//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "loopsimplify"
+#define DEBUG_TYPE "loop-simplify"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
+#include "llvm/IntrinsicInst.h"
#include "llvm/Function.h"
#include "llvm/LLVMContext.h"
#include "llvm/Type.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Support/CFG.h"
+#include "llvm/Support/Debug.h"
#include "llvm/ADT/SetOperations.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Statistic.h"
namespace {
struct LoopSimplify : public LoopPass {
static char ID; // Pass identification, replacement for typeid
- LoopSimplify() : LoopPass(&ID) {}
+ LoopSimplify() : LoopPass(ID) {
+ initializeLoopSimplifyPass(*PassRegistry::getPassRegistry());
+ }
// AA - If we have an alias analysis object to update, this is it, otherwise
// this is null.
AliasAnalysis *AA;
LoopInfo *LI;
DominatorTree *DT;
+ ScalarEvolution *SE;
Loop *L;
virtual bool runOnLoop(Loop *L, LPPassManager &LPM);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
// We need loop information to identify the loops...
- AU.addRequiredTransitive<LoopInfo>();
- AU.addRequiredTransitive<DominatorTree>();
+ AU.addRequired<DominatorTree>();
+ AU.addPreserved<DominatorTree>();
+ AU.addRequired<LoopInfo>();
AU.addPreserved<LoopInfo>();
- AU.addPreserved<DominatorTree>();
- AU.addPreserved<DominanceFrontier>();
+
AU.addPreserved<AliasAnalysis>();
AU.addPreserved<ScalarEvolution>();
AU.addPreservedID(BreakCriticalEdgesID); // No critical edges added.
}
char LoopSimplify::ID = 0;
-static RegisterPass<LoopSimplify>
-X("loopsimplify", "Canonicalize natural loops", true);
-
-// Publically exposed interface to pass...
-const PassInfo *const llvm::LoopSimplifyID = &X;
+INITIALIZE_PASS_BEGIN(LoopSimplify, "loop-simplify",
+ "Canonicalize natural loops", true, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTree)
+INITIALIZE_PASS_DEPENDENCY(LoopInfo)
+INITIALIZE_PASS_END(LoopSimplify, "loop-simplify",
+ "Canonicalize natural loops", true, false)
+
+// Publicly exposed interface to pass...
+char &llvm::LoopSimplifyID = LoopSimplify::ID;
Pass *llvm::createLoopSimplifyPass() { return new LoopSimplify(); }
/// runOnLoop - Run down all loops in the CFG (recursively, but we could do
LI = &getAnalysis<LoopInfo>();
AA = getAnalysisIfAvailable<AliasAnalysis>();
DT = &getAnalysis<DominatorTree>();
+ SE = getAnalysisIfAvailable<ScalarEvolution>();
Changed |= ProcessLoop(L, LPM);
bool Changed = false;
ReprocessLoop:
- // Check to see that no blocks (other than the header) in this loop that has
+ // Check to see that no blocks (other than the header) in this loop have
// predecessors that are not in the loop. This is not valid for natural
// loops, but can occur if the blocks are unreachable. Since they are
// unreachable we can just shamelessly delete those CFG edges!
BB != E; ++BB) {
if (*BB == L->getHeader()) continue;
- SmallPtrSet<BasicBlock *, 4> BadPreds;
- for (pred_iterator PI = pred_begin(*BB), PE = pred_end(*BB); PI != PE; ++PI)
- if (!L->contains(*PI))
- BadPreds.insert(*PI);
+ SmallPtrSet<BasicBlock*, 4> BadPreds;
+ for (pred_iterator PI = pred_begin(*BB),
+ PE = pred_end(*BB); PI != PE; ++PI) {
+ BasicBlock *P = *PI;
+ if (!L->contains(P))
+ BadPreds.insert(P);
+ }
// Delete each unique out-of-loop (and thus dead) predecessor.
