#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/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"
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
// We need loop information to identify the loops...
- AU.addRequiredTransitive<LoopInfo>();
AU.addRequiredTransitive<DominatorTree>();
-
- AU.addPreserved<LoopInfo>();
AU.addPreserved<DominatorTree>();
+
+ // Request DominanceFrontier now, even though LoopSimplify does
+ // not use it. This allows Pass Manager to schedule Dominance
+ // Frontier early enough such that one LPPassManager can handle
+ // multiple loop transformation passes.
+ AU.addRequired<DominanceFrontier>();
AU.addPreserved<DominanceFrontier>();
+
+ AU.addRequiredTransitive<LoopInfo>();
+ AU.addPreserved<LoopInfo>();
+
AU.addPreserved<AliasAnalysis>();
AU.addPreserved<ScalarEvolution>();
AU.addPreservedID(BreakCriticalEdgesID); // No critical edges added.
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 ";
+ WriteAsOperand(dbgs(), *I, false);
+ dbgs() << "\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 ";
+ WriteAsOperand(dbgs(), *I, false);
+ dbgs() << "\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;
}
}
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);
// 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;
}
}
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
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,
// 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");
+
assert(pred_begin(ExitingBlock) == pred_end(ExitingBlock));
Changed = true;
LI->removeBlock(ExitingBlock);
}
}
- // If there are duplicate phi nodes (for example, from loop rotation),
- // get rid of them.
- for (Loop::block_iterator BB = L->block_begin(), E = L->block_end();
- BB != E; ++BB)
- EliminateDuplicatePHINodes(*BB);
-
return Changed;
}
// 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 ";
+ WriteAsOperand(dbgs(), NewBB, false);
+ dbgs() << "\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 ";
+ WriteAsOperand(dbgs(), NewBB, false);
+ dbgs() << "\n");
+
return NewBB;
}
OuterLoopPreds.push_back(PN->getIncomingBlock(i));
}
+ DEBUG(dbgs() << "LoopSimplify: Splitting out a new outer loop\n");
+
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;
+ 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 ";
+ WriteAsOperand(dbgs(), BEBlock, false);
+ dbgs() << "\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);
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