llvm-6502/include/llvm/Analysis/LoopInfo.h

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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. 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
// * the trip count
// * etc...
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_LOOP_INFO_H
#define LLVM_ANALYSIS_LOOP_INFO_H
#include "llvm/Pass.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/GraphTraits.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Streams.h"
#include <algorithm>
#include <ostream>
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;
template<class N> class LoopInfoBase;
template<class N> class LoopBase;
typedef LoopBase<BasicBlock> Loop;
//===----------------------------------------------------------------------===//
/// LoopBase class - Instances of this class are used to represent loops that
/// are detected in the flow graph
///
template<class BlockT>
class LoopBase {
LoopBase<BlockT> *ParentLoop;
// SubLoops - Loops contained entirely within this one.
std::vector<LoopBase<BlockT>*> SubLoops;
// Blocks - The list of blocks in this loop. First entry is the header node.
std::vector<BlockT*> Blocks;
LoopBase(const LoopBase<BlockT> &); // DO NOT IMPLEMENT
const LoopBase<BlockT>&operator=(const LoopBase<BlockT> &);// DO NOT IMPLEMENT
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 LoopBase<BlockT> *CurLoop = ParentLoop; CurLoop;
CurLoop = CurLoop->ParentLoop)
++D;
return D;
}
BlockT *getHeader() const { return Blocks.front(); }
LoopBase<BlockT> *getParentLoop() const { return ParentLoop; }
/// contains - Return true if the specified basic block is in this loop
///
bool contains(const BlockT *BB) const {
return std::find(Blocks.begin(), Blocks.end(), BB) != Blocks.end();
}
/// iterator/begin/end - Return the loops contained entirely within this loop.
///
const std::vector<LoopBase<BlockT>*> &getSubLoops() const { return SubLoops; }
typedef typename std::vector<LoopBase<BlockT>*>::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(); }
/// isLoopExit - True if terminator in the block can branch to another block
/// that is outside of the current loop.
///
bool isLoopExit(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;
}
/// isLoopInvariant - Return true if the specified value is loop invariant
///
inline bool isLoopInvariant(Value *V) const {
if (Instruction *I = dyn_cast<Instruction>(V))
return !contains(I->getParent());
return true; // All non-instructions are loop invariant
}
//===--------------------------------------------------------------------===//
// 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 (typename std::vector<BlockT*>::const_iterator BI = Blocks.begin(),
BE = Blocks.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;
}
}
/// 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 (typename std::vector<BlockT*>::const_iterator BI = Blocks.begin(),
BE = Blocks.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);
}
/// 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 is in canonical form.
///
void getUniqueExitBlocks(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());
std::vector<BlockT*> switchExitBlocks;
for (typename std::vector<BlockT*>::const_iterator BI = Blocks.begin(),
BE = Blocks.end(); BI != BE; ++BI) {
BlockT *current = *BI;
switchExitBlocks.clear();
typedef GraphTraits<BlockT*> BlockTraits;
typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
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))
// If block is inside the loop then it is not a exit block.
continue;
typename InvBlockTraits::ChildIteratorType PI =
InvBlockTraits::child_begin(*I);
BlockT *firstPred = *PI;
// If current basic block is this exit block's first predecessor
// then only insert exit block in to the output ExitBlocks vector.
// This ensures that same exit block is not inserted twice into
// ExitBlocks vector.
if (current != firstPred)
continue;
// If a terminator has more then two successors, for example SwitchInst,
// then it is possible that there are multiple edges from current block
// to one exit block.
if (std::distance(BlockTraits::child_begin(current),
BlockTraits::child_end(current)) <= 2) {
ExitBlocks.push_back(*I);
continue;
}
// In case of multiple edges from current block to exit block, collect
// only one edge in ExitBlocks. Use switchExitBlocks to keep track of
// duplicate edges.
if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I)
== switchExitBlocks.end()) {
switchExitBlocks.push_back(*I);
ExitBlocks.push_back(*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 = 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)
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.
assert(Out && "Header of loop has no predecessors from outside loop?");
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.
