//
// This pass also guarantees that loops will have exactly one backedge.
//
+// Indirectbr instructions introduce several complications. If the loop
+// contains or is entered by an indirectbr instruction, it may not be possible
+// to transform the loop and make these guarantees. Client code should check
+// that these conditions are true before relying on them.
+//
// Note that the simplifycfg pass will clean up blocks which are split out but
// end up being unnecessary, so usage of this pass should not pessimize
// generated code.
//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "loopsimplify"
+#define DEBUG_TYPE "loop-simplify"
#include "llvm/Transforms/Scalar.h"
-#include "llvm/Constants.h"
-#include "llvm/Instructions.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/Dominators.h"
+#include "llvm/Analysis/DependenceAnalysis.h"
+#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/ScalarEvolution.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Dominators.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/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/Support/CFG.h"
-#include "llvm/Support/Compiler.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/LoopUtils.h"
using namespace llvm;
STATISTIC(NumInserted, "Number of pre-header or exit blocks inserted");
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<DominatorTreeWrapperPass>();
+ AU.addPreserved<DominatorTreeWrapperPass>();
+ AU.addRequired<LoopInfo>();
AU.addPreserved<LoopInfo>();
- AU.addPreserved<DominatorTree>();
- AU.addPreserved<DominanceFrontier>();
+
AU.addPreserved<AliasAnalysis>();
AU.addPreserved<ScalarEvolution>();
+ AU.addPreserved<DependenceAnalysis>();
AU.addPreservedID(BreakCriticalEdgesID); // No critical edges added.
}
- /// verifyAnalysis() - Verify loop nest.
- void verifyAnalysis() const {
- assert(L->isLoopSimplifyForm() && "LoopSimplify form not preserved!");
- }
+ /// verifyAnalysis() - Verify LoopSimplifyForm's guarantees.
+ void verifyAnalysis() const;
private:
bool ProcessLoop(Loop *L, LPPassManager &LPM);
BasicBlock *RewriteLoopExitBlock(Loop *L, BasicBlock *Exit);
- BasicBlock *InsertPreheaderForLoop(Loop *L);
- Loop *SeparateNestedLoop(Loop *L, LPPassManager &LPM);
- void InsertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader);
- void PlaceSplitBlockCarefully(BasicBlock *NewBB,
- SmallVectorImpl<BasicBlock*> &SplitPreds,
- Loop *L);
+ Loop *SeparateNestedLoop(Loop *L, LPPassManager &LPM,
+ BasicBlock *Preheader);
+ BasicBlock *InsertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader);
};
}
-char LoopSimplify::ID = 0;
-static RegisterPass<LoopSimplify>
-X("loopsimplify", "Canonicalize natural loops", true);
+static void PlaceSplitBlockCarefully(BasicBlock *NewBB,
+ SmallVectorImpl<BasicBlock*> &SplitPreds,
+ Loop *L);
-// Publically exposed interface to pass...
-const PassInfo *const llvm::LoopSimplifyID = &X;
+char LoopSimplify::ID = 0;
+INITIALIZE_PASS_BEGIN(LoopSimplify, "loop-simplify",
+ "Canonicalize natural loops", true, false)
+INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
+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(); }
-/// runOnFunction - Run down all loops in the CFG (recursively, but we could do
+/// runOnLoop - Run down all loops in the CFG (recursively, but we could do
/// it in any convenient order) inserting preheaders...
///
bool LoopSimplify::runOnLoop(Loop *l, LPPassManager &LPM) {
bool Changed = false;
LI = &getAnalysis<LoopInfo>();
AA = getAnalysisIfAvailable<AliasAnalysis>();
- DT = &getAnalysis<DominatorTree>();
+ DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+ 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))));
+
+ // 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);
- NumInserted++;
- Changed = true;
+ Preheader = InsertPreheaderForLoop(L, this);
+ if (Preheader) {
+ ++NumInserted;
+ Changed = true;
+ }
}
// Next, check to make sure that all exit nodes of the loop only have
// predecessors from outside of the loop, split the edge now.
SmallVector<BasicBlock*, 8> ExitBlocks;
L->getExitBlocks(ExitBlocks);
-
- SetVector<BasicBlock*> ExitBlockSet(ExitBlocks.begin(), ExitBlocks.end());
- for (SetVector<BasicBlock*>::iterator I = ExitBlockSet.begin(),
+
+ SmallSetVector<BasicBlock *, 8> ExitBlockSet(ExitBlocks.begin(),
+ ExitBlocks.end());
+ for (SmallSetVector<BasicBlock *, 8>::iterator I = ExitBlockSet.begin(),
E = ExitBlockSet.end(); I != E; ++I) {
BasicBlock *ExitBlock = *I;
for (pred_iterator PI = pred_begin(ExitBlock), PE = pred_end(ExitBlock);
// Must be exactly this loop: no subloops, parent loops, or non-loop preds
// allowed.
if (!L->contains(*PI)) {
- RewriteLoopExitBlock(L, ExitBlock);
- NumInserted++;
- Changed = true;
+ if (RewriteLoopExitBlock(L, ExitBlock)) {
+ ++NumInserted;
+ Changed = true;
+ }
break;
}
}
// If the header has more than two predecessors at this point (from the
// preheader and from multiple backedges), we must adjust the loop.
