//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "loop-rotate"
-
#include "llvm/Transforms/Scalar.h"
#include "llvm/Function.h"
-#include "llvm/Instructions.h"
+#include "llvm/IntrinsicInst.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/SmallVector.h"
-
using namespace llvm;
#define MAX_HEADER_SIZE 16
STATISTIC(NumRotated, "Number of loops rotated");
namespace {
- class VISIBILITY_HIDDEN RenameData {
+ class RenameData {
public:
RenameData(Instruction *O, Value *P, Instruction *H)
: Original(O), PreHeader(P), Header(H) { }
Instruction *Header; // New header replacement
};
- class VISIBILITY_HIDDEN LoopRotate : public LoopPass {
-
+ class LoopRotate : public LoopPass {
public:
static char ID; // Pass ID, replacement for typeid
LoopRotate() : LoopPass(&ID) {}
Pass *llvm::createLoopRotatePass() { return new LoopRotate(); }
/// Rotate Loop L as many times as possible. Return true if
-/// loop is rotated at least once.
+/// the loop is rotated at least once.
bool LoopRotate::runOnLoop(Loop *Lp, LPPassManager &LPM) {
bool RotatedOneLoop = false;
OrigPreHeader = L->getLoopPreheader();
OrigLatch = L->getLoopLatch();
- // If loop has only one block then there is not much to rotate.
+ // If the loop has only one block then there is not much to rotate.
if (L->getBlocks().size() == 1)
return false;
assert(OrigHeader && OrigLatch && OrigPreHeader &&
"Loop is not in canonical form");
- // If loop header is not one of the loop exit block then
- // either this loop is already rotated or it is not
+ // If the loop header is not one of the loop exiting blocks then
+ // either this loop is already rotated or it is not
// suitable for loop rotation transformations.
if (!L->isLoopExit(OrigHeader))
return false;
// Check size of original header and reject
// loop if it is very big.
- if (OrigHeader->size() > MAX_HEADER_SIZE)
+ unsigned Size = 0;
+
+ // FIXME: Use common api to estimate size.
+ for (BasicBlock::const_iterator OI = OrigHeader->begin(),
+ OE = OrigHeader->end(); OI != OE; ++OI) {
+ if (isa<PHINode>(OI))
+ continue; // PHI nodes don't count.
+ if (isa<DbgInfoIntrinsic>(OI))
+ continue; // Debug intrinsics don't count as size.
+ Size++;
+ }
+
+ if (Size > MAX_HEADER_SIZE)
return false;
// Now, this loop is suitable for rotation.
+ // Anything ScalarEvolution may know about this loop or the PHI nodes
+ // in its header will soon be invalidated.
+ if (ScalarEvolution *SE = getAnalysisIfAvailable<ScalarEvolution>())
+ SE->forgetLoopBackedgeTakenCount(L);
+
// Find new Loop header. NewHeader is a Header's one and only successor
// that is inside loop. Header's other successor is outside the
// loop. Otherwise loop is not suitable for rotation.
assert(NewHeader && "Unable to determine new loop header");
assert(L->contains(NewHeader) && !L->contains(Exit) &&
"Unable to determine loop header and exit blocks");
-
- // Copy PHI nodes and other instructions from original header
- // into original pre-header. Unlike original header, original pre-header is
- // not a member of loop.
+
+ // This code assumes that the new header has exactly one predecessor.
+ // Remove any single-entry PHI nodes in it.
+ assert(NewHeader->getSinglePredecessor() &&
+ "New header doesn't have one pred!");
+ FoldSingleEntryPHINodes(NewHeader);
+
+ // Copy PHI nodes and other instructions from the original header
+ // into the original pre-header. Unlike the original header, the original
+ // pre-header is not a member of the loop.
//
- // New loop header is one and only successor of original header that
+ // The new loop header is the one and only successor of original header that
// is inside the loop. All other original header successors are outside
- // the loop. Copy PHI Nodes from original header into new loop header.
+ // the loop. Copy PHI Nodes from the original header into the new loop header.
