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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150438 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick 2012-02-14 00:00:19 +00:00
parent bdf9db6f49
commit c3a825b76c
1 changed files with 30 additions and 30 deletions
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60
lib/Transforms/Scalar/LoopRotation.cpp
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@ -53,12 +53,12 @@ namespace {
bool runOnLoop(Loop *L, LPPassManager &LPM);
bool rotateLoop(Loop *L);
private:
LoopInfo *LI;
};
}
char LoopRotate::ID = 0;
INITIALIZE_PASS_BEGIN(LoopRotate, "loop-rotate", "Rotate Loops", false, false)
INITIALIZE_PASS_DEPENDENCY(LoopInfo)
@ -92,18 +92,18 @@ static void RewriteUsesOfClonedInstructions(BasicBlock *OrigHeader,
BasicBlock::iterator I, E = OrigHeader->end();
for (I = OrigHeader->begin(); PHINode *PN = dyn_cast<PHINode>(I); ++I)
PN->removeIncomingValue(PN->getBasicBlockIndex(OrigPreheader));
// Now fix up users of the instructions in OrigHeader, inserting PHI nodes
// as necessary.
SSAUpdater SSA;
for (I = OrigHeader->begin(); I != E; ++I) {
Value *OrigHeaderVal = I;
// If there are no uses of the value (e.g. because it returns void), there
// is nothing to rewrite.
if (OrigHeaderVal->use_empty())
continue;
Value *OrigPreHeaderVal = ValueMap[OrigHeaderVal];
// The value now exits in two versions: the initial value in the preheader
@ -111,27 +111,27 @@ static void RewriteUsesOfClonedInstructions(BasicBlock *OrigHeader,
SSA.Initialize(OrigHeaderVal->getType(), OrigHeaderVal->getName());
SSA.AddAvailableValue(OrigHeader, OrigHeaderVal);
SSA.AddAvailableValue(OrigPreheader, OrigPreHeaderVal);
// Visit each use of the OrigHeader instruction.
for (Value::use_iterator UI = OrigHeaderVal->use_begin(),
UE = OrigHeaderVal->use_end(); UI != UE; ) {
// Grab the use before incrementing the iterator.
Use &U = UI.getUse();
// Increment the iterator before removing the use from the list.
++UI;
// SSAUpdater can't handle a non-PHI use in the same block as an
// earlier def. We can easily handle those cases manually.
Instruction *UserInst = cast<Instruction>(U.getUser());
if (!isa<PHINode>(UserInst)) {
BasicBlock *UserBB = UserInst->getParent();
// The original users in the OrigHeader are already using the
// original definitions.
if (UserBB == OrigHeader)
continue;
// Users in the OrigPreHeader need to use the value to which the
// original definitions are mapped.
if (UserBB == OrigPreheader) {
@ -139,32 +139,32 @@ static void RewriteUsesOfClonedInstructions(BasicBlock *OrigHeader,
continue;
}
}
// Anything else can be handled by SSAUpdater.
SSA.RewriteUse(U);
}
}
}
}
/// Rotate loop LP. Return true if the loop is rotated.
bool LoopRotate::rotateLoop(Loop *L) {
// If the loop has only one block then there is not much to rotate.
if (L->getBlocks().size() == 1)
return false;
BasicBlock *OrigHeader = L->getHeader();
BranchInst *BI = dyn_cast<BranchInst>(OrigHeader->getTerminator());
if (BI == 0 || BI->isUnconditional())
return false;
// 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->isLoopExiting(OrigHeader))
return false;
// Updating PHInodes in loops with multiple exits adds complexity.
// Updating PHInodes in loops with multiple exits adds complexity.
// Keep it simple, and restrict loop rotation to loops with one exit only.
// In future, lift this restriction and support for multiple exits if
// required.
@ -184,7 +184,7 @@ bool LoopRotate::rotateLoop(Loop *L) {
// Now, this loop is suitable for rotation.
