#include "llvm/Instructions.h"
#include "llvm/Intrinsics.h"
#include "llvm/IntrinsicInst.h"
-#include "llvm/LLVMContext.h"
+#include "llvm/Metadata.h"
+#include "llvm/Operator.h"
+#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/DebugInfo.h"
+#include "llvm/Analysis/DIBuilder.h"
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/ProfileInfo.h"
+#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Target/TargetData.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
+#include "llvm/Support/IRBuilder.h"
#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/ValueHandle.h"
+#include "llvm/Support/raw_ostream.h"
using namespace llvm;
-//===----------------------------------------------------------------------===//
-// Local analysis.
-//
-
-/// isSafeToLoadUnconditionally - Return true if we know that executing a load
-/// from this value cannot trap. If it is not obviously safe to load from the
-/// specified pointer, we do a quick local scan of the basic block containing
-/// ScanFrom, to determine if the address is already accessed.
-bool llvm::isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom) {
- // If it is an alloca it is always safe to load from.
- if (isa<AllocaInst>(V)) return true;
-
- // If it is a global variable it is mostly safe to load from.
- if (const GlobalValue *GV = dyn_cast<GlobalVariable>(V))
- // Don't try to evaluate aliases. External weak GV can be null.
- return !isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage();
-
- // Otherwise, be a little bit agressive by scanning the local block where we
- // want to check to see if the pointer is already being loaded or stored
- // from/to. If so, the previous load or store would have already trapped,
- // so there is no harm doing an extra load (also, CSE will later eliminate
- // the load entirely).
- BasicBlock::iterator BBI = ScanFrom, E = ScanFrom->getParent()->begin();
-
- while (BBI != E) {
- --BBI;
-
- // If we see a free or a call which may write to memory (i.e. which might do
- // a free) the pointer could be marked invalid.
- if (isa<CallInst>(BBI) && BBI->mayWriteToMemory() &&
- !isa<DbgInfoIntrinsic>(BBI))
- return false;
-
- if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
- if (LI->getOperand(0) == V) return true;
- } else if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) {
- if (SI->getOperand(1) == V) return true;
- }
- }
- return false;
-}
-
-
//===----------------------------------------------------------------------===//
// Local constant propagation.
//
-// ConstantFoldTerminator - If a terminator instruction is predicated on a
-// constant value, convert it into an unconditional branch to the constant
-// destination.
-//
-bool llvm::ConstantFoldTerminator(BasicBlock *BB) {
+/// ConstantFoldTerminator - If a terminator instruction is predicated on a
+/// constant value, convert it into an unconditional branch to the constant
+/// destination. This is a nontrivial operation because the successors of this
+/// basic block must have their PHI nodes updated.
+/// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch
+/// conditions and indirectbr addresses this might make dead if
+/// DeleteDeadConditions is true.
+bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions) {
TerminatorInst *T = BB->getTerminator();
+ IRBuilder<> Builder(T);
// Branch - See if we are conditional jumping on constant
if (BranchInst *BI = dyn_cast<BranchInst>(T)) {
// Let the basic block know that we are letting go of it. Based on this,
// it will adjust it's PHI nodes.
- assert(BI->getParent() && "Terminator not inserted in block!");
- OldDest->removePredecessor(BI->getParent());
+ OldDest->removePredecessor(BB);
- // Set the unconditional destination, and change the insn to be an
- // unconditional branch.
- BI->setUnconditionalDest(Destination);
+ // Replace the conditional branch with an unconditional one.
+ Builder.CreateBr(Destination);
+ BI->eraseFromParent();
return true;
}
assert(BI->getParent() && "Terminator not inserted in block!");
Dest1->removePredecessor(BI->getParent());
- // Change a conditional branch to unconditional.
- BI->setUnconditionalDest(Dest1);
+ // Replace the conditional branch with an unconditional one.
+ Builder.CreateBr(Dest1);
+ Value *Cond = BI->getCondition();
+ BI->eraseFromParent();
+ if (DeleteDeadConditions)
+ RecursivelyDeleteTriviallyDeadInstructions(Cond);
return true;
}
return false;
// If we are switching on a constant, we can convert the switch into a
// single branch instruction!
ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition());
- BasicBlock *TheOnlyDest = SI->getSuccessor(0); // The default dest
+ BasicBlock *TheOnlyDest = SI->getDefaultDest();
BasicBlock *DefaultDest = TheOnlyDest;
- assert(TheOnlyDest == SI->getDefaultDest() &&
- "Default destination is not successor #0?");
// Figure out which case it goes to.
- for (unsigned i = 1, e = SI->getNumSuccessors(); i != e; ++i) {
+ for (SwitchInst::CaseIt i = SI->caseBegin(), e = SI->caseEnd();
+ i != e; ++i) {
// Found case matching a constant operand?
