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Start the process of making MachineLoopInfo possible by templating Loop.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44097 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson
2007-11-14 02:33:58 +00:00
parent ffb15de60e
commit 019b92a70c
6 changed files with 349 additions and 444 deletions
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lib/Analysis/LoopInfo.cpp
-396
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@@ -34,69 +34,9 @@ X("loops", "Natural Loop Construction", true);
//===----------------------------------------------------------------------===//
// Loop implementation
//
bool Loop::contains(const BasicBlock *BB) const {
return std::find(Blocks.begin(), Blocks.end(), BB) != Blocks.end();
}
bool Loop::isLoopExit(const BasicBlock *BB) const {
for (succ_const_iterator SI = succ_begin(BB), SE = succ_end(BB);
SI != SE; ++SI) {
if (!contains(*SI))
return true;
}
return false;
}
/// getNumBackEdges - Calculate the number of back edges to the loop header.
///
unsigned Loop::getNumBackEdges() const {
unsigned NumBackEdges = 0;
BasicBlock *H = getHeader();
for (pred_iterator I = pred_begin(H), E = pred_end(H); I != E; ++I)
if (contains(*I))
++NumBackEdges;
return NumBackEdges;
}
/// isLoopInvariant - Return true if the specified value is loop invariant
///
bool Loop::isLoopInvariant(Value *V) const {
if (Instruction *I = dyn_cast<Instruction>(V))
return !contains(I->getParent());
return true; // All non-instructions are loop invariant
}
void Loop::print(std::ostream &OS, unsigned Depth) 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);
}
/// verifyLoop - Verify loop structure
void Loop::verifyLoop() const {
#ifndef NDEBUG
assert (getHeader() && "Loop header is missing");
assert (getLoopPreheader() && "Loop preheader is missing");
assert (getLoopLatch() && "Loop latch is missing");
for (std::vector<Loop*>::const_iterator I = SubLoops.begin(), E = SubLoops.end();
I != E; ++I)
(*I)->verifyLoop();
#endif
}
void Loop::dump() const {
print(cerr);
}
//===----------------------------------------------------------------------===//
// LoopInfo implementation
@@ -341,341 +281,5 @@ void LoopInfo::removeBlock(BasicBlock *BB) {
}
}
//===----------------------------------------------------------------------===//
// APIs for simple analysis of the loop.
//
/// 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 Loop::getExitingBlocks(SmallVectorImpl<BasicBlock*> &ExitingBlocks) const {
// Sort the blocks vector so that we can use binary search to do quick
// lookups.
SmallVector<BasicBlock*, 128> LoopBBs(block_begin(), block_end());
std::sort(LoopBBs.begin(), LoopBBs.end());
for (std::vector<BasicBlock*>::const_iterator BI = Blocks.begin(),
BE = Blocks.end(); BI != BE; ++BI)
for (succ_iterator I = succ_begin(*BI), E = succ_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 Loop::getExitBlocks(SmallVectorImpl<BasicBlock*> &ExitBlocks) const {
// Sort the blocks vector so that we can use binary search to do quick
// lookups.
SmallVector<BasicBlock*, 128> LoopBBs(block_begin(), block_end());
std::sort(LoopBBs.begin(), LoopBBs.end());
for (std::vector<BasicBlock*>::const_iterator BI = Blocks.begin(),
BE = Blocks.end(); BI != BE; ++BI)
for (succ_iterator I = succ_begin(*BI), E = succ_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 Loop::getUniqueExitBlocks(SmallVectorImpl<BasicBlock*> &ExitBlocks) const {
// Sort the blocks vector so that we can use binary search to do quick
// lookups.
SmallVector<BasicBlock*, 128> LoopBBs(block_begin(), block_end());
std::sort(LoopBBs.begin(), LoopBBs.end());
std::vector<BasicBlock*> switchExitBlocks;
for (std::vector<BasicBlock*>::const_iterator BI = Blocks.begin(),
BE = Blocks.end(); BI != BE; ++BI) {
BasicBlock *current = *BI;
switchExitBlocks.clear();
for (succ_iterator I = succ_begin(*BI), E = succ_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;
pred_iterator PI = pred_begin(*I);
BasicBlock *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 (current->getTerminator()->getNumSuccessors() <= 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.
///
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.
assert(Out && "Header of loop has no predecessors from outside loop?");
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;
}
/// 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.
BasicBlock *Loop::getLoopLatch() const {
BasicBlock *Header = getHeader();
pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
if (PI == PE) return 0; // no preds?
BasicBlock *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.
///
PHINode *Loop::getCanonicalInductionVariable() const {
BasicBlock *H = getHeader();
BasicBlock *Incoming = 0, *Backedge = 0;
pred_iterator PI = pred_begin(H);
assert(PI != pred_end(H) && "Loop must have at least one backedge!");
Backedge = *PI++;
if (PI == pred_end(H)) return 0; // dead loop
Incoming = *PI++;
if (PI != pred_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 (BasicBlock::iterator I = H->begin(); isa<PHINode>(I); ++I) {
PHINode *PN = cast<PHINode>(I);
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.
///
Instruction *Loop::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.
///
Value *Loop::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));
BasicBlock *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;
}
/// isLCSSAForm - Return true if the Loop is in LCSSA form
bool Loop::isLCSSAForm() const {
// Sort the blocks vector so that we can use binary search to do quick
// lookups.
SmallPtrSet<BasicBlock*, 16> LoopBBs(block_begin(), block_end());
for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) {
BasicBlock *BB = *BI;
for (BasicBlock::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) {
BasicBlock *UserBB = cast<Instruction>(*UI)->getParent();
if (PHINode *P = dyn_cast<PHINode>(*UI)) {
unsigned OperandNo = UI.getOperandNo();
UserBB = P->getIncomingBlock(OperandNo/2);
}
// 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 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((Blocks.empty() || 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();
}
}
/// replaceChildLoopWith - This is used when splitting loops up. It replaces
/// the OldChild entry in our children list with NewChild, and updates the
/// parent pointers of the two loops as appropriate.
void Loop::replaceChildLoopWith(Loop *OldChild, Loop *NewChild) {
assert(OldChild->ParentLoop == this && "This loop is already broken!");
assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
std::vector<Loop*>::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.
///
void Loop::addChildLoop(Loop *NewChild) {
assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!");
NewChild->ParentLoop = this;
SubLoops.push_back(NewChild);
}
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);
}
/// 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.
Loop *Loop::removeChildLoop(iterator I) {
assert(I != SubLoops.end() && "Cannot remove end iterator!");
Loop *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;
}
/// removeBlockFromLoop - This removes the specified basic block from the
/// current loop, updating the Blocks and ExitBlocks lists as appropriate. This
/// does not update the mapping in the LoopInfo class.
void Loop::removeBlockFromLoop(BasicBlock *BB) {
RemoveFromVector(Blocks, BB);
}
// Ensure this file gets linked when LoopInfo.h is used.
DEFINING_FILE_FOR(LoopInfo)