#include "llvm/DerivedTypes.h"
#include "llvm/GlobalVariable.h"
#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/CFG.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/ConstantRange.h"
#include "llvm/Support/Debug.h"
+#include "llvm/Support/IRBuilder.h"
+#include "llvm/Support/NoFolder.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <set>
#include <map>
using namespace llvm;
+static cl::opt<unsigned>
+PHINodeFoldingThreshold("phi-node-folding-threshold", cl::Hidden, cl::init(1),
+ cl::desc("Control the amount of phi node folding to perform (default = 1)"));
+
+static cl::opt<bool>
+DupRet("simplifycfg-dup-ret", cl::Hidden, cl::init(false),
+ cl::desc("Duplicate return instructions into unconditional branches"));
+
STATISTIC(NumSpeculations, "Number of speculative executed instructions");
namespace {
BasicBlock *GetValueEqualityComparisonCases(TerminatorInst *TI,
std::vector<std::pair<ConstantInt*, BasicBlock*> > &Cases);
bool SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI,
- BasicBlock *Pred);
- bool FoldValueComparisonIntoPredecessors(TerminatorInst *TI);
+ BasicBlock *Pred,
+ IRBuilder<> &Builder);
+ bool FoldValueComparisonIntoPredecessors(TerminatorInst *TI,
+ IRBuilder<> &Builder);
- bool SimplifyReturn(ReturnInst *RI);
- bool SimplifyUnwind(UnwindInst *UI);
+ bool SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder);
+ bool SimplifyUnwind(UnwindInst *UI, IRBuilder<> &Builder);
bool SimplifyUnreachable(UnreachableInst *UI);
- bool SimplifySwitch(SwitchInst *SI);
+ bool SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder);
bool SimplifyIndirectBr(IndirectBrInst *IBI);
- bool SimplifyUncondBranch(BranchInst *BI);
- bool SimplifyCondBranch(BranchInst *BI);
+ bool SimplifyUncondBranch(BranchInst *BI, IRBuilder <> &Builder);
+ bool SimplifyCondBranch(BranchInst *BI, IRBuilder <>&Builder);
public:
explicit SimplifyCFGOpt(const TargetData *td) : TD(td) {}
/// 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());
// We can only handle branches. Other control flow will be lowered to
// branches if possible anyway.
- if (!isa<BranchInst>(Pred1->getTerminator()) ||
- !isa<BranchInst>(Pred2->getTerminator()))
+ BranchInst *Pred1Br = dyn_cast<BranchInst>(Pred1->getTerminator());
+ BranchInst *Pred2Br = dyn_cast<BranchInst>(Pred2->getTerminator());
+ if (Pred1Br == 0 || Pred2Br == 0)
return 0;
- BranchInst *Pred1Br = cast<BranchInst>(Pred1->getTerminator());
- BranchInst *Pred2Br = cast<BranchInst>(Pred2->getTerminator());
// Eliminate code duplication by ensuring that Pred1Br is conditional if
// either are.
}
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 &&
return 0;
}
- // 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 (++pred_begin(Pred2) != pred_end(Pred2))
- 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!
- if (pred_begin(Pred1) == pred_end(Pred1) ||
- ++pred_begin(Pred1) != pred_end(Pred1) ||
- pred_begin(Pred2) == pred_end(Pred2) ||
- ++pred_begin(Pred2) != pred_end(Pred2) ||
- *pred_begin(Pred1) != *pred_begin(Pred2))
+ BasicBlock *CommonPred = Pred1->getSinglePredecessor();
+ if (CommonPred == 0 || CommonPred != Pred2->getSinglePredecessor())
return 0;
// Otherwise, if this is a conditional branch, then we can use it!
- BasicBlock *CommonPred = *pred_begin(Pred1);
- if (BranchInst *BI = dyn_cast<BranchInst>(CommonPred->getTerminator())) {
- 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();
+ 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 0;
+ return BI->getCondition();
}
/// DominatesMergePoint - If we have a merge point of an "if condition" as
/// which works well enough for us.
///
/// If AggressiveInsts is non-null, and if V does not dominate BB, we check to
-/// see if V (which must be an instruction) is cheap to compute and is
-/// non-trapping. If both are true, the instruction is inserted into the set
-/// and true is returned.
+/// see if V (which must be an instruction) and its recursive operands
+/// that do not dominate BB have a combined cost lower than CostRemaining and
+/// are non-trapping. If both are true, the instruction is inserted into the
+/// set and true is returned.