- if (SI->getSuccessorValue(i) == CI) {
- TheOnlyDest = SI->getSuccessor(i);
+ if (i.getCaseValue() == CI) {
+ TheOnlyDest = i.getCaseSuccessor();
break;
}
// Check to see if this branch is going to the same place as the default
// dest. If so, eliminate it as an explicit compare.
- if (SI->getSuccessor(i) == DefaultDest) {
+ if (i.getCaseSuccessor() == DefaultDest) {
// Remove this entry.
DefaultDest->removePredecessor(SI->getParent());
SI->removeCase(i);
- --i; --e; // Don't skip an entry...
+ --i; --e;
continue;
}
// Otherwise, check to see if the switch only branches to one destination.
// We do this by reseting "TheOnlyDest" to null when we find two non-equal
// destinations.
- if (SI->getSuccessor(i) != TheOnlyDest) TheOnlyDest = 0;
+ if (i.getCaseSuccessor() != TheOnlyDest) TheOnlyDest = 0;
}
if (CI && !TheOnlyDest) {
// now.
if (TheOnlyDest) {
// Insert the new branch.
- BranchInst::Create(TheOnlyDest, SI);
+ Builder.CreateBr(TheOnlyDest);
BasicBlock *BB = SI->getParent();
// Remove entries from PHI nodes which we no longer branch to...
}
// Delete the old switch.
- BB->getInstList().erase(SI);
+ Value *Cond = SI->getCondition();
+ SI->eraseFromParent();
+ if (DeleteDeadConditions)
+ RecursivelyDeleteTriviallyDeadInstructions(Cond);
return true;
}
- if (SI->getNumSuccessors() == 2) {
+ if (SI->getNumCases() == 1) {
// Otherwise, we can fold this switch into a conditional branch
// instruction if it has only one non-default destination.
- Value *Cond = new ICmpInst(SI, ICmpInst::ICMP_EQ, SI->getCondition(),
- SI->getSuccessorValue(1), "cond");
+ SwitchInst::CaseIt FirstCase = SI->caseBegin();
+ Value *Cond = Builder.CreateICmpEQ(SI->getCondition(),
+ FirstCase.getCaseValue(), "cond");
+
// Insert the new branch.
- BranchInst::Create(SI->getSuccessor(1), SI->getSuccessor(0), Cond, SI);
+ Builder.CreateCondBr(Cond, FirstCase.getCaseSuccessor(),
+ SI->getDefaultDest());
// Delete the old switch.
SI->eraseFromParent();
dyn_cast<BlockAddress>(IBI->getAddress()->stripPointerCasts())) {
BasicBlock *TheOnlyDest = BA->getBasicBlock();
// Insert the new branch.
- BranchInst::Create(TheOnlyDest, IBI);
+ Builder.CreateBr(TheOnlyDest);
for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
if (IBI->getDestination(i) == TheOnlyDest)
else
IBI->getDestination(i)->removePredecessor(IBI->getParent());
}
+ Value *Address = IBI->getAddress();
IBI->eraseFromParent();
+ if (DeleteDeadConditions)
+ RecursivelyDeleteTriviallyDeadInstructions(Address);
// If we didn't find our destination in the IBI successor list, then we
// have undefined behavior. Replace the unconditional branch with an
//===----------------------------------------------------------------------===//
-// Local dead code elimination...
+// Local dead code elimination.
//
/// isInstructionTriviallyDead - Return true if the result produced by the
bool llvm::isInstructionTriviallyDead(Instruction *I) {
if (!I->use_empty() || isa<TerminatorInst>(I)) return false;
- // We don't want debug info removed by anything this general.
- if (isa<DbgInfoIntrinsic>(I)) return false;
+ // We don't want the landingpad instruction removed by anything this general.
+ if (isa<LandingPadInst>(I))
+ return false;
+
+ // We don't want debug info removed by anything this general, unless
+ // debug info is empty.
+ if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(I)) {
+ if (DDI->getAddress())
+ return false;
+ return true;
+ }
+ if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(I)) {
+ if (DVI->getValue())
+ return false;
+ return true;
+ }
if (!I->mayHaveSideEffects()) return true;
// Special case intrinsics that "may have side effects" but can be deleted
// when dead.
- if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I))
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
// Safe to delete llvm.stacksave if dead.
if (II->getIntrinsicID() == Intrinsic::stacksave)
return true;
+
+ // Lifetime intrinsics are dead when their right-hand is undef.
