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//===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- C++ -*-===//
//
// 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. A natural loop
// has exactly one entry-point, which is called the header. Note that natural
// loops may actually be several loops that share the same header node.
//
// This analysis calculates the nesting structure of loops in a function. For
// each natural loop identified, this analysis identifies natural loops
// contained entirely within the loop and the basic blocks the make up the loop.
//
// It can calculate on the fly various bits of information, for example:
//
// * whether there is a preheader for the loop
// * the number of back edges to the header
// * whether or not a particular block branches out of the loop
// * the successor blocks of the loop
// * the loop depth
// * etc...
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_LOOP_INFO_H
#define LLVM_ANALYSIS_LOOP_INFO_H
#include "llvm/Pass.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/GraphTraits.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <map>
namespace llvm {
template<typename T>
static void RemoveFromVector(std::vector<T*> &V, T *N) {
typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N);
assert(I != V.end() && "N is not in this list!");
V.erase(I);
}
class DominatorTree;
class LoopInfo;
class Loop;
class PHINode;
template<class N, class M> class LoopInfoBase;
template<class N, class M> class LoopBase;
//===----------------------------------------------------------------------===//
/// LoopBase class - Instances of this class are used to represent loops that
/// are detected in the flow graph
///
template<class BlockT, class LoopT>
class LoopBase {
LoopT *ParentLoop;
// SubLoops - Loops contained entirely within this one.
std::vector<LoopT *> SubLoops;
// Blocks - The list of blocks in this loop. First entry is the header node.
std::vector<BlockT*> Blocks;
// DO NOT IMPLEMENT
LoopBase(const LoopBase<BlockT, LoopT> &);
// DO NOT IMPLEMENT
const LoopBase<BlockT, LoopT>&operator=(const LoopBase<BlockT, LoopT> &);
public:
/// Loop ctor - This creates an empty loop.
LoopBase() : ParentLoop(0) {}
~LoopBase() {
for (size_t i = 0, e = SubLoops.size(); i != e; ++i)
delete SubLoops[i];
}
/// getLoopDepth - Return the nesting level of this loop. An outer-most
/// loop has depth 1, for consistency with loop depth values used for basic
/// blocks, where depth 0 is used for blocks not inside any loops.
unsigned getLoopDepth() const {
unsigned D = 1;
for (const LoopT *CurLoop = ParentLoop; CurLoop;
CurLoop = CurLoop->ParentLoop)
++D;
return D;
}
BlockT *getHeader() const { return Blocks.front(); }
LoopT *getParentLoop() const { return ParentLoop; }
/// contains - Return true if the specified loop is contained within in
/// this loop.
///
bool contains(const LoopT *L) const {
if (L == this) return true;
if (L == 0) return false;
return contains(L->getParentLoop());
}
/// contains - Return true if the specified basic block is in this loop.
///
bool contains(const BlockT *BB) const {
return std::find(block_begin(), block_end(), BB) != block_end();
}
/// contains - Return true if the specified instruction is in this loop.
///
template<class InstT>
bool contains(const InstT *Inst) const {
return contains(Inst->getParent());
}
/// iterator/begin/end - Return the loops contained entirely within this loop.
///
const std::vector<LoopT *> &getSubLoops() const { return SubLoops; }
typedef typename std::vector<LoopT *>::const_iterator iterator;
iterator begin() const { return SubLoops.begin(); }
iterator end() const { return SubLoops.end(); }
bool empty() const { return SubLoops.empty(); }
/// getBlocks - Get a list of the basic blocks which make up this loop.
///
const std::vector<BlockT*> &getBlocks() const { return Blocks; }
typedef typename std::vector<BlockT*>::const_iterator block_iterator;
block_iterator block_begin() const { return Blocks.begin(); }
block_iterator block_end() const { return Blocks.end(); }
/// getNumBlocks - Get the number of blocks in this loop in constant time.
unsigned getNumBlocks() const {
return Blocks.size();
}
/// isLoopExiting - True if terminator in the block can branch to another
/// block that is outside of the current loop.
