#define DEBUG_TYPE "simplifycfg"
#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/Constants.h"
-#include "llvm/DerivedTypes.h"
-#include "llvm/GlobalVariable.h"
-#include "llvm/IRBuilder.h"
-#include "llvm/Instructions.h"
-#include "llvm/IntrinsicInst.h"
-#include "llvm/LLVMContext.h"
-#include "llvm/MDBuilder.h"
-#include "llvm/Metadata.h"
-#include "llvm/Module.h"
-#include "llvm/Operator.h"
-#include "llvm/Type.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/MDBuilder.h"
+#include "llvm/IR/Metadata.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Operator.h"
+#include "llvm/IR/Type.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ConstantRange.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/NoFolder.h"
+#include "llvm/Support/PatternMatch.h"
#include "llvm/Support/raw_ostream.h"
-#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include <algorithm>
-#include <set>
#include <map>
+#include <set>
using namespace llvm;
+using namespace PatternMatch;
static cl::opt<unsigned>
PHINodeFoldingThreshold("phi-node-folding-threshold", cl::Hidden, cl::init(1),
DupRet("simplifycfg-dup-ret", cl::Hidden, cl::init(false),
cl::desc("Duplicate return instructions into unconditional branches"));
-STATISTIC(NumSpeculations, "Number of speculative executed instructions");
+static cl::opt<bool>
+SinkCommon("simplifycfg-sink-common", cl::Hidden, cl::init(true),
+ cl::desc("Sink common instructions down to the end block"));
+
+static cl::opt<bool>
+HoistCondStores("simplifycfg-hoist-cond-stores", cl::Hidden, cl::init(true),
+ cl::desc("Hoist conditional stores if an unconditional store preceeds"));
+
+STATISTIC(NumBitMaps, "Number of switch instructions turned into bitmaps");
STATISTIC(NumLookupTables, "Number of switch instructions turned into lookup tables");
+STATISTIC(NumSinkCommons, "Number of common instructions sunk down to the end block");
+STATISTIC(NumSpeculations, "Number of speculative executed instructions");
namespace {
/// ValueEqualityComparisonCase - Represents a case of a switch.
// Comparing pointers is ok as we only rely on the order for uniquing.
return Value < RHS.Value;
}
+
+ bool operator==(BasicBlock *RHSDest) const { return Dest == RHSDest; }
};
class SimplifyCFGOpt {
- const TargetData *const TD;
-
+ const TargetTransformInfo &TTI;
+ const DataLayout *const TD;
Value *isValueEqualityComparison(TerminatorInst *TI);
BasicBlock *GetValueEqualityComparisonCases(TerminatorInst *TI,
std::vector<ValueEqualityComparisonCase> &Cases);
bool SimplifyCondBranch(BranchInst *BI, IRBuilder <>&Builder);
public:
- explicit SimplifyCFGOpt(const TargetData *td) : TD(td) {}
+ SimplifyCFGOpt(const TargetTransformInfo &TTI, const DataLayout *TD)
+ : TTI(TTI), TD(TD) {}
bool run(BasicBlock *BB);
};
}
PN->addIncoming(PN->getIncomingValueForBlock(ExistPred), NewPred);
}
-
-/// GetIfCondition - Given a basic block (BB) with two predecessors (and at
-/// least one PHI node in it), check to see if the merge at this block is due
-/// to an "if condition". If so, return the boolean condition that determines
-/// which entry into BB will be taken. Also, return by references the block
-/// that will be entered from if the condition is true, and the block that will
-/// be entered if the condition is false.
-///
-/// This does no checking to see if the true/false blocks have large or unsavory
-/// instructions in them.
-static Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue,
- BasicBlock *&IfFalse) {
- PHINode *SomePHI = cast<PHINode>(BB->begin());
- assert(SomePHI->getNumIncomingValues() == 2 &&
- "Function can only handle blocks with 2 predecessors!");
- BasicBlock *Pred1 = SomePHI->getIncomingBlock(0);
- BasicBlock *Pred2 = SomePHI->getIncomingBlock(1);
-
- // We can only handle branches. Other control flow will be lowered to
- // branches if possible anyway.
- BranchInst *Pred1Br = dyn_cast<BranchInst>(Pred1->getTerminator());
- BranchInst *Pred2Br = dyn_cast<BranchInst>(Pred2->getTerminator());
- if (Pred1Br == 0 || Pred2Br == 0)
- return 0;
-
- // Eliminate code duplication by ensuring that Pred1Br is conditional if
- // either are.
- if (Pred2Br->isConditional()) {
- // If both branches are conditional, we don't have an "if statement". In
- // reality, we could transform this case, but since the condition will be
- // required anyway, we stand no chance of eliminating it, so the xform is
- // probably not profitable.
- if (Pred1Br->isConditional())
- return 0;
-
- std::swap(Pred1, Pred2);
- std::swap(Pred1Br, Pred2Br);
- }
-
- if (Pred1Br->isConditional()) {
- // The only thing we have to watch out for here is to make sure that Pred2
- // doesn't have incoming edges from other blocks. If it does, the condition
- // doesn't dominate BB.
- if (Pred2->getSinglePredecessor() == 0)
- return 0;
-
- // If we found a conditional branch predecessor, make sure that it branches
- // to BB and Pred2Br. If it doesn't, this isn't an "if statement".
- if (Pred1Br->getSuccessor(0) == BB &&
- Pred1Br->getSuccessor(1) == Pred2) {
- IfTrue = Pred1;
- IfFalse = Pred2;
- } else if (Pred1Br->getSuccessor(0) == Pred2 &&
- Pred1Br->getSuccessor(1) == BB) {
- IfTrue = Pred2;
- IfFalse = Pred1;
- } else {
- // We know that one arm of the conditional goes to BB, so the other must
- // go somewhere unrelated, and this must not be an "if statement".
- return 0;
- }
-
- return Pred1Br->getCondition();
- }
-
- // Ok, if we got here, both predecessors end with an unconditional branch to
- // BB. Don't panic! If both blocks only have a single (identical)
- // predecessor, and THAT is a conditional branch, then we're all ok!
- BasicBlock *CommonPred = Pred1->getSinglePredecessor();
- if (CommonPred == 0 || CommonPred != Pred2->getSinglePredecessor())
- return 0;
-
- // Otherwise, if this is a conditional branch, then we can use it!
- BranchInst *BI = dyn_cast<BranchInst>(CommonPred->getTerminator());
- if (BI == 0) return 0;
-
- assert(BI->isConditional() && "Two successors but not conditional?");
- if (BI->getSuccessor(0) == Pred1) {
- IfTrue = Pred1;
- IfFalse = Pred2;
- } else {
- IfTrue = Pred2;
- IfFalse = Pred1;
- }
- return BI->getCondition();
-}
-
-/// ComputeSpeculuationCost - Compute an abstract "cost" of speculating the
+/// ComputeSpeculationCost - Compute an abstract "cost" of speculating the
/// given instruction, which is assumed to be safe to speculate. 1 means
/// cheap, 2 means less cheap, and UINT_MAX means prohibitively expensive.
static unsigned ComputeSpeculationCost(const User *I) {
/// GetConstantInt - Extract ConstantInt from value, looking through IntToPtr
/// and PointerNullValue. Return NULL if value is not a constant int.
-static ConstantInt *GetConstantInt(Value *V, const TargetData *TD) {
+static ConstantInt *GetConstantInt(Value *V, const DataLayout *TD) {
// Normal constant int.
ConstantInt *CI = dyn_cast<ConstantInt>(V);
if (CI || !TD || !isa<Constant>(V) || !V->getType()->isPointerTy())
// This is some kind of pointer constant. Turn it into a pointer-sized
// ConstantInt if possible.
- IntegerType *PtrTy = TD->getIntPtrType(V->getContext());
+ IntegerType *PtrTy = cast<IntegerType>(TD->getIntPtrType(V->getType()));
// Null pointer means 0, see SelectionDAGBuilder::getValue(const Value*).
if (isa<ConstantPointerNull>(V))
/// Values vector.
static Value *
GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra,
- const TargetData *TD, bool isEQ, unsigned &UsedICmps) {
+ const DataLayout *TD, bool isEQ, unsigned &UsedICmps) {
Instruction *I = dyn_cast<Instruction>(V);
if (I == 0) return 0;
// If this is an icmp against a constant, handle this as one of the cases.
if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) {
if (ConstantInt *C = GetConstantInt(I->getOperand(1), TD)) {
+ Value *RHSVal;
+ ConstantInt *RHSC;
+
if (ICI->getPredicate() == (isEQ ? ICmpInst::ICMP_EQ:ICmpInst::ICMP_NE)) {
+ // (x & ~2^x) == y --> x == y || x == y|2^x
+ // This undoes a transformation done by instcombine to fuse 2 compares.
+ if (match(ICI->getOperand(0),
+ m_And(m_Value(RHSVal), m_ConstantInt(RHSC)))) {
+ APInt Not = ~RHSC->getValue();
+ if (Not.isPowerOf2()) {
+ Vals.push_back(C);
+ Vals.push_back(
+ ConstantInt::get(C->getContext(), C->getValue() | Not));
+ UsedICmps++;
+ return RHSVal;
+ }
+ }
+
UsedICmps++;
Vals.push_back(C);
return I->getOperand(0);
ConstantRange Span =
ConstantRange::makeICmpRegion(ICI->getPredicate(), C->getValue());
+ // Shift the range if the compare is fed by an add. This is the range
+ // compare idiom as emitted by instcombine.