+ if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
+ II->getIntrinsicID() == Intrinsic::lifetime_end)
+ return isa<UndefValue>(II->getArgOperand(1));
+ }
+
+ if (extractMallocCall(I)) return true;
+
+ if (CallInst *CI = isFreeCall(I))
+ if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0)))
+ return C->isNullValue() || isa<UndefValue>(C);
+
return false;
}
/// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
/// trivially dead instruction, delete it. If that makes any of its operands
-/// trivially dead, delete them too, recursively.
-void llvm::RecursivelyDeleteTriviallyDeadInstructions(Value *V) {
+/// trivially dead, delete them too, recursively. Return true if any
+/// instructions were deleted.
+bool llvm::RecursivelyDeleteTriviallyDeadInstructions(Value *V) {
Instruction *I = dyn_cast<Instruction>(V);
if (!I || !I->use_empty() || !isInstructionTriviallyDead(I))
- return;
+ return false;
SmallVector<Instruction*, 16> DeadInsts;
DeadInsts.push_back(I);
- while (!DeadInsts.empty()) {
+ do {
I = DeadInsts.pop_back_val();
// Null out all of the instruction's operands to see if any operand becomes
}
I->eraseFromParent();
+ } while (!DeadInsts.empty());
+
+ return true;
+}
+
+/// areAllUsesEqual - Check whether the uses of a value are all the same.
+/// This is similar to Instruction::hasOneUse() except this will also return
+/// true when there are no uses or multiple uses that all refer to the same
+/// value.
+static bool areAllUsesEqual(Instruction *I) {
+ Value::use_iterator UI = I->use_begin();
+ Value::use_iterator UE = I->use_end();
+ if (UI == UE)
+ return true;
+
+ User *TheUse = *UI;
+ for (++UI; UI != UE; ++UI) {
+ if (*UI != TheUse)
+ return false;
}
+ return true;
}
/// RecursivelyDeleteDeadPHINode - If the specified value is an effectively
/// dead PHI node, due to being a def-use chain of single-use nodes that
/// either forms a cycle or is terminated by a trivially dead instruction,
/// delete it. If that makes any of its operands trivially dead, delete them
-/// too, recursively.
-void
-llvm::RecursivelyDeleteDeadPHINode(PHINode *PN) {
- // We can remove a PHI if it is on a cycle in the def-use graph
- // where each node in the cycle has degree one, i.e. only one use,
- // and is an instruction with no side effects.
- if (!PN->hasOneUse())
- return;
-
- SmallPtrSet<PHINode *, 4> PHIs;
- PHIs.insert(PN);
- for (Instruction *J = cast<Instruction>(*PN->use_begin());
- J->hasOneUse() && !J->mayHaveSideEffects();
- J = cast<Instruction>(*J->use_begin()))
- // If we find a PHI more than once, we're on a cycle that
+/// too, recursively. Return true if a change was made.
+bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN) {
+ SmallPtrSet<Instruction*, 4> Visited;
+ for (Instruction *I = PN; areAllUsesEqual(I) && !I->mayHaveSideEffects();
+ I = cast<Instruction>(*I->use_begin())) {
+ if (I->use_empty())
+ return RecursivelyDeleteTriviallyDeadInstructions(I);
+
+ // If we find an instruction more than once, we're on a cycle that
// won't prove fruitful.
- if (PHINode *JP = dyn_cast<PHINode>(J))
- if (!PHIs.insert(cast<PHINode>(JP))) {
- // Break the cycle and delete the PHI and its operands.
- JP->replaceAllUsesWith(UndefValue::get(JP->getType()));
- RecursivelyDeleteTriviallyDeadInstructions(JP);
- break;
- }
+ if (!Visited.insert(I)) {
+ // Break the cycle and delete the instruction and its operands.
+ I->replaceAllUsesWith(UndefValue::get(I->getType()));
+ (void)RecursivelyDeleteTriviallyDeadInstructions(I);
+ return true;
+ }
+ }
+ return false;
+}
+
+/// SimplifyInstructionsInBlock - Scan the specified basic block and try to
+/// simplify any instructions in it and recursively delete dead instructions.
+///
+/// This returns true if it changed the code, note that it can delete
+/// instructions in other blocks as well in this block.
+bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB, const TargetData *TD) {
+ bool MadeChange = false;
+ for (BasicBlock::iterator BI = BB->begin(), E = BB->end(); BI != E; ) {
+ Instruction *Inst = BI++;
+
+ if (Value *V = SimplifyInstruction(Inst, TD)) {
+ WeakVH BIHandle(BI);
+ ReplaceAndSimplifyAllUses(Inst, V, TD);
+ MadeChange = true;
+ if (BIHandle != BI)
+ BI = BB->begin();
+ continue;
+ }
+
+ if (Inst->isTerminator())
+ break;
+
+ WeakVH BIHandle(BI);
+ MadeChange |= RecursivelyDeleteTriviallyDeadInstructions(Inst);
+ if (BIHandle != BI)
+ BI = BB->begin();
+ }
+ return MadeChange;
}
//===----------------------------------------------------------------------===//
-// Control Flow Graph Restructuring...