// If there is exactly one preheader, return it. If there was zero, then
// Out is still null.
return Out;
}
/// getLoopLatch - If there is a latch block for this loop, return it. A
/// latch block is the canonical backedge for a loop. A loop header in normal
/// form has two edges into it: one from a preheader and one from a latch
/// block.
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);
if (PI == PE) return 0; // no preds?
BlockT *Latch = 0;
if (contains(*PI))
Latch = *PI;
++PI;
if (PI == PE) return 0; // only one pred?
if (contains(*PI)) {
if (Latch) return 0; // multiple backedges
Latch = *PI;
}
++PI;
if (PI != PE) return 0; // more than two preds
return Latch;
}
/// 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.
///
inline PHINode *getCanonicalInductionVariable() const {
BlockT *H = getHeader();
BlockT *Incoming = 0, *Backedge = 0;
typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits;
typename InvBlockTraits::ChildIteratorType PI =
InvBlockTraits::child_begin(H);
assert(PI != InvBlockTraits::child_end(H) &&
"Loop must have at least one backedge!");
Backedge = *PI++;
if (PI == InvBlockTraits::child_end(H)) return 0; // dead loop
Incoming = *PI++;
if (PI != InvBlockTraits::child_end(H)) return 0; // multiple backedges?
if (contains(Incoming)) {
if (contains(Backedge))
return 0;
std::swap(Incoming, Backedge);
} else if (!contains(Backedge))
return 0;
// Loop over all of the PHI nodes, looking for a canonical indvar.
for (typename BlockT::iterator I = H->begin(); isa<PHINode>(I); ++I) {
PHINode *PN = cast<PHINode>(I);
if (ConstantInt *CI =
dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming)))
if (CI->isNullValue())
if (Instruction *Inc =
dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge)))
if (Inc->getOpcode() == Instruction::Add &&
Inc->getOperand(0) == PN)
if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1)))
if (CI->equalsInt(1))
return PN;
}
return 0;
}
/// getCanonicalInductionVariableIncrement - Return the LLVM value that holds
/// the canonical induction variable value for the "next" iteration of the
/// loop. This always succeeds if getCanonicalInductionVariable succeeds.
///
inline Instruction *getCanonicalInductionVariableIncrement() const {
if (PHINode *PN = getCanonicalInductionVariable()) {
bool P1InLoop = contains(PN->getIncomingBlock(1));
return cast<Instruction>(PN->getIncomingValue(P1InLoop));
}
return 0;
}
/// getTripCount - Return a loop-invariant LLVM value indicating the number of
/// times the loop will be executed. Note that this means that the backedge
/// of the loop executes N-1 times. If the trip-count cannot be determined,
/// this returns null.
///
inline Value *getTripCount() const {
// Canonical loops will end with a 'cmp ne I, V', where I is the incremented
// canonical induction variable and V is the trip count of the loop.
Instruction *Inc = getCanonicalInductionVariableIncrement();
if (Inc == 0) return 0;
PHINode *IV = cast<PHINode>(Inc->getOperand(0));
BlockT *BackedgeBlock =
IV->getIncomingBlock(contains(IV->getIncomingBlock(1)));
if (BranchInst *BI = dyn_cast<BranchInst>(BackedgeBlock->getTerminator()))
if (BI->isConditional()) {
if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) {
if (ICI->getOperand(0) == Inc) {
if (BI->getSuccessor(0) == getHeader()) {
if (ICI->getPredicate() == ICmpInst::ICMP_NE)
return ICI->getOperand(1);
} else if (ICI->getPredicate() == ICmpInst::ICMP_EQ) {
return ICI->getOperand(1);
}
}
}
}
return 0;
}
/// getSmallConstantTripCount - Returns the trip count of this loop as a
/// normal unsigned value, if possible. Returns 0 if the trip count is unknown
/// of not constant. Will also return 0 if the trip count is very large
/// (>= 2^32)
inline unsigned getSmallConstantTripCount() const {
Value* TripCount = this->getTripCount();
if (TripCount) {
if (ConstantInt *TripCountC = dyn_cast<ConstantInt>(TripCount)) {
// Guard against huge trip counts.
if (TripCountC->getValue().getActiveBits() <= 32) {
return (unsigned)TripCountC->getZExtValue();
}
}
}
return 0;
}
/// getSmallConstantTripMultiple - Returns the largest constant divisor of the
/// trip count of this loop as a normal unsigned value, if possible. This
/// means that the actual trip count is always a multiple of the returned
/// value (don't forget the trip count could very well be zero as well!).