+///
+/// The cost for most non-trapping instructions is defined as 1 except for
+/// Select whose cost is 2.
+///
+/// After this function returns, CostRemaining is decreased by the cost of
+/// V plus its non-dominating operands. If that cost is greater than
+/// CostRemaining, false is returned and CostRemaining is undefined.
static bool DominatesMergePoint(Value *V, BasicBlock *BB,
- std::set<Instruction*> *AggressiveInsts) {
+ SmallPtrSet<Instruction*, 4> *AggressiveInsts,
+ unsigned &CostRemaining) {
Instruction *I = dyn_cast<Instruction>(V);
if (!I) {
// Non-instructions all dominate instructions, but not all constantexprs
// If this instruction is defined in a block that contains an unconditional
// branch to BB, then it must be in the 'conditional' part of the "if
- // statement".
- if (BranchInst *BI = dyn_cast<BranchInst>(PBB->getTerminator()))
- if (BI->isUnconditional() && BI->getSuccessor(0) == BB) {
- if (!AggressiveInsts) return false;
- // Okay, it looks like the instruction IS in the "condition". Check to
- // see if it's a cheap instruction to unconditionally compute, and if it
- // only uses stuff defined outside of the condition. If so, hoist it out.
- if (!I->isSafeToSpeculativelyExecute())
- return false;
+ // statement". If not, it definitely dominates the region.
+ BranchInst *BI = dyn_cast<BranchInst>(PBB->getTerminator());
+ if (BI == 0 || BI->isConditional() || BI->getSuccessor(0) != BB)
+ return true;
- switch (I->getOpcode()) {
- default: return false; // Cannot hoist this out safely.
- case Instruction::Load: {
- // We have to check to make sure there are no instructions before the
- // load in its basic block, as we are going to hoist the loop out to
- // its predecessor.
- BasicBlock::iterator IP = PBB->begin();
- while (isa<DbgInfoIntrinsic>(IP))
- IP++;
- if (IP != BasicBlock::iterator(I))
- return false;
- break;
- }
- case Instruction::Add:
- case Instruction::Sub:
- case Instruction::And:
- case Instruction::Or:
- case Instruction::Xor:
- case Instruction::Shl:
- case Instruction::LShr:
- case Instruction::AShr:
- case Instruction::ICmp:
- break; // These are all cheap and non-trapping instructions.
- }
+ // If we aren't allowing aggressive promotion anymore, then don't consider
+ // instructions in the 'if region'.
+ if (AggressiveInsts == 0) return false;
+
+ // If we have seen this instruction before, don't count it again.
+ if (AggressiveInsts->count(I)) return true;
- // Okay, we can only really hoist these out if their operands are not
- // defined in the conditional region.
- for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
- if (!DominatesMergePoint(*i, BB, 0))
- return false;
- // Okay, it's safe to do this! Remember this instruction.
- AggressiveInsts->insert(I);
- }
+ // Okay, it looks like the instruction IS in the "condition". Check to
+ // see if it's a cheap instruction to unconditionally compute, and if it
+ // only uses stuff defined outside of the condition. If so, hoist it out.
+ if (!I->isSafeToSpeculativelyExecute())
+ return false;
+ unsigned Cost = 0;
+
+ switch (I->getOpcode()) {
+ default: return false; // Cannot hoist this out safely.
+ case Instruction::Load:
+ // We have to check to make sure there are no instructions before the
+ // load in its basic block, as we are going to hoist the load out to its
+ // predecessor.
+ if (PBB->getFirstNonPHIOrDbg() != I)
+ return false;
+ Cost = 1;
+ break;
+ case Instruction::GetElementPtr:
+ // GEPs are cheap if all indices are constant.
+ if (!cast<GetElementPtrInst>(I)->hasAllConstantIndices())
+ return false;
+ Cost = 1;
+ break;
+ case Instruction::Add:
+ case Instruction::Sub:
+ case Instruction::And:
+ case Instruction::Or:
+ case Instruction::Xor:
+ case Instruction::Shl:
+ case Instruction::LShr:
+ case Instruction::AShr:
+ case Instruction::ICmp:
+ case Instruction::Trunc:
+ case Instruction::ZExt:
+ case Instruction::SExt:
+ Cost = 1;
+ break; // These are all cheap and non-trapping instructions.