+// Control Flow Graph Restructuring.
//
+
+/// RemovePredecessorAndSimplify - Like BasicBlock::removePredecessor, this
+/// method is called when we're about to delete Pred as a predecessor of BB. If
+/// BB contains any PHI nodes, this drops the entries in the PHI nodes for Pred.
+///
+/// Unlike the removePredecessor method, this attempts to simplify uses of PHI
+/// nodes that collapse into identity values. For example, if we have:
+/// x = phi(1, 0, 0, 0)
+/// y = and x, z
+///
+/// .. and delete the predecessor corresponding to the '1', this will attempt to
+/// recursively fold the and to 0.
+void llvm::RemovePredecessorAndSimplify(BasicBlock *BB, BasicBlock *Pred,
+ TargetData *TD) {
+ // This only adjusts blocks with PHI nodes.
+ if (!isa<PHINode>(BB->begin()))
+ return;
+
+ // Remove the entries for Pred from the PHI nodes in BB, but do not simplify
+ // them down. This will leave us with single entry phi nodes and other phis
+ // that can be removed.
+ BB->removePredecessor(Pred, true);
+
+ WeakVH PhiIt = &BB->front();
+ while (PHINode *PN = dyn_cast<PHINode>(PhiIt)) {
+ PhiIt = &*++BasicBlock::iterator(cast<Instruction>(PhiIt));
+
+ Value *PNV = SimplifyInstruction(PN, TD);
+ if (PNV == 0) continue;
+
+ // If we're able to simplify the phi to a single value, substitute the new
+ // value into all of its uses.
+ assert(PNV != PN && "SimplifyInstruction broken!");
+
+ Value *OldPhiIt = PhiIt;
+ ReplaceAndSimplifyAllUses(PN, PNV, TD);
+
+ // If recursive simplification ended up deleting the next PHI node we would
+ // iterate to, then our iterator is invalid, restart scanning from the top
+ // of the block.
+ if (PhiIt != OldPhiIt) PhiIt = &BB->front();
+ }
+}
+
+
/// MergeBasicBlockIntoOnlyPred - DestBB is a block with one predecessor and its
/// predecessor is known to have one successor (DestBB!). Eliminate the edge
/// between them, moving the instructions in the predecessor into DestBB and
BasicBlock *PredBB = DestBB->getSinglePredecessor();
assert(PredBB && "Block doesn't have a single predecessor!");
- // Splice all the instructions from PredBB to DestBB.
- PredBB->getTerminator()->eraseFromParent();
- DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList());
+ // Zap anything that took the address of DestBB. Not doing this will give the
+ // address an invalid value.
+ if (DestBB->hasAddressTaken()) {
+ BlockAddress *BA = BlockAddress::get(DestBB);
+ Constant *Replacement =
+ ConstantInt::get(llvm::Type::getInt32Ty(BA->getContext()), 1);
+ BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement,
+ BA->getType()));
+ BA->destroyConstant();
+ }
// Anything that branched to PredBB now branches to DestBB.
PredBB->replaceAllUsesWith(DestBB);
+ // Splice all the instructions from PredBB to DestBB.
+ PredBB->getTerminator()->eraseFromParent();
+ DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList());
+
if (P) {
+ DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>();
+ if (DT) {
+ BasicBlock *PredBBIDom = DT->getNode(PredBB)->getIDom()->getBlock();
+ DT->changeImmediateDominator(DestBB, PredBBIDom);
+ DT->eraseNode(PredBB);
+ }
ProfileInfo *PI = P->getAnalysisIfAvailable<ProfileInfo>();
if (PI) {
PI->replaceAllUses(PredBB, DestBB);
PredBB->eraseFromParent();
}
-/// OnlyUsedByDbgIntrinsics - Return true if the instruction I is only used
-/// by DbgIntrinsics. If DbgInUses is specified then the vector is filled
-/// with the DbgInfoIntrinsic that use the instruction I.
-bool llvm::OnlyUsedByDbgInfoIntrinsics(Instruction *I,
- SmallVectorImpl<DbgInfoIntrinsic *> *DbgInUses) {
- if (DbgInUses)
- DbgInUses->clear();
-
- for (Value::use_iterator UI = I->use_begin(), UE = I->use_end(); UI != UE;
- ++UI) {
- if (DbgInfoIntrinsic *DI = dyn_cast<DbgInfoIntrinsic>(*UI)) {
- if (DbgInUses)
- DbgInUses->push_back(DI);
+/// CanPropagatePredecessorsForPHIs - Return true if we can fold BB, an
+/// almost-empty BB ending in an unconditional branch to Succ, into succ.