+ bool hasAdd =
+ match(I->getOperand(0), m_Add(m_Value(RHSVal), m_ConstantInt(RHSC)));
+ if (hasAdd)
+ Span = Span.subtract(RHSC->getValue());
+
// If this is an and/!= check then we want to optimize "x ugt 2" into
// x != 0 && x != 1.
if (!isEQ)
for (APInt Tmp = Span.getLower(); Tmp != Span.getUpper(); ++Tmp)
Vals.push_back(ConstantInt::get(V->getContext(), Tmp));
UsedICmps++;
- return I->getOperand(0);
+ return hasAdd ? RHSVal : I->getOperand(0);
}
return 0;
}
} else if (BranchInst *BI = dyn_cast<BranchInst>(TI))
if (BI->isConditional() && BI->getCondition()->hasOneUse())
if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition()))
- if ((ICI->getPredicate() == ICmpInst::ICMP_EQ ||
- ICI->getPredicate() == ICmpInst::ICMP_NE) &&
- GetConstantInt(ICI->getOperand(1), TD))
+ if (ICI->isEquality() && GetConstantInt(ICI->getOperand(1), TD))
CV = ICI->getOperand(0);
// Unwrap any lossless ptrtoint cast.
- if (TD && CV && CV->getType() == TD->getIntPtrType(CV->getContext()))
- if (PtrToIntInst *PTII = dyn_cast<PtrToIntInst>(CV))
- CV = PTII->getOperand(0);
+ if (TD && CV) {
+ if (PtrToIntInst *PTII = dyn_cast<PtrToIntInst>(CV)) {
+ Value *Ptr = PTII->getPointerOperand();
+ if (PTII->getType() == TD->getIntPtrType(Ptr->getType()))
+ CV = Ptr;
+ }
+ }
return CV;
}
/// in the list that match the specified block.
static void EliminateBlockCases(BasicBlock *BB,
std::vector<ValueEqualityComparisonCase> &Cases) {
- for (unsigned i = 0, e = Cases.size(); i != e; ++i)
- if (Cases[i].Dest == BB) {
- Cases.erase(Cases.begin()+i);
- --i; --e;
- }
+ Cases.erase(std::remove(Cases.begin(), Cases.end(), BB), Cases.end());
}
/// ValuesOverlap - Return true if there are any keys in C1 that exist in C2 as
SI->removeCase(i);
}
}
- if (HasWeight)
+ if (HasWeight && Weights.size() >= 2)
SI->setMetadata(LLVMContext::MD_prof,
MDBuilder(SI->getParent()->getContext()).
createBranchWeights(Weights));
};
}
-static int ConstantIntSortPredicate(const void *P1, const void *P2) {
- const ConstantInt *LHS = *(const ConstantInt*const*)P1;
- const ConstantInt *RHS = *(const ConstantInt*const*)P2;
+static int ConstantIntSortPredicate(ConstantInt *const *P1,
+ ConstantInt *const *P2) {
+ const ConstantInt *LHS = *P1;
+ const ConstantInt *RHS = *P2;
if (LHS->getValue().ult(RHS->getValue()))
return 1;
if (LHS->getValue() == RHS->getValue())
if (PredHasWeights) {
GetBranchWeights(PTI, Weights);
- // branch-weight metadata is inconsistant here.
+ // branch-weight metadata is inconsistent here.
if (Weights.size() != 1 + PredCases.size())
PredHasWeights = SuccHasWeights = false;
} else if (SuccHasWeights)
SmallVector<uint64_t, 8> SuccWeights;
if (SuccHasWeights) {
GetBranchWeights(TI, SuccWeights);
- // branch-weight metadata is inconsistant here.
+ // branch-weight metadata is inconsistent here.
if (SuccWeights.size() != 1 + BBCases.size())
PredHasWeights = SuccHasWeights = false;
} else if (PredHasWeights)
for (std::set<ConstantInt*, ConstantIntOrdering>::iterator I =
PTIHandled.begin(),
E = PTIHandled.end(); I != E; ++I) {
- if (PredHasWeights || SuccHasWeights)
- Weights.push_back(WeightsForHandled[*I]);
+ if (PredHasWeights || SuccHasWeights)
+ Weights.push_back(WeightsForHandled[*I]);
PredCases.push_back(ValueEqualityComparisonCase(*I, BBDefault));
NewSuccessors.push_back(BBDefault);
}
Builder.SetInsertPoint(PTI);
// Convert pointer to int before we switch.
if (CV->getType()->isPointerTy()) {
- assert(TD && "Cannot switch on pointer without TargetData");
- CV = Builder.CreatePtrToInt(CV, TD->getIntPtrType(CV->getContext()),
+ assert(TD && "Cannot switch on pointer without DataLayout");
+ CV = Builder.CreatePtrToInt(CV, TD->getIntPtrType(CV->getType()),
"magicptr");
}
(isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2)))
return false;
- // If we get here, we can hoist at least one instruction.
BasicBlock *BIParent = BI->getParent();
+ bool Changed = false;
do {
// If we are hoisting the terminator instruction, don't move one (making a
// broken BB), instead clone it, and remove BI.
I2->replaceAllUsesWith(I1);
I1->intersectOptionalDataWith(I2);
I2->eraseFromParent();
+ Changed = true;
I1 = BB1_Itr++;
I2 = BB2_Itr++;
HoistTerminator:
// It may not be possible to hoist an invoke.
if (isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2))
- return true;
+ return Changed;
+
+ for (succ_iterator SI = succ_begin(BB1), E = succ_end(BB1); SI != E; ++SI) {
+ PHINode *PN;
+ for (BasicBlock::iterator BBI = SI->begin();
+ (PN = dyn_cast<PHINode>(BBI)); ++BBI) {
+ Value *BB1V = PN->getIncomingValueForBlock(BB1);
+ Value *BB2V = PN->getIncomingValueForBlock(BB2);
+ if (BB1V == BB2V)
+ continue;
+
+ if (isa<ConstantExpr>(BB1V) && !isSafeToSpeculativelyExecute(BB1V))
+ return Changed;
+ if (isa<ConstantExpr>(BB2V) && !isSafeToSpeculativelyExecute(BB2V))
+ return Changed;
+ }
+ }
// Okay, it is safe to hoist the terminator.
Instruction *NT = I1->clone();
return true;
}
-/// SpeculativelyExecuteBB - Given a conditional branch that goes to BB1
-/// and an BB2 and the only successor of BB1 is BB2, hoist simple code
-/// (for now, restricted to a single instruction that's side effect free) from
-/// the BB1 into the branch block to speculatively execute it.
+/// SinkThenElseCodeToEnd - Given an unconditional branch that goes to BBEnd,
+/// check whether BBEnd has only two predecessors and the other predecessor
+/// ends with an unconditional branch. If it is true, sink any common code
+/// in the two predecessors to BBEnd.
+static bool SinkThenElseCodeToEnd(BranchInst *BI1) {
+ assert(BI1->isUnconditional());
+ BasicBlock *BB1 = BI1->getParent();
+ BasicBlock *BBEnd = BI1->getSuccessor(0);
+
+ // Check that BBEnd has two predecessors and the other predecessor ends with
+ // an unconditional branch.
+ pred_iterator PI = pred_begin(BBEnd), PE = pred_end(BBEnd);
+ BasicBlock *Pred0 = *PI++;
+ if (PI == PE) // Only one predecessor.
+ return false;
+ BasicBlock *Pred1 = *PI++;
+ if (PI != PE) // More than two predecessors.
+ return false;
+ BasicBlock *BB2 = (Pred0 == BB1) ? Pred1 : Pred0;
+ BranchInst *BI2 = dyn_cast<BranchInst>(BB2->getTerminator());
+ if (!BI2 || !BI2->isUnconditional())
+ return false;
+
+ // Gather the PHI nodes in BBEnd.
+ std::map<Value*, std::pair<Value*, PHINode*> > MapValueFromBB1ToBB2;
+ Instruction *FirstNonPhiInBBEnd = 0;
+ for (BasicBlock::iterator I = BBEnd->begin(), E = BBEnd->end();
+ I != E; ++I) {
+ if (PHINode *PN = dyn_cast<PHINode>(I)) {
+ Value *BB1V = PN->getIncomingValueForBlock(BB1);
+ Value *BB2V = PN->getIncomingValueForBlock(BB2);
+ MapValueFromBB1ToBB2[BB1V] = std::make_pair(BB2V, PN);
+ } else {
+ FirstNonPhiInBBEnd = &*I;
+ break;
+ }
+ }
+ if (!FirstNonPhiInBBEnd)
+ return false;
+
+
+ // This does very trivial matching, with limited scanning, to find identical
+ // instructions in the two blocks. We scan backward for obviously identical
+ // instructions in an identical order.
+ BasicBlock::InstListType::reverse_iterator RI1 = BB1->getInstList().rbegin(),
+ RE1 = BB1->getInstList().rend(), RI2 = BB2->getInstList().rbegin(),
+ RE2 = BB2->getInstList().rend();
+ // Skip debug info.
+ while (RI1 != RE1 && isa<DbgInfoIntrinsic>(&*RI1)) ++RI1;
+ if (RI1 == RE1)
+ return false;
+ while (RI2 != RE2 && isa<DbgInfoIntrinsic>(&*RI2)) ++RI2;
+ if (RI2 == RE2)
+ return false;
+ // Skip the unconditional branches.
+ ++RI1;
+ ++RI2;
+
+ bool Changed = false;
+ while (RI1 != RE1 && RI2 != RE2) {
+ // Skip debug info.
+ while (RI1 != RE1 && isa<DbgInfoIntrinsic>(&*RI1)) ++RI1;
+ if (RI1 == RE1)
+ return Changed;
+ while (RI2 != RE2 && isa<DbgInfoIntrinsic>(&*RI2)) ++RI2;
+ if (RI2 == RE2)
+ return Changed;
+
+ Instruction *I1 = &*RI1, *I2 = &*RI2;
+ // I1 and I2 should have a single use in the same PHI node, and they
+ // perform the same operation.
+ // Cannot move control-flow-involving, volatile loads, vaarg, etc.
+ if (isa<PHINode>(I1) || isa<PHINode>(I2) ||
+ isa<TerminatorInst>(I1) || isa<TerminatorInst>(I2) ||
+ isa<LandingPadInst>(I1) || isa<LandingPadInst>(I2) ||
+ isa<AllocaInst>(I1) || isa<AllocaInst>(I2) ||
+ I1->mayHaveSideEffects() || I2->mayHaveSideEffects() ||
+ I1->mayReadOrWriteMemory() || I2->mayReadOrWriteMemory() ||
+ !I1->hasOneUse() || !I2->hasOneUse() ||
+ MapValueFromBB1ToBB2.find(I1) == MapValueFromBB1ToBB2.end() ||
+ MapValueFromBB1ToBB2[I1].first != I2)
+ return Changed;
+
+ // Check whether we should swap the operands of ICmpInst.