///
bool isLoopExiting(const BlockT *BB) const {
typedef GraphTraits<BlockT*> BlockTraits;
for (typename BlockTraits::ChildIteratorType SI =
BlockTraits::child_begin(const_cast<BlockT*>(BB)),
SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) {
if (!contains(*SI))
return true;
}
return false;
}
/// getNumBackEdges - Calculate the number of back edges to the loop header
///
unsigned getNumBackEdges() const {
unsigned NumBackEdges = 0;
BlockT *H = getHeader();
typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
for (typename InvBlockTraits::ChildIteratorType I =
InvBlockTraits::child_begin(const_cast<BlockT*>(H)),
E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I)
if (contains(*I))
++NumBackEdges;
return NumBackEdges;
}
//===--------------------------------------------------------------------===//
// APIs for simple analysis of the loop.
//
// Note that all of these methods can fail on general loops (ie, there may not
// be a preheader, etc). For best success, the loop simplification and
// induction variable canonicalization pass should be used to normalize loops
// for easy analysis. These methods assume canonical loops.
/// getExitingBlocks - Return all blocks inside the loop that have successors
/// outside of the loop. These are the blocks _inside of the current loop_
/// which branch out. The returned list is always unique.
///
void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const {
// Sort the blocks vector so that we can use binary search to do quick
// lookups.
SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
std::sort(LoopBBs.begin(), LoopBBs.end());
typedef GraphTraits<BlockT*> BlockTraits;
for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
for (typename BlockTraits::ChildIteratorType I =
BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
I != E; ++I)
if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) {
// Not in current loop? It must be an exit block.
ExitingBlocks.push_back(*BI);
break;
}
}
/// getExitingBlock - If getExitingBlocks would return exactly one block,
/// return that block. Otherwise return null.
BlockT *getExitingBlock() const {
SmallVector<BlockT*, 8> ExitingBlocks;
getExitingBlocks(ExitingBlocks);
if (ExitingBlocks.size() == 1)
return ExitingBlocks[0];
return 0;
}
/// getExitBlocks - Return all of the successor blocks of this loop. These
/// are the blocks _outside of the current loop_ which are branched to.
///
void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const {
// Sort the blocks vector so that we can use binary search to do quick
// lookups.
SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
std::sort(LoopBBs.begin(), LoopBBs.end());
typedef GraphTraits<BlockT*> BlockTraits;
for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
for (typename BlockTraits::ChildIteratorType I =
BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
I != E; ++I)
if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
// Not in current loop? It must be an exit block.
ExitBlocks.push_back(*I);
}
/// getExitBlock - If getExitBlocks would return exactly one block,
/// return that block. Otherwise return null.
BlockT *getExitBlock() const {
SmallVector<BlockT*, 8> ExitBlocks;
getExitBlocks(ExitBlocks);
if (ExitBlocks.size() == 1)
return ExitBlocks[0];
return 0;
}
/// Edge type.
typedef std::pair<BlockT*, BlockT*> Edge;
/// getExitEdges - Return all pairs of (_inside_block_,_outside_block_).
template <typename EdgeT>
void getExitEdges(SmallVectorImpl<EdgeT> &ExitEdges) const {
// Sort the blocks vector so that we can use binary search to do quick
// lookups.
SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
array_pod_sort(LoopBBs.begin(), LoopBBs.end());
typedef GraphTraits<BlockT*> BlockTraits;
for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI)
for (typename BlockTraits::ChildIteratorType I =
BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI);
I != E; ++I)
if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I))
// Not in current loop? It must be an exit block.
ExitEdges.push_back(EdgeT(*BI, *I));
}
/// 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.
///
/// This method returns null if there is no preheader for the loop.
///
BlockT *getLoopPreheader() const {
// Keep track of nodes outside the loop branching to the header...
BlockT *Out = getLoopPredecessor();
if (!Out) return 0;
// Make sure there is only one exit out of the preheader.
typedef GraphTraits<BlockT*> BlockTraits;
typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out);
++SI;
if (SI != BlockTraits::child_end(Out))
return 0; // Multiple exits from the block, must not be a preheader.
// The predecessor has exactly one successor, so it is a preheader.
return Out;
}
/// getLoopPredecessor - If the given loop's header has exactly one unique
/// predecessor outside the loop, return it. Otherwise return null.
/// This is less strict that the loop "preheader" concept, which requires
/// the predecessor to have exactly one successor.
///
BlockT *getLoopPredecessor() const {
// Keep track of nodes outside the loop branching to the header...
BlockT *Out = 0;
// Loop over the predecessors of the header node...