+
+ case Instruction::Select:
+ Cost = 2;
+ break;
+ }
+
+ if (Cost > CostRemaining)
+ return false;
+
+ CostRemaining -= Cost;
+
+ // Okay, we can only really hoist these out if their operands do
+ // not take us over the cost threshold.
+ for (User::op_iterator i = I->op_begin(), e = I->op_end(); i != e; ++i)
+ if (!DominatesMergePoint(*i, BB, AggressiveInsts, CostRemaining))
+ return false;
+ // Okay, it's safe to do this! Remember this instruction.
+ AggressiveInsts->insert(I);
return true;
}
/// Values vector.
static Value *
GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra,
- const TargetData *TD, bool isEQ) {
+ const TargetData *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 (ICI->getPredicate() == (isEQ ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE))
- if (ConstantInt *C = GetConstantInt(I->getOperand(1), TD)) {
+ if (ConstantInt *C = GetConstantInt(I->getOperand(1), TD)) {
+ if (ICI->getPredicate() == (isEQ ? ICmpInst::ICMP_EQ:ICmpInst::ICMP_NE)) {
+ UsedICmps++;
Vals.push_back(C);
return I->getOperand(0);
}
+
+ // If we have "x ult 3" comparison, for example, then we can add 0,1,2 to
+ // the set.
+ ConstantRange Span =
+ ConstantRange::makeICmpRegion(ICI->getPredicate(), C->getValue());
+
+ // If this is an and/!= check then we want to optimize "x ugt 2" into
+ // x != 0 && x != 1.
+ if (!isEQ)
+ Span = Span.inverse();
+
+ // If there are a ton of values, we don't want to make a ginormous switch.
+ if (Span.getSetSize().ugt(8) || Span.isEmptySet() ||
+ // We don't handle wrapped sets yet.
+ Span.isWrappedSet())
+ return 0;
+
+ for (APInt Tmp = Span.getLower(); Tmp != Span.getUpper(); ++Tmp)
+ Vals.push_back(ConstantInt::get(V->getContext(), Tmp));
+ UsedICmps++;
+ return I->getOperand(0);
+ }
return 0;
}
return 0;
unsigned NumValsBeforeLHS = Vals.size();
+ unsigned UsedICmpsBeforeLHS = UsedICmps;
if (Value *LHS = GatherConstantCompares(I->getOperand(0), Vals, Extra, TD,
- isEQ)) {
+ isEQ, UsedICmps)) {
unsigned NumVals = Vals.size();
+ unsigned UsedICmpsBeforeRHS = UsedICmps;
if (Value *RHS = GatherConstantCompares(I->getOperand(1), Vals, Extra, TD,
- isEQ)) {
+ isEQ, UsedICmps)) {
if (LHS == RHS)
return LHS;
Vals.resize(NumVals);
+ UsedICmps = UsedICmpsBeforeRHS;
}
// The RHS of the or/and can't be folded in and we haven't used "Extra" yet,
}
Vals.resize(NumValsBeforeLHS);
+ UsedICmps = UsedICmpsBeforeLHS;
return 0;
}
Value *OldExtra = Extra;
Extra = I->getOperand(0);
if (Value *RHS = GatherConstantCompares(I->getOperand(1), Vals, Extra, TD,
- isEQ))
+ isEQ, UsedICmps))
return RHS;
assert(Vals.size() == NumValsBeforeLHS);
Extra = OldExtra;
/// form of jump threading.
bool SimplifyCFGOpt::
SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI,
- BasicBlock *Pred) {
+ BasicBlock *Pred,
+ IRBuilder<> &Builder) {
Value *PredVal = isValueEqualityComparison(Pred->getTerminator());
if (!PredVal) return false; // Not a value comparison in predecessor.
// uncond br.
assert(ThisCases.size() == 1 && "Branch can only have one case!");
// Insert the new branch.
- Instruction *NI = BranchInst::Create(ThisDef, TI);
+ Instruction *NI = Builder.CreateBr(ThisDef);
(void) NI;
// Remove PHI node entries for the dead edge.
CheckEdge = 0;
// Insert the new branch.
