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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206730 91177308-0d34-0410-b5e6-96231b3b80d8
280 lines
10 KiB
C++
280 lines
10 KiB
C++
//===- LazyCallGraph.cpp - Analysis of a Module's call graph --------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "lcg"
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#include "llvm/Analysis/LazyCallGraph.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/IR/CallSite.h"
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#include "llvm/IR/InstVisitor.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/PassManager.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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static void findCallees(
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SmallVectorImpl<Constant *> &Worklist, SmallPtrSetImpl<Constant *> &Visited,
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SmallVectorImpl<PointerUnion<Function *, LazyCallGraph::Node *>> &Callees,
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SmallPtrSetImpl<Function *> &CalleeSet) {
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while (!Worklist.empty()) {
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Constant *C = Worklist.pop_back_val();
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if (Function *F = dyn_cast<Function>(C)) {
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// Note that we consider *any* function with a definition to be a viable
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// edge. Even if the function's definition is subject to replacement by
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// some other module (say, a weak definition) there may still be
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// optimizations which essentially speculate based on the definition and
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// a way to check that the specific definition is in fact the one being
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// used. For example, this could be done by moving the weak definition to
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// a strong (internal) definition and making the weak definition be an
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// alias. Then a test of the address of the weak function against the new
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// strong definition's address would be an effective way to determine the
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// safety of optimizing a direct call edge.
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if (!F->isDeclaration() && CalleeSet.insert(F)) {
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DEBUG(dbgs() << " Added callable function: " << F->getName()
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<< "\n");
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Callees.push_back(F);
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}
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continue;
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}
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for (Value *Op : C->operand_values())
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if (Visited.insert(cast<Constant>(Op)))
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Worklist.push_back(cast<Constant>(Op));
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}
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}
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LazyCallGraph::Node::Node(LazyCallGraph &G, Function &F)
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: G(&G), F(F), DFSNumber(0), LowLink(0) {
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DEBUG(dbgs() << " Adding functions called by '" << F.getName()
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<< "' to the graph.\n");
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SmallVector<Constant *, 16> Worklist;
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SmallPtrSet<Constant *, 16> Visited;
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// Find all the potential callees in this function. First walk the
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// instructions and add every operand which is a constant to the worklist.
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for (BasicBlock &BB : F)
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for (Instruction &I : BB)
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for (Value *Op : I.operand_values())
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if (Constant *C = dyn_cast<Constant>(Op))
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if (Visited.insert(C))
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Worklist.push_back(C);
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// We've collected all the constant (and thus potentially function or
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// function containing) operands to all of the instructions in the function.
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// Process them (recursively) collecting every function found.
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findCallees(Worklist, Visited, Callees, CalleeSet);
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}
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LazyCallGraph::LazyCallGraph(Module &M) : NextDFSNumber(0) {
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DEBUG(dbgs() << "Building CG for module: " << M.getModuleIdentifier()
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<< "\n");
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for (Function &F : M)
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if (!F.isDeclaration() && !F.hasLocalLinkage())
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if (EntryNodeSet.insert(&F)) {
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DEBUG(dbgs() << " Adding '" << F.getName()
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<< "' to entry set of the graph.\n");
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EntryNodes.push_back(&F);
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}
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// Now add entry nodes for functions reachable via initializers to globals.