- for (SmallPtrSet<BasicBlock *, 4>::iterator I = BadPreds.begin(),
+ for (SmallPtrSet<BasicBlock*, 4>::iterator I = BadPreds.begin(),
E = BadPreds.end(); I != E; ++I) {
+
+ DEBUG(dbgs() << "LoopSimplify: Deleting edge from dead predecessor "
+ << (*I)->getName() << "\n");
+
// Inform each successor of each dead pred.
for (succ_iterator SI = succ_begin(*I), SE = succ_end(*I); SI != SE; ++SI)
(*SI)->removePredecessor(*I);
}
}
+ // If there are exiting blocks with branches on undef, resolve the undef in
+ // the direction which will exit the loop. This will help simplify loop
+ // trip count computations.
+ SmallVector<BasicBlock*, 8> ExitingBlocks;
+ L->getExitingBlocks(ExitingBlocks);
+ for (SmallVectorImpl<BasicBlock *>::iterator I = ExitingBlocks.begin(),
+ E = ExitingBlocks.end(); I != E; ++I)
+ if (BranchInst *BI = dyn_cast<BranchInst>((*I)->getTerminator()))
+ if (BI->isConditional()) {
+ if (UndefValue *Cond = dyn_cast<UndefValue>(BI->getCondition())) {
+
+ DEBUG(dbgs() << "LoopSimplify: Resolving \"br i1 undef\" to exit in "
+ << (*I)->getName() << "\n");
+
+ BI->setCondition(ConstantInt::get(Cond->getType(),
+ !L->contains(BI->getSuccessor(0))));
+ Changed = true;
+ }
+ }
+
// Does the loop already have a preheader? If so, don't insert one.
BasicBlock *Preheader = L->getLoopPreheader();
if (!Preheader) {
Preheader = InsertPreheaderForLoop(L);
if (Preheader) {
- NumInserted++;
+ ++NumInserted;
Changed = true;
}
}
// allowed.
if (!L->contains(*PI)) {
if (RewriteLoopExitBlock(L, ExitBlock)) {
- NumInserted++;
+ ++NumInserted;
Changed = true;
}
break;
// loop header.
LoopLatch = InsertUniqueBackedgeBlock(L, Preheader);
if (LoopLatch) {
- NumInserted++;
+ ++NumInserted;
Changed = true;
}
}
PHINode *PN;
for (BasicBlock::iterator I = L->getHeader()->begin();
(PN = dyn_cast<PHINode>(I++)); )
- if (Value *V = PN->hasConstantValue(DT)) {
+ if (Value *V = SimplifyInstruction(PN, 0, DT)) {
if (AA) AA->deleteValue(PN);
+ if (SE) SE->forgetValue(PN);
PN->replaceAllUsesWith(V);
PN->eraseFromParent();
}
break;
}
if (UniqueExit) {
- SmallVector<BasicBlock*, 8> ExitingBlocks;
- L->getExitingBlocks(ExitingBlocks);
for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
BasicBlock *ExitingBlock = ExitingBlocks[i];
if (!ExitingBlock->getSinglePredecessor()) continue;
bool AllInvariant = true;
for (BasicBlock::iterator I = ExitingBlock->begin(); &*I != BI; ) {
Instruction *Inst = I++;
+ // Skip debug info intrinsics.
+ if (isa<DbgInfoIntrinsic>(Inst))
+ continue;
if (Inst == CI)
continue;
if (!L->makeLoopInvariant(Inst, Changed,
if (!FoldBranchToCommonDest(BI)) continue;
// Success. The block is now dead, so remove it from the loop,
- // update the dominator tree and dominance frontier, and delete it.
+ // update the dominator tree and delete it.
