//
//===----------------------------------------------------------------------===//
-#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/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/SetOperations.h"
+#include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Analysis/ScalarEvolution.h"
+#include "llvm/Analysis/DependenceAnalysis.h"
#include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopPass.h"
-#include "llvm/Transforms/Utils/BasicBlockUtils.h"
-#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Analysis/ScalarEvolution.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Type.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"
-#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Utils/LoopUtils.h"
using namespace llvm;
STATISTIC(NumInserted, "Number of pre-header or exit blocks inserted");
AU.addPreserved<AliasAnalysis>();
AU.addPreserved<ScalarEvolution>();
+ AU.addPreserved<DependenceAnalysis>();
AU.addPreservedID(BreakCriticalEdgesID); // No critical edges added.
- AU.addPreserved<DominanceFrontier>();
- AU.addPreservedID(LCSSAID);
}
/// verifyAnalysis() - Verify LoopSimplifyForm's guarantees.
private:
bool ProcessLoop(Loop *L, LPPassManager &LPM);
BasicBlock *RewriteLoopExitBlock(Loop *L, BasicBlock *Exit);
- BasicBlock *InsertPreheaderForLoop(Loop *L);
- Loop *SeparateNestedLoop(Loop *L, LPPassManager &LPM);
+ Loop *SeparateNestedLoop(Loop *L, LPPassManager &LPM,
+ BasicBlock *Preheader);
BasicBlock *InsertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader);
- void PlaceSplitBlockCarefully(BasicBlock *NewBB,
- SmallVectorImpl<BasicBlock*> &SplitPreds,
- Loop *L);
};
}
+static void PlaceSplitBlockCarefully(BasicBlock *NewBB,
+ SmallVectorImpl<BasicBlock*> &SplitPreds,
+ Loop *L);
+
char LoopSimplify::ID = 0;
-INITIALIZE_PASS_BEGIN(LoopSimplify, "loopsimplify",
+INITIALIZE_PASS_BEGIN(LoopSimplify, "loop-simplify",
"Canonicalize natural loops", true, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTree)
INITIALIZE_PASS_DEPENDENCY(LoopInfo)
-INITIALIZE_PASS_END(LoopSimplify, "loopsimplify",
+INITIALIZE_PASS_END(LoopSimplify, "loop-simplify",
"Canonicalize natural loops", true, false)
-// Publically exposed interface to pass...
+// Publicly exposed interface to pass...
char &llvm::LoopSimplifyID = LoopSimplify::ID;
Pass *llvm::createLoopSimplifyPass() { return new LoopSimplify(); }
for (SmallPtrSet<BasicBlock*, 4>::iterator I = BadPreds.begin(),
E = BadPreds.end(); I != E; ++I) {
- DEBUG(dbgs() << "LoopSimplify: Deleting edge from dead predecessor ";
- WriteAsOperand(dbgs(), *I, false);
- dbgs() << "\n");
+ 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)
if (BI->isConditional()) {
if (UndefValue *Cond = dyn_cast<UndefValue>(BI->getCondition())) {
- DEBUG(dbgs() << "LoopSimplify: Resolving \"br i1 undef\" to exit in ";
- WriteAsOperand(dbgs(), *I, false);
- dbgs() << "\n");
+ DEBUG(dbgs() << "LoopSimplify: Resolving \"br i1 undef\" to exit in "
+ << (*I)->getName() << "\n");
BI->setCondition(ConstantInt::get(Cond->getType(),
!L->contains(BI->getSuccessor(0))));
+
+ // This may make the loop analyzable, force SCEV recomputation.
+ if (SE)
+ SE->forgetLoop(L);
+
Changed = true;
}
}
// Does the loop already have a preheader? If so, don't insert one.
BasicBlock *Preheader = L->getLoopPreheader();
if (!Preheader) {
- Preheader = InsertPreheaderForLoop(L);
+ Preheader = InsertPreheaderForLoop(L, this);
if (Preheader) {
++NumInserted;
Changed = true;
// predecessors from outside of the loop, split the edge now.
SmallVector<BasicBlock*, 8> ExitBlocks;
L->getExitBlocks(ExitBlocks);
-
+
SmallSetVector<BasicBlock *, 8> ExitBlockSet(ExitBlocks.begin(),
ExitBlocks.end());
for (SmallSetVector<BasicBlock *, 8>::iterator I = ExitBlockSet.begin(),
// this for loops with a giant number of backedges, just factor them into a
// common backedge instead.
if (L->getNumBackEdges() < 8) {
- if (SeparateNestedLoop(L, LPM)) {
+ if (SeparateNestedLoop(L, LPM, Preheader)) {
++NumNested;
// This is a big restructuring change, reprocess the whole loop.