+ ICmpInst *ICmp1 = dyn_cast<ICmpInst>(I1), *ICmp2 = dyn_cast<ICmpInst>(I2);
+ bool SwapOpnds = false;
+ if (ICmp1 && ICmp2 &&
+ ICmp1->getOperand(0) != ICmp2->getOperand(0) &&
+ ICmp1->getOperand(1) != ICmp2->getOperand(1) &&
+ (ICmp1->getOperand(0) == ICmp2->getOperand(1) ||
+ ICmp1->getOperand(1) == ICmp2->getOperand(0))) {
+ ICmp2->swapOperands();
+ SwapOpnds = true;
+ }
+ if (!I1->isSameOperationAs(I2)) {
+ if (SwapOpnds)
+ ICmp2->swapOperands();
+ return Changed;
+ }
+
+ // The operands should be either the same or they need to be generated
+ // with a PHI node after sinking. We only handle the case where there is
+ // a single pair of different operands.
+ Value *DifferentOp1 = 0, *DifferentOp2 = 0;
+ unsigned Op1Idx = 0;
+ for (unsigned I = 0, E = I1->getNumOperands(); I != E; ++I) {
+ if (I1->getOperand(I) == I2->getOperand(I))
+ continue;
+ // Early exit if we have more-than one pair of different operands or
+ // the different operand is already in MapValueFromBB1ToBB2.
+ // Early exit if we need a PHI node to replace a constant.
+ if (DifferentOp1 ||
+ MapValueFromBB1ToBB2.find(I1->getOperand(I)) !=
+ MapValueFromBB1ToBB2.end() ||
+ isa<Constant>(I1->getOperand(I)) ||
+ isa<Constant>(I2->getOperand(I))) {
+ // If we can't sink the instructions, undo the swapping.
+ if (SwapOpnds)
+ ICmp2->swapOperands();
+ return Changed;
+ }
+ DifferentOp1 = I1->getOperand(I);
+ Op1Idx = I;
+ DifferentOp2 = I2->getOperand(I);
+ }
+
+ // We insert the pair of different operands to MapValueFromBB1ToBB2 and
+ // remove (I1, I2) from MapValueFromBB1ToBB2.
+ if (DifferentOp1) {
+ PHINode *NewPN = PHINode::Create(DifferentOp1->getType(), 2,
+ DifferentOp1->getName() + ".sink",
+ BBEnd->begin());
+ MapValueFromBB1ToBB2[DifferentOp1] = std::make_pair(DifferentOp2, NewPN);
+ // I1 should use NewPN instead of DifferentOp1.
+ I1->setOperand(Op1Idx, NewPN);
+ NewPN->addIncoming(DifferentOp1, BB1);
+ NewPN->addIncoming(DifferentOp2, BB2);
+ DEBUG(dbgs() << "Create PHI node " << *NewPN << "\n";);
+ }
+ PHINode *OldPN = MapValueFromBB1ToBB2[I1].second;
+ MapValueFromBB1ToBB2.erase(I1);
+
+ DEBUG(dbgs() << "SINK common instructions " << *I1 << "\n";);
+ DEBUG(dbgs() << " " << *I2 << "\n";);
+ // We need to update RE1 and RE2 if we are going to sink the first
+ // instruction in the basic block down.
+ bool UpdateRE1 = (I1 == BB1->begin()), UpdateRE2 = (I2 == BB2->begin());
+ // Sink the instruction.
+ BBEnd->getInstList().splice(FirstNonPhiInBBEnd, BB1->getInstList(), I1);
+ if (!OldPN->use_empty())
+ OldPN->replaceAllUsesWith(I1);
+ OldPN->eraseFromParent();
+
+ if (!I2->use_empty())
+ I2->replaceAllUsesWith(I1);
+ I1->intersectOptionalDataWith(I2);
+ I2->eraseFromParent();
+
+ if (UpdateRE1)
+ RE1 = BB1->getInstList().rend();
+ if (UpdateRE2)
+ RE2 = BB2->getInstList().rend();
+ FirstNonPhiInBBEnd = I1;
+ NumSinkCommons++;
+ Changed = true;
+ }
+ return Changed;
+}
+
+/// \brief Determine if we can hoist sink a sole store instruction out of a
+/// conditional block.
+///
+/// We are looking for code like the following:
+/// BrBB:
+/// store i32 %add, i32* %arrayidx2
+/// ... // No other stores or function calls (we could be calling a memory
+/// ... // function).
+/// %cmp = icmp ult %x, %y
+/// br i1 %cmp, label %EndBB, label %ThenBB
+/// ThenBB:
+/// store i32 %add5, i32* %arrayidx2
+/// br label EndBB
+/// EndBB:
+/// ...
+/// We are going to transform this into:
+/// BrBB:
+/// store i32 %add, i32* %arrayidx2
+/// ... //
+/// %cmp = icmp ult %x, %y
+/// %add.add5 = select i1 %cmp, i32 %add, %add5
+/// store i32 %add.add5, i32* %arrayidx2
+/// ...
+///
+/// \return The pointer to the value of the previous store if the store can be
+/// hoisted into the predecessor block. 0 otherwise.
+static Value *isSafeToSpeculateStore(Instruction *I, BasicBlock *BrBB,
+ BasicBlock *StoreBB, BasicBlock *EndBB) {
+ StoreInst *StoreToHoist = dyn_cast<StoreInst>(I);
+ if (!StoreToHoist)
+ return 0;
+
+ // Volatile or atomic.
+ if (!StoreToHoist->isSimple())
+ return 0;
+
+ Value *StorePtr = StoreToHoist->getPointerOperand();
+
+ // Look for a store to the same pointer in BrBB.
+ unsigned MaxNumInstToLookAt = 10;
+ for (BasicBlock::reverse_iterator RI = BrBB->rbegin(),
+ RE = BrBB->rend(); RI != RE && (--MaxNumInstToLookAt); ++RI) {
+ Instruction *CurI = &*RI;
+
+ // Could be calling an instruction that effects memory like free().
+ if (CurI->mayHaveSideEffects() && !isa<StoreInst>(CurI))
+ return 0;
+
+ StoreInst *SI = dyn_cast<StoreInst>(CurI);
+ // Found the previous store make sure it stores to the same location.
+ if (SI && SI->getPointerOperand() == StorePtr)
+ // Found the previous store, return its value operand.
+ return SI->getValueOperand();
+ else if (SI)
+ return 0; // Unknown store.
+ }
+
+ return 0;
+}
+
+/// \brief Speculate a conditional basic block flattening the CFG.
+///
+/// Note that this is a very risky transform currently. Speculating
+/// instructions like this is most often not desirable. Instead, there is an MI
+/// pass which can do it with full awareness of the resource constraints.
+/// However, some cases are "obvious" and we should do directly. An example of
+/// this is speculating a single, reasonably cheap instruction.
///
-/// Turn
-/// BB:
-/// %t1 = icmp
-/// br i1 %t1, label %BB1, label %BB2
-/// BB1:
-/// %t3 = add %t2, c
+/// There is only one distinct advantage to flattening the CFG at the IR level:
+/// it makes very common but simplistic optimizations such as are common in
+/// instcombine and the DAG combiner more powerful by removing CFG edges and
+/// modeling their effects with easier to reason about SSA value graphs.
+///
+///
+/// An illustration of this transform is turning this IR:
+/// \code
+/// BB:
+/// %cmp = icmp ult %x, %y
+/// br i1 %cmp, label %EndBB, label %ThenBB
+/// ThenBB:
+/// %sub = sub %x, %y
/// br label BB2
-/// BB2:
-/// =>
-/// BB:
-/// %t1 = icmp
-/// %t4 = add %t2, c
-/// %t3 = select i1 %t1, %t2, %t3
-static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) {
- // Only speculatively execution a single instruction (not counting the
- // terminator) for now.
- Instruction *HInst = NULL;
- Instruction *Term = BB1->getTerminator();
- for (BasicBlock::iterator BBI = BB1->begin(), BBE = BB1->end();
+/// EndBB:
+/// %phi = phi [ %sub, %ThenBB ], [ 0, %EndBB ]
+/// ...
+/// \endcode
+///
+/// Into this IR:
+/// \code
+/// BB:
+/// %cmp = icmp ult %x, %y
+/// %sub = sub %x, %y
+/// %cond = select i1 %cmp, 0, %sub
+/// ...
+/// \endcode
+///
+/// \returns true if the conditional block is removed.
+static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB) {
+ // Be conservative for now. FP select instruction can often be expensive.
+ Value *BrCond = BI->getCondition();
+ if (isa<FCmpInst>(BrCond))
+ return false;
+
+ BasicBlock *BB = BI->getParent();
+ BasicBlock *EndBB = ThenBB->getTerminator()->getSuccessor(0);
+
+ // If ThenBB is actually on the false edge of the conditional branch, remember
+ // to swap the select operands later.
+ bool Invert = false;
+ if (ThenBB != BI->getSuccessor(0)) {
+ assert(ThenBB == BI->getSuccessor(1) && "No edge from 'if' block?");
+ Invert = true;
+ }
+ assert(EndBB == BI->getSuccessor(!Invert) && "No edge from to end block");
+
+ // Keep a count of how many times instructions are used within CondBB when
+ // they are candidates for sinking into CondBB. Specifically:
+ // - They are defined in BB, and
+ // - They have no side effects, and
+ // - All of their uses are in CondBB.
+ SmallDenseMap<Instruction *, unsigned, 4> SinkCandidateUseCounts;
+
+ unsigned SpeculationCost = 0;
+ Value *SpeculatedStoreValue = 0;
+ StoreInst *SpeculatedStore = 0;
+ for (BasicBlock::iterator BBI = ThenBB->begin(),
+ BBE = llvm::prior(ThenBB->end());
BBI != BBE; ++BBI) {
Instruction *I = BBI;
// Skip debug info.