BlockT *Header = getHeader();
typedef GraphTraits<BlockT*> BlockTraits;
typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
for (typename InvBlockTraits::ChildIteratorType PI =
InvBlockTraits::child_begin(Header),
PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) {
typename InvBlockTraits::NodeType *N = *PI;
if (!contains(N)) { // If the block is not in the loop...
if (Out && Out != N)
return 0; // Multiple predecessors outside the loop
Out = N;
}
}
// Make sure there is only one exit out of the preheader.
assert(Out && "Header of loop has no predecessors from outside loop?");
return Out;
}
/// getLoopLatch - If there is a single latch block for this loop, return it.
/// A latch block is a block that contains a branch back to the header.
BlockT *getLoopLatch() const {
BlockT *Header = getHeader();
typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
typename InvBlockTraits::ChildIteratorType PI =
InvBlockTraits::child_begin(Header);
typename InvBlockTraits::ChildIteratorType PE =
InvBlockTraits::child_end(Header);
BlockT *Latch = 0;
for (; PI != PE; ++PI) {
typename InvBlockTraits::NodeType *N = *PI;
if (contains(N)) {
if (Latch) return 0;
Latch = N;
}
}
return Latch;
}
//===--------------------------------------------------------------------===//
// APIs for updating loop information after changing the CFG
//
/// addBasicBlockToLoop - This method 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 addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI);
/// replaceChildLoopWith - This is used when splitting loops up. It replaces
/// the OldChild entry in our children list with NewChild, and updates the
/// parent pointer of OldChild to be null and the NewChild to be this loop.
/// This updates the loop depth of the new child.
void replaceChildLoopWith(LoopT *OldChild,
LoopT *NewChild) {
assert(OldChild->ParentLoop == this && "This loop is already broken!");
assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
typename std::vector<LoopT *>::iterator I =
std::find(SubLoops.begin(), SubLoops.end(), OldChild);
assert(I != SubLoops.end() && "OldChild not in loop!");
*I = NewChild;
OldChild->ParentLoop = 0;
NewChild->ParentLoop = static_cast<LoopT *>(this);
}
/// addChildLoop - Add the specified loop to be a child of this loop. This
/// updates the loop depth of the new child.
///
void addChildLoop(LoopT *NewChild) {
assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
NewChild->ParentLoop = static_cast<LoopT *>(this);
SubLoops.push_back(NewChild);
}
/// removeChildLoop - This removes the specified child from being a subloop of
/// this loop. The loop is not deleted, as it will presumably be inserted
/// into another loop.
LoopT *removeChildLoop(iterator I) {
assert(I != SubLoops.end() && "Cannot remove end iterator!");
LoopT *Child = *I;
assert(Child->ParentLoop == this && "Child is not a child of this loop!");
SubLoops.erase(SubLoops.begin()+(I-begin()));
Child->ParentLoop = 0;
return Child;
}
/// addBlockEntry - This adds a basic block directly to the basic block list.
/// This should only be used by transformations that create new loops. Other
/// transformations should use addBasicBlockToLoop.
void addBlockEntry(BlockT *BB) {
Blocks.push_back(BB);
}
/// moveToHeader - This method is used to move BB (which must be part of this
/// loop) to be the loop header of the loop (the block that dominates all
/// others).
void moveToHeader(BlockT *BB) {
if (Blocks[0] == BB) return;
for (unsigned i = 0; ; ++i) {
assert(i != Blocks.size() && "Loop does not contain BB!");
if (Blocks[i] == BB) {
Blocks[i] = Blocks[0];
Blocks[0] = BB;
return;
}
}
}
/// removeBlockFromLoop - This removes the specified basic block from the
/// current loop, updating the Blocks as appropriate. This does not update
/// the mapping in the LoopInfo class.
void removeBlockFromLoop(BlockT *BB) {
RemoveFromVector(Blocks, BB);
}
/// verifyLoop - Verify loop structure
void verifyLoop() const {
#ifndef NDEBUG
assert(!Blocks.empty() && "Loop header is missing");
// Setup for using a depth-first iterator to visit every block in the loop.