+ DEBUG(dbgs() << "LoopSimplify: Eliminating exiting block "
+ << ExitingBlock->getName() << "\n");
+
assert(pred_begin(ExitingBlock) == pred_end(ExitingBlock));
Changed = true;
LI->removeBlock(ExitingBlock);
- DominanceFrontier *DF = getAnalysisIfAvailable<DominanceFrontier>();
DomTreeNode *Node = DT->getNode(ExitingBlock);
const std::vector<DomTreeNodeBase<BasicBlock> *> &Children =
Node->getChildren();
while (!Children.empty()) {
DomTreeNode *Child = Children.front();
DT->changeImmediateDominator(Child, Node->getIDom());
- if (DF) DF->changeImmediateDominator(Child->getBlock(),
- Node->getIDom()->getBlock(),
- DT);
}
DT->eraseNode(ExitingBlock);
- if (DF) DF->removeBlock(ExitingBlock);
BI->getSuccessor(0)->removePredecessor(ExitingBlock);
BI->getSuccessor(1)->removePredecessor(ExitingBlock);
// Compute the set of predecessors of the loop that are not in the loop.
SmallVector<BasicBlock*, 8> OutsideBlocks;
for (pred_iterator PI = pred_begin(Header), PE = pred_end(Header);
- PI != PE; ++PI)
- if (!L->contains(*PI)) { // Coming in from outside the loop?
+ PI != PE; ++PI) {
+ BasicBlock *P = *PI;
+ if (!L->contains(P)) { // Coming in from outside the loop?
// If the loop is branched to from an indirect branch, we won't
// be able to fully transform the loop, because it prohibits
// edge splitting.
- if (isa<IndirectBrInst>((*PI)->getTerminator())) return 0;
+ if (isa<IndirectBrInst>(P->getTerminator())) return 0;
// Keep track of it.
- OutsideBlocks.push_back(*PI);
+ OutsideBlocks.push_back(P);
}
+ }
// Split out the loop pre-header.
BasicBlock *NewBB =
SplitBlockPredecessors(Header, &OutsideBlocks[0], OutsideBlocks.size(),
".preheader", this);
+ DEBUG(dbgs() << "LoopSimplify: Creating pre-header " << NewBB->getName()
+ << "\n");
+
// Make sure that NewBB is put someplace intelligent, which doesn't mess up
// code layout too horribly.
PlaceSplitBlockCarefully(NewBB, OutsideBlocks, L);
/// outside of the loop.
BasicBlock *LoopSimplify::RewriteLoopExitBlock(Loop *L, BasicBlock *Exit) {
SmallVector<BasicBlock*, 8> LoopBlocks;
- for (pred_iterator I = pred_begin(Exit), E = pred_end(Exit); I != E; ++I)
- if (L->contains(*I)) {
+ for (pred_iterator I = pred_begin(Exit), E = pred_end(Exit); I != E; ++I) {
+ BasicBlock *P = *I;
+ if (L->contains(P)) {
// Don't do this if the loop is exited via an indirect branch.
- if (isa<IndirectBrInst>((*I)->getTerminator())) return 0;
+ if (isa<IndirectBrInst>(P->getTerminator())) return 0;
- LoopBlocks.push_back(*I);
+ LoopBlocks.push_back(P);
}
+ }
assert(!LoopBlocks.empty() && "No edges coming in from outside the loop?");
BasicBlock *NewBB = SplitBlockPredecessors(Exit, &LoopBlocks[0],
LoopBlocks.size(), ".loopexit",
this);
+ DEBUG(dbgs() << "LoopSimplify: Creating dedicated exit block "
+ << NewBB->getName() << "\n");
return NewBB;
}
/// FindPHIToPartitionLoops - The first part of loop-nestification is to find a
/// PHI node that tells us how to partition the loops.
static PHINode *FindPHIToPartitionLoops(Loop *L, DominatorTree *DT,
- AliasAnalysis *AA) {
+ AliasAnalysis *AA, LoopInfo *LI) {
for (BasicBlock::iterator I = L->getHeader()->begin(); isa<PHINode>(I); ) {
PHINode *PN = cast<PHINode>(I);
++I;
- if (Value *V = PN->hasConstantValue(DT)) {
+ if (Value *V = SimplifyInstruction(PN, 0, DT)) {
// This is a degenerate PHI already, don't modify it!
