-//===- LoopInfo.cpp - Natural Loop Calculator -------------------------------=//
+//===- LoopInfo.cpp - Natural Loop Calculator -----------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
//
// This file defines the LoopInfo class that is used to identify natural loops
// and determine the loop depth of various nodes of the CFG. Note that the
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Constants.h"
+#include "llvm/Instructions.h"
#include "llvm/Analysis/Dominators.h"
-#include "llvm/Support/CFG.h"
#include "llvm/Assembly/Writer.h"
-#include "Support/DepthFirstIterator.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/Support/Streams.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SmallPtrSet.h"
#include <algorithm>
+#include <ostream>
+using namespace llvm;
-static RegisterAnalysis<LoopInfo>
-X("loops", "Natural Loop Construction", true);
+char LoopInfo::ID = 0;
+static RegisterPass<LoopInfo>
+X("loops", "Natural Loop Construction", true, true);
//===----------------------------------------------------------------------===//
// Loop implementation
//
-bool Loop::contains(const BasicBlock *BB) const {
- return find(Blocks.begin(), Blocks.end(), BB) != Blocks.end();
-}
-
-bool Loop::isLoopExit(const BasicBlock *BB) const {
- for (BasicBlock::succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB);
- SI != SE; ++SI) {
- if (! contains(*SI))
- return true;
- }
- return false;
-}
-
-unsigned Loop::getNumBackEdges() const {
- unsigned numBackEdges = 0;
- BasicBlock *header = Blocks.front();
-
- for (std::vector<BasicBlock*>::const_iterator I = Blocks.begin(),
- E = Blocks.end(); I != E; ++I) {
- for (BasicBlock::succ_iterator SI = succ_begin(*I), SE = succ_end(*I);
- SI != SE; ++SI)
- if (header == *SI)
- ++numBackEdges;
- }
- return numBackEdges;
-}
-void Loop::print(std::ostream &OS) const {
- OS << std::string(getLoopDepth()*2, ' ') << "Loop Containing: ";
-
- for (unsigned i = 0; i < getBlocks().size(); ++i) {
- if (i) OS << ",";
- WriteAsOperand(OS, (const Value*)getBlocks()[i]);
- }
- OS << "\n";
-
- for (unsigned i = 0, e = getSubLoops().size(); i != e; ++i)
- getSubLoops()[i]->print(OS);
-}
+/// getNumBackEdges - Calculate the number of back edges to the loop header.
+///
//===----------------------------------------------------------------------===//
// LoopInfo implementation
//
-void LoopInfo::stub() {}
-
bool LoopInfo::runOnFunction(Function &) {
releaseMemory();
- Calculate(getAnalysis<DominatorSet>()); // Update
+ LI->Calculate(getAnalysis<DominatorTree>().getBase()); // Update
return false;
}
-void LoopInfo::releaseMemory() {
- for (std::vector<Loop*>::iterator I = TopLevelLoops.begin(),
- E = TopLevelLoops.end(); I != E; ++I)
- delete *I; // Delete all of the loops...
-
- BBMap.clear(); // Reset internal state of analysis
- TopLevelLoops.clear();
-}
-
-
-void LoopInfo::Calculate(const DominatorSet &DS) {
- BasicBlock *RootNode = DS.getRoot();
-
- for (df_iterator<BasicBlock*> NI = df_begin(RootNode),
- NE = df_end(RootNode); NI != NE; ++NI)
- if (Loop *L = ConsiderForLoop(*NI, DS))
- TopLevelLoops.push_back(L);
-
- for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
- TopLevelLoops[i]->setLoopDepth(1);
-}
-
void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
- AU.addRequired<DominatorSet>();
-}
-
-void LoopInfo::print(std::ostream &OS) const {
- for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
- TopLevelLoops[i]->print(OS);
-}
-
-Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) {
- if (BBMap.find(BB) != BBMap.end()) return 0; // Haven't processed this node?
-
- std::vector<BasicBlock *> TodoStack;
-
- // Scan the predecessors of BB, checking to see if BB dominates any of
- // them.
- for (pred_iterator I = pred_begin(BB), E = pred_end(BB); I != E; ++I)
- if (DS.dominates(BB, *I)) // If BB dominates it's predecessor...
- TodoStack.push_back(*I);
-
- if (TodoStack.empty()) return 0; // Doesn't dominate any predecessors...