+///
+/// Assumption: Succ is the single successor for BB.
+///
+static bool CanPropagatePredecessorsForPHIs(BasicBlock *BB, BasicBlock *Succ) {
+ assert(*succ_begin(BB) == Succ && "Succ is not successor of BB!");
+
+ DEBUG(dbgs() << "Looking to fold " << BB->getName() << " into "
+ << Succ->getName() << "\n");
+ // Shortcut, if there is only a single predecessor it must be BB and merging
+ // is always safe
+ if (Succ->getSinglePredecessor()) return true;
+
+ // Make a list of the predecessors of BB
+ SmallPtrSet<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB));
+
+ // Look at all the phi nodes in Succ, to see if they present a conflict when
+ // merging these blocks
+ for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
+ PHINode *PN = cast<PHINode>(I);
+
+ // If the incoming value from BB is again a PHINode in
+ // BB which has the same incoming value for *PI as PN does, we can
+ // merge the phi nodes and then the blocks can still be merged
+ PHINode *BBPN = dyn_cast<PHINode>(PN->getIncomingValueForBlock(BB));
+ if (BBPN && BBPN->getParent() == BB) {
+ for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
+ BasicBlock *IBB = PN->getIncomingBlock(PI);
+ if (BBPreds.count(IBB) &&
+ BBPN->getIncomingValueForBlock(IBB) != PN->getIncomingValue(PI)) {
+ DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in "
+ << Succ->getName() << " is conflicting with "
+ << BBPN->getName() << " with regard to common predecessor "
+ << IBB->getName() << "\n");
+ return false;
+ }
+ }
} else {
- if (DbgInUses)
- DbgInUses->clear();
- return false;
+ Value* Val = PN->getIncomingValueForBlock(BB);
+ for (unsigned PI = 0, PE = PN->getNumIncomingValues(); PI != PE; ++PI) {
+ // See if the incoming value for the common predecessor is equal to the
+ // one for BB, in which case this phi node will not prevent the merging
+ // of the block.
+ BasicBlock *IBB = PN->getIncomingBlock(PI);
+ if (BBPreds.count(IBB) && Val != PN->getIncomingValue(PI)) {
+ DEBUG(dbgs() << "Can't fold, phi node " << PN->getName() << " in "
+ << Succ->getName() << " is conflicting with regard to common "
+ << "predecessor " << IBB->getName() << "\n");
+ return false;
+ }
+ }
+ }
+ }
+
+ return true;
+}
+
+/// TryToSimplifyUncondBranchFromEmptyBlock - BB is known to contain an
+/// unconditional branch, and contains no instructions other than PHI nodes,
+/// potential side-effect free intrinsics and the branch. If possible,
+/// eliminate BB by rewriting all the predecessors to branch to the successor
+/// block and return true. If we can't transform, return false.
+bool llvm::TryToSimplifyUncondBranchFromEmptyBlock(BasicBlock *BB) {
+ assert(BB != &BB->getParent()->getEntryBlock() &&
+ "TryToSimplifyUncondBranchFromEmptyBlock called on entry block!");
+
+ // We can't eliminate infinite loops.
+ BasicBlock *Succ = cast<BranchInst>(BB->getTerminator())->getSuccessor(0);
+ if (BB == Succ) return false;
+
+ // Check to see if merging these blocks would cause conflicts for any of the
+ // phi nodes in BB or Succ. If not, we can safely merge.
+ if (!CanPropagatePredecessorsForPHIs(BB, Succ)) return false;
+
+ // Check for cases where Succ has multiple predecessors and a PHI node in BB
+ // has uses which will not disappear when the PHI nodes are merged. It is
+ // possible to handle such cases, but difficult: it requires checking whether
+ // BB dominates Succ, which is non-trivial to calculate in the case where
+ // Succ has multiple predecessors. Also, it requires checking whether
+ // constructing the necessary self-referential PHI node doesn't intoduce any
+ // conflicts; this isn't too difficult, but the previous code for doing this
+ // was incorrect.
+ //
+ // Note that if this check finds a live use, BB dominates Succ, so BB is
+ // something like a loop pre-header (or rarely, a part of an irreducible CFG);
+ // folding the branch isn't profitable in that case anyway.