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SmallVector<Constant *, 16> Worklist;
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SmallPtrSet<Constant *, 16> Visited;
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for (GlobalVariable &GV : M.globals())
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if (GV.hasInitializer())
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if (Visited.insert(GV.getInitializer()))
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Worklist.push_back(GV.getInitializer());
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DEBUG(dbgs() << " Adding functions referenced by global initializers to the "
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"entry set.\n");
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findCallees(Worklist, Visited, EntryNodes, EntryNodeSet);
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for (auto &Entry : EntryNodes)
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if (Function *F = Entry.dyn_cast<Function *>())
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SCCEntryNodes.insert(F);
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else
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SCCEntryNodes.insert(&Entry.get<Node *>()->getFunction());
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}
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LazyCallGraph::LazyCallGraph(LazyCallGraph &&G)
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: BPA(std::move(G.BPA)), NodeMap(std::move(G.NodeMap)),
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EntryNodes(std::move(G.EntryNodes)),
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EntryNodeSet(std::move(G.EntryNodeSet)), SCCBPA(std::move(G.SCCBPA)),
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SCCMap(std::move(G.SCCMap)), LeafSCCs(std::move(G.LeafSCCs)),
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DFSStack(std::move(G.DFSStack)),
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SCCEntryNodes(std::move(G.SCCEntryNodes)),
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NextDFSNumber(G.NextDFSNumber) {
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updateGraphPtrs();
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}
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LazyCallGraph &LazyCallGraph::operator=(LazyCallGraph &&G) {
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BPA = std::move(G.BPA);
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NodeMap = std::move(G.NodeMap);
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EntryNodes = std::move(G.EntryNodes);
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EntryNodeSet = std::move(G.EntryNodeSet);
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SCCBPA = std::move(G.SCCBPA);
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SCCMap = std::move(G.SCCMap);
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LeafSCCs = std::move(G.LeafSCCs);
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DFSStack = std::move(G.DFSStack);
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SCCEntryNodes = std::move(G.SCCEntryNodes);
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NextDFSNumber = G.NextDFSNumber;
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updateGraphPtrs();
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return *this;
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}
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LazyCallGraph::Node *LazyCallGraph::insertInto(Function &F, Node *&MappedN) {
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return new (MappedN = BPA.Allocate()) Node(*this, F);
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}
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void LazyCallGraph::updateGraphPtrs() {
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// Process all nodes updating the graph pointers.
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SmallVector<Node *, 16> Worklist;
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for (auto &Entry : EntryNodes)
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if (Node *EntryN = Entry.dyn_cast<Node *>())
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Worklist.push_back(EntryN);
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while (!Worklist.empty()) {
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Node *N = Worklist.pop_back_val();
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N->G = this;
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for (auto &Callee : N->Callees)
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if (Node *CalleeN = Callee.dyn_cast<Node *>())
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Worklist.push_back(CalleeN);
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}
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}
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LazyCallGraph::SCC *LazyCallGraph::getNextSCCInPostOrder() {
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// When the stack is empty, there are no more SCCs to walk in this graph.
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if (DFSStack.empty()) {
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// If we've handled all candidate entry nodes to the SCC forest, we're done.
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if (SCCEntryNodes.empty())
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return nullptr;
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Node *N = get(*SCCEntryNodes.pop_back_val());
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DFSStack.push_back(std::make_pair(N, N->begin()));
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}
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Node *N = DFSStack.back().first;
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if (N->DFSNumber == 0) {
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// This node hasn't been visited before, assign it a DFS number and remove
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// it from the entry set.
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N->LowLink = N->DFSNumber = NextDFSNumber++;
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SCCEntryNodes.remove(&N->getFunction());
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}
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for (auto I = DFSStack.back().second, E = N->end(); I != E; ++I) {
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Node *ChildN = *I;
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if (ChildN->DFSNumber == 0) {
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// Mark that we should start at this child when next this node is the
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// top of the stack. We don't start at the next child to ensure this
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// child's lowlink is reflected.
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// FIXME: I don't actually think this is required, and we could start
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// at the next child.
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DFSStack.back().second = I;
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// Recurse onto this node via a tail call.
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DFSStack.push_back(std::make_pair(ChildN, ChildN->begin()));
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return LazyCallGraph::getNextSCCInPostOrder();
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}
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// Track the lowest link of the childen, if any are still in the stack.