///
/// Returns 1 if the trip count is unknown or not guaranteed to be the
/// multiple of a constant (which is also the case if the trip count is simply
/// constant, use getSmallConstantTripCount for that case), Will also return 1
/// if the trip count is very large (>= 2^32).
inline unsigned getSmallConstantTripMultiple() const {
Value* TripCount = this->getTripCount();
// This will hold the ConstantInt result, if any
ConstantInt *Result = NULL;
if (TripCount) {
// See if the trip count is constant itself
Result = dyn_cast<ConstantInt>(TripCount);
// if not, see if it is a multiplication
if (!Result)
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TripCount)) {
switch (BO->getOpcode()) {
case BinaryOperator::Mul:
Result = dyn_cast<ConstantInt>(BO->getOperand(1));
break;
default:
break;
}
}
}
// Guard against huge trip counts.
if (Result && Result->getValue().getActiveBits() <= 32) {
return (unsigned)Result->getZExtValue();
} else {
return 1;
}
}
/// isLCSSAForm - Return true if the Loop is in LCSSA form
inline bool isLCSSAForm() const {
// Sort the blocks vector so that we can use binary search to do quick
// lookups.
SmallPtrSet<BlockT*, 16> LoopBBs(block_begin(), block_end());
for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) {
BlockT *BB = *BI;
for (typename BlockT::iterator I = BB->begin(), E = BB->end(); I != E;++I)
for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
++UI) {
BlockT *UserBB = cast<Instruction>(*UI)->getParent();
if (PHINode *P = dyn_cast<PHINode>(*UI)) {
UserBB = P->getIncomingBlock(UI);
}
// Check the current block, as a fast-path. Most values are used in
// the same block they are defined in.
if (UserBB != BB && !LoopBBs.count(UserBB))
return false;
}
}
return true;
}
//===--------------------------------------------------------------------===//
// 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> &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(LoopBase<BlockT> *OldChild,
LoopBase<BlockT> *NewChild) {
assert(OldChild->ParentLoop == this && "This loop is already broken!");
assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
typename std::vector<LoopBase<BlockT>*>::iterator I =
std::find(SubLoops.begin(), SubLoops.end(), OldChild);
assert(I != SubLoops.end() && "OldChild not in loop!");
*I = NewChild;
OldChild->ParentLoop = 0;
NewChild->ParentLoop = this;
}
/// addChildLoop - Add the specified loop to be a child of this loop. This
/// updates the loop depth of the new child.
///
void addChildLoop(LoopBase<BlockT> *NewChild) {
assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
NewChild->ParentLoop = 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.
LoopBase<BlockT> *removeChildLoop(iterator I) {
assert(I != SubLoops.end() && "Cannot remove end iterator!");
LoopBase<BlockT> *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 (getHeader() && "Loop header is missing");
assert (getLoopPreheader() && "Loop preheader is missing");
assert (getLoopLatch() && "Loop latch is missing");
for (typename std::vector<LoopBase<BlockT>*>::const_iterator I =
SubLoops.begin(), E = SubLoops.end(); I != E; ++I)
(*I)->verifyLoop();
#endif
}
void print(std::ostream &OS, unsigned Depth = 0) const {
OS << std::string(Depth*2, ' ') << "Loop Containing: ";
for (unsigned i = 0; i < getBlocks().size(); ++i) {
if (i) OS << ",";
WriteAsOperand(OS, getBlocks()[i], false);
}
OS << "\n";
for (iterator I = begin(), E = end(); I != E; ++I)
(*I)->print(OS, Depth+2);
}
void print(std::ostream *O, unsigned Depth = 0) const {
if (O) print(*O, Depth);
}
void dump() const {
print(cerr);
}
private:
friend class LoopInfoBase<BlockT>;
explicit LoopBase(BlockT *BB) : ParentLoop(0) {
Blocks.push_back(BB);
}
};
//===----------------------------------------------------------------------===//
/// LoopInfo - This class builds and contains all of the top level loop
/// structures in the specified function.