- if (isa<DbgInfoIntrinsic>(I)) continue;
- if (I == Term) break;
+ if (isa<DbgInfoIntrinsic>(I))
+ continue;
- if (HInst)
+ // Only speculatively execution a single instruction (not counting the
+ // terminator) for now.
+ ++SpeculationCost;
+ if (SpeculationCost > 1)
return false;
- HInst = I;
- }
-
- BasicBlock *BIParent = BI->getParent();
- // Check the instruction to be hoisted, if there is one.
- if (HInst) {
// Don't hoist the instruction if it's unsafe or expensive.
- if (!isSafeToSpeculativelyExecute(HInst))
+ if (!isSafeToSpeculativelyExecute(I) &&
+ !(HoistCondStores &&
+ (SpeculatedStoreValue = isSafeToSpeculateStore(I, BB, ThenBB,
+ EndBB))))
return false;
- if (ComputeSpeculationCost(HInst) > PHINodeFoldingThreshold)
+ if (!SpeculatedStoreValue &&
+ ComputeSpeculationCost(I) > PHINodeFoldingThreshold)
return false;
+ // Store the store speculation candidate.
+ if (SpeculatedStoreValue)
+ SpeculatedStore = cast<StoreInst>(I);
+
// Do not hoist the instruction if any of its operands are defined but not
- // used in this BB. The transformation will prevent the operand from
+ // used in BB. The transformation will prevent the operand from
// being sunk into the use block.
- for (User::op_iterator i = HInst->op_begin(), e = HInst->op_end();
+ for (User::op_iterator i = I->op_begin(), e = I->op_end();
i != e; ++i) {
Instruction *OpI = dyn_cast<Instruction>(*i);
- if (OpI && OpI->getParent() == BIParent &&
- !OpI->mayHaveSideEffects() &&
- !OpI->isUsedInBasicBlock(BIParent))
- return false;
+ if (!OpI || OpI->getParent() != BB ||
+ OpI->mayHaveSideEffects())
+ continue; // Not a candidate for sinking.
+
+ ++SinkCandidateUseCounts[OpI];
}
}
- // Be conservative for now. FP select instruction can often be expensive.
- Value *BrCond = BI->getCondition();
- if (isa<FCmpInst>(BrCond))
- return false;
-
- // If BB1 is actually on the false edge of the conditional branch, remember
- // to swap the select operands later.
- bool Invert = false;
- if (BB1 != BI->getSuccessor(0)) {
- assert(BB1 == BI->getSuccessor(1) && "No edge from 'if' block?");
- Invert = true;
- }
+ // Consider any sink candidates which are only used in CondBB as costs for
+ // speculation. Note, while we iterate over a DenseMap here, we are summing
+ // and so iteration order isn't significant.
+ for (SmallDenseMap<Instruction *, unsigned, 4>::iterator I =
+ SinkCandidateUseCounts.begin(), E = SinkCandidateUseCounts.end();
+ I != E; ++I)
+ if (I->first->getNumUses() == I->second) {
+ ++SpeculationCost;
+ if (SpeculationCost > 1)
+ return false;
+ }
- // Collect interesting PHIs, and scan for hazards.
- SmallSetVector<std::pair<Value *, Value *>, 4> PHIs;
- BasicBlock *BB2 = BB1->getTerminator()->getSuccessor(0);
- for (BasicBlock::iterator I = BB2->begin();
+ // Check that the PHI nodes can be converted to selects.
+ bool HaveRewritablePHIs = false;
+ for (BasicBlock::iterator I = EndBB->begin();
PHINode *PN = dyn_cast<PHINode>(I); ++I) {
- Value *BB1V = PN->getIncomingValueForBlock(BB1);
- Value *BIParentV = PN->getIncomingValueForBlock(BIParent);
+ Value *OrigV = PN->getIncomingValueForBlock(BB);
+ Value *ThenV = PN->getIncomingValueForBlock(ThenBB);
+ // FIXME: Try to remove some of the duplication with HoistThenElseCodeToIf.
// Skip PHIs which are trivial.
- if (BB1V == BIParentV)
+ if (ThenV == OrigV)
continue;
- // Check for saftey.
- if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BB1V)) {
- // An unfolded ConstantExpr could end up getting expanded into
- // Instructions. Don't speculate this and another instruction at
- // the same time.
- if (HInst)
- return false;
- if (!isSafeToSpeculativelyExecute(CE))
- return false;
- if (ComputeSpeculationCost(CE) > PHINodeFoldingThreshold)
- return false;
- }
+ HaveRewritablePHIs = true;
+ ConstantExpr *OrigCE = dyn_cast<ConstantExpr>(OrigV);
+ ConstantExpr *ThenCE = dyn_cast<ConstantExpr>(ThenV);
+ if (!OrigCE && !ThenCE)
+ continue; // Known safe and cheap.
- // Ok, we may insert a select for this PHI.
- PHIs.insert(std::make_pair(BB1V, BIParentV));
+ if ((ThenCE && !isSafeToSpeculativelyExecute(ThenCE)) ||
+ (OrigCE && !isSafeToSpeculativelyExecute(OrigCE)))
+ return false;
+ unsigned OrigCost = OrigCE ? ComputeSpeculationCost(OrigCE) : 0;
+ unsigned ThenCost = ThenCE ? ComputeSpeculationCost(ThenCE) : 0;
+ if (OrigCost + ThenCost > 2 * PHINodeFoldingThreshold)
+ return false;
+
+ // Account for the cost of an unfolded ConstantExpr which could end up
+ // getting expanded into Instructions.
+ // FIXME: This doesn't account for how many operations are combined in the
+ // constant expression.
+ ++SpeculationCost;
+ if (SpeculationCost > 1)
+ return false;
}
// If there are no PHIs to process, bail early. This helps ensure idempotence
// as well.
- if (PHIs.empty())
+ if (!HaveRewritablePHIs && !(HoistCondStores && SpeculatedStoreValue))
return false;
// If we get here, we can hoist the instruction and if-convert.
- DEBUG(dbgs() << "SPECULATIVELY EXECUTING BB" << *BB1 << "\n";);
+ DEBUG(dbgs() << "SPECULATIVELY EXECUTING BB" << *ThenBB << "\n";);
+
+ // Insert a select of the value of the speculated store.
+ if (SpeculatedStoreValue) {
+ IRBuilder<true, NoFolder> Builder(BI);
+ Value *TrueV = SpeculatedStore->getValueOperand();
+ Value *FalseV = SpeculatedStoreValue;
+ if (Invert)
+ std::swap(TrueV, FalseV);
+ Value *S = Builder.CreateSelect(BrCond, TrueV, FalseV, TrueV->getName() +
+ "." + FalseV->getName());
+ SpeculatedStore->setOperand(0, S);
+ }
- // Hoist the instruction.
- if (HInst)
- BIParent->getInstList().splice(BI, BB1->getInstList(), HInst);
+ // Hoist the instructions.
+ BB->getInstList().splice(BI, ThenBB->getInstList(), ThenBB->begin(),
+ llvm::prior(ThenBB->end()));
// Insert selects and rewrite the PHI operands.
IRBuilder<true, NoFolder> Builder(BI);
- for (unsigned i = 0, e = PHIs.size(); i != e; ++i) {
- Value *TrueV = PHIs[i].first;
- Value *FalseV = PHIs[i].second;
+ for (BasicBlock::iterator I = EndBB->begin();
+ PHINode *PN = dyn_cast<PHINode>(I); ++I) {
+ unsigned OrigI = PN->getBasicBlockIndex(BB);
+ unsigned ThenI = PN->getBasicBlockIndex(ThenBB);
+ Value *OrigV = PN->getIncomingValue(OrigI);
+ Value *ThenV = PN->getIncomingValue(ThenI);
+
+ // Skip PHIs which are trivial.
+ if (OrigV == ThenV)
+ continue;
// Create a select whose true value is the speculatively executed value and
- // false value is the previously determined FalseV.
- SelectInst *SI;
+ // false value is the preexisting value. Swap them if the branch
+ // destinations were inverted.
+ Value *TrueV = ThenV, *FalseV = OrigV;
if (Invert)
- SI = cast<SelectInst>
- (Builder.CreateSelect(BrCond, FalseV, TrueV,
- FalseV->getName() + "." + TrueV->getName()));
- else
- SI = cast<SelectInst>
- (Builder.CreateSelect(BrCond, TrueV, FalseV,
- TrueV->getName() + "." + FalseV->getName()));
-
- // Make the PHI node use the select for all incoming values for "then" and
- // "if" blocks.
- for (BasicBlock::iterator I = BB2->begin();
- PHINode *PN = dyn_cast<PHINode>(I); ++I) {
- unsigned BB1I = PN->getBasicBlockIndex(BB1);
- unsigned BIParentI = PN->getBasicBlockIndex(BIParent);
- Value *BB1V = PN->getIncomingValue(BB1I);
- Value *BIParentV = PN->getIncomingValue(BIParentI);
- if (TrueV == BB1V && FalseV == BIParentV) {
- PN->setIncomingValue(BB1I, SI);
- PN->setIncomingValue(BIParentI, SI);
- }
- }
+ std::swap(TrueV, FalseV);
+ Value *V = Builder.CreateSelect(BrCond, TrueV, FalseV,
+ TrueV->getName() + "." + FalseV->getName());
+ PN->setIncomingValue(OrigI, V);
+ PN->setIncomingValue(ThenI, V);
}
++NumSpeculations;
return true;
}
+/// \returns True if this block contains a CallInst with the NoDuplicate
+/// attribute.
+static bool HasNoDuplicateCall(const BasicBlock *BB) {
+ for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
+ const CallInst *CI = dyn_cast<CallInst>(I);
+ if (!CI)
+ continue;
+ if (CI->cannotDuplicate())
+ return true;
+ }
+ return false;
+}
+
/// BlockIsSimpleEnoughToThreadThrough - Return true if we can thread a branch
/// across this block.
static bool BlockIsSimpleEnoughToThreadThrough(BasicBlock *BB) {
/// that is defined in the same block as the branch and if any PHI entries are
/// constants, thread edges corresponding to that entry to be branches to their
/// ultimate destination.