// Add second incoming value, from original loop pre-header into these phi
// nodes. If a value defined in original header is used outside original
// header then new loop header will need new phi nodes with two incoming
// are directly propagated.
Value *NPV = PN->getIncomingValueForBlock(OrigPreHeader);
- // Create new PHI node with two incoming values for NewHeader.
- // One incoming value is from OrigLatch (through OrigHeader) and
+ // Create a new PHI node with two incoming values for NewHeader.
+ // One incoming value is from OrigLatch (through OrigHeader) and the
// second incoming value is from original pre-header.
PHINode *NH = PHINode::Create(PN->getType(), PN->getName(),
NewHeader->begin());
// Add second incoming argument from new Pre header.
UPhi->addIncoming(ILoopHeaderInfo.PreHeader, OrigPreHeader);
} else {
- // Used outside Exit block. Create a new PHI node from exit block
- // to receive value from ne new header ane pre header.
+ // Used outside Exit block. Create a new PHI node in the exit block
+ // to receive the value from the new header and pre-header.
PHINode *PN = PHINode::Create(U->getType(), U->getName(),
Exit->begin());
PN->addIncoming(ILoopHeaderInfo.PreHeader, OrigPreHeader);
// Removing incoming branch from loop preheader to original header.
// Now original header is inside the loop.
- for (BasicBlock::iterator I = OrigHeader->begin(), E = OrigHeader->end();
- I != E; ++I)
- if (PHINode *PN = dyn_cast<PHINode>(I))
- PN->removeIncomingValue(OrigPreHeader);
+ for (BasicBlock::iterator I = OrigHeader->begin();
+ (PN = dyn_cast<PHINode>(I)); ++I)
+ PN->removeIncomingValue(OrigPreHeader);
// Make NewHeader as the new header for the loop.
L->moveToHeader(NewHeader);
}
/// Make sure all Exit block PHINodes have required incoming values.
-/// If incoming value is constant or defined outside the loop then
-/// PHINode may not have an entry for original pre-header.
+/// If an incoming value is constant or defined outside the loop then
+/// PHINode may not have an entry for the original pre-header.
void LoopRotate::updateExitBlock() {
- for (BasicBlock::iterator I = Exit->begin(), E = Exit->end();
- I != E; ++I) {
-
- PHINode *PN = dyn_cast<PHINode>(I);
- if (!PN)
- break;
+ PHINode *PN;
+ for (BasicBlock::iterator I = Exit->begin();
+ (PN = dyn_cast<PHINode>(I)); ++I) {
// There is already one incoming value from original pre-header block.
if (PN->getBasicBlockIndex(OrigPreHeader) != -1)
const RenameData *ILoopHeaderInfo;
Value *V = PN->getIncomingValueForBlock(OrigHeader);
- if (isa<Instruction>(V) &&
+ if (isa<Instruction>(V) &&
(ILoopHeaderInfo = findReplacementData(cast<Instruction>(V)))) {
assert(ILoopHeaderInfo->PreHeader && "Missing New Preheader Instruction");
PN->addIncoming(ILoopHeaderInfo->PreHeader, OrigPreHeader);
// Right now original pre-header has two successors, new header and
// exit block. Insert new block between original pre-header and
// new header such that loop's new pre-header has only one successor.