+ if (!Succ->getSinglePredecessor()) {
+ BasicBlock::iterator BBI = BB->begin();
+ while (isa<PHINode>(*BBI)) {
+ for (Value::use_iterator UI = BBI->use_begin(), E = BBI->use_end();
+ UI != E; ++UI) {
+ if (PHINode* PN = dyn_cast<PHINode>(*UI)) {
+ if (PN->getIncomingBlock(UI) != BB)
+ return false;
+ } else {
+ return false;
+ }
+ }
+ ++BBI;
+ }
+ }
+
+ DEBUG(dbgs() << "Killing Trivial BB: \n" << *BB);
+
+ if (isa<PHINode>(Succ->begin())) {
+ // If there is more than one pred of succ, and there are PHI nodes in
+ // the successor, then we need to add incoming edges for the PHI nodes
+ //
+ const SmallVector<BasicBlock*, 16> BBPreds(pred_begin(BB), pred_end(BB));
+
+ // Loop over all of the PHI nodes in the successor of BB.
+ for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
+ PHINode *PN = cast<PHINode>(I);
+ Value *OldVal = PN->removeIncomingValue(BB, false);
+ assert(OldVal && "No entry in PHI for Pred BB!");
+
+ // If this incoming value is one of the PHI nodes in BB, the new entries
+ // in the PHI node are the entries from the old PHI.
+ if (isa<PHINode>(OldVal) && cast<PHINode>(OldVal)->getParent() == BB) {
+ PHINode *OldValPN = cast<PHINode>(OldVal);
+ for (unsigned i = 0, e = OldValPN->getNumIncomingValues(); i != e; ++i)
+ // Note that, since we are merging phi nodes and BB and Succ might
+ // have common predecessors, we could end up with a phi node with
+ // identical incoming branches. This will be cleaned up later (and
+ // will trigger asserts if we try to clean it up now, without also
+ // simplifying the corresponding conditional branch).
+ PN->addIncoming(OldValPN->getIncomingValue(i),
+ OldValPN->getIncomingBlock(i));
+ } else {
+ // Add an incoming value for each of the new incoming values.
+ for (unsigned i = 0, e = BBPreds.size(); i != e; ++i)
+ PN->addIncoming(OldVal, BBPreds[i]);
+ }
+ }
+ }
+
+ if (Succ->getSinglePredecessor()) {
+ // BB is the only predecessor of Succ, so Succ will end up with exactly
+ // the same predecessors BB had.
+
+ // Copy over any phi, debug or lifetime instruction.
+ BB->getTerminator()->eraseFromParent();
+ Succ->getInstList().splice(Succ->getFirstNonPHI(), BB->getInstList());
+ } else {
+ while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
+ // We explicitly check for such uses in CanPropagatePredecessorsForPHIs.
+ assert(PN->use_empty() && "There shouldn't be any uses here!");
+ PN->eraseFromParent();
+ }
+ }
+
+ // Everything that jumped to BB now goes to Succ.
+ BB->replaceAllUsesWith(Succ);
+ if (!Succ->hasName()) Succ->takeName(BB);
+ BB->eraseFromParent(); // Delete the old basic block.
+ return true;
+}
+
+/// EliminateDuplicatePHINodes - Check for and eliminate duplicate PHI
+/// nodes in this block. This doesn't try to be clever about PHI nodes
+/// which differ only in the order of the incoming values, but instcombine
+/// orders them so it usually won't matter.
+///
+bool llvm::EliminateDuplicatePHINodes(BasicBlock *BB) {
+ bool Changed = false;
+
+ // This implementation doesn't currently consider undef operands
+ // specially. Theoretically, two phis which are identical except for
+ // one having an undef where the other doesn't could be collapsed.
+
+ // Map from PHI hash values to PHI nodes. If multiple PHIs have
+ // the same hash value, the element is the first PHI in the
+ // linked list in CollisionMap.
+ DenseMap<uintptr_t, PHINode *> HashMap;
+
+ // Maintain linked lists of PHI nodes with common hash values.
+ DenseMap<PHINode *, PHINode *> CollisionMap;
+
+ // Examine each PHI.
+ for (BasicBlock::iterator I = BB->begin();
+ PHINode *PN = dyn_cast<PHINode>(I++); ) {
+ // Compute a hash value on the operands. Instcombine will likely have sorted
+ // them, which helps expose duplicates, but we have to check all the
+ // operands to be safe in case instcombine hasn't run.
+ uintptr_t Hash = 0;
+ // This hash algorithm is quite weak as hash functions go, but it seems
+ // to do a good enough job for this particular purpose, and is very quick.
+ for (User::op_iterator I = PN->op_begin(), E = PN->op_end(); I != E; ++I) {
+ Hash ^= reinterpret_cast<uintptr_t>(static_cast<Value *>(*I));
+ Hash = (Hash << 7) | (Hash >> (sizeof(uintptr_t) * CHAR_BIT - 7));
+ }
+ for (PHINode::block_iterator I = PN->block_begin(), E = PN->block_end();
+ I != E; ++I) {
+ Hash ^= reinterpret_cast<uintptr_t>(static_cast<BasicBlock *>(*I));
+ Hash = (Hash << 7) | (Hash >> (sizeof(uintptr_t) * CHAR_BIT - 7));
+ }
+ // Avoid colliding with the DenseMap sentinels ~0 and ~0-1.
