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Do not create new pre-header. Reuse original pre-header.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35825 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Devang Patel 2007-04-09 19:04:21 +00:00
parent fa3e91242f
commit e98815469c
1 changed files with 57 additions and 73 deletions
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130
lib/Transforms/Scalar/LoopRotation.cpp
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@ -33,11 +33,11 @@ namespace {
class VISIBILITY_HIDDEN RenameData {
public:
RenameData(Instruction *O, Instruction *P, Instruction *H)
RenameData(Instruction *O, Value *P, Instruction *H)
: Original(O), PreHeader(P), Header(H) { }
public:
Instruction *Original; // Original instruction
Instruction *PreHeader; // New pre-header replacement
Value *PreHeader; // Original pre-header replacement
Instruction *Header; // New header replacement
};
@ -65,7 +65,7 @@ namespace {
/// 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 new pre-header.
/// PHINode may not have an entry for original pre-header.
void updateExitBlock();
/// Return true if this instruction is used outside original header.
@ -82,7 +82,6 @@ namespace {
BasicBlock *OrigPreHeader;
BasicBlock *OrigLatch;
BasicBlock *NewHeader;
BasicBlock *NewPreHeader;
BasicBlock *Exit;
SmallVector<RenameData, MAX_HEADER_SIZE> LoopHeaderInfo;
@ -125,6 +124,9 @@ bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
if (!OrigHeader || !OrigLatch || !OrigPreHeader)
return false;
if (!OrigHeader || !OrigLatch || !OrigPreHeader)
return false;
// If loop header is not one of the loop exit block then
// either this loop is already rotated or it is not
// suitable for loop rotation transformations.
@ -164,42 +166,40 @@ bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
// Now, this loop is suitable for rotation.
// Copy PHI nodes and other instructions from original header
// into new pre-header. Unlike original header, new pre-header is
// not a member of loop. New pre-header has only one predecessor,
// that is original loop pre-header.
// into original pre-header. Unlike original header, original pre-header is
// not a member of loop.
//
// New loop header is 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.
// Add second incoming value, from new loop pre-header into these phi
// 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
// values, one definition from original header and second definition is
// from new loop pre-header (which is a clone of original header definition).
// from original loop pre-header.
NewPreHeader = new BasicBlock("bb.nph", OrigHeader->getParent(), OrigHeader);
// Remove terminator from Original pre-header. Original pre-header will
// receive a clone of original header terminator as a new terminator.
OrigPreHeader->getInstList().pop_back();
BasicBlock::iterator I = OrigHeader->begin(), E = OrigHeader->end();
PHINode *PN = NULL;
for (; (PN = dyn_cast<PHINode>(I)); ++I) {
Instruction *In = I;
// Create new PHI node with one value incoming from OrigPreHeader.
// NewPreHeader has only one predecessor, OrigPreHeader.
PHINode *NPH = new PHINode(In->getType(), In->getName());
NPH->addIncoming(PN->getIncomingValueForBlock(OrigPreHeader),
OrigPreHeader);
NewPreHeader->getInstList().push_back(NPH);
// PHI nodes are not copied into original pre-header. Instead their values
// 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
// second incoming value is from NewPreHeader.
// second incoming value is from original pre-header.
PHINode *NH = new PHINode(In->getType(), In->getName());
NH->addIncoming(PN->getIncomingValueForBlock(OrigLatch), OrigHeader);
NH->addIncoming(NPH, NewPreHeader);
NH->addIncoming(NPV, OrigPreHeader);
NewHeader->getInstList().push_front(NH);
// "In" can be replaced by NPH or NH at various places.
LoopHeaderInfo.push_back(RenameData(In, NPH, NH));
// "In" can be replaced by NH at various places.
LoopHeaderInfo.push_back(RenameData(In, NPV, NH));
}
// Now, handle non-phi instructions.
@ -207,20 +207,36 @@ bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
Instruction *In = I;
assert (!isa<PHINode>(In) && "PHINode is not expected here");
// This is not a PHI instruction. Insert its clone into NewPreHeader.
// This is not a PHI instruction. Insert its clone into original pre-header.
// If this instruction is using a value from same basic block then
// update it to use value from cloned instruction.
Instruction *C = In->clone();
C->setName(In->getName());
NewPreHeader->getInstList().push_back(C);
OrigPreHeader->getInstList().push_back(C);
for (unsigned opi = 0, e = In->getNumOperands(); opi != e; ++opi) {
if (Instruction *OpPhi = dyn_cast<PHINode>(In->getOperand(opi))) {
if (const RenameData *D = findReplacementData(OpPhi)) {
// This is using values from original header PHI node.
// Here, directly used incoming value from original pre-header.
C->setOperand(opi, D->PreHeader);
}
}
else if (Instruction *OpInsn =
dyn_cast<Instruction>(In->getOperand(opi))) {
if (const RenameData *D = findReplacementData(OpInsn))
C->setOperand(opi, D->PreHeader);
}
}
// If this instruction is used outside this basic block then
// create new PHINode for this instruction.