-static bool FoldCondBranchOnPHI(BranchInst *BI, const TargetData *TD) {
+static bool FoldCondBranchOnPHI(BranchInst *BI, const DataLayout *TD) {
BasicBlock *BB = BI->getParent();
PHINode *PN = dyn_cast<PHINode>(BI->getCondition());
// NOTE: we currently cannot transform this case if the PHI node is used
// Now we know that this block has multiple preds and two succs.
if (!BlockIsSimpleEnoughToThreadThrough(BB)) return false;
+ if (HasNoDuplicateCall(BB)) return false;
+
// Okay, this is a simple enough basic block. See if any phi values are
// constants.
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
/// FoldTwoEntryPHINode - Given a BB that starts with the specified two-entry
/// PHI node, see if we can eliminate it.
-static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) {
+static bool FoldTwoEntryPHINode(PHINode *PN, const DataLayout *TD) {
// Ok, this is a two entry PHI node. Check to see if this is a simple "if
// statement", which has a very simple dominance structure. Basically, we
// are trying to find the condition that is being branched on, which
///
/// We prefer to split the edge to 'end' so that there is a true/false entry to
/// the PHI, merging the third icmp into the switch.
-static bool TryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI,
- const TargetData *TD,
- IRBuilder<> &Builder) {
+static bool TryToSimplifyUncondBranchWithICmpInIt(
+ ICmpInst *ICI, IRBuilder<> &Builder, const TargetTransformInfo &TTI,
+ const DataLayout *TD) {
BasicBlock *BB = ICI->getParent();
// If the block has any PHIs in it or the icmp has multiple uses, it is too
ICI->eraseFromParent();
}
// BB is now empty, so it is likely to simplify away.
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
}
// Ok, the block is reachable from the default dest. If the constant we're
ICI->replaceAllUsesWith(V);
ICI->eraseFromParent();
// BB is now empty, so it is likely to simplify away.
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
}
// The use of the icmp has to be in the 'end' block, by the only PHI node in
/// SimplifyBranchOnICmpChain - The specified branch is a conditional branch.
/// Check to see if it is branching on an or/and chain of icmp instructions, and
/// fold it into a switch instruction if so.
-static bool SimplifyBranchOnICmpChain(BranchInst *BI, const TargetData *TD,
+static bool SimplifyBranchOnICmpChain(BranchInst *BI, const DataLayout *TD,
IRBuilder<> &Builder) {
Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
if (Cond == 0) return false;
Builder.SetInsertPoint(BI);
// Convert pointer to int before we switch.
if (CompVal->getType()->isPointerTy()) {
- assert(TD && "Cannot switch on pointer without TargetData");
+ assert(TD && "Cannot switch on pointer without DataLayout");
CompVal = Builder.CreatePtrToInt(CompVal,
- TD->getIntPtrType(CompVal->getContext()),
+ TD->getIntPtrType(CompVal->getType()),
"magicptr");
}
return false;
// Turn all invokes that unwind here into calls and delete the basic block.
+ bool InvokeRequiresTableEntry = false;
+ bool Changed = false;
for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE;) {
InvokeInst *II = cast<InvokeInst>((*PI++)->getTerminator());
+
+ if (II->hasFnAttr(Attribute::UWTable)) {
+ // Don't remove an `invoke' instruction if the ABI requires an entry into
+ // the table.
+ InvokeRequiresTableEntry = true;
+ continue;
+ }
+
SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3);
+
// Insert a call instruction before the invoke.
CallInst *Call = CallInst::Create(II->getCalledValue(), Args, "", II);
Call->takeName(II);
// Finally, delete the invoke instruction!
II->eraseFromParent();
+ Changed = true;
}
- // The landingpad is now unreachable. Zap it.
- BB->eraseFromParent();
- return true;
+ if (!InvokeRequiresTableEntry)
+ // The landingpad is now unreachable. Zap it.
+ BB->eraseFromParent();
+
+ return Changed;
}
bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder) {
Value *Sub = SI->getCondition();
if (!Offset->isNullValue())
Sub = Builder.CreateAdd(Sub, Offset, Sub->getName()+".off");
- Value *Cmp = Builder.CreateICmpULT(Sub, NumCases, "switch");
- Builder.CreateCondBr(
+ Value *Cmp;
+ // If NumCases overflowed, then all possible values jump to the successor.
+ if (NumCases->isNullValue() && SI->getNumCases() != 0)
+ Cmp = ConstantInt::getTrue(SI->getContext());
+ else
+ Cmp = Builder.CreateICmpULT(Sub, NumCases, "switch");
+ BranchInst *NewBI = Builder.CreateCondBr(
Cmp, SI->case_begin().getCaseSuccessor(), SI->getDefaultDest());
+ // Update weight for the newly-created conditional branch.
+ SmallVector<uint64_t, 8> Weights;
+ bool HasWeights = HasBranchWeights(SI);
+ if (HasWeights) {
+ GetBranchWeights(SI, Weights);
+ if (Weights.size() == 1 + SI->getNumCases()) {
+ // Combine all weights for the cases to be the true weight of NewBI.
+ // We assume that the sum of all weights for a Terminator can fit into 32
+ // bits.
+ uint32_t NewTrueWeight = 0;
+ for (unsigned I = 1, E = Weights.size(); I != E; ++I)
+ NewTrueWeight += (uint32_t)Weights[I];
+ NewBI->setMetadata(LLVMContext::MD_prof,
+ MDBuilder(SI->getContext()).
+ createBranchWeights(NewTrueWeight,
+ (uint32_t)Weights[0]));
+ }
+ }
+
// Prune obsolete incoming values off the successor's PHI nodes.
for (BasicBlock::iterator BBI = SI->case_begin().getCaseSuccessor()->begin();
isa<PHINode>(BBI); ++BBI) {
/// and use it to remove dead cases.
static bool EliminateDeadSwitchCases(SwitchInst *SI) {
Value *Cond = SI->getCondition();
- unsigned Bits = cast<IntegerType>(Cond->getType())->getBitWidth();
+ unsigned Bits = Cond->getType()->getIntegerBitWidth();
APInt KnownZero(Bits, 0), KnownOne(Bits, 0);
ComputeMaskedBits(Cond, KnownZero, KnownOne);
}
}
+ SmallVector<uint64_t, 8> Weights;
+ bool HasWeight = HasBranchWeights(SI);
+ if (HasWeight) {
+ GetBranchWeights(SI, Weights);
+ HasWeight = (Weights.size() == 1 + SI->getNumCases());
+ }
+
// Remove dead cases from the switch.
for (unsigned I = 0, E = DeadCases.size(); I != E; ++I) {
SwitchInst::CaseIt Case = SI->findCaseValue(DeadCases[I]);
assert(Case != SI->case_default() &&
"Case was not found. Probably mistake in DeadCases forming.");
+ if (HasWeight) {
+ std::swap(Weights[Case.getCaseIndex()+1], Weights.back());
+ Weights.pop_back();
+ }
+
// Prune unused values from PHI nodes.
Case.getCaseSuccessor()->removePredecessor(SI->getParent());
SI->removeCase(Case);
}
+ if (HasWeight) {
+ SmallVector<uint32_t, 8> MDWeights(Weights.begin(), Weights.end());
+ SI->setMetadata(LLVMContext::MD_prof,
+ MDBuilder(SI->getParent()->getContext()).
+ createBranchWeights(MDWeights));
+ }
return !DeadCases.empty();
}
for (ForwardingNodesMap::iterator I = ForwardingNodes.begin(),
E = ForwardingNodes.end(); I != E; ++I) {
PHINode *Phi = I->first;
- SmallVector<int,4> &Indexes = I->second;
+ SmallVectorImpl<int> &Indexes = I->second;
if (Indexes.size() < 2) continue;
isa<UndefValue>(C);
}
-/// GetCaseResulsts - Try to determine the resulting constant values in phi
-/// nodes at the common destination basic block for one of the case
-/// destinations of a switch instruction.
-static bool GetCaseResults(SwitchInst *SI,
- BasicBlock *CaseDest,
- BasicBlock **CommonDest,
- SmallVector<std::pair<PHINode*,Constant*>, 4> &Res) {
- // The block from which we enter the common destination.
- BasicBlock *Pred = SI->getParent();
+/// LookupConstant - If V is a Constant, return it. Otherwise, try to look up
+/// its constant value in ConstantPool, returning 0 if it's not there.
+static Constant *LookupConstant(Value *V,
+ const SmallDenseMap<Value*, Constant*>& ConstantPool) {
+ if (Constant *C = dyn_cast<Constant>(V))
+ return C;
+ return ConstantPool.lookup(V);
+}
- // If CaseDest is empty, continue to its successor.
- if (CaseDest->getFirstNonPHIOrDbg() == CaseDest->getTerminator() &&
- !isa<PHINode>(CaseDest->begin())) {
+/// ConstantFold - Try to fold instruction I into a constant. This works for
+/// simple instructions such as binary operations where both operands are
+/// constant or can be replaced by constants from the ConstantPool. Returns the
+/// resulting constant on success, 0 otherwise.