-
- // Create a new loop to represent this basic block...
- Loop *L = new Loop(BB);
- BBMap[BB] = L;
-
- while (!TodoStack.empty()) { // Process all the nodes in the loop
- BasicBlock *X = TodoStack.back();
- TodoStack.pop_back();
-
- if (!L->contains(X)) { // As of yet unprocessed??
- L->Blocks.push_back(X);
-
- // Add all of the predecessors of X to the end of the work stack...
- TodoStack.insert(TodoStack.end(), pred_begin(X), pred_end(X));
- }
- }
-
- // Add the basic blocks that comprise this loop to the BBMap so that this
- // loop can be found for them. Also check subsidary basic blocks to see if
- // they start subloops of their own.
- //
- for (std::vector<BasicBlock*>::reverse_iterator I = L->Blocks.rbegin(),
- E = L->Blocks.rend(); I != E; ++I)
-
- // Check to see if this block starts a new loop
- if (*I != BB)
- if (Loop *NewLoop = ConsiderForLoop(*I, DS)) {
- L->SubLoops.push_back(NewLoop);
- NewLoop->ParentLoop = L;
- } else {
- std::map<BasicBlock*, Loop*>::iterator BBMI = BBMap.lower_bound(*I);
- if (BBMI == BBMap.end() || BBMI->first != *I) { // Not in map yet...
- BBMap.insert(BBMI, std::make_pair(*I, L));
- } else {
- // If this is already in the BBMap then this means that we already added
- // a loop for it, but incorrectly added the loop to a higher level loop
- // instead of the current loop we are creating. Fix this now by moving
- // the loop into the correct subloop.
- //
- Loop *SubLoop = BBMI->second;
- Loop *OldSubLoopParent = SubLoop->getParentLoop();
- if (OldSubLoopParent != L) {
- // Remove SubLoop from OldSubLoopParent's list of subloops...
- std::vector<Loop*>::iterator I =
- std::find(OldSubLoopParent->SubLoops.begin(),
- OldSubLoopParent->SubLoops.end(), SubLoop);
- assert(I != OldSubLoopParent->SubLoops.end()
- && "Loop parent doesn't contain loop?");
- OldSubLoopParent->SubLoops.erase(I);
- SubLoop->ParentLoop = L;
- L->SubLoops.push_back(SubLoop);
- }
- }
- }
-
- return L;
-}
-
-/// getLoopPreheader - If there is a preheader for this loop, return it. A
-/// loop has a preheader if there is only one edge to the header of the loop
-/// from outside of the loop. If this is the case, the block branching to the
-/// header of the loop is the preheader node. The "preheaders" pass can be
-/// "Required" to ensure that there is always a preheader node for every loop.
-///
-/// This method returns null if there is no preheader for the loop (either
-/// because the loop is dead or because multiple blocks branch to the header
-/// node of this loop).
-///
-BasicBlock *Loop::getLoopPreheader() const {
- // Keep track of nodes outside the loop branching to the header...
- BasicBlock *Out = 0;
-
- // Loop over the predecessors of the header node...
- BasicBlock *Header = getHeader();
- for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
- PI != PE; ++PI)
- if (!contains(*PI)) { // If the block is not in the loop...
- if (Out && Out != *PI)
- return 0; // Multiple predecessors outside the loop
- Out = *PI;
- }
-
- // If there is exactly one preheader, return it. If there was zero, then Out
- // is still null.
- return Out;
-}
-
-/// addBasicBlockToLoop - This function is used by other analyses to update loop
-/// information. NewBB is set to be a new member of the current loop. Because
-/// of this, it is added as a member of all parent loops, and is added to the
-/// specified LoopInfo object as being in the current basic block. It is not
-/// valid to replace the loop header with this method.
-///
-void Loop::addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI) {
- assert(LI[getHeader()] == this && "Incorrect LI specified for this loop!");
- assert(NewBB && "Cannot add a null basic block to the loop!");
- assert(LI[NewBB] == 0 && "BasicBlock already in the loop!");
-
- // Add the loop mapping to the LoopInfo object...
- LI.BBMap[NewBB] = this;
-
- // Add the basic block to this loop and all parent loops...
- Loop *L = this;
- while (L) {
- L->Blocks.push_back(NewBB);
- L = L->getParentLoop();
- }
+ AU.addRequired<DominatorTree>();
}