
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// lower-complexity version can be enabled with the following #define:
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//
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#define BALANCE_IDOM_TREE 0
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//
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//===----------------------------------------------------------------------===//
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static RegisterAnalysis<ImmediateDominators>
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C("idom", "Immediate Dominators Construction", true);
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unsigned ImmediateDominators::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 (succ_iterator SI = succ_begin(V), E = succ_end(V); SI != E; ++SI) {
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InfoRec &SuccVInfo = Info[*SI];
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if (SuccVInfo.Semi == 0) {
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SuccVInfo.Parent = V;
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N = DFSPass(*SI, 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 ImmediateDominators::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 *ImmediateDominators::Eval(BasicBlock *V) {
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InfoRec &VInfo = Info[V];
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#if !BALANCE_IDOM_TREE
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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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#else
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// Lower-complexity but slower implementation
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if (VInfo.Ancestor == 0)
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return VInfo.Label;
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Compress(V, VInfo);
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BasicBlock *VLabel = VInfo.Label;
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BasicBlock *VAncestorLabel = Info[VInfo.Ancestor].Label;
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if (Info[VAncestorLabel].Semi >= Info[VLabel].Semi)
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return VLabel;
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else
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return VAncestorLabel;
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#endif
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}
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void ImmediateDominators::Link(BasicBlock *V, BasicBlock *W, InfoRec &WInfo){
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#if !BALANCE_IDOM_TREE
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// Higher-complexity but faster implementation
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WInfo.Ancestor = V;
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#else
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// Lower-complexity but slower implementation
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BasicBlock *WLabel = WInfo.Label;
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unsigned WLabelSemi = Info[WLabel].Semi;
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BasicBlock *S = W;
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InfoRec *SInfo = &Info[S];
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BasicBlock *SChild = SInfo->Child;
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InfoRec *SChildInfo = &Info[SChild];
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while (WLabelSemi < Info[SChildInfo->Label].Semi) {
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BasicBlock *SChildChild = SChildInfo->Child;
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if (SInfo->Size+Info[SChildChild].Size >= 2*SChildInfo->Size) {
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SChildInfo->Ancestor = S;
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SInfo->Child = SChild = SChildChild;
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SChildInfo = &Info[SChild];
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} else {
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SChildInfo->Size = SInfo->Size;
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S = SInfo->Ancestor = SChild;
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SInfo = SChildInfo;
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SChild = SChildChild;
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SChildInfo = &Info[SChild];
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}
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}
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InfoRec &VInfo = Info[V];
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SInfo->Label = WLabel;
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assert(V != W && "The optimization here will not work in this case!");
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unsigned WSize = WInfo.Size;
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unsigned VSize = (VInfo.Size += WSize);
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if (VSize < 2*WSize)
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std::swap(S, VInfo.Child);
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while (S) {
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SInfo = &Info[S];
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SInfo->Ancestor = V;
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S = SInfo->Child;
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}
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#endif
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}
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bool ImmediateDominators::runOnFunction(Function &F) {
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IDoms.clear(); // Reset from the last time we were run...
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BasicBlock *Root = &F.getEntryBlock();
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Roots.clear();
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Roots.push_back(Root);
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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]], 0);
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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 (pred_iterator PI = pred_begin(W), E = pred_end(W); PI != E; ++PI)
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if (Info.count(*PI)) { // Only if this predecessor is reachable!
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unsigned SemiU = Info[Eval(*PI)].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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void ImmediateDominatorsBase::print(std::ostream &o, const Module* ) const {
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Function *F = getRoots()[0]->getParent();
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for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
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o << " Immediate Dominator For Basic Block:";
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WriteAsOperand(o, I, false);
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o << " is:";
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if (BasicBlock *ID = get(I))
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WriteAsOperand(o, ID, false);
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else
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o << " <<exit node>>";
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o << "\n";
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}
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o << "\n";
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}
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//===----------------------------------------------------------------------===//
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// DominatorSet Implementation
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//===----------------------------------------------------------------------===//
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static RegisterAnalysis<DominatorSet>
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B("domset", "Dominator Set Construction", true);
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// dominates - Return true if A dominates B. This performs the special checks
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// necessary if A and B are in the same basic block.
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//
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bool DominatorSetBase::dominates(Instruction *A, Instruction *B) const {
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BasicBlock *BBA = A->getParent(), *BBB = B->getParent();
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if (BBA != BBB) return dominates(BBA, BBB);
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// Loop through the basic block until we find A or B.
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BasicBlock::iterator I = BBA->begin();
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for (; &*I != A && &*I != B; ++I) /*empty*/;
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if(!IsPostDominators) {
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// A dominates B if it is found first in the basic block.
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return &*I == A;
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} else {
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// A post-dominates B if B is found first in the basic block.
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return &*I == B;
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}
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}
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// runOnFunction - This method calculates the forward dominator sets for the
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// specified function.