SmallVector<BlockT*, 8> ExitBBs;
getExitBlocks(ExitBBs);
llvm::SmallPtrSet<BlockT*, 8> VisitSet;
VisitSet.insert(ExitBBs.begin(), ExitBBs.end());
df_ext_iterator<BlockT*, llvm::SmallPtrSet<BlockT*, 8> >
BI = df_ext_begin(getHeader(), VisitSet),
BE = df_ext_end(getHeader(), VisitSet);
// Keep track of the number of BBs visited.
unsigned NumVisited = 0;
// Sort the blocks vector so that we can use binary search to do quick
// lookups.
SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end());
std::sort(LoopBBs.begin(), LoopBBs.end());
// Check the individual blocks.
for ( ; BI != BE; ++BI) {
BlockT *BB = *BI;
bool HasInsideLoopSuccs = false;
bool HasInsideLoopPreds = false;
SmallVector<BlockT *, 2> OutsideLoopPreds;
typedef GraphTraits<BlockT*> BlockTraits;
for (typename BlockTraits::ChildIteratorType SI =
BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB);
SI != SE; ++SI)
if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *SI)) {
HasInsideLoopSuccs = true;
break;
}
typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
for (typename InvBlockTraits::ChildIteratorType PI =
InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB);
PI != PE; ++PI) {
BlockT *N = *PI;
if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), N))
HasInsideLoopPreds = true;
else
OutsideLoopPreds.push_back(N);
}
if (BB == getHeader()) {
assert(!OutsideLoopPreds.empty() && "Loop is unreachable!");
} else if (!OutsideLoopPreds.empty()) {
// A non-header loop shouldn't be reachable from outside the loop,
// though it is permitted if the predecessor is not itself actually
// reachable.
BlockT *EntryBB = BB->getParent()->begin();
for (df_iterator<BlockT *> NI = df_begin(EntryBB),
NE = df_end(EntryBB); NI != NE; ++NI)
for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i)
assert(*NI != OutsideLoopPreds[i] &&
"Loop has multiple entry points!");
}
assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!");
assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!");
assert(BB != getHeader()->getParent()->begin() &&
"Loop contains function entry block!");
NumVisited++;
}
assert(NumVisited == getNumBlocks() && "Unreachable block in loop");
// Check the subloops.
for (iterator I = begin(), E = end(); I != E; ++I)
// Each block in each subloop should be contained within this loop.
for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end();
BI != BE; ++BI) {
assert(std::binary_search(LoopBBs.begin(), LoopBBs.end(), *BI) &&
"Loop does not contain all the blocks of a subloop!");
}
// Check the parent loop pointer.
if (ParentLoop) {
assert(std::find(ParentLoop->begin(), ParentLoop->end(), this) !=
ParentLoop->end() &&
"Loop is not a subloop of its parent!");
}
#endif
}
/// verifyLoop - Verify loop structure of this loop and all nested loops.
void verifyLoopNest(DenseSet<const LoopT*> *Loops) const {
Loops->insert(static_cast<const LoopT *>(this));
// Verify this loop.
verifyLoop();
// Verify the subloops.
for (iterator I = begin(), E = end(); I != E; ++I)
(*I)->verifyLoopNest(Loops);
}
void print(raw_ostream &OS, unsigned Depth = 0) const {
OS.indent(Depth*2) << "Loop at depth " << getLoopDepth()
<< " containing: ";
for (unsigned i = 0; i < getBlocks().size(); ++i) {
if (i) OS << ",";
BlockT *BB = getBlocks()[i];
WriteAsOperand(OS, BB, false);
if (BB == getHeader()) OS << "<header>";
if (BB == getLoopLatch()) OS << "<latch>";
if (isLoopExiting(BB)) OS << "<exiting>";
}
OS << "\n";
for (iterator I = begin(), E = end(); I != E; ++I)
(*I)->print(OS, Depth+2);
}
protected:
friend class LoopInfoBase<BlockT, LoopT>;
explicit LoopBase(BlockT *BB) : ParentLoop(0) {
Blocks.push_back(BB);
}
};
template<class BlockT, class LoopT>
raw_ostream& operator<<(raw_ostream &OS, const LoopBase<BlockT, LoopT> &Loop) {
Loop.print(OS);
return OS;
}
class Loop : public LoopBase<BasicBlock, Loop> {
public:
Loop() {}
/// isLoopInvariant - Return true if the specified value is loop invariant
///
bool isLoopInvariant(Value *V) const;
/// hasLoopInvariantOperands - Return true if all the operands of the
/// specified instruction are loop invariant.
bool hasLoopInvariantOperands(Instruction *I) const;
/// makeLoopInvariant - If the given value is an instruction inside of the
/// loop and it can be hoisted, do so to make it trivially loop-invariant.
