#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
+#include "llvm/IntrinsicInst.h"
#include "llvm/Constant.h"
#include "llvm/Type.h"
+#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/Dominators.h"
+#include "llvm/Target/TargetData.h"
#include <algorithm>
using namespace llvm;
+/// DeleteDeadBlock - Delete the specified block, which must have no
+/// predecessors.
+void llvm::DeleteDeadBlock(BasicBlock *BB) {
+ assert((pred_begin(BB) == pred_end(BB) ||
+ // Can delete self loop.
+ BB->getSinglePredecessor() == BB) && "Block is not dead!");
+ TerminatorInst *BBTerm = BB->getTerminator();
+ Value *DbgRegionEndContext = NULL;
+ // Loop through all of our successors and make sure they know that one
+ // of their predecessors is going away.
+ for (unsigned i = 0, e = BBTerm->getNumSuccessors(); i != e; ++i)
+ BBTerm->getSuccessor(i)->removePredecessor(BB);
+
+ // Zap all the instructions in the block.
+ while (!BB->empty()) {
+ Instruction &I = BB->back();
+ // It is possible to have multiple llvm.dbg.region.end in a block.
+ if (DbgRegionEndInst *DREI = dyn_cast<DbgRegionEndInst>(&I))
+ DbgRegionEndContext = DREI->getContext();
+
+ // If this instruction is used, replace uses with an arbitrary value.
+ // Because control flow can't get here, we don't care what we replace the
+ // value with. Note that since this block is unreachable, and all values
+ // contained within it must dominate their uses, that all uses will
+ // eventually be removed (they are themselves dead).
+ if (!I.use_empty())
+ I.replaceAllUsesWith(UndefValue::get(I.getType()));
+ BB->getInstList().pop_back();
+ }
+
+ if (DbgRegionEndContext) {
+ // Delete corresponding llvm.dbg.func.start from entry block.
+ BasicBlock &Entry = BB->getParent()->getEntryBlock();
+ DbgFuncStartInst *DbgFuncStart = NULL;
+ for (BasicBlock::iterator BI = Entry.begin(), BE = Entry.end();
+ BI != BE; ++BI) {
+ if (DbgFuncStartInst *DFSI = dyn_cast<DbgFuncStartInst>(BI)) {
+ DbgFuncStart = DFSI;
+ break;
+ }
+ }
+ if (DbgFuncStart && DbgFuncStart->getSubprogram() == DbgRegionEndContext)
+ DbgFuncStart->eraseFromParent();
+ }
+
+ // Zap the block!
+ BB->eraseFromParent();
+}
+
+/// FoldSingleEntryPHINodes - We know that BB has one predecessor. If there are
+/// any single-entry PHI nodes in it, fold them away. This handles the case
+/// when all entries to the PHI nodes in a block are guaranteed equal, such as
+/// when the block has exactly one predecessor.
+void llvm::FoldSingleEntryPHINodes(BasicBlock *BB) {
+ if (!isa<PHINode>(BB->begin()))
+ return;
+
+ while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
+ if (PN->getIncomingValue(0) != PN)
+ PN->replaceAllUsesWith(PN->getIncomingValue(0));
+ else
+ PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
+ PN->eraseFromParent();
+ }
+}
+
+
+/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
+/// if possible. The return value indicates success or failure.
+bool llvm::MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P) {
+ pred_iterator PI(pred_begin(BB)), PE(pred_end(BB));
+ // Can't merge the entry block.
+ if (pred_begin(BB) == pred_end(BB)) return false;
+
+ BasicBlock *PredBB = *PI++;
+ for (; PI != PE; ++PI) // Search all predecessors, see if they are all same
+ if (*PI != PredBB) {
+ PredBB = 0; // There are multiple different predecessors...
+ break;
+ }
+
+ // Can't merge if there are multiple predecessors.
+ if (!PredBB) return false;
+ // Don't break self-loops.
+ if (PredBB == BB) return false;
+ // Don't break invokes.
+ if (isa<InvokeInst>(PredBB->getTerminator())) return false;
+
+ succ_iterator SI(succ_begin(PredBB)), SE(succ_end(PredBB));
+ BasicBlock* OnlySucc = BB;
+ for (; SI != SE; ++SI)
+ if (*SI != OnlySucc) {
+ OnlySucc = 0; // There are multiple distinct successors!