+static Constant *ConstantFold(Instruction *I,
+ const SmallDenseMap<Value*, Constant*>& ConstantPool) {
+ if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
+ Constant *A = LookupConstant(BO->getOperand(0), ConstantPool);
+ if (!A)
+ return 0;
+ Constant *B = LookupConstant(BO->getOperand(1), ConstantPool);
+ if (!B)
+ return 0;
+ return ConstantExpr::get(BO->getOpcode(), A, B);
+ }
- TerminatorInst *Terminator = CaseDest->getTerminator();
- if (Terminator->getNumSuccessors() != 1)
- return false;
+ if (CmpInst *Cmp = dyn_cast<CmpInst>(I)) {
+ Constant *A = LookupConstant(I->getOperand(0), ConstantPool);
+ if (!A)
+ return 0;
+ Constant *B = LookupConstant(I->getOperand(1), ConstantPool);
+ if (!B)
+ return 0;
+ return ConstantExpr::getCompare(Cmp->getPredicate(), A, B);
+ }
- Pred = CaseDest;
- CaseDest = Terminator->getSuccessor(0);
+ if (SelectInst *Select = dyn_cast<SelectInst>(I)) {
+ Constant *A = LookupConstant(Select->getCondition(), ConstantPool);
+ if (!A)
+ return 0;
+ if (A->isAllOnesValue())
+ return LookupConstant(Select->getTrueValue(), ConstantPool);
+ if (A->isNullValue())
+ return LookupConstant(Select->getFalseValue(), ConstantPool);
+ return 0;
+ }
+
+ if (CastInst *Cast = dyn_cast<CastInst>(I)) {
+ Constant *A = LookupConstant(I->getOperand(0), ConstantPool);
+ if (!A)
+ return 0;
+ return ConstantExpr::getCast(Cast->getOpcode(), A, Cast->getDestTy());
+ }
+
+ return 0;
+}
+
+/// GetCaseResults - Try to determine the resulting constant values in phi nodes
+/// at the common destination basic block, *CommonDest, for one of the case
+/// destionations CaseDest corresponding to value CaseVal (0 for the default
+/// case), of a switch instruction SI.
+static bool
+GetCaseResults(SwitchInst *SI,
+ ConstantInt *CaseVal,
+ BasicBlock *CaseDest,
+ BasicBlock **CommonDest,
+ SmallVectorImpl<std::pair<PHINode*,Constant*> > &Res) {
+ // The block from which we enter the common destination.
+ BasicBlock *Pred = SI->getParent();
+
+ // If CaseDest is empty except for some side-effect free instructions through
+ // which we can constant-propagate the CaseVal, continue to its successor.
+ SmallDenseMap<Value*, Constant*> ConstantPool;
+ ConstantPool.insert(std::make_pair(SI->getCondition(), CaseVal));
+ for (BasicBlock::iterator I = CaseDest->begin(), E = CaseDest->end(); I != E;
+ ++I) {
+ if (TerminatorInst *T = dyn_cast<TerminatorInst>(I)) {
+ // If the terminator is a simple branch, continue to the next block.
+ if (T->getNumSuccessors() != 1)
+ return false;
+ Pred = CaseDest;
+ CaseDest = T->getSuccessor(0);
+ } else if (isa<DbgInfoIntrinsic>(I)) {
+ // Skip debug intrinsic.
+ continue;
+ } else if (Constant *C = ConstantFold(I, ConstantPool)) {
+ // Instruction is side-effect free and constant.
+ ConstantPool.insert(std::make_pair(I, C));
+ } else {
+ break;
+ }
}
// If we did not have a CommonDest before, use the current one.
if (Idx == -1)
continue;
- Constant *ConstVal = dyn_cast<Constant>(PHI->getIncomingValue(Idx));
+ Constant *ConstVal = LookupConstant(PHI->getIncomingValue(Idx),
+ ConstantPool);
if (!ConstVal)
return false;
+ // Note: If the constant comes from constant-propagating the case value
+ // through the CaseDest basic block, it will be safe to remove the
+ // instructions in that block. They cannot be used (except in the phi nodes
+ // we visit) outside CaseDest, because that block does not dominate its
+ // successor. If it did, we would not be in this phi node.
+
// Be conservative about which kinds of constants we support.
if (!ValidLookupTableConstant(ConstVal))
return false;
return true;
}
-/// BuildLookupTable - Build a lookup table with the contents of Results, using
-/// DefaultResult to fill the holes in the table. If the table ends up
-/// containing the same result in each element, set *SingleResult to that value
-/// and return NULL.
-static GlobalVariable *BuildLookupTable(Module &M,
- uint64_t TableSize,
- ConstantInt *Offset,
- const SmallVector<std::pair<ConstantInt*, Constant*>, 4>& Results,
- Constant *DefaultResult,
- Constant **SingleResult) {
- assert(Results.size() && "Need values to build lookup table");
- assert(TableSize >= Results.size() && "Table needs to hold all values");
+namespace {
+ /// SwitchLookupTable - This class represents a lookup table that can be used
+ /// to replace a switch.
+ class SwitchLookupTable {
+ public:
+ /// SwitchLookupTable - Create a lookup table to use as a switch replacement
+ /// with the contents of Values, using DefaultValue to fill any holes in the
+ /// table.
+ SwitchLookupTable(Module &M,
+ uint64_t TableSize,
+ ConstantInt *Offset,
+ const SmallVectorImpl<std::pair<ConstantInt*, Constant*> >& Values,
+ Constant *DefaultValue,
+ const DataLayout *TD);
+
+ /// BuildLookup - Build instructions with Builder to retrieve the value at
+ /// the position given by Index in the lookup table.
+ Value *BuildLookup(Value *Index, IRBuilder<> &Builder);
+
+ /// WouldFitInRegister - Return true if a table with TableSize elements of
+ /// type ElementType would fit in a target-legal register.
+ static bool WouldFitInRegister(const DataLayout *TD,
+ uint64_t TableSize,
+ const Type *ElementType);
+
+ private:
+ // Depending on the contents of the table, it can be represented in
+ // different ways.
+ enum {
+ // For tables where each element contains the same value, we just have to
+ // store that single value and return it for each lookup.
+ SingleValueKind,
+
+ // For small tables with integer elements, we can pack them into a bitmap
+ // that fits into a target-legal register. Values are retrieved by
+ // shift and mask operations.
+ BitMapKind,
+
+ // The table is stored as an array of values. Values are retrieved by load
+ // instructions from the table.
+ ArrayKind
+ } Kind;
+
+ // For SingleValueKind, this is the single value.
+ Constant *SingleValue;
+
+ // For BitMapKind, this is the bitmap.
+ ConstantInt *BitMap;
+ IntegerType *BitMapElementTy;
+
+ // For ArrayKind, this is the array.
+ GlobalVariable *Array;
+ };
+}
+
+SwitchLookupTable::SwitchLookupTable(Module &M,
+ uint64_t TableSize,
+ ConstantInt *Offset,
+ const SmallVectorImpl<std::pair<ConstantInt*, Constant*> >& Values,
+ Constant *DefaultValue,
+ const DataLayout *TD)
+ : SingleValue(0), BitMap(0), BitMapElementTy(0), Array(0) {
+ assert(Values.size() && "Can't build lookup table without values!");
+ assert(TableSize >= Values.size() && "Can't fit values in table!");
// If all values in the table are equal, this is that value.
- Constant *SameResult = Results.begin()->second;
+ SingleValue = Values.begin()->second;
// Build up the table contents.
- std::vector<Constant*> TableContents(TableSize);
- for (size_t I = 0, E = Results.size(); I != E; ++I) {
- ConstantInt *CaseVal = Results[I].first;
- Constant *CaseRes = Results[I].second;
-
- uint64_t Idx = (CaseVal->getValue() - Offset->getValue()).getLimitedValue();
+ SmallVector<Constant*, 64> TableContents(TableSize);
+ for (size_t I = 0, E = Values.size(); I != E; ++I) {
+ ConstantInt *CaseVal = Values[I].first;
+ Constant *CaseRes = Values[I].second;
+ assert(CaseRes->getType() == DefaultValue->getType());
+
+ uint64_t Idx = (CaseVal->getValue() - Offset->getValue())
+ .getLimitedValue();
TableContents[Idx] = CaseRes;
- if (CaseRes != SameResult)
- SameResult = NULL;
+ if (CaseRes != SingleValue)
+ SingleValue = 0;
}
// Fill in any holes in the table with the default result.
- if (Results.size() < TableSize) {
- for (unsigned i = 0; i < TableSize; ++i) {
- if (!TableContents[i])
- TableContents[i] = DefaultResult;
+ if (Values.size() < TableSize) {
+ for (uint64_t I = 0; I < TableSize; ++I) {
+ if (!TableContents[I])
+ TableContents[I] = DefaultValue;
}
- if (DefaultResult != SameResult)
- SameResult = NULL;
+ if (DefaultValue != SingleValue)
+ SingleValue = 0;
}
- // Same result was used in the entire table; just return that.
- if (SameResult) {
- *SingleResult = SameResult;
- return NULL;
+ // If each element in the table contains the same value, we only need to store
+ // that single value.
+ if (SingleValue) {
+ Kind = SingleValueKind;
+ return;
}
- ArrayType *ArrayTy = ArrayType::get(DefaultResult->getType(), TableSize);
+ // If the type is integer and the table fits in a register, build a bitmap.
+ if (WouldFitInRegister(TD, TableSize, DefaultValue->getType())) {
+ IntegerType *IT = cast<IntegerType>(DefaultValue->getType());
+ APInt TableInt(TableSize * IT->getBitWidth(), 0);
+ for (uint64_t I = TableSize; I > 0; --I) {
+ TableInt <<= IT->getBitWidth();
+ // Insert values into the bitmap. Undef values are set to zero.
+ if (!isa<UndefValue>(TableContents[I - 1])) {
+ ConstantInt *Val = cast<ConstantInt>(TableContents[I - 1]);
+ TableInt |= Val->getValue().zext(TableInt.getBitWidth());
+ }
+ }
+ BitMap = ConstantInt::get(M.getContext(), TableInt);
+ BitMapElementTy = IT;
+ Kind = BitMapKind;
+ ++NumBitMaps;
+ return;
+ }
+
+ // Store the table in an array.
+ ArrayType *ArrayTy = ArrayType::get(DefaultValue->getType(), TableSize);
Constant *Initializer = ConstantArray::get(ArrayTy, TableContents);
- GlobalVariable *GV = new GlobalVariable(M, ArrayTy, /*constant=*/ true,
- GlobalVariable::PrivateLinkage,
- Initializer,
- "switch.table");
- GV->setUnnamedAddr(true);
- return GV;
+ Array = new GlobalVariable(M, ArrayTy, /*constant=*/ true,
+ GlobalVariable::PrivateLinkage,
+ Initializer,
+ "switch.table");
+ Array->setUnnamedAddr(true);
+ Kind = ArrayKind;
+}
+
+Value *SwitchLookupTable::BuildLookup(Value *Index, IRBuilder<> &Builder) {
+ switch (Kind) {
+ case SingleValueKind:
+ return SingleValue;
+ case BitMapKind: {
+ // Type of the bitmap (e.g. i59).