/// Return true if the value after any hoisting is loop invariant. This
/// function can be used as a slightly more aggressive replacement for
/// isLoopInvariant.
///
/// If InsertPt is specified, it is the point to hoist instructions to.
/// If null, the terminator of the loop preheader is used.
///
bool makeLoopInvariant(Value *V, bool &Changed,
Instruction *InsertPt = 0) const;
/// makeLoopInvariant - If the given instruction is inside of the
/// loop and it can be hoisted, do so to make it trivially loop-invariant.
/// Return true if the instruction after any hoisting is loop invariant. This
/// function can be used as a slightly more aggressive replacement for
/// isLoopInvariant.
///
/// If InsertPt is specified, it is the point to hoist instructions to.
/// If null, the terminator of the loop preheader is used.
///
bool makeLoopInvariant(Instruction *I, bool &Changed,
Instruction *InsertPt = 0) const;
/// getCanonicalInductionVariable - Check to see if the loop has a canonical
/// induction variable: an integer recurrence that starts at 0 and increments
/// by one each time through the loop. If so, return the phi node that
/// corresponds to it.
///
/// The IndVarSimplify pass transforms loops to have a canonical induction
/// variable.
///
PHINode *getCanonicalInductionVariable() const;
/// isLCSSAForm - Return true if the Loop is in LCSSA form
bool isLCSSAForm(DominatorTree &DT) const;
/// isLoopSimplifyForm - Return true if the Loop is in the form that
/// the LoopSimplify form transforms loops to, which is sometimes called
/// normal form.
bool isLoopSimplifyForm() const;
/// isSafeToClone - Return true if the loop body is safe to clone in practice.
bool isSafeToClone() const;
/// hasDedicatedExits - Return true if no exit block for the loop
/// has a predecessor that is outside the loop.
bool hasDedicatedExits() const;
/// getUniqueExitBlocks - Return all unique successor blocks of this loop.
/// These are the blocks _outside of the current loop_ which are branched to.
/// This assumes that loop exits are in canonical form.
///
void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const;
/// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one
/// block, return that block. Otherwise return null.
BasicBlock *getUniqueExitBlock() const;
void dump() const;
private:
friend class LoopInfoBase<BasicBlock, Loop>;
explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {}
};
//===----------------------------------------------------------------------===//
/// LoopInfo - This class builds and contains all of the top level loop
/// structures in the specified function.
///
template<class BlockT, class LoopT>
class LoopInfoBase {
// BBMap - Mapping of basic blocks to the inner most loop they occur in
DenseMap<BlockT *, LoopT *> BBMap;
std::vector<LoopT *> TopLevelLoops;
friend class LoopBase<BlockT, LoopT>;
friend class LoopInfo;
void operator=(const LoopInfoBase &); // do not implement
LoopInfoBase(const LoopInfo &); // do not implement
public:
LoopInfoBase() { }
~LoopInfoBase() { releaseMemory(); }
void releaseMemory() {
for (typename std::vector<LoopT *>::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();
}
/// iterator/begin/end - The interface to the top-level loops in the current
/// function.
///
typedef typename std::vector<LoopT *>::const_iterator iterator;
iterator begin() const { return TopLevelLoops.begin(); }
iterator end() const { return TopLevelLoops.end(); }
bool empty() const { return TopLevelLoops.empty(); }
/// getLoopFor - Return the inner most loop that BB lives in. If a basic
/// block is in no loop (for example the entry node), null is returned.
///
LoopT *getLoopFor(const BlockT *BB) const {
return BBMap.lookup(const_cast<BlockT*>(BB));
}
/// operator[] - same as getLoopFor...
///
const LoopT *operator[](const BlockT *BB) const {
return getLoopFor(BB);
}
/// getLoopDepth - Return the loop nesting level of the specified block. A
/// depth of 0 means the block is not inside any loop.