- Instruction *NI = BranchInst::Create(TheRealDest, TI);
+ Instruction *NI = Builder.CreateBr(TheRealDest);
(void) NI;
DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
static int ConstantIntSortPredicate(const void *P1, const void *P2) {
const ConstantInt *LHS = *(const ConstantInt**)P1;
const ConstantInt *RHS = *(const ConstantInt**)P2;
- return LHS->getValue().ult(RHS->getValue()) ? 1 : -1;
+ if (LHS->getValue().ult(RHS->getValue()))
+ return 1;
+ if (LHS->getValue() == RHS->getValue())
+ return 0;
+ return -1;
}
/// FoldValueComparisonIntoPredecessors - The specified terminator is a value
/// equality comparison instruction (either a switch or a branch on "X == c").
/// See if any of the predecessors of the terminator block are value comparisons
/// on the same value. If so, and if safe to do so, fold them together.
-bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI) {
+bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI,
+ IRBuilder<> &Builder) {
BasicBlock *BB = TI->getParent();
Value *CV = isValueEqualityComparison(TI); // CondVal
assert(CV && "Not a comparison?");
for (unsigned i = 0, e = NewSuccessors.size(); i != e; ++i)
AddPredecessorToBlock(NewSuccessors[i], Pred, BB);
+ Builder.SetInsertPoint(PTI);
// Convert pointer to int before we switch.
if (CV->getType()->isPointerTy()) {
assert(TD && "Cannot switch on pointer without TargetData");
- CV = new PtrToIntInst(CV, TD->getIntPtrType(CV->getContext()),
- "magicptr", PTI);
+ CV = Builder.CreatePtrToInt(CV, TD->getIntPtrType(CV->getContext()),
+ "magicptr");
}
// Now that the successors are updated, create the new Switch instruction.
- SwitchInst *NewSI = SwitchInst::Create(CV, PredDefault,
- PredCases.size(), PTI);
+ SwitchInst *NewSI = Builder.CreateSwitch(CV, PredDefault,
+ PredCases.size());
+ NewSI->setDebugLoc(PTI->getDebugLoc());
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
NewSI->addCase(PredCases[i].first, PredCases[i].second);
BasicBlock::iterator BB2_Itr = BB2->begin();
Instruction *I1 = BB1_Itr++, *I2 = BB2_Itr++;
- while (isa<DbgInfoIntrinsic>(I1))
- I1 = BB1_Itr++;
- while (isa<DbgInfoIntrinsic>(I2))
- I2 = BB2_Itr++;
- if (I1->getOpcode() != I2->getOpcode() || isa<PHINode>(I1) ||
- !I1->isIdenticalToWhenDefined(I2) ||
+ // Skip debug info if it is not identical.
+ DbgInfoIntrinsic *DBI1 = dyn_cast<DbgInfoIntrinsic>(I1);
+ DbgInfoIntrinsic *DBI2 = dyn_cast<DbgInfoIntrinsic>(I2);
+ if (!DBI1 || !DBI2 || !DBI1->isIdenticalToWhenDefined(DBI2)) {
+ while (isa<DbgInfoIntrinsic>(I1))
+ I1 = BB1_Itr++;
+ while (isa<DbgInfoIntrinsic>(I2))
+ I2 = BB2_Itr++;
+ }
+ if (isa<PHINode>(I1) || !I1->isIdenticalToWhenDefined(I2) ||
(isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2)))
return false;
I2->eraseFromParent();
I1 = BB1_Itr++;
- while (isa<DbgInfoIntrinsic>(I1))
- I1 = BB1_Itr++;
I2 = BB2_Itr++;
- while (isa<DbgInfoIntrinsic>(I2))
- I2 = BB2_Itr++;
- } while (I1->getOpcode() == I2->getOpcode() &&
- I1->isIdenticalToWhenDefined(I2));
+ // Skip debug info if it is not identical.
+ DbgInfoIntrinsic *DBI1 = dyn_cast<DbgInfoIntrinsic>(I1);
+ DbgInfoIntrinsic *DBI2 = dyn_cast<DbgInfoIntrinsic>(I2);
+ if (!DBI1 || !DBI2 || !DBI1->isIdenticalToWhenDefined(DBI2)) {
+ while (isa<DbgInfoIntrinsic>(I1))
+ I1 = BB1_Itr++;
+ while (isa<DbgInfoIntrinsic>(I2))
+ I2 = BB2_Itr++;
+ }
+ } while (I1->isIdenticalToWhenDefined(I2));
return true;
NT->takeName(I1);
}
+ IRBuilder<true, NoFolder> Builder(NT);
// Hoisting one of the terminators from our successor is a great thing.
// Unfortunately, the successors of the if/else blocks may have PHI nodes in
// them. If they do, all PHI entries for BB1/BB2 must agree for all PHI
// These values do not agree. Insert a select instruction before NT
// that determines the right value.