BasicBlock *OrigPreheader = L->getLoopPreheader();
BasicBlock *OrigLatch = L->getLoopLatch();
// If the loop could not be converted to canonical form, it must have an
// indirectbr in it, just give up.
if (OrigPreheader == 0 || OrigLatch == 0)
@ -203,9 +203,9 @@ bool LoopRotate::rotateLoop(Loop *L) {
if (L->contains(Exit))
std::swap(Exit, NewHeader);
assert(NewHeader && "Unable to determine new loop header");
assert(L->contains(NewHeader) && !L->contains(Exit) &&
assert(L->contains(NewHeader) && !L->contains(Exit) &&
"Unable to determine loop header and exit blocks");
// This code assumes that the new header has exactly one predecessor.
// Remove any single-entry PHI nodes in it.
assert(NewHeader->getSinglePredecessor() &&
@ -227,7 +227,7 @@ bool LoopRotate::rotateLoop(Loop *L) {
TerminatorInst *LoopEntryBranch = OrigPreheader->getTerminator();
while (I != E) {
Instruction *Inst = I++;
// If the instruction's operands are invariant and it doesn't read or write
// memory, then it is safe to hoist. Doing this doesn't change the order of
// execution in the preheader, but does prevent the instruction from
@ -240,14 +240,14 @@ bool LoopRotate::rotateLoop(Loop *L) {
Inst->moveBefore(LoopEntryBranch);
continue;
}
// Otherwise, create a duplicate of the instruction.
Instruction *C = Inst->clone();
// Eagerly remap the operands of the instruction.
RemapInstruction(C, ValueMap,
RF_NoModuleLevelChanges|RF_IgnoreMissingEntries);
// With the operands remapped, see if the instruction constant folds or is
// otherwise simplifyable. This commonly occurs because the entry from PHI
// nodes allows icmps and other instructions to fold.
@ -287,7 +287,7 @@ bool LoopRotate::rotateLoop(Loop *L) {
L->moveToHeader(NewHeader);
assert(L->getHeader() == NewHeader && "Latch block is our new header");
// At this point, we've finished our major CFG changes. As part of cloning
// the loop into the preheader we've simplified instructions and the
// duplicated conditional branch may now be branching on a constant. If it is
@ -308,16 +308,16 @@ bool LoopRotate::rotateLoop(Loop *L) {
// the dominator of Exit.
DT->changeImmediateDominator(Exit, OrigPreheader);
DT->changeImmediateDominator(NewHeader, OrigPreheader);
// Update OrigHeader to be dominated by the new header block.
DT->changeImmediateDominator(OrigHeader, OrigLatch);
}
// Right now OrigPreHeader has two successors, NewHeader and ExitBlock, and
// thus is not a preheader anymore. Split the edge to form a real preheader.
BasicBlock *NewPH = SplitCriticalEdge(OrigPreheader, NewHeader, this);
NewPH->setName(NewHeader->getName() + ".lr.ph");
// Preserve canonical loop form, which means that 'Exit' should have only one
// predecessor.
BasicBlock *ExitSplit = SplitCriticalEdge(L->getLoopLatch(), Exit, this);
@ -329,7 +329,7 @@ bool LoopRotate::rotateLoop(Loop *L) {
BranchInst *NewBI = BranchInst::Create(NewHeader, PHBI);
NewBI->setDebugLoc(PHBI->getDebugLoc());
PHBI->eraseFromParent();
// With our CFG finalized, update DomTree if it is available.
if (DominatorTree *DT = getAnalysisIfAvailable<DominatorTree>()) {
// Update OrigHeader to be dominated by the new header block.
@ -337,7 +337,7 @@ bool LoopRotate::rotateLoop(Loop *L) {
DT->changeImmediateDominator(OrigHeader, OrigLatch);
}
}
assert(L->getLoopPreheader() && "Invalid loop preheader after loop rotation");
assert(L->getLoopLatch() && "Invalid loop latch after loop rotation");
@ -346,7 +346,7 @@ bool LoopRotate::rotateLoop(Loop *L) {
// connected by an unconditional branch. This is just a cleanup so the
// emitted code isn't too gross in this common case.
MergeBlockIntoPredecessor(OrigHeader, this);
++NumRotated;
return true;
}