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if (ChildN->LowLink < N->LowLink && !SCCMap.count(&ChildN->getFunction()))
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N->LowLink = ChildN->LowLink;
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}
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// The tail of the stack is the new SCC. Allocate the SCC and pop the stack
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// into it.
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SCC *NewSCC = new (SCCBPA.Allocate()) SCC();
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// Because we don't follow the strict Tarjan recursive formulation, walk
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// from the top of the stack down, propagating the lowest link and stopping
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// when the DFS number is the lowest link.
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int LowestLink = N->LowLink;
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do {
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Node *SCCN = DFSStack.pop_back_val().first;
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SCCMap.insert(std::make_pair(&SCCN->getFunction(), NewSCC));
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NewSCC->Nodes.push_back(SCCN);
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LowestLink = std::min(LowestLink, SCCN->LowLink);
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bool Inserted =
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NewSCC->NodeSet.insert(&SCCN->getFunction());
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(void)Inserted;
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assert(Inserted && "Cannot have duplicates in the DFSStack!");
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} while (!DFSStack.empty() && LowestLink <= DFSStack.back().first->DFSNumber);
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assert(LowestLink == NewSCC->Nodes.back()->DFSNumber &&
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"Cannot stop with a DFS number greater than the lowest link!");
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// A final pass over all edges in the SCC (this remains linear as we only
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// do this once when we build the SCC) to connect it to the parent sets of
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// its children.
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bool IsLeafSCC = true;
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for (Node *SCCN : NewSCC->Nodes)
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for (Node *SCCChildN : *SCCN) {
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if (NewSCC->NodeSet.count(&SCCChildN->getFunction()))
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continue;
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SCC *ChildSCC = SCCMap.lookup(&SCCChildN->getFunction());
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assert(ChildSCC &&
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"Must have all child SCCs processed when building a new SCC!");
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ChildSCC->ParentSCCs.insert(NewSCC);
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IsLeafSCC = false;
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}
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// For the SCCs where we fine no child SCCs, add them to the leaf list.
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if (IsLeafSCC)
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LeafSCCs.push_back(NewSCC);
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return NewSCC;
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}
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char LazyCallGraphAnalysis::PassID;
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LazyCallGraphPrinterPass::LazyCallGraphPrinterPass(raw_ostream &OS) : OS(OS) {}
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static void printNodes(raw_ostream &OS, LazyCallGraph::Node &N,
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SmallPtrSetImpl<LazyCallGraph::Node *> &Printed) {
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// Recurse depth first through the nodes.
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for (LazyCallGraph::Node *ChildN : N)
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if (Printed.insert(ChildN))
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printNodes(OS, *ChildN, Printed);
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OS << " Call edges in function: " << N.getFunction().getName() << "\n";
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for (LazyCallGraph::iterator I = N.begin(), E = N.end(); I != E; ++I)
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OS << " -> " << I->getFunction().getName() << "\n";
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OS << "\n";
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}
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static void printSCC(raw_ostream &OS, LazyCallGraph::SCC &SCC) {
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ptrdiff_t SCCSize = std::distance(SCC.begin(), SCC.end());
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OS << " SCC with " << SCCSize << " functions:\n";
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for (LazyCallGraph::Node *N : SCC)
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OS << " " << N->getFunction().getName() << "\n";
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OS << "\n";
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}
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PreservedAnalyses LazyCallGraphPrinterPass::run(Module *M,
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ModuleAnalysisManager *AM) {
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LazyCallGraph &G = AM->getResult<LazyCallGraphAnalysis>(M);
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OS << "Printing the call graph for module: " << M->getModuleIdentifier()
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<< "\n\n";
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SmallPtrSet<LazyCallGraph::Node *, 16> Printed;
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for (LazyCallGraph::Node *N : G)
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if (Printed.insert(N))
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printNodes(OS, *N, Printed);
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for (LazyCallGraph::SCC *SCC : G.postorder_sccs())
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printSCC(OS, *SCC);
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return PreservedAnalyses::all();
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}
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