#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Support/CFG.h"
+#include "llvm/Assembly/Writer.h"
#include "Support/DepthFirstIterator.h"
#include <algorithm>
-AnalysisID LoopInfo::ID(AnalysisID::create<LoopInfo>());
+static RegisterAnalysis<LoopInfo>
+X("loops", "Natural Loop Construction", true);
//===----------------------------------------------------------------------===//
// Loop implementation
//
-bool Loop::contains(BasicBlock *BB) const {
+bool Loop::contains(const BasicBlock *BB) const {
return find(Blocks.begin(), Blocks.end(), BB) != Blocks.end();
}
-void LoopInfo::releaseMemory() {
- for (std::vector<Loop*>::iterator I = TopLevelLoops.begin(),
- E = TopLevelLoops.end(); I != E; ++I)
- delete *I; // Delete all of the loops...
+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;
+}
- BBMap.clear(); // Reset internal state of analysis
- TopLevelLoops.clear();
+unsigned Loop::getNumBackEdges() const {
+ unsigned NumBackEdges = 0;
+ BasicBlock *H = getHeader();
+
+ 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 (*SI == H)
+ ++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, getBlocks()[i], false);
+ }
+ if (!ExitBlocks.empty()) {
+ OS << "\tExitBlocks: ";
+ for (unsigned i = 0; i < getExitBlocks().size(); ++i) {
+ if (i) OS << ",";
+ WriteAsOperand(OS, getExitBlocks()[i], false);
+ }
+ }
+
+ OS << "\n";
+
+ for (unsigned i = 0, e = getSubLoops().size(); i != e; ++i)
+ getSubLoops()[i]->print(OS);
+}
+
+void Loop::dump() const {
+ print(std::cerr);
}
//===----------------------------------------------------------------------===//
// LoopInfo implementation
//
-bool LoopInfo::runOnFunction(Function *F) {
+void LoopInfo::stub() {}
+
+bool LoopInfo::runOnFunction(Function &) {
releaseMemory();
Calculate(getAnalysis<DominatorSet>()); // 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();
void LoopInfo::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
- AU.addRequired(DominatorSet::ID);
- AU.addProvided(ID);
+ AU.addRequired<DominatorSet>();
}
+void LoopInfo::print(std::ostream &OS) const {
+ for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
+ TopLevelLoops[i]->print(OS);
+#if 0
+ for (std::map<BasicBlock*, Loop*>::const_iterator I = BBMap.begin(),
+ E = BBMap.end(); I != E; ++I)
+ OS << "BB '" << I->first->getName() << "' level = "
+ << I->second->LoopDepth << "\n";
+#endif
+}
Loop *LoopInfo::ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS) {
- if (BBMap.find(BB) != BBMap.end()) return 0; // Havn't processed this node?
+ 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.
+ // them. This identifies backedges which target this node...
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...
+ if (TodoStack.empty()) return 0; // No backedges to this block...
// Create a new loop to represent this basic block...
Loop *L = new Loop(BB);
BasicBlock *X = TodoStack.back();
TodoStack.pop_back();
- if (!L->contains(X)) { // As of yet unprocessed??
- L->Blocks.push_back(X);
+ if (!L->contains(X)) { // As of yet unprocessed??
+ // Check to see if this block already belongs to a loop. If this occurs
+ // then we have a case where a loop that is supposed to be a child of the
+ // current loop was processed before the current loop. When this occurs,
+ // this child loop gets added to a part of the current loop, making it a
+ // sibling to the current loop. We have to reparent this loop.
+ if (Loop *SubLoop = const_cast<Loop*>(getLoopFor(X)))
+ if (SubLoop->getHeader() == X && X != BB) {
+ // Remove the subloop from it's current parent...
+ assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
+ Loop *SLP = SubLoop->ParentLoop; // SubLoopParent
+ std::vector<Loop*>::iterator I =
+ std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop);
+ assert(I != SLP->SubLoops.end() && "SubLoop not a child of parent?");
+ SLP->SubLoops.erase(I); // Remove from parent...
+
+ // Add the subloop to THIS loop...
+ SubLoop->ParentLoop = L;
+ L->SubLoops.push_back(SubLoop);
+ }
+ // Normal case, add the block to our loop...
+ 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 there are any loops nested within this loop, create them now!
+ for (std::vector<BasicBlock*>::iterator I = L->Blocks.begin(),
+ E = L->Blocks.end(); I != E; ++I)
if (Loop *NewLoop = ConsiderForLoop(*I, DS)) {
L->SubLoops.push_back(NewLoop);
NewLoop->ParentLoop = L;
}
-
- if (BBMap.find(*I) == BBMap.end())
- BBMap.insert(std::make_pair(*I, L));
+
+
+ // Add the basic blocks that comprise this loop to the BBMap so that this
+ // loop can be found for them.
+ //
+ for (std::vector<BasicBlock*>::iterator I = L->Blocks.begin(),
+ E = L->Blocks.end(); I != E; ++I) {
+ 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)); // Must be at this level
}
+ // Now that we know all of the blocks that make up this loop, see if there are
+ // any branches to outside of the loop... building the ExitBlocks list.
+ for (std::vector<BasicBlock*>::iterator BI = L->Blocks.begin(),
+ BE = L->Blocks.end(); BI != BE; ++BI)
+ for (succ_iterator I = succ_begin(*BI), E = succ_end(*BI); I != E; ++I)
+ if (!L->contains(*I)) // Not in current loop?
+ L->ExitBlocks.push_back(*I); // It must be an exit block...
+
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;
+ }
+
+ // Make sure there is only one exit out of the preheader...
+ succ_iterator SI = succ_begin(Out);
+ ++SI;
+ if (SI != succ_end(Out))
+ return 0; // Multiple exits from the block, must not be a preheader.
+
+
+ // 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();
+ }
+}
+
+/// changeExitBlock - This method is used to update loop information. All
+/// instances of the specified Old basic block are removed from the exit list
+/// and replaced with New.
+///
+void Loop::changeExitBlock(BasicBlock *Old, BasicBlock *New) {
+ assert(Old != New && "Cannot changeExitBlock to the same thing!");
+ assert(Old && New && "Cannot changeExitBlock to or from a null node!");
+ assert(hasExitBlock(Old) && "Old exit block not found!");
+ std::vector<BasicBlock*>::iterator
+ I = std::find(ExitBlocks.begin(), ExitBlocks.end(), Old);
+ while (I != ExitBlocks.end()) {
+ *I = New;
+ I = std::find(I+1, ExitBlocks.end(), Old);
+ }
+}
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