+ Hash >>= 1;
+ // If we've never seen this hash value before, it's a unique PHI.
+ std::pair<DenseMap<uintptr_t, PHINode *>::iterator, bool> Pair =
+ HashMap.insert(std::make_pair(Hash, PN));
+ if (Pair.second) continue;
+ // Otherwise it's either a duplicate or a hash collision.
+ for (PHINode *OtherPN = Pair.first->second; ; ) {
+ if (OtherPN->isIdenticalTo(PN)) {
+ // A duplicate. Replace this PHI with its duplicate.
+ PN->replaceAllUsesWith(OtherPN);
+ PN->eraseFromParent();
+ Changed = true;
+ break;
+ }
+ // A non-duplicate hash collision.
+ DenseMap<PHINode *, PHINode *>::iterator I = CollisionMap.find(OtherPN);
+ if (I == CollisionMap.end()) {
+ // Set this PHI to be the head of the linked list of colliding PHIs.
+ PHINode *Old = Pair.first->second;
+ Pair.first->second = PN;
+ CollisionMap[PN] = Old;
+ break;
+ }
+ // Procede to the next PHI in the list.
+ OtherPN = I->second;
+ }
+ }
+
+ return Changed;
+}
+
+/// enforceKnownAlignment - If the specified pointer points to an object that
+/// we control, modify the object's alignment to PrefAlign. This isn't
+/// often possible though. If alignment is important, a more reliable approach
+/// is to simply align all global variables and allocation instructions to
+/// their preferred alignment from the beginning.
+///
+static unsigned enforceKnownAlignment(Value *V, unsigned Align,
+ unsigned PrefAlign, const TargetData *TD) {
+ V = V->stripPointerCasts();
+
+ if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
+ // If the preferred alignment is greater than the natural stack alignment
+ // then don't round up. This avoids dynamic stack realignment.
+ if (TD && TD->exceedsNaturalStackAlignment(PrefAlign))
+ return Align;
+ // If there is a requested alignment and if this is an alloca, round up.
+ if (AI->getAlignment() >= PrefAlign)
+ return AI->getAlignment();
+ AI->setAlignment(PrefAlign);
+ return PrefAlign;
+ }
+
+ if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
+ // If there is a large requested alignment and we can, bump up the alignment
+ // of the global.
+ if (GV->isDeclaration()) return Align;
+ // If the memory we set aside for the global may not be the memory used by
+ // the final program then it is impossible for us to reliably enforce the
+ // preferred alignment.
+ if (GV->isWeakForLinker()) return Align;
+
+ if (GV->getAlignment() >= PrefAlign)
+ return GV->getAlignment();
+ // We can only increase the alignment of the global if it has no alignment
+ // specified or if it is not assigned a section. If it is assigned a
+ // section, the global could be densely packed with other objects in the
+ // section, increasing the alignment could cause padding issues.
+ if (!GV->hasSection() || GV->getAlignment() == 0)
+ GV->setAlignment(PrefAlign);
+ return GV->getAlignment();
+ }
+
+ return Align;
+}
+
+/// getOrEnforceKnownAlignment - If the specified pointer has an alignment that
+/// we can determine, return it, otherwise return 0. If PrefAlign is specified,
+/// and it is more than the alignment of the ultimate object, see if we can
+/// increase the alignment of the ultimate object, making this check succeed.
+unsigned llvm::getOrEnforceKnownAlignment(Value *V, unsigned PrefAlign,
+ const TargetData *TD) {
+ assert(V->getType()->isPointerTy() &&
+ "getOrEnforceKnownAlignment expects a pointer!");
+ unsigned BitWidth = TD ? TD->getPointerSizeInBits() : 64;
+ APInt Mask = APInt::getAllOnesValue(BitWidth);
+ APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
+ ComputeMaskedBits(V, Mask, KnownZero, KnownOne, TD);
+ unsigned TrailZ = KnownZero.countTrailingOnes();
+
+ // Avoid trouble with rediculously large TrailZ values, such as
+ // those computed from a null pointer.
+ TrailZ = std::min(TrailZ, unsigned(sizeof(unsigned) * CHAR_BIT - 1));
+
+ unsigned Align = 1u << std::min(BitWidth - 1, TrailZ);
+
+ // LLVM doesn't support alignments larger than this currently.