SelectInst *&SI = InsertedSelects[std::make_pair(BB1V, BB2V)];
- if (SI == 0)
- SI = SelectInst::Create(BI->getCondition(), BB1V, BB2V,
- BB1V->getName()+"."+BB2V->getName(), NT);
+ if (SI == 0)
+ SI = cast<SelectInst>
+ (Builder.CreateSelect(BI->getCondition(), BB1V, BB2V,
+ BB1V->getName()+"."+BB2V->getName()));
+
// Make the PHI node use the select for all incoming values for BB1/BB2
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (PN->getIncomingBlock(i) == BB1 || PN->getIncomingBlock(i) == BB2)
// Create a select whose true value is the speculatively executed value and
// false value is the previously determined FalseV.
+ IRBuilder<true, NoFolder> Builder(BI);
SelectInst *SI;
if (Invert)
- SI = SelectInst::Create(BrCond, FalseV, HInst,
- FalseV->getName() + "." + HInst->getName(), BI);
+ SI = cast<SelectInst>
+ (Builder.CreateSelect(BrCond, FalseV, HInst,
+ FalseV->getName() + "." + HInst->getName()));
else
- SI = SelectInst::Create(BrCond, HInst, FalseV,
- HInst->getName() + "." + FalseV->getName(), BI);
+ SI = cast<SelectInst>
+ (Builder.CreateSelect(BrCond, HInst, FalseV,
+ HInst->getName() + "." + FalseV->getName()));
// Make the PHI node use the select for all incoming values for "then" and
// "if" blocks.
BasicBlock *BB = PN->getParent();
BasicBlock *IfTrue, *IfFalse;
Value *IfCond = GetIfCondition(BB, IfTrue, IfFalse);
- if (!IfCond) return false;
+ if (!IfCond ||
+ // Don't bother if the branch will be constant folded trivially.
+ isa<ConstantInt>(IfCond))
+ return false;
// Okay, we found that we can merge this two-entry phi node into a select.
// Doing so would require us to fold *all* two entry phi nodes in this block.
if (NumPhis > 2)
return false;
- DEBUG(dbgs() << "FOUND IF CONDITION! " << *IfCond << " T: "
- << IfTrue->getName() << " F: " << IfFalse->getName() << "\n");
-
// Loop over the PHI's seeing if we can promote them all to select
// instructions. While we are at it, keep track of the instructions
// that need to be moved to the dominating block.
- std::set<Instruction*> AggressiveInsts;
-
- BasicBlock::iterator AfterPHIIt = BB->begin();
- while (isa<PHINode>(AfterPHIIt)) {
- PHINode *PN = cast<PHINode>(AfterPHIIt++);
- if (PN->getIncomingValue(0) == PN->getIncomingValue(1)) {
- if (PN->getIncomingValue(0) != PN)
- PN->replaceAllUsesWith(PN->getIncomingValue(0));
- else
- PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
- } else if (!DominatesMergePoint(PN->getIncomingValue(0), BB,
- &AggressiveInsts) ||
- !DominatesMergePoint(PN->getIncomingValue(1), BB,
- &AggressiveInsts)) {
- return false;
+ SmallPtrSet<Instruction*, 4> AggressiveInsts;
+ unsigned MaxCostVal0 = PHINodeFoldingThreshold,
+ MaxCostVal1 = PHINodeFoldingThreshold;
+
+ for (BasicBlock::iterator II = BB->begin(); isa<PHINode>(II);) {
+ PHINode *PN = cast<PHINode>(II++);
+ if (Value *V = SimplifyInstruction(PN, TD)) {
+ PN->replaceAllUsesWith(V);
+ PN->eraseFromParent();
+ continue;
}
+
+ if (!DominatesMergePoint(PN->getIncomingValue(0), BB, &AggressiveInsts,
+ MaxCostVal0) ||
+ !DominatesMergePoint(PN->getIncomingValue(1), BB, &AggressiveInsts,
+ MaxCostVal1))
+ return false;
}
+ // If we folded the the first phi, PN dangles at this point. Refresh it. If
+ // we ran out of PHIs then we simplified them all.
+ PN = dyn_cast<PHINode>(BB->begin());
+ if (PN == 0) return true;
+
+ // Don't fold i1 branches on PHIs which contain binary operators. These can
+ // often be turned into switches and other things.