+ break;
+ }
+
+ // Can't merge if there are multiple successors.
+ if (!OnlySucc) return false;
+
+ // Can't merge if there is PHI loop.
+ for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI) {
+ if (PHINode *PN = dyn_cast<PHINode>(BI)) {
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (PN->getIncomingValue(i) == PN)
+ return false;
+ } else
+ break;
+ }
+
+ // Begin by getting rid of unneeded PHIs.
+ while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
+ PN->replaceAllUsesWith(PN->getIncomingValue(0));
+ BB->getInstList().pop_front(); // Delete the phi node...
+ }
+
+ // Delete the unconditional branch from the predecessor...
+ PredBB->getInstList().pop_back();
+
+ // Move all definitions in the successor to the predecessor...
+ PredBB->getInstList().splice(PredBB->end(), BB->getInstList());
+
+ // Make all PHI nodes that referred to BB now refer to Pred as their
+ // source...
+ BB->replaceAllUsesWith(PredBB);
+
+ // Inherit predecessors name if it exists.
+ if (!PredBB->hasName())
+ PredBB->takeName(BB);
+
+ // Finally, erase the old block and update dominator info.
+ if (P) {
+ if (DominatorTree* DT = P->getAnalysisIfAvailable<DominatorTree>()) {
+ DomTreeNode* DTN = DT->getNode(BB);
+ DomTreeNode* PredDTN = DT->getNode(PredBB);
+
+ if (DTN) {
+ SmallPtrSet<DomTreeNode*, 8> Children(DTN->begin(), DTN->end());
+ for (SmallPtrSet<DomTreeNode*, 8>::iterator DI = Children.begin(),
+ DE = Children.end(); DI != DE; ++DI)
+ DT->changeImmediateDominator(*DI, PredDTN);
+
+ DT->eraseNode(BB);
+ }
+ }
+ }
+
+ BB->eraseFromParent();
+
+
+ return true;
+}
+
/// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
/// with a value, then remove and delete the original instruction.
///
RetVal = Constant::getNullValue(BB->getParent()->getReturnType());
// Create the return...
- NewTI = new ReturnInst(RetVal);
+ NewTI = ReturnInst::Create(RetVal);
}
break;
BasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, Pass *P) {
TerminatorInst *LatchTerm = BB->getTerminator();
unsigned SuccNum = 0;
- for (unsigned i = 0, e = LatchTerm->getNumSuccessors(); ; ++i) {
+#ifndef NDEBUG
+ unsigned e = LatchTerm->getNumSuccessors();
+#endif
+ for (unsigned i = 0; ; ++i) {
assert(i != e && "Didn't find edge?");
if (LatchTerm->getSuccessor(i) == Succ) {
SuccNum = i;
// If the successor only has a single pred, split the top of the successor
// block.
assert(SP == BB && "CFG broken");
+ SP = NULL;
return SplitBlock(Succ, Succ->begin(), P);
} else {
// Otherwise, if BB has a single successor, split it at the bottom of the
/// the loop info is updated.
///
BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) {
-
- LoopInfo &LI = P->getAnalysis<LoopInfo>();
BasicBlock::iterator SplitIt = SplitPt;
while (isa<PHINode>(SplitIt))
++SplitIt;
BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split");
// The new block lives in whichever loop the old one did.
- if (Loop *L = LI.getLoopFor(Old))
- L->addBasicBlockToLoop(New, LI.getBase());
+ if (LoopInfo* LI = P->getAnalysisIfAvailable<LoopInfo>())
+ if (Loop *L = LI->getLoopFor(Old))
+ L->addBasicBlockToLoop(New, LI->getBase());
- if (DominatorTree *DT = P->getAnalysisToUpdate<DominatorTree>())
+ if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>())
{
// Old dominates New. New node domiantes all other nodes dominated by Old.
