//
// The LLVM Compiler Infrastructure
//
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/ProfileInfo.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/Type.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Compiler.h"
+#include "llvm/Support/ErrorHandling.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;
STATISTIC(NumBroken, "Number of blocks inserted");
namespace {
- struct VISIBILITY_HIDDEN BreakCriticalEdges : public FunctionPass {
+ struct BreakCriticalEdges : public FunctionPass {
static char ID; // Pass identification, replacement for typeid
- BreakCriticalEdges() : FunctionPass((intptr_t)&ID) {}
+ BreakCriticalEdges() : FunctionPass(&ID) {}
virtual bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addPreserved<ETForest>();
AU.addPreserved<DominatorTree>();
AU.addPreserved<DominanceFrontier>();
AU.addPreserved<LoopInfo>();
+ AU.addPreserved<ProfileInfo>();
// No loop canonicalization guarantees are broken by this pass.
AU.addPreservedID(LoopSimplifyID);
}
};
-
- char BreakCriticalEdges::ID = 0;
- RegisterPass<BreakCriticalEdges> X("break-crit-edges",
- "Break critical edges in CFG");
}
+char BreakCriticalEdges::ID = 0;
+static RegisterPass<BreakCriticalEdges>
+X("break-crit-edges", "Break critical edges in CFG");
+
// Publically exposed interface to pass...
-const PassInfo *llvm::BreakCriticalEdgesID = X.getPassInfo();
+const PassInfo *const llvm::BreakCriticalEdgesID = &X;
FunctionPass *llvm::createBreakCriticalEdgesPass() {
return new BreakCriticalEdges();
}
// If AllowIdenticalEdges is true, then we allow this edge to be considered
// non-critical iff all preds come from TI's block.
- for (; I != E; ++I)
- if (*I != FirstPred) return true;
+ while (I != E) {
+ if (*I != FirstPred)
+ return true;
+ // Note: leave this as is until no one ever compiles with either gcc 4.0.1
+ // or Xcode 2. This seems to work around the pred_iterator assert in PR 2207
+ E = pred_end(*I);
+ ++I;
+ }
return false;
}
-// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
-// split the critical edge. This will update ETForest, ImmediateDominator,
-// DominatorTree, and DominatorFrontier information if it is available, thus
-// calling this pass will not invalidate any of them. This returns true if
-// the edge was split, false otherwise. This ensures that all edges to that
-// dest go to one block instead of each going to a different block.
+/// CreatePHIsForSplitLoopExit - When a loop exit edge is split, LCSSA form
+/// may require new PHIs in the new exit block. This function inserts the
+/// new PHIs, as needed. Preds is a list of preds inside the loop, SplitBB
+/// is the new loop exit block, and DestBB is the old loop exit, now the
+/// successor of SplitBB.
+static void CreatePHIsForSplitLoopExit(SmallVectorImpl<BasicBlock *> &Preds,
+ BasicBlock *SplitBB,
+ BasicBlock *DestBB) {
+ // SplitBB shouldn't have anything non-trivial in it yet.
+ assert(SplitBB->getFirstNonPHI() == SplitBB->getTerminator() &&
+ "SplitBB has non-PHI nodes!");
+
+ // For each PHI in the destination block...
+ for (BasicBlock::iterator I = DestBB->begin();
+ PHINode *PN = dyn_cast<PHINode>(I); ++I) {
+ unsigned Idx = PN->getBasicBlockIndex(SplitBB);
+ Value *V = PN->getIncomingValue(Idx);
+ // If the input is a PHI which already satisfies LCSSA, don't create
+ // a new one.
+ if (const PHINode *VP = dyn_cast<PHINode>(V))
+ if (VP->getParent() == SplitBB)
+ continue;
+ // Otherwise a new PHI is needed. Create one and populate it.
+ PHINode *NewPN = PHINode::Create(PN->getType(), "split",
+ SplitBB->getTerminator());
+ for (unsigned i = 0, e = Preds.size(); i != e; ++i)
+ NewPN->addIncoming(V, Preds[i]);
+ // Update the original PHI.
+ PN->setIncomingValue(Idx, NewPN);
+ }
+}
+
+/// SplitCriticalEdge - If this edge is a critical edge, insert a new node to
+/// split the critical edge. This will update DominatorTree and
+/// DominatorFrontier information if it is available, thus calling this pass
+/// will not invalidate any of them. This returns true if the edge was split,
+/// false otherwise. This ensures that all edges to that dest go to one block
+/// instead of each going to a different block.