+ if (PN->getType()->isIntegerTy(1) &&
+ (isa<BinaryOperator>(PN->getIncomingValue(0)) ||
+ isa<BinaryOperator>(PN->getIncomingValue(1)) ||
+ isa<BinaryOperator>(IfCond)))
+ return false;
+
// If we all PHI nodes are promotable, check to make sure that all
// instructions in the predecessor blocks can be promoted as well. If
// not, we won't be able to get rid of the control flow, so it's not
// worth promoting to select instructions.
- BasicBlock *DomBlock = 0, *IfBlock1 = 0, *IfBlock2 = 0;
- PN = cast<PHINode>(BB->begin());
- BasicBlock *Pred = PN->getIncomingBlock(0);
- if (cast<BranchInst>(Pred->getTerminator())->isUnconditional()) {
- IfBlock1 = Pred;
- DomBlock = *pred_begin(Pred);
- for (BasicBlock::iterator I = Pred->begin();
- !isa<TerminatorInst>(I); ++I)
+ BasicBlock *DomBlock = 0;
+ BasicBlock *IfBlock1 = PN->getIncomingBlock(0);
+ BasicBlock *IfBlock2 = PN->getIncomingBlock(1);
+ if (cast<BranchInst>(IfBlock1->getTerminator())->isConditional()) {
+ IfBlock1 = 0;
+ } else {
+ DomBlock = *pred_begin(IfBlock1);
+ for (BasicBlock::iterator I = IfBlock1->begin();!isa<TerminatorInst>(I);++I)
if (!AggressiveInsts.count(I) && !isa<DbgInfoIntrinsic>(I)) {
// This is not an aggressive instruction that we can promote.
// Because of this, we won't be able to get rid of the control
}
}
- Pred = PN->getIncomingBlock(1);
- if (cast<BranchInst>(Pred->getTerminator())->isUnconditional()) {
- IfBlock2 = Pred;
- DomBlock = *pred_begin(Pred);
- for (BasicBlock::iterator I = Pred->begin();
- !isa<TerminatorInst>(I); ++I)
+ if (cast<BranchInst>(IfBlock2->getTerminator())->isConditional()) {
+ IfBlock2 = 0;
+ } else {
+ DomBlock = *pred_begin(IfBlock2);
+ for (BasicBlock::iterator I = IfBlock2->begin();!isa<TerminatorInst>(I);++I)
if (!AggressiveInsts.count(I) && !isa<DbgInfoIntrinsic>(I)) {
// This is not an aggressive instruction that we can promote.
// Because of this, we won't be able to get rid of the control
return false;
}
}
+
+ DEBUG(dbgs() << "FOUND IF CONDITION! " << *IfCond << " T: "
+ << IfTrue->getName() << " F: " << IfFalse->getName() << "\n");
// If we can still promote the PHI nodes after this gauntlet of tests,
// do all of the PHI's now.
-
+ Instruction *InsertPt = DomBlock->getTerminator();
+ IRBuilder<true, NoFolder> Builder(InsertPt);
+
// Move all 'aggressive' instructions, which are defined in the
// conditional parts of the if's up to the dominating block.
if (IfBlock1)
- DomBlock->getInstList().splice(DomBlock->getTerminator(),
+ DomBlock->getInstList().splice(InsertPt,
IfBlock1->getInstList(), IfBlock1->begin(),
IfBlock1->getTerminator());
if (IfBlock2)
- DomBlock->getInstList().splice(DomBlock->getTerminator(),
+ DomBlock->getInstList().splice(InsertPt,
IfBlock2->getInstList(), IfBlock2->begin(),
IfBlock2->getTerminator());
Value *TrueVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse);
Value *FalseVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue);
- Value *NV;
- if (Value *V = SimplifySelectInst(IfCond, TrueVal, FalseVal, TD))
- NV = V;
- else if (TrueVal->getType()->isIntegerTy(1) && isa<ConstantInt>(TrueVal) &&
- cast<ConstantInt>(TrueVal)->isOne()) {
- if (Value *V = SimplifyOrInst(IfCond, FalseVal, TD))
- NV = V;
- else
- NV = BinaryOperator::CreateOr(IfCond, FalseVal, "", AfterPHIIt);
- } else
- NV = SelectInst::Create(IfCond, TrueVal, FalseVal, "", AfterPHIIt);
+ SelectInst *NV =
+ cast<SelectInst>(Builder.CreateSelect(IfCond, TrueVal, FalseVal, ""));
PN->replaceAllUsesWith(NV);
NV->takeName(PN);
PN->eraseFromParent();
}
+
+ // At this point, IfBlock1 and IfBlock2 are both empty, so our if statement
+ // has been flattened. Change DomBlock to jump directly to our new block to
+ // avoid other simplifycfg's kicking in on the diamond.