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//
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bool DominatorSet::runOnFunction(Function &F) {
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BasicBlock *Root = &F.getEntryBlock();
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Roots.clear();
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Roots.push_back(Root);
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assert(pred_begin(Root) == pred_end(Root) &&
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"Root node has predecessors in function!");
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ImmediateDominators &ID = getAnalysis<ImmediateDominators>();
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Doms.clear();
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if (Roots.empty()) return 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 *IDom = ID[I]) { // Get idom if block is reachable
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DomSetType &DS = Doms[I];
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assert(DS.empty() && "Domset 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 (IDom) {
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// If we have already computed the dominator sets for our immediate
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// dominator, just use it instead of walking all the way up to the root.
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DomSetType &IDS = Doms[IDom];
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if (!IDS.empty()) {
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DS.insert(IDS.begin(), IDS.end());
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break;
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} else {
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DS.insert(IDom);
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IDom = ID[IDom];
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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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void DominatorSet::stub() {}
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namespace llvm {
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static std::ostream &operator<<(std::ostream &o,
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const std::set<BasicBlock*> &BBs) {
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for (std::set<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
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I != E; ++I)
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if (*I)
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WriteAsOperand(o, *I, false);
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else
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o << " <<exit node>>";
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return o;
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}
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}
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void DominatorSetBase::print(std::ostream &o, const Module* ) const {
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for (const_iterator I = begin(), E = end(); I != E; ++I) {
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o << " DomSet For BB: ";
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if (I->first)
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WriteAsOperand(o, I->first, false);
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else
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o << " <<exit node>>";
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o << " is:\t" << I->second << "\n";
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}
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}
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//===----------------------------------------------------------------------===//
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// DominatorTree Implementation
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//===----------------------------------------------------------------------===//
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static RegisterAnalysis<DominatorTree>
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E("domtree", "Dominator Tree Construction", true);
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// DominatorTreeBase::reset - Free all of the tree node memory.
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//
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void DominatorTreeBase::reset() {
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for (NodeMapType::iterator I = Nodes.begin(), E = Nodes.end(); I != E; ++I)
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delete I->second;
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Nodes.clear();
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RootNode = 0;
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}
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void DominatorTreeBase::Node::setIDom(Node *NewIDom) {
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assert(IDom && "No immediate dominator?");
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if (IDom != NewIDom) {
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std::vector<Node*>::iterator I =
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std::find(IDom->Children.begin(), IDom->Children.end(), this);
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assert(I != IDom->Children.end() &&
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"Not in immediate dominator children set!");
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// I am no longer your child...
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IDom->Children.erase(I);
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// Switch to new dominator
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IDom = NewIDom;
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IDom->Children.push_back(this);
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}
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}
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DominatorTreeBase::Node *DominatorTree::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 dominator.
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BasicBlock *IDom = getAnalysis<ImmediateDominators>()[BB];
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Node *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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return BBNode = IDomNode->addChild(new Node(BB, IDomNode));
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}
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void DominatorTree::calculate(const ImmediateDominators &ID) {
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assert(Roots.size() == 1 && "DominatorTree should have 1 root block!");
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BasicBlock *Root = Roots[0];
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Nodes[Root] = RootNode = new Node(Root, 0); // Add a node for the root...
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Function *F = Root->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 *ImmDom = ID.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 *IDomNode = getNodeForBlock(ImmDom);
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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 = IDomNode->addChild(new Node(I, IDomNode));
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}
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}
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}
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static std::ostream &operator<<(std::ostream &o,
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const DominatorTreeBase::Node *Node) {
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if (Node->getBlock())
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WriteAsOperand(o, Node->getBlock(), false);
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else
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o << " <<exit node>>";
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return o << "\n";
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}
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static void PrintDomTree(const DominatorTreeBase::Node *N, std::ostream &o,
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unsigned Lev) {
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o << std::string(2*Lev, ' ') << "[" << Lev << "] " << N;
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for (DominatorTreeBase::Node::const_iterator I = N->begin(), E = N->end();
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I != E; ++I)
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PrintDomTree(*I, o, Lev+1);
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}
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void DominatorTreeBase::print(std::ostream &o, const Module* ) const {
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o << "=============================--------------------------------\n"
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<< "Inorder Dominator Tree:\n";
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PrintDomTree(getRootNode(), o, 1);
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}
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//===----------------------------------------------------------------------===//
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// DominanceFrontier Implementation
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//===----------------------------------------------------------------------===//
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static RegisterAnalysis<DominanceFrontier>
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G("domfrontier", "Dominance Frontier Construction", true);
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const DominanceFrontier::DomSetType &
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DominanceFrontier::calculate(const DominatorTree &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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for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
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SI != SE; ++SI) {
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// Does Node immediately dominate this successor?
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if (DT[*SI]->getIDom() != Node)
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S.insert(*SI);
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}
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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 (DominatorTree::Node::const_iterator NI = Node->begin(), NE = Node->end();
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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->dominates(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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void DominanceFrontierBase::print(std::ostream &o, const Module* ) const {
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for (const_iterator I = begin(), E = end(); I != E; ++I) {
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o << " DomFrontier for BB";
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if (I->first)
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WriteAsOperand(o, I->first, false);
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else
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o << " <<exit node>>";
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o << " is:\t" << I->second << "\n";
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}
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}
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