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, 0, DT)) {
if (AA) AA->deleteValue(PN);
+ if (SE) SE->forgetValue(PN);
PN->replaceAllUsesWith(V);
PN->eraseFromParent();
}
// Attempt to hoist out all instructions except for the
// comparison and the branch.
bool AllInvariant = true;
+ bool AnyInvariant = false;
for (BasicBlock::iterator I = ExitingBlock->begin(); &*I != BI; ) {
Instruction *Inst = I++;
// Skip debug info intrinsics.
continue;
if (Inst == CI)
continue;
- if (!L->makeLoopInvariant(Inst, Changed,
- Preheader ? Preheader->getTerminator() : 0)) {
+ if (!L->makeLoopInvariant(Inst, AnyInvariant,
+ Preheader ? Preheader->getTerminator() : 0)) {
AllInvariant = false;
break;
}
}
+ if (AnyInvariant) {
+ Changed = true;
+ // If any reachable control flow within this loop has changed, notify
+ // ScalarEvolution. Currently assume the parent loop doesn't change
+ // (spliting edges doesn't count). If blocks, CFG edges, or other values
+ // in the parent loop change, then we need call to forgetLoop() for the
+ // parent instead.
+ if (SE) {
+ SE->forgetLoop(L);
+ // The loop disposition of all SCEV expressions that depend on any
+ // hoisted values have also changed.
+ SE->forgetLoopDispositions(L);
+ }
+ }
if (!AllInvariant) continue;
// The block has now been cleared of all instructions except for
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.
-
- DEBUG(dbgs() << "LoopSimplify: Eliminating exiting block ";
- WriteAsOperand(dbgs(), ExitingBlock, false);
- dbgs() << "\n");
+ // 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);
/// preheader, this method is called to insert one. This method has two phases:
/// preheader insertion and analysis updating.
///
-BasicBlock *LoopSimplify::InsertPreheaderForLoop(Loop *L) {
+BasicBlock *llvm::InsertPreheaderForLoop(Loop *L, Pass *PP) {
BasicBlock *Header = L->getHeader();
// Compute the set of predecessors of the loop that are not in the loop.
}
// Split out the loop pre-header.
- BasicBlock *NewBB =
- SplitBlockPredecessors(Header, &OutsideBlocks[0], OutsideBlocks.size(),
- ".preheader", this);
+ BasicBlock *PreheaderBB;
+ if (!Header->isLandingPad()) {
+ PreheaderBB = SplitBlockPredecessors(Header, OutsideBlocks, ".preheader",
+ PP);
+ } else {
+ SmallVector<BasicBlock*, 2> NewBBs;
+ SplitLandingPadPredecessors(Header, OutsideBlocks, ".preheader",
+ ".split-lp", PP, NewBBs);
+ PreheaderBB = NewBBs[0];
+ }
- DEBUG(dbgs() << "LoopSimplify: Creating pre-header ";
- WriteAsOperand(dbgs(), NewBB, false);
- dbgs() << "\n");
+ PreheaderBB->getTerminator()->setDebugLoc(
+ Header->getFirstNonPHI()->getDebugLoc());
+ DEBUG(dbgs() << "LoopSimplify: Creating pre-header "
+ << PreheaderBB->getName() << "\n");
// Make sure that NewBB is put someplace intelligent, which doesn't mess up
// code layout too horribly.
- PlaceSplitBlockCarefully(NewBB, OutsideBlocks, L);
+ PlaceSplitBlockCarefully(PreheaderBB, OutsideBlocks, L);
- return NewBB;
+ return PreheaderBB;
}
/// RewriteLoopExitBlock - Ensure that the loop preheader dominates all exit
}
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 ";
- WriteAsOperand(dbgs(), NewBB, false);
- dbgs() << "\n");
+ BasicBlock *NewExitBB = 0;
+
+ if (Exit->isLandingPad()) {
+ SmallVector<BasicBlock*, 2> NewBBs;
+ SplitLandingPadPredecessors(Exit, ArrayRef<BasicBlock*>(&LoopBlocks[0],
+ LoopBlocks.size()),
+ ".loopexit", ".nonloopexit",
+ this, NewBBs);
+ NewExitBB = NewBBs[0];
+ } else {
+ NewExitBB = SplitBlockPredecessors(Exit, LoopBlocks, ".loopexit", this);
+ }
- return NewBB;
+ DEBUG(dbgs() << "LoopSimplify: Creating dedicated exit block "
+ << NewExitBB->getName() << "\n");
+ return NewExitBB;
}
/// AddBlockAndPredsToSet - Add the specified block, and all of its
/// 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, 0, DT)) {
// This is a degenerate PHI already, don't modify it!