///
unsigned getLoopDepth(const BlockT *BB) const {
const LoopT *L = getLoopFor(BB);
return L ? L->getLoopDepth() : 0;
}
// isLoopHeader - True if the block is a loop header node
bool isLoopHeader(BlockT *BB) const {
const LoopT *L = getLoopFor(BB);
return L && L->getHeader() == BB;
}
/// removeLoop - This removes the specified top-level loop from this loop info
/// object. The loop is not deleted, as it will presumably be inserted into
/// another loop.
LoopT *removeLoop(iterator I) {
assert(I != end() && "Cannot remove end iterator!");
LoopT *L = *I;
assert(L->getParentLoop() == 0 && "Not a top-level loop!");
TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin()));
return L;
}
/// changeLoopFor - Change the top-level loop that contains BB to the
/// specified loop. This should be used by transformations that restructure
/// the loop hierarchy tree.
void changeLoopFor(BlockT *BB, LoopT *L) {
if (!L) {
BBMap.erase(BB);
return;
}
BBMap[BB] = L;
}
/// changeTopLevelLoop - Replace the specified loop in the top-level loops
/// list with the indicated loop.
void changeTopLevelLoop(LoopT *OldLoop,
LoopT *NewLoop) {
typename std::vector<LoopT *>::iterator I =
std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop);
assert(I != TopLevelLoops.end() && "Old loop not at top level!");
*I = NewLoop;
assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 &&
"Loops already embedded into a subloop!");
}
/// addTopLevelLoop - This adds the specified loop to the collection of
/// top-level loops.
void addTopLevelLoop(LoopT *New) {
assert(New->getParentLoop() == 0 && "Loop already in subloop!");
TopLevelLoops.push_back(New);
}
/// removeBlock - This method completely removes BB from all data structures,
/// including all of the Loop objects it is nested in and our mapping from
/// BasicBlocks to loops.
void removeBlock(BlockT *BB) {
typename DenseMap<BlockT *, LoopT *>::iterator I = BBMap.find(BB);
if (I != BBMap.end()) {
for (LoopT *L = I->second; L; L = L->getParentLoop())
L->removeBlockFromLoop(BB);
BBMap.erase(I);
}
}
// Internals
static bool isNotAlreadyContainedIn(const LoopT *SubLoop,
const LoopT *ParentLoop) {
if (SubLoop == 0) return true;
if (SubLoop == ParentLoop) return false;
return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop);
}
void Calculate(DominatorTreeBase<BlockT> &DT) {
BlockT *RootNode = DT.getRootNode()->getBlock();
for (df_iterator<BlockT*> NI = df_begin(RootNode),
NE = df_end(RootNode); NI != NE; ++NI)
if (LoopT *L = ConsiderForLoop(*NI, DT))
TopLevelLoops.push_back(L);
}
LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) {
if (BBMap.count(BB)) return 0; // Haven't processed this node?
std::vector<BlockT *> TodoStack;
// Scan the predecessors of BB, checking to see if BB dominates any of
// them. This identifies backedges which target this node...
typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
for (typename InvBlockTraits::ChildIteratorType I =
InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB);
I != E; ++I) {
typename InvBlockTraits::NodeType *N = *I;
// If BB dominates its predecessor...
if (DT.dominates(BB, N) && DT.isReachableFromEntry(N))
TodoStack.push_back(N);
}
if (TodoStack.empty()) return 0; // No backedges to this block...
// Create a new loop to represent this basic block...
LoopT *L = new LoopT(BB);
BBMap[BB] = L;
while (!TodoStack.empty()) { // Process all the nodes in the loop
BlockT *X = TodoStack.back();
TodoStack.pop_back();
if (!L->contains(X) && // As of yet unprocessed??
DT.isReachableFromEntry(X)) {
// 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 (LoopT *SubLoop =
const_cast<LoopT *>(getLoopFor(X)))
if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
// Remove the subloop from its current parent...
assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent
typename std::vector<LoopT *>::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);
typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
// Add all of the predecessors of X to the end of the work stack...
TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X),
InvBlockTraits::child_end(X));
}
}
// If there are any loops nested within this loop, create them now!
for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
E = L->Blocks.end(); I != E; ++I)
if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) {
L->SubLoops.push_back(NewLoop);
NewLoop->ParentLoop = L;
}
// Add the basic blocks that comprise this loop to the BBMap so that this
// loop can be found for them.
