//===----------------------------------------------------------------------===//
//
// 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
+// 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
#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"
BlockT *getHeader() const { return Blocks.front(); }
LoopT *getParentLoop() const { return ParentLoop; }
- /// contains - Return true if the specified basic block is in this loop
+ /// 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; }
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.
+ /// isLoopExiting - True if terminator in the block can branch to another
+ /// block that is outside of the current loop.
///
- bool isLoopExit(const BlockT *BB) const {
+ bool isLoopExiting(const BlockT *BB) const {
typedef GraphTraits<BlockT*> BlockTraits;
for (typename BlockTraits::ChildIteratorType SI =
BlockTraits::child_begin(const_cast<BlockT*>(BB)),
return 0;
}
+ /// Edge type.
+ typedef std::pair<BlockT*, BlockT*> Edge;
+
/// getExitEdges - Return all pairs of (_inside_block_,_outside_block_).
- typedef std::pair<const BlockT*,const BlockT*> Edge;
- void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const {
+ 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());
- std::sort(LoopBBs.begin(), LoopBBs.end());
+ array_pod_sort(LoopBBs.begin(), LoopBBs.end());
typedef GraphTraits<BlockT*> BlockTraits;
for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++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(std::make_pair(*BI, *I));
+ ExitEdges.push_back(EdgeT(*BI, *I));
}
/// getLoopPreheader - If there is a preheader for this loop, return it. A
/// 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;
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)
+ 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 = *PI;
+ Out = N;
}
+ }
// 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 single latch block for this loop, return it.
/// A latch block is a block that contains a branch back to the header.
- /// 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;
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;
+ for (; PI != PE; ++PI) {
+ typename InvBlockTraits::NodeType *N = *PI;
+ if (contains(N)) {
+ if (Latch) return 0;
+ Latch = N;
+ }
}
- ++PI;
- if (PI != PE) return 0; // more than two preds
return Latch;
}
void verifyLoop() const {
#ifndef NDEBUG
assert(!Blocks.empty() && "Loop header is missing");
- assert(getHeader() && "Loop header is missing");
- // Verify the individual blocks.
+ // 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 (block_iterator I = block_begin(), E = block_end(); I != E; ++I) {
BlockT *BB = *I;
bool HasInsideLoopSuccs = false;
for (typename BlockTraits::ChildIteratorType SI =
BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB);
SI != SE; ++SI)
- if (contains(*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) {
- if (contains(*PI))
+ typename InvBlockTraits::NodeType *N = *PI;
+ if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), N))
HasInsideLoopPreds = true;
else
- OutsideLoopPreds.push_back(*PI);
+ OutsideLoopPreds.push_back(N);
}
if (BB == getHeader()) {
"Loop contains function entry block!");
}
- // Verify the subloops.
- for (iterator I = begin(), E = end(); I != E; ++I) {
+ // 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(contains(*BI) &&
+ assert(std::binary_search(LoopBBs.begin(), LoopBBs.end(), *BI) &&
"Loop does not contain all the blocks of a subloop!");
}
- // Recursively check the subloop.
- (*I)->verifyLoop();
- }
- // Verify the parent loop.
+ // Check the parent loop pointer.
if (ParentLoop) {
- bool FoundSelf = false;
- for (iterator I = ParentLoop->begin(), E = ParentLoop->end(); I != E; ++I)
- if (*I == this) {
- FoundSelf = true;
- break;
- }
- assert(FoundSelf && "Loop is not a subloop of its parent!");
+ 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() const {
+ // Verify this loop.
+ verifyLoop();
+ // Verify the subloops.
+ for (iterator I = begin(), E = end(); I != E; ++I)
+ (*I)->verifyLoopNest();
+ }
+
void print(raw_ostream &OS, unsigned Depth = 0) const {
OS.indent(Depth*2) << "Loop at depth " << getLoopDepth()
<< " containing: ";
WriteAsOperand(OS, BB, false);
if (BB == getHeader()) OS << "<header>";
if (BB == getLoopLatch()) OS << "<latch>";
- if (isLoopExit(BB)) OS << "<exit>";
+ if (isLoopExiting(BB)) OS << "<exiting>";
}
OS << "\n";
for (iterator I = begin(), E = end(); I != E; ++I)
(*I)->print(OS, Depth+2);
}
-
- void dump() const {
- print(errs());
- }
-
+
protected:
friend class LoopInfoBase<BlockT, LoopT>;
explicit LoopBase(BlockT *BB) : ParentLoop(0) {
}
};
+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() {}
///
bool isLoopInvariant(Value *V) const;
- /// isLoopInvariant - Return true if the specified instruction is
- /// loop-invariant.
- ///
- bool isLoopInvariant(Instruction *I) 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.
///
PHINode *getCanonicalInductionVariable() const;
- /// 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.
- ///
- Instruction *getCanonicalInductionVariableIncrement() const;
-
/// 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,
/// 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)
+ ///
+ /// The IndVarSimplify pass transforms loops to have a form that this
+ /// function easily understands.
+ ///
unsigned getSmallConstantTripCount() const;
/// getSmallConstantTripMultiple - Returns the largest constant divisor of the
unsigned getSmallConstantTripMultiple() const;
/// isLCSSAForm - Return true if the Loop is in LCSSA form
- bool isLCSSAForm() const;
+ 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;
+ /// 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 is in canonical form.
+ /// This assumes that loop exits are in canonical form.
///
void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const;
/// 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) {}
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);
+ I != E; ++I) {
+ typename InvBlockTraits::NodeType *N = *I;
+ if (DT.dominates(BB, N)) // If BB dominates its predecessor...
+ TodoStack.push_back(N);
+ }
if (TodoStack.empty()) return 0; // No backedges to this block...
if (LoopT *SubLoop =
const_cast<LoopT *>(getLoopFor(X)))
if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){
- // Remove the subloop from it's current parent...
+ // Remove the subloop from its current parent...
assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L);
LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent
typename std::vector<LoopT *>::iterator I =
} else if (BlockLoop != Child) {
LoopT *SubLoop = BlockLoop;
// Reparent all of the blocks which used to belong to BlockLoops
- for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j)
+ 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
public:
static char ID; // Pass identification, replacement for typeid
- LoopInfo() : FunctionPass(&ID) {}
+ LoopInfo() : FunctionPass(ID) {
+ initializeLoopInfoPass(*PassRegistry::getPassRegistry());
+ }
LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; }
void removeBlock(BasicBlock *BB) {
LI.removeBlock(BB);
}
-
- static bool isNotAlreadyContainedIn(const Loop *SubLoop,
- const Loop *ParentLoop) {
- return
- LoopInfoBase<BasicBlock, Loop>::isNotAlreadyContainedIn(SubLoop,
- ParentLoop);
- }
};
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