PN->replaceAllUsesWith(V);
if (AA) AA->deleteValue(PN);
/// created.
///
Loop *LoopSimplify::SeparateNestedLoop(Loop *L, LPPassManager &LPM) {
- PHINode *PN = FindPHIToPartitionLoops(L, DT, AA);
+ PHINode *PN = FindPHIToPartitionLoops(L, DT, AA, LI);
if (PN == 0) return 0; // No known way to partition.
// Pull out all predecessors that have varying values in the loop. This
OuterLoopPreds.push_back(PN->getIncomingBlock(i));
}
+ DEBUG(dbgs() << "LoopSimplify: Splitting out a new outer loop\n");
+
+ // If ScalarEvolution is around and knows anything about values in
+ // this loop, tell it to forget them, because we're about to
+ // substantially change it.
+ if (SE)
+ SE->forgetLoop(L);
+
BasicBlock *Header = L->getHeader();
BasicBlock *NewBB = SplitBlockPredecessors(Header, &OuterLoopPreds[0],
OuterLoopPreds.size(),
// Determine which blocks should stay in L and which should be moved out to
// the Outer loop now.
std::set<BasicBlock*> BlocksInL;
- for (pred_iterator PI = pred_begin(Header), E = pred_end(Header); PI!=E; ++PI)
- if (DT->dominates(Header, *PI))
- AddBlockAndPredsToSet(*PI, Header, BlocksInL);
-
+ for (pred_iterator PI=pred_begin(Header), E = pred_end(Header); PI!=E; ++PI) {
+ BasicBlock *P = *PI;
+ if (DT->dominates(Header, P))
+ AddBlockAndPredsToSet(P, Header, BlocksInL);
+ }
// Scan all of the loop children of L, moving them to OuterLoop if they are
// not part of the inner loop.
// Figure out which basic blocks contain back-edges to the loop header.
std::vector<BasicBlock*> BackedgeBlocks;
- for (pred_iterator I = pred_begin(Header), E = pred_end(Header); I != E; ++I)
- if (*I != Preheader) BackedgeBlocks.push_back(*I);
+ for (pred_iterator I = pred_begin(Header), E = pred_end(Header); I != E; ++I){
+ BasicBlock *P = *I;
+
+ // Indirectbr edges cannot be split, so we must fail if we find one.
+ if (isa<IndirectBrInst>(P->getTerminator()))
+ return 0;
+
+ if (P != Preheader) BackedgeBlocks.push_back(P);
+ }
// Create and insert the new backedge block...
BasicBlock *BEBlock = BasicBlock::Create(Header->getContext(),
Header->getName()+".backedge", F);
BranchInst *BETerminator = BranchInst::Create(Header, BEBlock);
+ DEBUG(dbgs() << "LoopSimplify: Inserting unique backedge block "
+ << BEBlock->getName() << "\n");
+
// Move the new backedge block to right after the last backedge block.
Function::iterator InsertPos = BackedgeBlocks.back(); ++InsertPos;
F->getBasicBlockList().splice(InsertPos, F->getBasicBlockList(), BEBlock);
// the backedge block which correspond to any PHI nodes in the header block.
for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
PHINode *PN = cast<PHINode>(I);
- PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".be",
- BETerminator);
- NewPN->reserveOperandSpace(BackedgeBlocks.size());
+ PHINode *NewPN = PHINode::Create(PN->getType(), BackedgeBlocks.size(),
+ PN->getName()+".be", BETerminator);
if (AA) AA->copyValue(PN, NewPN);
// Loop over the PHI node, moving all entries except the one for the
// Update dominator information
DT->splitBlock(BEBlock);
- if (DominanceFrontier *DF = getAnalysisIfAvailable<DominanceFrontier>())
- DF->splitBlock(BEBlock);
return BEBlock;
}
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