//
for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(),
E = L->Blocks.end(); I != E; ++I)
BBMap.insert(std::make_pair(*I, L));
// Now that we have a list of all of the child loops of this loop, check to
// see if any of them should actually be nested inside of each other. We
// can accidentally pull loops our of their parents, so we must make sure to
// organize the loop nests correctly now.
{
std::map<BlockT *, LoopT *> ContainingLoops;
for (unsigned i = 0; i != L->SubLoops.size(); ++i) {
LoopT *Child = L->SubLoops[i];
assert(Child->getParentLoop() == L && "Not proper child loop?");
if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) {
// If there is already a loop which contains this loop, move this loop
// into the containing loop.
MoveSiblingLoopInto(Child, ContainingLoop);
--i; // The loop got removed from the SubLoops list.
} else {
// This is currently considered to be a top-level loop. Check to see
// if any of the contained blocks are loop headers for subloops we
// have already processed.
for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) {
LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]];
if (BlockLoop == 0) { // Child block not processed yet...
BlockLoop = Child;
} else if (BlockLoop != Child) {
LoopT *SubLoop = BlockLoop;
// Reparent all of the blocks which used to belong to BlockLoops
for (unsigned j = 0, f = SubLoop->Blocks.size(); j != f; ++j)
ContainingLoops[SubLoop->Blocks[j]] = Child;
// There is already a loop which contains this block, that means
// that we should reparent the loop which the block is currently
// considered to belong to to be a child of this loop.
MoveSiblingLoopInto(SubLoop, Child);
--i; // We just shrunk the SubLoops list.
}
}
}
}
}
return L;
}
/// MoveSiblingLoopInto - This method moves the NewChild loop to live inside
/// of the NewParent Loop, instead of being a sibling of it.
void MoveSiblingLoopInto(LoopT *NewChild,
LoopT *NewParent) {
LoopT *OldParent = NewChild->getParentLoop();
assert(OldParent && OldParent == NewParent->getParentLoop() &&
NewChild != NewParent && "Not sibling loops!");
// Remove NewChild from being a child of OldParent
typename std::vector<LoopT *>::iterator I =
std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(),
NewChild);
assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??");
OldParent->SubLoops.erase(I); // Remove from parent's subloops list
NewChild->ParentLoop = 0;
InsertLoopInto(NewChild, NewParent);
}
/// InsertLoopInto - This inserts loop L into the specified parent loop. If
/// the parent loop contains a loop which should contain L, the loop gets
/// inserted into L instead.
void InsertLoopInto(LoopT *L, LoopT *Parent) {
BlockT *LHeader = L->getHeader();
assert(Parent->contains(LHeader) &&
"This loop should not be inserted here!");
// Check to see if it belongs in a child loop...
for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size());
i != e; ++i)
if (Parent->SubLoops[i]->contains(LHeader)) {
InsertLoopInto(L, Parent->SubLoops[i]);
return;
}
// If not, insert it here!
Parent->SubLoops.push_back(L);
L->ParentLoop = Parent;
}
// Debugging
void print(raw_ostream &OS) const {
for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
TopLevelLoops[i]->print(OS);
#if 0
for (DenseMap<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(),
E = BBMap.end(); I != E; ++I)
OS << "BB '" << I->first->getName() << "' level = "
<< I->second->getLoopDepth() << "\n";
#endif
}
};
class LoopInfo : public FunctionPass {
LoopInfoBase<BasicBlock, Loop> LI;
friend class LoopBase<BasicBlock, Loop>;
void operator=(const LoopInfo &); // do not implement
LoopInfo(const LoopInfo &); // do not implement
public:
static char ID; // Pass identification, replacement for typeid
LoopInfo() : FunctionPass(ID) {
initializeLoopInfoPass(*PassRegistry::getPassRegistry());
}
LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; }
/// iterator/begin/end - The interface to the top-level loops in the current
/// function.
///
typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator;
inline iterator begin() const { return LI.begin(); }
inline iterator end() const { return LI.end(); }
bool empty() const { return LI.empty(); }
/// getLoopFor - Return the inner most loop that BB lives in. If a basic
/// block is in no loop (for example the entry node), null is returned.
///
inline Loop *getLoopFor(const BasicBlock *BB) const {
return LI.getLoopFor(BB);
}
/// operator[] - same as getLoopFor...
///
inline const Loop *operator[](const BasicBlock *BB) const {
return LI.getLoopFor(BB);
}
/// getLoopDepth - Return the loop nesting level of the specified block. A
/// depth of 0 means the block is not inside any loop.