///
template<class BlockT>
class LoopInfoBase {
// BBMap - Mapping of basic blocks to the inner most loop they occur in
std::map<BlockT*, LoopBase<BlockT>*> BBMap;
std::vector<LoopBase<BlockT>*> TopLevelLoops;
friend class LoopBase<BlockT>;
public:
LoopInfoBase() { }
~LoopInfoBase() { releaseMemory(); }
void releaseMemory() {
for (typename std::vector<LoopBase<BlockT>* >::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<LoopBase<BlockT>*>::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.
///
LoopBase<BlockT> *getLoopFor(const BlockT *BB) const {
typename std::map<BlockT *, LoopBase<BlockT>*>::const_iterator I=
BBMap.find(const_cast<BlockT*>(BB));
return I != BBMap.end() ? I->second : 0;
}
/// operator[] - same as getLoopFor...
///
const LoopBase<BlockT> *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 LoopBase<BlockT> *L = getLoopFor(BB);
return L ? L->getLoopDepth() : 0;
}
// isLoopHeader - True if the block is a loop header node
bool isLoopHeader(BlockT *BB) const {
const LoopBase<BlockT> *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.
LoopBase<BlockT> *removeLoop(iterator I) {
assert(I != end() && "Cannot remove end iterator!");
LoopBase<BlockT> *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, LoopBase<BlockT> *L) {
LoopBase<BlockT> *&OldLoop = BBMap[BB];
assert(OldLoop && "Block not in a loop yet!");
OldLoop = L;
}
/// changeTopLevelLoop - Replace the specified loop in the top-level loops
/// list with the indicated loop.
void changeTopLevelLoop(LoopBase<BlockT> *OldLoop,
LoopBase<BlockT> *NewLoop) {
typename std::vector<LoopBase<BlockT>*>::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(LoopBase<BlockT> *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 std::map<BlockT *, LoopBase<BlockT>*>::iterator I = BBMap.find(BB);
if (I != BBMap.end()) {
for (LoopBase<BlockT> *L = I->second; L; L = L->getParentLoop())
L->removeBlockFromLoop(BB);
BBMap.erase(I);
}
}
// Internals
Fix the time regression I introduced in 464.h264ref with my earlier patch to this file. The issue there was that all uses of an IV inside a loop are actually references to Base[IV*2], and there was one use outside that was the same but LSR didn't see the base or the scaling because it didn't recurse into uses outside the loop; thus, it used base+IV*scale mode inside the loop instead of pulling base out of the loop. This was extra bad because register pressure later forced both base and IV into memory. Doing that recursion, at least enough to figure out addressing modes, is a good idea in general; the change in AddUsersIfInteresting does this. However, there were side effects.... It is also possible for recursing outside the loop to introduce another IV where there was only 1 before (if the refs inside are not scaled and the ref outside is). I don't think this is a common case, but it's in the testsuite. It is right to be very aggressive about getting rid of such introduced IVs (CheckForIVReuse and the handling of nonzero RewriteFactor in StrengthReduceStridedIVUsers). In the testcase in question the new IV produced this way has both a nonconstant stride and a nonzero base, neither of which was handled before. And when inserting new code that feeds into a PHI, it's right to put such code at the original location rather than in the PHI's immediate predecessor(s) when the original location is outside the loop (a case that couldn't happen before) (RewriteInstructionToUseNewBase); better to avoid making multiple copies of it in this case. Also, the mechanism for keeping SCEV's corresponding to GEP's no longer works, as the GEP might change after its SCEV is remembered, invalidating the SCEV, and we might get a bad SCEV value when looking up the GEP again for a later loop. This also couldn't happen before, as we weren't recursing into GEP's outside the loop. Also, when we build an expression that involves a (possibly non-affine) IV from a different loop as well as an IV from the one we're interested in (containsAddRecFromDifferentLoop), don't recurse into that. We can't do much with it and will get in trouble if we try to create new non-affine IVs or something. More testcases are coming. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@62212 91177308-0d34-0410-b5e6-96231b3b80d8
2009-01-14 02:35:31 +00:00
static bool isNotAlreadyContainedIn(const LoopBase<BlockT> *SubLoop,
const LoopBase<BlockT> *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 (LoopBase<BlockT> *L = ConsiderForLoop(*NI, DT))
TopLevelLoops.push_back(L);
}
LoopBase<BlockT> *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) {
if (BBMap.find(BB) != BBMap.end()) 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)
if (DT.dominates(BB, *I)) // If BB dominates it's predecessor...