Instruction *NewHeaderReplacement = NULL;
if (usedOutsideOriginalHeader(In)) {
PHINode *PN = new PHINode(In->getType(), In->getName());
PN->addIncoming(In, OrigHeader);
PN->addIncoming(C, NewPreHeader);
PN->addIncoming(C, OrigPreHeader);
NewHeader->getInstList().push_front(PN);
NewHeaderReplacement = PN;
}
@ -229,38 +245,8 @@ bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
LoopHeaderInfo.push_back(RenameData(In, C, NewHeaderReplacement));
}
// Update new pre-header.
// Rename values that are defined in original header to reflects values
// defined in new pre-header.
for(unsigned LHI = 0, LHI_E = LoopHeaderInfo.size(); LHI != LHI_E; ++LHI) {
const RenameData &ILoopHeaderInfo = LoopHeaderInfo[LHI];
Instruction *In = ILoopHeaderInfo.Original;
Instruction *C = ILoopHeaderInfo.PreHeader;
// If this instruction is not from new pre-header then is not new
// pre-header then this instruction is not handled here.
if (C->getParent() != NewPreHeader)
continue;
// PHINodes uses value from pre-header predecessors.
if (isa<PHINode>(In))
continue;
for (unsigned opi = 0, e = In->getNumOperands(); opi != e; ++opi) {
if (Instruction *OpPhi = dyn_cast<PHINode>(In->getOperand(opi))) {
if (const RenameData *D = findReplacementData(OpPhi))
C->setOperand(opi, D->PreHeader);
}
else if (Instruction *OpInsn =
dyn_cast<Instruction>(In->getOperand(opi))) {
if (const RenameData *D = findReplacementData(OpInsn))
C->setOperand(opi, D->PreHeader);
}
}
}
// Rename uses of original header instructions to reflect their new
// definitions (either from new pre-header node or from newly created
// definitions (either from original pre-header node or from newly created
// new header PHINodes.
//
// Original header instructions are used in
@ -268,7 +254,7 @@ bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
//
// If instruction is used in non-phi instructions then it is using
// defintion from original heder iteself. Do not replace this use
// with definition from new header or new pre-header.
// with definition from new header or original pre-header.
//
// If instruction is used in phi node then it is an incoming
// value. Rename its use to reflect new definition from new-preheader
@ -334,7 +320,7 @@ bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
// UPhi already has one incoming argument from original header.
// Add second incoming argument from new Pre header.
UPhi->addIncoming(ILoopHeaderInfo.PreHeader, NewPreHeader);
UPhi->addIncoming(ILoopHeaderInfo.PreHeader, OrigPreHeader);
}
}
@ -345,16 +331,15 @@ bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
// Removing incoming branch from loop preheader to original header.
// Now original header is inside the loop.
OrigHeader->removePredecessor(OrigPreHeader);
for (BasicBlock::iterator I = OrigHeader->begin(), E = OrigHeader->end();
I != E; ++I) {
Instruction *In = I;
PHINode *PN = dyn_cast<PHINode>(In);
if (!PN)
break;
// Establish NewPreHeader as loop preheader. Add unconditional branch
// from original loop pre-header to new loop pre-header. Add NewPreHEader
// in loop nest.
BranchInst *PH_BI = cast<BranchInst>(OrigPreHeader->getTerminator());
PH_BI->setSuccessor(0, NewPreHeader);
LoopInfo &LI = LPM.getAnalysis<LoopInfo>();
if (Loop *PL = LI.getLoopFor(OrigPreHeader))
PL->addBasicBlockToLoop(NewPreHeader, LI);
PN->removeIncomingValue(OrigPreHeader);
}
// Make NewHeader as the new header for the loop.
L->moveToHeader(NewHeader);
@ -365,7 +350,7 @@ bool LoopRotate::rotateLoop(Loop *Lp, LPPassManager &LPM) {
/// 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 new pre-header.
/// PHINode may not have an entry for original pre-header.
void LoopRotate::updateExitBlock() {
for (BasicBlock::iterator I = Exit->begin(), E = Exit->end();
@ -375,8 +360,8 @@ void LoopRotate::updateExitBlock() {
if (!PN)
break;
// There is already one incoming value from new pre-header block.
if (PN->getBasicBlockIndex(NewPreHeader) != -1)
// There is already one incoming value from original pre-header block.
if (PN->getBasicBlockIndex(OrigPreHeader) != -1)
return;
const RenameData *ILoopHeaderInfo;
@ -384,9 +369,9 @@ void LoopRotate::updateExitBlock() {
if (isa<Instruction>(V) &&
(ILoopHeaderInfo = findReplacementData(cast<Instruction>(V)))) {
assert (ILoopHeaderInfo->PreHeader && "Missing New Preheader Instruction");
PN->addIncoming(ILoopHeaderInfo->PreHeader, NewPreHeader);
PN->addIncoming(ILoopHeaderInfo->PreHeader, OrigPreHeader);
} else {
PN->addIncoming(V, NewPreHeader);
PN->addIncoming(V, OrigPreHeader);
}
}
}
@ -397,7 +382,6 @@ void LoopRotate::initialize() {
OrigHeader = NULL;
OrigPreHeader = NULL;
NewHeader = NULL;
NewPreHeader = NULL;
Exit = NULL;
LoopHeaderInfo.clear();