- BasicBlock *NewPreHeader = BasicBlock::Create("bb.nph",
+ BasicBlock *NewPreHeader = BasicBlock::Create(OrigHeader->getContext(),
+ "bb.nph",
OrigHeader->getParent(),
NewHeader);
LoopInfo &LI = LPM.getAnalysis<LoopInfo>();
"Unexpected original pre-header terminator");
OrigPH_BI->setSuccessor(1, NewPreHeader);
}
-
- for (BasicBlock::iterator I = NewHeader->begin(), E = NewHeader->end();
- I != E; ++I) {
- PHINode *PN = dyn_cast<PHINode>(I);
- if (!PN)
- break;
+ PHINode *PN;
+ for (BasicBlock::iterator I = NewHeader->begin();
+ (PN = dyn_cast<PHINode>(I)); ++I) {
int index = PN->getBasicBlockIndex(OrigPreHeader);
assert(index != -1 && "Expected incoming value from Original PreHeader");
PN->setIncomingBlock(index, NewPreHeader);
"Expected only one incoming value from Original PreHeader");
}
- if (DominatorTree *DT = getAnalysisToUpdate<DominatorTree>()) {
+ if (DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>()) {
DT->addNewBlock(NewPreHeader, OrigPreHeader);
DT->changeImmediateDominator(L->getHeader(), NewPreHeader);
DT->changeImmediateDominator(Exit, OrigPreHeader);
DT->changeImmediateDominator(OrigHeader, OrigLatch);
}
- if (DominanceFrontier *DF = getAnalysisToUpdate<DominanceFrontier>()) {
+ if (DominanceFrontier *DF = getAnalysisIfAvailable<DominanceFrontier>()) {
// New Preheader's dominance frontier is Exit block.
DominanceFrontier::DomSetType NewPHSet;
NewPHSet.insert(Exit);
DF->addBasicBlock(L->getHeader(), LatchSet);
}
- // If a loop block dominates new loop latch then its frontier is
- // new header and Exit.
+ // If a loop block dominates new loop latch then add to its frontiers
+ // new header and Exit and remove new latch (which is equal to original
+ // header).
BasicBlock *NewLatch = L->getLoopLatch();
- DominatorTree *DT = getAnalysisToUpdate<DominatorTree>();
- for (Loop::block_iterator BI = L->block_begin(), BE = L->block_end();
- BI != BE; ++BI) {
- BasicBlock *B = *BI;
- if (DT->dominates(B, NewLatch)) {
- DominanceFrontier::iterator BDFI = DF->find(B);
- if (BDFI != DF->end()) {
- DominanceFrontier::DomSetType &BSet = BDFI->second;
- BSet = BDFI->second;
- BSet.clear();
- BSet.insert(L->getHeader());
- BSet.insert(Exit);
- } else {
- DominanceFrontier::DomSetType BSet;
- BSet.insert(L->getHeader());
- BSet.insert(Exit);
- DF->addBasicBlock(B, BSet);
+
+ assert(NewLatch == OrigHeader && "NewLatch is inequal to OrigHeader");
+
+ if (DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>()) {
+ for (Loop::block_iterator BI = L->block_begin(), BE = L->block_end();
+ BI != BE; ++BI) {
+ BasicBlock *B = *BI;
+ if (DT->dominates(B, NewLatch)) {
+ DominanceFrontier::iterator BDFI = DF->find(B);
+ if (BDFI != DF->end()) {
+ DominanceFrontier::DomSetType &BSet = BDFI->second;
+ BSet.erase(NewLatch);
+ BSet.insert(L->getHeader());
+ BSet.insert(Exit);
+ } else {
+ DominanceFrontier::DomSetType BSet;
+ BSet.insert(L->getHeader());
+ BSet.insert(Exit);
+ DF->addBasicBlock(B, BSet);
+ }
}
}
}
// Preserve canonical loop form, which means Exit block should
// have only one predecessor.
- BasicBlock *NExit = SplitEdge(L->getLoopLatch(), Exit, this);
-
- // Preserve LCSSA.
- BasicBlock::iterator I = Exit->begin(), E = Exit->end();
- PHINode *PN = NULL;
- for (; (PN = dyn_cast<PHINode>(I)); ++I) {
- unsigned N = PN->getNumIncomingValues();
- for (unsigned index = 0; index < N; ++index)
- if (PN->getIncomingBlock(index) == NExit) {
- PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName(),
- NExit->begin());
- NewPN->addIncoming(PN->getIncomingValue(index), L->getLoopLatch());
- PN->setIncomingValue(index, NewPN);
- PN->setIncomingBlock(index, NExit);
- break;
- }
- }
+ SplitEdge(L->getLoopLatch(), Exit, this);
assert(NewHeader && L->getHeader() == NewHeader &&
"Invalid loop header after loop rotation");
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