//
-bool llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum, Pass *P,
- bool MergeIdenticalEdges) {
- if (!isCriticalEdge(TI, SuccNum, MergeIdenticalEdges)) return false;
+BasicBlock *llvm::SplitCriticalEdge(TerminatorInst *TI, unsigned SuccNum,
+ Pass *P, bool MergeIdenticalEdges) {
+ if (!isCriticalEdge(TI, SuccNum, MergeIdenticalEdges)) return 0;
BasicBlock *TIBB = TI->getParent();
BasicBlock *DestBB = TI->getSuccessor(SuccNum);
// Create a new basic block, linking it into the CFG.
- BasicBlock *NewBB = new BasicBlock(TIBB->getName() + "." +
- DestBB->getName() + "_crit_edge");
+ BasicBlock *NewBB = BasicBlock::Create(TI->getContext(),
+ TIBB->getName() + "." + DestBB->getName() + "_crit_edge");
// Create our unconditional branch...
- new BranchInst(DestBB, NewBB);
+ BranchInst::Create(DestBB, NewBB);
// Branch to the new block, breaking the edge.
TI->setSuccessor(SuccNum, NewBB);
// If we don't have a pass object, we can't update anything...
- if (P == 0) return true;
+ if (P == 0) return NewBB;
// Now update analysis information. Since the only predecessor of NewBB is
// the TIBB, TIBB clearly dominates NewBB. TIBB usually doesn't dominate
bool NewBBDominatesDestBB = true;
- // Update the forest?
- if (ETForest *EF = P->getAnalysisToUpdate<ETForest>()) {
- // NewBB is dominated by TIBB.
- EF->addNewBlock(NewBB, TIBB);
-
- // If NewBBDominatesDestBB hasn't been computed yet, do so with EF.
- if (!OtherPreds.empty()) {
- while (!OtherPreds.empty() && NewBBDominatesDestBB) {
- NewBBDominatesDestBB = EF->dominates(DestBB, OtherPreds.back());
- OtherPreds.pop_back();
- }
- OtherPreds.clear();
- }
-
- // If NewBBDominatesDestBB, then NewBB dominates DestBB, otherwise it
- // doesn't dominate anything.
- if (NewBBDominatesDestBB)
- EF->setImmediateDominator(DestBB, NewBB);
- }
-
// Should we update DominatorTree information?
- if (DominatorTree *DT = P->getAnalysisToUpdate<DominatorTree>()) {
- DominatorTree::Node *TINode = DT->getNode(TIBB);
+ if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>()) {
+ DomTreeNode *TINode = DT->getNode(TIBB);
// The new block is not the immediate dominator for any other nodes, but
// TINode is the immediate dominator for the new node.
//
if (TINode) { // Don't break unreachable code!
- DominatorTree::Node *NewBBNode = DT->createNewNode(NewBB, TINode);
- DominatorTree::Node *DestBBNode = 0;
+ DomTreeNode *NewBBNode = DT->addNewBlock(NewBB, TIBB);
+ DomTreeNode *DestBBNode = 0;
// If NewBBDominatesDestBB hasn't been computed yet, do so with DT.
if (!OtherPreds.empty()) {
DestBBNode = DT->getNode(DestBB);
while (!OtherPreds.empty() && NewBBDominatesDestBB) {
- if (DominatorTree::Node *OPNode = DT->getNode(OtherPreds.back()))
- NewBBDominatesDestBB = DestBBNode->dominates(OPNode);
+ if (DomTreeNode *OPNode = DT->getNode(OtherPreds.back()))
+ NewBBDominatesDestBB = DT->dominates(DestBBNode, OPNode);
OtherPreds.pop_back();
}
OtherPreds.clear();
}
// Should we update DominanceFrontier information?
- if (DominanceFrontier *DF = P->getAnalysisToUpdate<DominanceFrontier>()) {
+ if (DominanceFrontier *DF = P->getAnalysisIfAvailable<DominanceFrontier>()) {
// If NewBBDominatesDestBB hasn't been computed yet, do so with DF.
if (!OtherPreds.empty()) {
// FIXME: IMPLEMENT THIS!
- assert(0 && "Requiring domfrontiers but not idom/domtree/domset."
- " not implemented yet!");
+ llvm_unreachable("Requiring domfrontiers but not idom/domtree/domset."
+ " not implemented yet!");
}
// Since the new block is dominated by its only predecessor TIBB,
DominanceFrontier::DomSetType NewDFSet;
if (NewBBDominatesDestBB) {
DominanceFrontier::iterator I = DF->find(DestBB);
- if (I != DF->end())
+ if (I != DF->end()) {
DF->addBasicBlock(NewBB, I->second);
+
+ if (I->second.count(DestBB)) {
+ // However NewBB's frontier does not include DestBB.
+ DominanceFrontier::iterator NF = DF->find(NewBB);
+ DF->removeFromFrontier(NF, DestBB);
+ }
+ }
else
DF->addBasicBlock(NewBB, DominanceFrontier::DomSetType());
} else {
}
// Update LoopInfo if it is around.