+ IntegerType *MapTy = BitMap->getType();
+
+ // Cast Index to the same type as the bitmap.
+ // Note: The Index is <= the number of elements in the table, so
+ // truncating it to the width of the bitmask is safe.
+ Value *ShiftAmt = Builder.CreateZExtOrTrunc(Index, MapTy, "switch.cast");
+
+ // Multiply the shift amount by the element width.
+ ShiftAmt = Builder.CreateMul(ShiftAmt,
+ ConstantInt::get(MapTy, BitMapElementTy->getBitWidth()),
+ "switch.shiftamt");
+
+ // Shift down.
+ Value *DownShifted = Builder.CreateLShr(BitMap, ShiftAmt,
+ "switch.downshift");
+ // Mask off.
+ return Builder.CreateTrunc(DownShifted, BitMapElementTy,
+ "switch.masked");
+ }
+ case ArrayKind: {
+ Value *GEPIndices[] = { Builder.getInt32(0), Index };
+ Value *GEP = Builder.CreateInBoundsGEP(Array, GEPIndices,
+ "switch.gep");
+ return Builder.CreateLoad(GEP, "switch.load");
+ }
+ }
+ llvm_unreachable("Unknown lookup table kind!");
+}
+
+bool SwitchLookupTable::WouldFitInRegister(const DataLayout *TD,
+ uint64_t TableSize,
+ const Type *ElementType) {
+ if (!TD)
+ return false;
+ const IntegerType *IT = dyn_cast<IntegerType>(ElementType);
+ if (!IT)
+ return false;
+ // FIXME: If the type is wider than it needs to be, e.g. i8 but all values
+ // are <= 15, we could try to narrow the type.
+
+ // Avoid overflow, fitsInLegalInteger uses unsigned int for the width.
+ if (TableSize >= UINT_MAX/IT->getBitWidth())
+ return false;
+ return TD->fitsInLegalInteger(TableSize * IT->getBitWidth());
+}
+
+/// ShouldBuildLookupTable - Determine whether a lookup table should be built
+/// for this switch, based on the number of cases, size of the table and the
+/// types of the results.
+static bool ShouldBuildLookupTable(SwitchInst *SI,
+ uint64_t TableSize,
+ const TargetTransformInfo &TTI,
+ const DataLayout *TD,
+ const SmallDenseMap<PHINode*, Type*>& ResultTypes) {
+ if (SI->getNumCases() > TableSize || TableSize >= UINT64_MAX / 10)
+ return false; // TableSize overflowed, or mul below might overflow.
+
+ bool AllTablesFitInRegister = true;
+ bool HasIllegalType = false;
+ for (SmallDenseMap<PHINode*, Type*>::const_iterator I = ResultTypes.begin(),
+ E = ResultTypes.end(); I != E; ++I) {
+ Type *Ty = I->second;
+
+ // Saturate this flag to true.
+ HasIllegalType = HasIllegalType || !TTI.isTypeLegal(Ty);
+
+ // Saturate this flag to false.
+ AllTablesFitInRegister = AllTablesFitInRegister &&
+ SwitchLookupTable::WouldFitInRegister(TD, TableSize, Ty);
+
+ // If both flags saturate, we're done. NOTE: This *only* works with
+ // saturating flags, and all flags have to saturate first due to the
+ // non-deterministic behavior of iterating over a dense map.
+ if (HasIllegalType && !AllTablesFitInRegister)
+ break;
+ }
+
+ // If each table would fit in a register, we should build it anyway.
+ if (AllTablesFitInRegister)
+ return true;
+
+ // Don't build a table that doesn't fit in-register if it has illegal types.
+ if (HasIllegalType)
+ return false;
+
+ // The table density should be at least 40%. This is the same criterion as for
+ // jump tables, see SelectionDAGBuilder::handleJTSwitchCase.
+ // FIXME: Find the best cut-off.
+ return SI->getNumCases() * 10 >= TableSize * 4;
}
/// SwitchToLookupTable - If the switch is only used to initialize one or more
/// phi nodes in a common successor block with different constant values,
/// replace the switch with lookup tables.
static bool SwitchToLookupTable(SwitchInst *SI,
- IRBuilder<> &Builder) {
+ IRBuilder<> &Builder,
+ const TargetTransformInfo &TTI,
+ const DataLayout* TD) {
assert(SI->getNumCases() > 1 && "Degenerate switch?");
- // FIXME: Handle unreachable cases.
+
+ // Only build lookup table when we have a target that supports it.
+ if (!TTI.shouldBuildLookupTables())
+ return false;
// FIXME: If the switch is too sparse for a lookup table, perhaps we could
// split off a dense part and build a lookup table for that.
- // FIXME: If the results are all integers and the lookup table would fit in a
- // target-legal register, we should store them as a bitmap and use shift/mask
- // to look up the result.
-
// FIXME: This creates arrays of GEPs to constant strings, which means each
// GEP needs a runtime relocation in PIC code. We should just build one big
// string and lookup indices into that.
- // Ignore the switch if the number of cases are too small.
+ // Ignore the switch if the number of cases is too small.
// This is similar to the check when building jump tables in
// SelectionDAGBuilder::handleJTSwitchCase.
// FIXME: Determine the best cut-off.
ConstantInt *MinCaseVal = CI.getCaseValue();
ConstantInt *MaxCaseVal = CI.getCaseValue();
- BasicBlock *CommonDest = NULL;
+ BasicBlock *CommonDest = 0;
typedef SmallVector<std::pair<ConstantInt*, Constant*>, 4> ResultListTy;
SmallDenseMap<PHINode*, ResultListTy> ResultLists;
SmallDenseMap<PHINode*, Constant*> DefaultResults;
// Resulting value at phi nodes for this case value.
typedef SmallVector<std::pair<PHINode*, Constant*>, 4> ResultsTy;
ResultsTy Results;
- if (!GetCaseResults(SI, CI.getCaseSuccessor(), &CommonDest, Results))
+ if (!GetCaseResults(SI, CaseVal, CI.getCaseSuccessor(), &CommonDest,
+ Results))
return false;
// Append the result from this case to the list for each phi.
// Get the resulting values for the default case.
SmallVector<std::pair<PHINode*, Constant*>, 4> DefaultResultsList;
- if (!GetCaseResults(SI, SI->getDefaultDest(), &CommonDest, DefaultResultsList))
+ if (!GetCaseResults(SI, 0, SI->getDefaultDest(), &CommonDest,
+ DefaultResultsList))
return false;
for (size_t I = 0, E = DefaultResultsList.size(); I != E; ++I) {
PHINode *PHI = DefaultResultsList[I].first;
}
APInt RangeSpread = MaxCaseVal->getValue() - MinCaseVal->getValue();
- // The table density should be at lest 40%. This is the same criterion as for
- // jump tables, see SelectionDAGBuilder::handleJTSwitchCase.
- // FIXME: Find the best cut-off.
- // Be careful to avoid overlow in the density computation.
- if (RangeSpread.zextOrSelf(64).ugt(UINT64_MAX / 4 - 1))
- return false;
uint64_t TableSize = RangeSpread.getLimitedValue() + 1;
- if (SI->getNumCases() * 10 < TableSize * 4)
+ if (!ShouldBuildLookupTable(SI, TableSize, TTI, TD, ResultTypes))
return false;
- // Build the lookup tables.
- SmallDenseMap<PHINode*, GlobalVariable*> LookupTables;
- SmallDenseMap<PHINode*, Constant*> SingleResults;
-
- Module &Mod = *CommonDest->getParent()->getParent();
- for (SmallVector<PHINode*, 4>::iterator I = PHIs.begin(), E = PHIs.end();
- I != E; ++I) {
- PHINode *PHI = *I;
-
- Constant *SingleResult = NULL;
- LookupTables[PHI] = BuildLookupTable(Mod, TableSize, MinCaseVal,
- ResultLists[PHI], DefaultResults[PHI],
- &SingleResult);
- SingleResults[PHI] = SingleResult;
- }
-
// Create the BB that does the lookups.
+ Module &Mod = *CommonDest->getParent()->getParent();
BasicBlock *LookupBB = BasicBlock::Create(Mod.getContext(),
"switch.lookup",
CommonDest->getParent(),
CommonDest);
- // Check whether the condition value is within the case range, and branch to
- // the new BB.
+ // Compute the table index value.
Builder.SetInsertPoint(SI);
Value *TableIndex = Builder.CreateSub(SI->getCondition(), MinCaseVal,
"switch.tableidx");
- Value *Cmp = Builder.CreateICmpULT(TableIndex, ConstantInt::get(
- MinCaseVal->getType(), TableSize));
- Builder.CreateCondBr(Cmp, LookupBB, SI->getDefaultDest());
+
+ // Compute the maximum table size representable by the integer type we are
+ // switching upon.
+ unsigned CaseSize = MinCaseVal->getType()->getPrimitiveSizeInBits();
+ uint64_t MaxTableSize = CaseSize > 63? UINT64_MAX : 1ULL << CaseSize;
+ assert(MaxTableSize >= TableSize &&
+ "It is impossible for a switch to have more entries than the max "
+ "representable value of its input integer type's size.");
+
+ // If we have a fully covered lookup table, unconditionally branch to the
+ // lookup table BB. Otherwise, check if the condition value is within the case
+ // range. If it is so, branch to the new BB. Otherwise branch to SI's default
+ // destination.
+ const bool GeneratingCoveredLookupTable = MaxTableSize == TableSize;
+ if (GeneratingCoveredLookupTable) {
+ Builder.CreateBr(LookupBB);
+ SI->getDefaultDest()->removePredecessor(SI->getParent());
+ } else {
+ Value *Cmp = Builder.CreateICmpULT(TableIndex, ConstantInt::get(
+ MinCaseVal->getType(), TableSize));
+ Builder.CreateCondBr(Cmp, LookupBB, SI->getDefaultDest());
+ }
// Populate the BB that does the lookups.