- unsigned NumBackedges = L->getNumBackEdges();
- if (NumBackedges != 1) {
+ BasicBlock *LoopLatch = L->getLoopLatch();
+ if (!LoopLatch) {
// If this is really a nested loop, rip it out into a child loop. Don't do
// this for loops with a giant number of backedges, just factor them into a
// common backedge instead.
- if (NumBackedges < 8) {
- if (SeparateNestedLoop(L, LPM)) {
+ if (L->getNumBackEdges() < 8) {
+ if (SeparateNestedLoop(L, LPM, Preheader)) {
++NumNested;
// This is a big restructuring change, reprocess the whole loop.
Changed = true;
// If we either couldn't, or didn't want to, identify nesting of the loops,
// insert a new block that all backedges target, then make it jump to the
// loop header.
- InsertUniqueBackedgeBlock(L, Preheader);
- NumInserted++;
- Changed = true;
+ LoopLatch = InsertUniqueBackedgeBlock(L, Preheader);
+ if (LoopLatch) {
+ ++NumInserted;
+ Changed = true;
+ }
}
// Scan over the PHI nodes in the loop header. Since they now have only two
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();
}
- // If this loop has muliple exits and the exits all go to the same
+ // If this loop has multiple exits and the exits all go to the same
// block, attempt to merge the exits. This helps several passes, such
// as LoopRotation, which do not support loops with multiple exits.
// SimplifyCFG also does this (and this code uses the same utility
// loop-invariant instructions out of the way to open up more
// opportunities, and the disadvantage of having the responsibility
// to preserve dominator information.
- if (ExitBlocks.size() > 1 && L->getUniqueExitBlock()) {
- SmallVector<BasicBlock*, 8> ExitingBlocks;
- L->getExitingBlocks(ExitingBlocks);
+ bool UniqueExit = true;
+ if (!ExitBlocks.empty())
+ for (unsigned i = 1, e = ExitBlocks.size(); i != e; ++i)
+ if (ExitBlocks[i] != ExitBlocks[0]) {
+ UniqueExit = false;
+ break;
+ }
+ if (UniqueExit) {
for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
BasicBlock *ExitingBlock = ExitingBlocks[i];
if (!ExitingBlock->getSinglePredecessor()) continue;
// 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.
+ if (isa<DbgInfoIntrinsic>(Inst))
+ continue;
if (Inst == CI)
continue;
- if (!L->makeLoopInvariant(Inst, Changed, Preheader->getTerminator())) {
+ if (!L->makeLoopInvariant(Inst, AnyInvariant,
+ Preheader ? Preheader->getTerminator() : 0)) {
AllInvariant = false;
break;
}
}
+ if (AnyInvariant) {
+ Changed = true;
+ // The loop disposition of all SCEV expressions that depend on any
+ // hoisted values have also changed.
+ if (SE)
+ 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.
+ // update the dominator tree and delete it.
+ DEBUG(dbgs() << "LoopSimplify: Eliminating exiting block "
+ << ExitingBlock->getName() << "\n");
+
+ // Notify ScalarEvolution before deleting this block. 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);
+
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.
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?
- OutsideBlocks.push_back(*PI); // Keep track of it...
+ 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>(P->getTerminator())) return 0;
+
+ // Keep track of it.
+ OutsideBlocks.push_back(P);
+ }
+ }
// 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];
+ }
+
+ 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
/// 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))
- LoopBlocks.push_back(*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>(P->getTerminator())) return 0;
+
+ 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);
+ 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)))
+ !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
+ // 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(),
- ".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();
// 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.
/// backedges to target a new basic block and have that block branch to the loop
/// header. This ensures that loops have exactly one backedge.
///
-void LoopSimplify::InsertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader) {
+BasicBlock *
+LoopSimplify::InsertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader) {
assert(L->getNumBackEdges() > 1 && "Must have > 1 backedge!");
// Get information about the loop
BasicBlock *Header = L->getHeader();
Function *F = Header->getParent();
+ // Unique backedge insertion currently depends on having a preheader.
+ 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)
- 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;
+}
+
+void LoopSimplify::verifyAnalysis() const {
+ // It used to be possible to just assert L->isLoopSimplifyForm(), however
+ // with the introduction of indirectbr, there are now cases where it's
+ // not possible to transform a loop as necessary. We can at least check
+ // that there is an indirectbr near any time there's trouble.
+
+ // Indirectbr can interfere with preheader and unique backedge insertion.
+ if (!L->getLoopPreheader() || !L->getLoopLatch()) {
+ bool HasIndBrPred = false;
+ for (pred_iterator PI = pred_begin(L->getHeader()),
+ PE = pred_end(L->getHeader()); PI != PE; ++PI)
+ if (isa<IndirectBrInst>((*PI)->getTerminator())) {
+ HasIndBrPred = true;
+ break;
+ }
+ assert(HasIndBrPred &&
+ "LoopSimplify has no excuse for missing loop header info!");
+ (void)HasIndBrPred;
+ }
+
+ // Indirectbr can interfere with exit block canonicalization.
+ if (!L->hasDedicatedExits()) {
+ bool HasIndBrExiting = false;
+ SmallVector<BasicBlock*, 8> ExitingBlocks;
+ L->getExitingBlocks(ExitingBlocks);
+ 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;
+ }
}
projects / oota-llvm.git / blobdiff