+ Align = std::min(Align, +Value::MaximumAlignment);
+
+ if (PrefAlign > Align)
+ Align = enforceKnownAlignment(V, Align, PrefAlign, TD);
+
+ // We don't need to make any adjustment.
+ return Align;
+}
+
+///===---------------------------------------------------------------------===//
+/// Dbg Intrinsic utilities
+///
+
+/// Inserts a llvm.dbg.value instrinsic before the stores to an alloca'd value
+/// that has an associated llvm.dbg.decl intrinsic.
+bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
+ StoreInst *SI, DIBuilder &Builder) {
+ DIVariable DIVar(DDI->getVariable());
+ if (!DIVar.Verify())
+ return false;
+
+ Instruction *DbgVal = NULL;
+ // If an argument is zero extended then use argument directly. The ZExt
+ // may be zapped by an optimization pass in future.
+ Argument *ExtendedArg = NULL;
+ if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
+ ExtendedArg = dyn_cast<Argument>(ZExt->getOperand(0));
+ if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
+ ExtendedArg = dyn_cast<Argument>(SExt->getOperand(0));
+ if (ExtendedArg)
+ DbgVal = Builder.insertDbgValueIntrinsic(ExtendedArg, 0, DIVar, SI);
+ else
+ DbgVal = Builder.insertDbgValueIntrinsic(SI->getOperand(0), 0, DIVar, SI);
+
+ // Propagate any debug metadata from the store onto the dbg.value.
+ DebugLoc SIDL = SI->getDebugLoc();
+ if (!SIDL.isUnknown())
+ DbgVal->setDebugLoc(SIDL);
+ // Otherwise propagate debug metadata from dbg.declare.
+ else
+ DbgVal->setDebugLoc(DDI->getDebugLoc());
+ return true;
+}
+
+/// Inserts a llvm.dbg.value instrinsic before the stores to an alloca'd value
+/// that has an associated llvm.dbg.decl intrinsic.
+bool llvm::ConvertDebugDeclareToDebugValue(DbgDeclareInst *DDI,
+ LoadInst *LI, DIBuilder &Builder) {
+ DIVariable DIVar(DDI->getVariable());
+ if (!DIVar.Verify())
+ return false;
+
+ Instruction *DbgVal =
+ Builder.insertDbgValueIntrinsic(LI->getOperand(0), 0,
+ DIVar, LI);
+
+ // Propagate any debug metadata from the store onto the dbg.value.
+ DebugLoc LIDL = LI->getDebugLoc();
+ if (!LIDL.isUnknown())
+ DbgVal->setDebugLoc(LIDL);
+ // Otherwise propagate debug metadata from dbg.declare.
+ else
+ DbgVal->setDebugLoc(DDI->getDebugLoc());
+ return true;
+}
+
+/// LowerDbgDeclare - Lowers llvm.dbg.declare intrinsics into appropriate set
+/// of llvm.dbg.value intrinsics.
+bool llvm::LowerDbgDeclare(Function &F) {
+ DIBuilder DIB(*F.getParent());
+ SmallVector<DbgDeclareInst *, 4> Dbgs;
+ for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI)
+ for (BasicBlock::iterator BI = FI->begin(), BE = FI->end(); BI != BE; ++BI) {
+ if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(BI))
+ Dbgs.push_back(DDI);
+ }
+ if (Dbgs.empty())
+ return false;
+
+ for (SmallVector<DbgDeclareInst *, 4>::iterator I = Dbgs.begin(),
+ E = Dbgs.end(); I != E; ++I) {
+ DbgDeclareInst *DDI = *I;
+ if (AllocaInst *AI = dyn_cast_or_null<AllocaInst>(DDI->getAddress())) {
+ bool RemoveDDI = true;
+ for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
+ UI != E; ++UI)
+ if (StoreInst *SI = dyn_cast<StoreInst>(*UI))
+ ConvertDebugDeclareToDebugValue(DDI, SI, DIB);
+ else if (LoadInst *LI = dyn_cast<LoadInst>(*UI))
+ ConvertDebugDeclareToDebugValue(DDI, LI, DIB);
+ else
+ RemoveDDI = false;
+ if (RemoveDDI)
+ DDI->eraseFromParent();
}
}
return true;
}
+/// FindAllocaDbgDeclare - Finds the llvm.dbg.declare intrinsic describing the
+/// alloca 'V', if any.
+DbgDeclareInst *llvm::FindAllocaDbgDeclare(Value *V) {
+ if (MDNode *DebugNode = MDNode::getIfExists(V->getContext(), V))
+ for (Value::use_iterator UI = DebugNode->use_begin(),
+ E = DebugNode->use_end(); UI != E; ++UI)
+ if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(*UI))
+ return DDI;
+
+ return 0;
+}
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