DomTreeNode *OldNode = DT->getNode(Old);
DT->changeImmediateDominator(*I, NewNode);
}
- if (DominanceFrontier *DF = P->getAnalysisToUpdate<DominanceFrontier>())
+ if (DominanceFrontier *DF = P->getAnalysisIfAvailable<DominanceFrontier>())
DF->splitBlock(Old);
return New;
}
+
+
+/// SplitBlockPredecessors - This method transforms BB by introducing a new
+/// basic block into the function, and moving some of the predecessors of BB to
+/// be predecessors of the new block. The new predecessors are indicated by the
+/// Preds array, which has NumPreds elements in it. The new block is given a
+/// suffix of 'Suffix'.
+///
+/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree and
+/// DominanceFrontier, but no other analyses.
+BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
+ BasicBlock *const *Preds,
+ unsigned NumPreds, const char *Suffix,
+ Pass *P) {
+ // Create new basic block, insert right before the original block.
+ BasicBlock *NewBB =
+ BasicBlock::Create(BB->getName()+Suffix, BB->getParent(), BB);
+
+ // The new block unconditionally branches to the old block.
+ BranchInst *BI = BranchInst::Create(BB, NewBB);
+
+ // Move the edges from Preds to point to NewBB instead of BB.
+ for (unsigned i = 0; i != NumPreds; ++i)
+ Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
+
+ // Update dominator tree and dominator frontier if available.
+ DominatorTree *DT = P ? P->getAnalysisIfAvailable<DominatorTree>() : 0;
+ if (DT)
+ DT->splitBlock(NewBB);
+ if (DominanceFrontier *DF = P ? P->getAnalysisIfAvailable<DominanceFrontier>():0)
+ DF->splitBlock(NewBB);
+ AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0;
+
+
+ // Insert a new PHI node into NewBB for every PHI node in BB and that new PHI
+ // node becomes an incoming value for BB's phi node. However, if the Preds
+ // list is empty, we need to insert dummy entries into the PHI nodes in BB to
+ // account for the newly created predecessor.
+ if (NumPreds == 0) {
+ // Insert dummy values as the incoming value.
+ for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++I)
+ cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB);
+ return NewBB;
+ }
+
+ // Otherwise, create a new PHI node in NewBB for each PHI node in BB.
+ for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ) {
+ PHINode *PN = cast<PHINode>(I++);
+
+ // Check to see if all of the values coming in are the same. If so, we
+ // don't need to create a new PHI node.
+ Value *InVal = PN->getIncomingValueForBlock(Preds[0]);
+ for (unsigned i = 1; i != NumPreds; ++i)
+ if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
+ InVal = 0;
+ break;
+ }
+
+ if (InVal) {
+ // If all incoming values for the new PHI would be the same, just don't
+ // make a new PHI. Instead, just remove the incoming values from the old
+ // PHI.
+ for (unsigned i = 0; i != NumPreds; ++i)
+ PN->removeIncomingValue(Preds[i], false);
+ } else {
+ // If the values coming into the block are not the same, we need a PHI.
+ // Create the new PHI node, insert it into NewBB at the end of the block
+ PHINode *NewPHI =
+ PHINode::Create(PN->getType(), PN->getName()+".ph", BI);
+ if (AA) AA->copyValue(PN, NewPHI);
+
+ // Move all of the PHI values for 'Preds' to the new PHI.
+ for (unsigned i = 0; i != NumPreds; ++i) {
+ Value *V = PN->removeIncomingValue(Preds[i], false);
+ NewPHI->addIncoming(V, Preds[i]);
+ }
+ InVal = NewPHI;
+ }
+
+ // Add an incoming value to the PHI node in the loop for the preheader
+ // edge.
+ PN->addIncoming(InVal, NewBB);
+
+ // Check to see if we can eliminate this phi node.
+ if (Value *V = PN->hasConstantValue(DT != 0)) {
+ Instruction *I = dyn_cast<Instruction>(V);
+ if (!I || DT == 0 || DT->dominates(I, PN)) {
+ PN->replaceAllUsesWith(V);
+ if (AA) AA->deleteValue(PN);
+ PN->eraseFromParent();
+ }
+ }
+ }
+
+ return NewBB;
+}
+
+/// AreEquivalentAddressValues - Test if A and B will obviously have the same
+/// value. This includes recognizing that %t0 and %t1 will have the same
+/// value in code like this:
+/// %t0 = getelementptr @a, 0, 3
+/// store i32 0, i32* %t0
+/// %t1 = getelementptr @a, 0, 3
+/// %t2 = load i32* %t1
+///
+static bool AreEquivalentAddressValues(const Value *A, const Value *B) {
+ // Test if the values are trivially equivalent.