///
inline unsigned getLoopDepth(const BasicBlock *BB) const {
return LI.getLoopDepth(BB);
}
// isLoopHeader - True if the block is a loop header node
inline bool isLoopHeader(BasicBlock *BB) const {
return LI.isLoopHeader(BB);
}
/// runOnFunction - Calculate the natural loop information.
///
virtual bool runOnFunction(Function &F);
virtual void verifyAnalysis() const;
virtual void releaseMemory() { LI.releaseMemory(); }
virtual void print(raw_ostream &O, const Module* M = 0) const;
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
/// removeLoop - This removes the specified top-level loop from this loop info
/// object. The loop is not deleted, as it will presumably be inserted into
/// another loop.
inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); }
/// changeLoopFor - Change the top-level loop that contains BB to the
/// specified loop. This should be used by transformations that restructure
/// the loop hierarchy tree.
inline void changeLoopFor(BasicBlock *BB, Loop *L) {
LI.changeLoopFor(BB, L);
}
/// changeTopLevelLoop - Replace the specified loop in the top-level loops
/// list with the indicated loop.
inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) {
LI.changeTopLevelLoop(OldLoop, NewLoop);
}
/// addTopLevelLoop - This adds the specified loop to the collection of
/// top-level loops.
inline void addTopLevelLoop(Loop *New) {
LI.addTopLevelLoop(New);
}
/// removeBlock - This method completely removes BB from all data structures,
/// including all of the Loop objects it is nested in and our mapping from
/// BasicBlocks to loops.
void removeBlock(BasicBlock *BB) {
LI.removeBlock(BB);
}
/// updateUnloop - Update LoopInfo after removing the last backedge from a
/// loop--now the "unloop". This updates the loop forest and parent loops for
/// each block so that Unloop is no longer referenced, but the caller must
/// actually delete the Unloop object.
void updateUnloop(Loop *Unloop);
/// replacementPreservesLCSSAForm - Returns true if replacing From with To
/// everywhere is guaranteed to preserve LCSSA form.
bool replacementPreservesLCSSAForm(Instruction *From, Value *To) {
// Preserving LCSSA form is only problematic if the replacing value is an
// instruction.
Instruction *I = dyn_cast<Instruction>(To);
if (!I) return true;
// If both instructions are defined in the same basic block then replacement
// cannot break LCSSA form.
if (I->getParent() == From->getParent())
return true;
// If the instruction is not defined in a loop then it can safely replace
// anything.
Loop *ToLoop = getLoopFor(I->getParent());
if (!ToLoop) return true;
// If the replacing instruction is defined in the same loop as the original
// instruction, or in a loop that contains it as an inner loop, then using
// it as a replacement will not break LCSSA form.
return ToLoop->contains(getLoopFor(From->getParent()));
}
};
// Allow clients to walk the list of nested loops...
template <> struct GraphTraits<const Loop*> {
typedef const Loop NodeType;
typedef LoopInfo::iterator ChildIteratorType;
static NodeType *getEntryNode(const Loop *L) { return L; }
static inline ChildIteratorType child_begin(NodeType *N) {
return N->begin();
}
static inline ChildIteratorType child_end(NodeType *N) {
return N->end();
}
};
template <> struct GraphTraits<Loop*> {
typedef Loop NodeType;
typedef LoopInfo::iterator ChildIteratorType;
static NodeType *getEntryNode(Loop *L) { return L; }
static inline ChildIteratorType child_begin(NodeType *N) {
return N->begin();
}
static inline ChildIteratorType child_end(NodeType *N) {
return N->end();
}
};
template<class BlockT, class LoopT>
void
LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB,
LoopInfoBase<BlockT, LoopT> &LIB) {
assert((Blocks.empty() || LIB[getHeader()] == this) &&
"Incorrect LI specified for this loop!");
assert(NewBB && "Cannot add a null basic block to the loop!");
assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!");
LoopT *L = static_cast<LoopT *>(this);
// Add the loop mapping to the LoopInfo object...
LIB.BBMap[NewBB] = L;
// Add the basic block to this loop and all parent loops...
while (L) {
L->Blocks.push_back(NewBB);
L = L->getParentLoop();
}
}
} // End llvm namespace
#endif