- if (LoopInfo *LI = P->getAnalysisToUpdate<LoopInfo>()) {
- // If one or the other blocks were not in a loop, the new block is not
- // either, and thus LI doesn't need to be updated.
- if (Loop *TIL = LI->getLoopFor(TIBB))
+ if (LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>()) {
+ if (Loop *TIL = LI->getLoopFor(TIBB)) {
+ // If one or the other blocks were not in a loop, the new block is not
+ // either, and thus LI doesn't need to be updated.
if (Loop *DestLoop = LI->getLoopFor(DestBB)) {
if (TIL == DestLoop) {
// Both in the same loop, the NewBB joins loop.
- DestLoop->addBasicBlockToLoop(NewBB, *LI);
+ DestLoop->addBasicBlockToLoop(NewBB, LI->getBase());
} else if (TIL->contains(DestLoop->getHeader())) {
// Edge from an outer loop to an inner loop. Add to the outer loop.
- TIL->addBasicBlockToLoop(NewBB, *LI);
+ TIL->addBasicBlockToLoop(NewBB, LI->getBase());
} else if (DestLoop->contains(TIL->getHeader())) {
// Edge from an inner loop to an outer loop. Add to the outer loop.
- DestLoop->addBasicBlockToLoop(NewBB, *LI);
+ DestLoop->addBasicBlockToLoop(NewBB, LI->getBase());
} else {
// Edge from two loops with no containment relation. Because these
// are natural loops, we know that the destination block must be the
assert(DestLoop->getHeader() == DestBB &&
"Should not create irreducible loops!");
if (Loop *P = DestLoop->getParentLoop())
- P->addBasicBlockToLoop(NewBB, *LI);
+ P->addBasicBlockToLoop(NewBB, LI->getBase());
+ }
+ }
+ // If TIBB is in a loop and DestBB is outside of that loop, split the
+ // other exit blocks of the loop that also have predecessors outside
+ // the loop, to maintain a LoopSimplify guarantee.
+ if (!TIL->contains(DestBB) &&
+ P->mustPreserveAnalysisID(LoopSimplifyID)) {
+ assert(!TIL->contains(NewBB) &&
+ "Split point for loop exit is contained in loop!");
+
+ // Update LCSSA form in the newly created exit block.
+ if (P->mustPreserveAnalysisID(LCSSAID)) {
+ SmallVector<BasicBlock *, 1> OrigPred;
+ OrigPred.push_back(TIBB);
+ CreatePHIsForSplitLoopExit(OrigPred, NewBB, DestBB);
+ }
+
+ // For each unique exit block...
+ SmallVector<BasicBlock *, 4> ExitBlocks;
+ TIL->getExitBlocks(ExitBlocks);
+ for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
+ // Collect all the preds that are inside the loop, and note
+ // whether there are any preds outside the loop.
+ SmallVector<BasicBlock *, 4> Preds;
+ bool HasPredOutsideOfLoop = false;
+ BasicBlock *Exit = ExitBlocks[i];
+ for (pred_iterator I = pred_begin(Exit), E = pred_end(Exit);
+ I != E; ++I)
+ if (TIL->contains(*I))
+ Preds.push_back(*I);
+ else
+ HasPredOutsideOfLoop = true;
+ // If there are any preds not in the loop, we'll need to split
+ // the edges. The Preds.empty() check is needed because a block
+ // may appear multiple times in the list. We can't use
+ // getUniqueExitBlocks above because that depends on LoopSimplify
+ // form, which we're in the process of restoring!
+ if (!Preds.empty() && HasPredOutsideOfLoop) {
+ BasicBlock *NewExitBB =
+ SplitBlockPredecessors(Exit, Preds.data(), Preds.size(),
+ "split", P);
+ if (P->mustPreserveAnalysisID(LCSSAID))
+ CreatePHIsForSplitLoopExit(Preds, NewExitBB, Exit);
+ }
}
}
+ // LCSSA form was updated above for the case where LoopSimplify is
+ // available, which means that all predecessors of loop exit blocks
+ // are within the loop. Without LoopSimplify form, it would be
+ // necessary to insert a new phi.
+ assert((!P->mustPreserveAnalysisID(LCSSAID) ||
+ P->mustPreserveAnalysisID(LoopSimplifyID)) &&
+ "SplitCriticalEdge doesn't know how to update LCCSA form "
+ "without LoopSimplify!");
+ }
}
- return true;
+
+ // Update ProfileInfo if it is around.
+ if (ProfileInfo *PI = P->getAnalysisIfAvailable<ProfileInfo>()) {
+ PI->splitEdge(TIBB,DestBB,NewBB,MergeIdenticalEdges);
+ }
+
+ return NewBB;
}
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