+ if (A == B) return true;
+
+ // Test if the values come form identical arithmetic instructions.
+ if (isa<BinaryOperator>(A) || isa<CastInst>(A) ||
+ isa<PHINode>(A) || isa<GetElementPtrInst>(A))
+ if (const Instruction *BI = dyn_cast<Instruction>(B))
+ if (cast<Instruction>(A)->isIdenticalTo(BI))
+ return true;
+
+ // Otherwise they may not be equivalent.
+ return false;
+}
+
+/// FindAvailableLoadedValue - Scan the ScanBB block backwards (starting at the
+/// instruction before ScanFrom) checking to see if we have the value at the
+/// memory address *Ptr locally available within a small number of instructions.
+/// If the value is available, return it.
+///
+/// If not, return the iterator for the last validated instruction that the
+/// value would be live through. If we scanned the entire block and didn't find
+/// something that invalidates *Ptr or provides it, ScanFrom would be left at
+/// begin() and this returns null. ScanFrom could also be left
+///
+/// MaxInstsToScan specifies the maximum instructions to scan in the block. If
+/// it is set to 0, it will scan the whole block. You can also optionally
+/// specify an alias analysis implementation, which makes this more precise.
+Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
+ BasicBlock::iterator &ScanFrom,
+ unsigned MaxInstsToScan,
+ AliasAnalysis *AA) {
+ if (MaxInstsToScan == 0) MaxInstsToScan = ~0U;
+
+ // If we're using alias analysis to disambiguate get the size of *Ptr.
+ unsigned AccessSize = 0;
+ if (AA) {
+ const Type *AccessTy = cast<PointerType>(Ptr->getType())->getElementType();
+ AccessSize = AA->getTargetData().getTypeStoreSizeInBits(AccessTy);
+ }
+
+ while (ScanFrom != ScanBB->begin()) {
+ // Don't scan huge blocks.
+ if (MaxInstsToScan-- == 0) return 0;
+
+ Instruction *Inst = --ScanFrom;
+
+ // If this is a load of Ptr, the loaded value is available.
+ if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
+ if (AreEquivalentAddressValues(LI->getOperand(0), Ptr))
+ return LI;
+
+ if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+ // If this is a store through Ptr, the value is available!
+ if (AreEquivalentAddressValues(SI->getOperand(1), Ptr))
+ return SI->getOperand(0);
+
+ // If Ptr is an alloca and this is a store to a different alloca, ignore
+ // the store. This is a trivial form of alias analysis that is important
+ // for reg2mem'd code.
+ if ((isa<AllocaInst>(Ptr) || isa<GlobalVariable>(Ptr)) &&
+ (isa<AllocaInst>(SI->getOperand(1)) ||
+ isa<GlobalVariable>(SI->getOperand(1))))
+ continue;
+
+ // If we have alias analysis and it says the store won't modify the loaded
+ // value, ignore the store.
+ if (AA &&
+ (AA->getModRefInfo(SI, Ptr, AccessSize) & AliasAnalysis::Mod) == 0)
+ continue;
+
+ // Otherwise the store that may or may not alias the pointer, bail out.
+ ++ScanFrom;
+ return 0;
+ }
+
+ // If this is some other instruction that may clobber Ptr, bail out.
+ if (Inst->mayWriteToMemory()) {
+ // If alias analysis claims that it really won't modify the load,
+ // ignore it.
+ if (AA &&
+ (AA->getModRefInfo(Inst, Ptr, AccessSize) & AliasAnalysis::Mod) == 0)
+ continue;
+
+ // May modify the pointer, bail out.
+ ++ScanFrom;
+ return 0;
+ }
+ }
+
+ // Got to the start of the block, we didn't find it, but are done for this
+ // block.
+ return 0;
+}