PN->replaceAllUsesWith(V);
if (AA) AA->deleteValue(PN);
// PlaceSplitBlockCarefully - If the block isn't already, move the new block to
// right after some 'outside block' block. This prevents the preheader from
// being placed inside the loop body, e.g. when the loop hasn't been rotated.
-void LoopSimplify::PlaceSplitBlockCarefully(BasicBlock *NewBB,
- SmallVectorImpl<BasicBlock*> &SplitPreds,
- Loop *L) {
+void PlaceSplitBlockCarefully(BasicBlock *NewBB,
+ SmallVectorImpl<BasicBlock*> &SplitPreds,
+ Loop *L) {
// Check to see if NewBB is already well placed.
Function::iterator BBI = NewBB; --BBI;
for (unsigned i = 0, e = SplitPreds.size(); i != e; ++i) {
if (&*BBI == SplitPreds[i])
return;
}
-
+
// If it isn't already after an outside block, move it after one. This is
// always good as it makes the uncond branch from the outside block into a
// fall-through.
-
+
// Figure out *which* outside block to put this after. Prefer an outside
// block that neighbors a BB actually in the loop.
BasicBlock *FoundBB = 0;
for (unsigned i = 0, e = SplitPreds.size(); i != e; ++i) {
Function::iterator BBI = SplitPreds[i];
- if (++BBI != NewBB->getParent()->end() &&
+ if (++BBI != NewBB->getParent()->end() &&
L->contains(BBI)) {
FoundBB = SplitPreds[i];
break;
}
}
-
+
// If our heuristic for a *good* bb to place this after doesn't find
// anything, just pick something. It's likely better than leaving it within
// the loop.
/// If we are able to separate out a loop, return the new outer loop that was
/// created.
///
-Loop *LoopSimplify::SeparateNestedLoop(Loop *L, LPPassManager &LPM) {
- PHINode *PN = FindPHIToPartitionLoops(L, DT, AA);
+Loop *LoopSimplify::SeparateNestedLoop(Loop *L, LPPassManager &LPM,
+ BasicBlock *Preheader) {
+ // Don't try to separate loops without a preheader.
+ if (!Preheader)
+ return 0;
+
+ // The header is not a landing pad; preheader insertion should ensure this.
+ assert(!L->getHeader()->isLandingPad() &&
+ "Can't insert backedge to landing pad");
+
+ 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
// handles the case when a PHI node has multiple instances of itself as
// arguments.
SmallVector<BasicBlock*, 8> OuterLoopPreds;
- for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
if (PN->getIncomingValue(i) != PN ||
!L->contains(PN->getIncomingBlock(i))) {
// We can't split indirectbr edges.
if (isa<IndirectBrInst>(PN->getIncomingBlock(i)->getTerminator()))
return 0;
-
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
SE->forgetLoop(L);
BasicBlock *Header = L->getHeader();
- BasicBlock *NewBB = SplitBlockPredecessors(Header, &OuterLoopPreds[0],
- OuterLoopPreds.size(),
- ".outer", this);
+ BasicBlock *NewBB =
+ SplitBlockPredecessors(Header, OuterLoopPreds, ".outer", this);
// Make sure that NewBB is put someplace intelligent, which doesn't mess up
// code layout too horribly.
PlaceSplitBlockCarefully(NewBB, OuterLoopPreds, L);
-
+
// Create the new outer loop.
Loop *NewOuter = new Loop();
if (!Preheader)
return 0;
+ // The header is not a landing pad; preheader insertion should ensure this.
+ assert(!Header->isLandingPad() && "Can't insert backedge to landing pad");
+
// 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){
Header->getName()+".backedge", F);
BranchInst *BETerminator = BranchInst::Create(Header, BEBlock);
- DEBUG(dbgs() << "LoopSimplify: Inserting unique backedge block ";
- WriteAsOperand(dbgs(), BEBlock, false);
- dbgs() << "\n");
+ 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;
// 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;
}
}
assert(HasIndBrPred &&
"LoopSimplify has no excuse for missing loop header info!");
+ (void)HasIndBrPred;
}
// Indirectbr can interfere with exit block canonicalization.
bool HasIndBrExiting = false;
SmallVector<BasicBlock*, 8> ExitingBlocks;
L->getExitingBlocks(ExitingBlocks);
- for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i)
+ for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
if (isa<IndirectBrInst>((ExitingBlocks[i])->getTerminator())) {
HasIndBrExiting = true;
break;
}
+ }
+
assert(HasIndBrExiting &&
"LoopSimplify has no excuse for missing exit block info!");
+ (void)HasIndBrExiting;
}
}