Builder.SetInsertPoint(LookupBB);
bool ReturnedEarly = false;
- for (SmallVector<PHINode*, 4>::iterator I = PHIs.begin(), E = PHIs.end();
- I != E; ++I) {
- PHINode *PHI = *I;
- // There was a single result for this phi; just use that.
- if (Constant *SingleResult = SingleResults[PHI]) {
- PHI->addIncoming(SingleResult, LookupBB);
- continue;
- }
+ for (size_t I = 0, E = PHIs.size(); I != E; ++I) {
+ PHINode *PHI = PHIs[I];
- Value *GEPIndices[] = { Builder.getInt32(0), TableIndex };
- Value *GEP = Builder.CreateInBoundsGEP(LookupTables[PHI], GEPIndices,
- "switch.gep");
- Value *Result = Builder.CreateLoad(GEP, "switch.load");
-
- // If the result is only going to be used to return from the function,
- // we want to do that right here.
- if (PHI->hasOneUse() && isa<ReturnInst>(*PHI->use_begin())) {
- if (CommonDest->getFirstNonPHIOrDbg() == CommonDest->getTerminator()) {
- Builder.CreateRet(Result);
- ReturnedEarly = true;
- }
+ SwitchLookupTable Table(Mod, TableSize, MinCaseVal, ResultLists[PHI],
+ DefaultResults[PHI], TD);
+
+ Value *Result = Table.BuildLookup(TableIndex, Builder);
+
+ // If the result is used to return immediately from the function, we want to
+ // do that right here.
+ if (PHI->hasOneUse() && isa<ReturnInst>(*PHI->use_begin()) &&
+ *PHI->use_begin() == CommonDest->getFirstNonPHIOrDbg()) {
+ Builder.CreateRet(Result);
+ ReturnedEarly = true;
+ break;
}
- if (!ReturnedEarly)
- PHI->addIncoming(Result, LookupBB);
+ PHI->addIncoming(Result, LookupBB);
}
if (!ReturnedEarly)
Builder.CreateBr(CommonDest);
// Remove the switch.
- for (unsigned i = 0; i < SI->getNumSuccessors(); ++i) {
+ for (unsigned i = 0, e = SI->getNumSuccessors(); i < e; ++i) {
BasicBlock *Succ = SI->getSuccessor(i);
- if (Succ == SI->getDefaultDest()) continue;
+
+ if (Succ == SI->getDefaultDest())
+ continue;
Succ->removePredecessor(SI->getParent());
}
SI->eraseFromParent();
}
bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder) {
- // If this switch is too complex to want to look at, ignore it.
- if (!isValueEqualityComparison(SI))
- return false;
-
BasicBlock *BB = SI->getParent();
- // If we only have one predecessor, and if it is a branch on this value,
- // see if that predecessor totally determines the outcome of this switch.
- if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
- if (SimplifyEqualityComparisonWithOnlyPredecessor(SI, OnlyPred, Builder))
- return SimplifyCFG(BB) | true;
+ if (isValueEqualityComparison(SI)) {
+ // If we only have one predecessor, and if it is a branch on this value,
+ // see if that predecessor totally determines the outcome of this switch.
+ if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
+ if (SimplifyEqualityComparisonWithOnlyPredecessor(SI, OnlyPred, Builder))
+ return SimplifyCFG(BB, TTI, TD) | true;
- Value *Cond = SI->getCondition();
- if (SelectInst *Select = dyn_cast<SelectInst>(Cond))
- if (SimplifySwitchOnSelect(SI, Select))
- return SimplifyCFG(BB) | true;
+ Value *Cond = SI->getCondition();
+ if (SelectInst *Select = dyn_cast<SelectInst>(Cond))
+ if (SimplifySwitchOnSelect(SI, Select))
+ return SimplifyCFG(BB, TTI, TD) | true;
- // If the block only contains the switch, see if we can fold the block
- // away into any preds.
- BasicBlock::iterator BBI = BB->begin();
- // Ignore dbg intrinsics.
- while (isa<DbgInfoIntrinsic>(BBI))
- ++BBI;
- if (SI == &*BBI)
- if (FoldValueComparisonIntoPredecessors(SI, Builder))
- return SimplifyCFG(BB) | true;
+ // If the block only contains the switch, see if we can fold the block
+ // away into any preds.
+ BasicBlock::iterator BBI = BB->begin();
+ // Ignore dbg intrinsics.
+ while (isa<DbgInfoIntrinsic>(BBI))
+ ++BBI;
+ if (SI == &*BBI)
+ if (FoldValueComparisonIntoPredecessors(SI, Builder))
+ return SimplifyCFG(BB, TTI, TD) | true;
+ }
// Try to transform the switch into an icmp and a branch.
if (TurnSwitchRangeIntoICmp(SI, Builder))
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
// Remove unreachable cases.
if (EliminateDeadSwitchCases(SI))
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
if (ForwardSwitchConditionToPHI(SI))
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
- if (SwitchToLookupTable(SI, Builder))
- return SimplifyCFG(BB) | true;
+ if (SwitchToLookupTable(SI, Builder, TTI, TD))
+ return SimplifyCFG(BB, TTI, TD) | true;
return false;
}
if (SelectInst *SI = dyn_cast<SelectInst>(IBI->getAddress())) {
if (SimplifyIndirectBrOnSelect(IBI, SI))
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
}
return Changed;
}
bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder){
BasicBlock *BB = BI->getParent();
+ if (SinkCommon && SinkThenElseCodeToEnd(BI))
+ return true;
+
// If the Terminator is the only non-phi instruction, simplify the block.
BasicBlock::iterator I = BB->getFirstNonPHIOrDbgOrLifetime();
if (I->isTerminator() && BB != &BB->getParent()->getEntryBlock() &&
for (++I; isa<DbgInfoIntrinsic>(I); ++I)
;
if (I->isTerminator() &&
- TryToSimplifyUncondBranchWithICmpInIt(ICI, TD, Builder))
+ TryToSimplifyUncondBranchWithICmpInIt(ICI, Builder, TTI, TD))
return true;
}
// predecessor and use logical operations to update the incoming value
// for PHI nodes in common successor.
if (FoldBranchToCommonDest(BI))
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
return false;
}
// switch.
if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
if (SimplifyEqualityComparisonWithOnlyPredecessor(BI, OnlyPred, Builder))
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
// This block must be empty, except for the setcond inst, if it exists.
// Ignore dbg intrinsics.
++I;
if (&*I == BI) {
if (FoldValueComparisonIntoPredecessors(BI, Builder))
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
} else if (&*I == cast<Instruction>(BI->getCondition())){
++I;
// Ignore dbg intrinsics.
while (isa<DbgInfoIntrinsic>(I))
++I;
if (&*I == BI && FoldValueComparisonIntoPredecessors(BI, Builder))
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
}
}
// branches to us and one of our successors, fold the comparison into the
// predecessor and use logical operations to pick the right destination.
if (FoldBranchToCommonDest(BI))
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
// We have a conditional branch to two blocks that are only reachable
// from BI. We know that the condbr dominates the two blocks, so see if
if (BI->getSuccessor(0)->getSinglePredecessor() != 0) {
if (BI->getSuccessor(1)->getSinglePredecessor() != 0) {
if (HoistThenElseCodeToIf(BI))
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
} else {
// If Successor #1 has multiple preds, we may be able to conditionally
// execute Successor #0 if it branches to successor #1.
if (Succ0TI->getNumSuccessors() == 1 &&
Succ0TI->getSuccessor(0) == BI->getSuccessor(1))
if (SpeculativelyExecuteBB(BI, BI->getSuccessor(0)))
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
}
} else if (BI->getSuccessor(1)->getSinglePredecessor() != 0) {
// If Successor #0 has multiple preds, we may be able to conditionally
if (Succ1TI->getNumSuccessors() == 1 &&
Succ1TI->getSuccessor(0) == BI->getSuccessor(0))
if (SpeculativelyExecuteBB(BI, BI->getSuccessor(1)))
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
}
// If this is a branch on a phi node in the current block, thread control
if (PHINode *PN = dyn_cast<PHINode>(BI->getCondition()))
if (PN->getParent() == BI->getParent())
if (FoldCondBranchOnPHI(BI, TD))
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
// Scan predecessor blocks for conditional branches.
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
if (BranchInst *PBI = dyn_cast<BranchInst>((*PI)->getTerminator()))
if (PBI != BI && PBI->isConditional())
if (SimplifyCondBranchToCondBranch(PBI, BI))
- return SimplifyCFG(BB) | true;
+ return SimplifyCFG(BB, TTI, TD) | true;
return false;
}
if (!C)
return false;
- if (!I->hasOneUse()) // Only look at single-use instructions, for compile time
+ if (I->use_empty())
return false;
if (C->isNullValue()) {
- Instruction *Use = I->use_back();
+ // Only look at the first use, avoid hurting compile time with long uselists
+ User *Use = *I->use_begin();
// Now make sure that there are no instructions in between that can alter
// control flow (eg. calls)
// Load from null is undefined.
if (LoadInst *LI = dyn_cast<LoadInst>(Use))
- return LI->getPointerAddressSpace() == 0;
+ if (!LI->isVolatile())
+ return LI->getPointerAddressSpace() == 0;
// Store to null is undefined.
if (StoreInst *SI = dyn_cast<StoreInst>(Use))
- return SI->getPointerAddressSpace() == 0 && SI->getPointerOperand() == I;
+ if (!SI->isVolatile())
+ return SI->getPointerAddressSpace() == 0 && SI->getPointerOperand() == I;
}
return false;
}
/// eliminates unreachable basic blocks, and does other "peephole" optimization
/// of the CFG. It returns true if a modification was made.
///
-bool llvm::SimplifyCFG(BasicBlock *BB, const TargetData *TD) {
- return SimplifyCFGOpt(TD).run(BB);
+bool llvm::SimplifyCFG(BasicBlock *BB, const TargetTransformInfo &TTI,
+ const DataLayout *TD) {
+ return SimplifyCFGOpt(TTI, TD).run(BB);
}