TodoStack.push_back(*I);
if (TodoStack.empty()) return 0; // No backedges to this block...
// Create a new loop to represent this basic block...
LoopBase<BlockT> *L = new LoopBase<BlockT>(BB);
BBMap[BB] = L;
BlockT *EntryBlock = BB->getParent()->begin();
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.dominates(EntryBlock, X)) { // X is reachable from entry block?
// 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 (LoopBase<BlockT> *SubLoop =
const_cast<LoopBase<BlockT>*>(getLoopFor(X)))
if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
// Remove the subloop from it's current parent...
assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
LoopBase<BlockT> *SLP = SubLoop->ParentLoop; // SubLoopParent
typename std::vector<LoopBase<BlockT>*>::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 (LoopBase<BlockT> *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) {
typename std::map<BlockT*, LoopBase<BlockT>*>::iterator BBMI =
BBMap.find(*I);
if (BBMI == BBMap.end()) // Not in map yet...
BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level
}
// 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*, LoopBase<BlockT>*> ContainingLoops;
for (unsigned i = 0; i != L->SubLoops.size(); ++i) {
LoopBase<BlockT> *Child = L->SubLoops[i];
assert(Child->getParentLoop() == L && "Not proper child loop?");
if (LoopBase<BlockT> *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) {
LoopBase<BlockT> *&BlockLoop = ContainingLoops[Child->Blocks[b]];
if (BlockLoop == 0) { // Child block not processed yet...
BlockLoop = Child;
} else if (BlockLoop != Child) {
LoopBase<BlockT> *SubLoop = BlockLoop;
// Reparent all of the blocks which used to belong to BlockLoops
for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++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(LoopBase<BlockT> *NewChild,
LoopBase<BlockT> *NewParent) {
LoopBase<BlockT> *OldParent = NewChild->getParentLoop();
assert(OldParent && OldParent == NewParent->getParentLoop() &&
NewChild != NewParent && "Not sibling loops!");
// Remove NewChild from being a child of OldParent
typename std::vector<LoopBase<BlockT>*>::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(LoopBase<BlockT> *L, LoopBase<BlockT> *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(std::ostream &OS, const Module* ) 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->getLoopDepth() << "\n";
#endif
}
};
class LoopInfo : public FunctionPass {
LoopInfoBase<BasicBlock>* LI;
friend class LoopBase<BasicBlock>;
public:
static char ID; // Pass identification, replacement for typeid
LoopInfo() : FunctionPass(intptr_t(&ID)) {
LI = new LoopInfoBase<BasicBlock>();
}
~LoopInfo() { delete LI; }
LoopInfoBase<BasicBlock>& getBase() { return *LI; }
/// iterator/begin/end - The interface to the top-level loops in the current
/// function.
///
typedef std::vector<Loop*>::const_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 releaseMemory() { LI->releaseMemory(); }
virtual void print(std::ostream &O, const Module* M = 0) const {
if (O) LI->print(O, M);
}
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);
}
};
// Allow clients to walk the list of nested loops...
template <> struct GraphTraits<const Loop*> {
typedef const Loop NodeType;
typedef std::vector<Loop*>::const_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 std::vector<Loop*>::const_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>
void LoopBase<BlockT>::addBasicBlockToLoop(BlockT *NewBB,
LoopInfoBase<BlockT> &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!");
// Add the loop mapping to the LoopInfo object...
LIB.BBMap[NewBB] = this;
// Add the basic block to this loop and all parent loops...
LoopBase<BlockT> *L = this;
while (L) {
L->Blocks.push_back(NewBB);
L = L->getParentLoop();
}
}
} // End llvm namespace
#endif