+ TerminatorInst *OldTI = DomBlock->getTerminator();
+ Builder.SetInsertPoint(OldTI);
+ Builder.CreateBr(BB);
+ OldTI->eraseFromParent();
return true;
}
/// SimplifyCondBranchToTwoReturns - If we found a conditional branch that goes
/// to two returning blocks, try to merge them together into one return,
/// introducing a select if the return values disagree.
-static bool SimplifyCondBranchToTwoReturns(BranchInst *BI) {
+static bool SimplifyCondBranchToTwoReturns(BranchInst *BI,
+ IRBuilder<> &Builder) {
assert(BI->isConditional() && "Must be a conditional branch");
BasicBlock *TrueSucc = BI->getSuccessor(0);
BasicBlock *FalseSucc = BI->getSuccessor(1);
if (!FalseSucc->getFirstNonPHIOrDbg()->isTerminator())
return false;
+ Builder.SetInsertPoint(BI);
// Okay, we found a branch that is going to two return nodes. If
// there is no return value for this function, just change the
// branch into a return.
if (FalseRet->getNumOperands() == 0) {
TrueSucc->removePredecessor(BI->getParent());
FalseSucc->removePredecessor(BI->getParent());
- ReturnInst::Create(BI->getContext(), 0, BI);
+ Builder.CreateRetVoid();
EraseTerminatorInstAndDCECond(BI);
return true;
}
} else if (isa<UndefValue>(TrueValue)) {
TrueValue = FalseValue;
} else {
- TrueValue = SelectInst::Create(BrCond, TrueValue,
- FalseValue, "retval", BI);
+ TrueValue = Builder.CreateSelect(BrCond, TrueValue,
+ FalseValue, "retval");
}
}
- Value *RI = !TrueValue ?
- ReturnInst::Create(BI->getContext(), BI) :
- ReturnInst::Create(BI->getContext(), TrueValue, BI);
+ Value *RI = !TrueValue ?
+ Builder.CreateRetVoid() : Builder.CreateRet(TrueValue);
+
(void) RI;
DEBUG(dbgs() << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:"
return true;
}
-/// FoldBranchToCommonDest - If this basic block is ONLY a setcc and a branch,
-/// and if a predecessor branches to us and one of our successors, fold the
-/// setcc into the predecessor and use logical operations to pick the right
-/// destination.
+/// FoldBranchToCommonDest - If this basic block is simple enough, and if a
+/// predecessor branches to us and one of our successors, fold the block into
+/// the predecessor and use logical operations to pick the right destination.
bool llvm::FoldBranchToCommonDest(BranchInst *BI) {
BasicBlock *BB = BI->getParent();
+
Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
if (Cond == 0 || (!isa<CmpInst>(Cond) && !isa<BinaryOperator>(Cond)) ||
Cond->getParent() != BB || !Cond->hasOneUse())
return false;
-
+
// Only allow this if the condition is a simple instruction that can be
// executed unconditionally. It must be in the same block as the branch, and
// must be at the front of the block.
BasicBlock::iterator FrontIt = BB->front();
+
// Ignore dbg intrinsics.
- while (isa<DbgInfoIntrinsic>(FrontIt))
- ++FrontIt;
+ while (isa<DbgInfoIntrinsic>(FrontIt)) ++FrontIt;
// Allow a single instruction to be hoisted in addition to the compare
// that feeds the branch. We later ensure that any values that _it_ uses
FrontIt->isSafeToSpeculativelyExecute()) {
BonusInst = &*FrontIt;
++FrontIt;
+
+ // Ignore dbg intrinsics.
+ while (isa<DbgInfoIntrinsic>(FrontIt)) ++FrontIt;
}
-
+
// Only a single bonus inst is allowed.
if (&*FrontIt != Cond)
return false;
// Make sure the instruction after the condition is the cond branch.
BasicBlock::iterator CondIt = Cond; ++CondIt;
+
// Ingore dbg intrinsics.
- while(isa<DbgInfoIntrinsic>(CondIt))
- ++CondIt;
- if (&*CondIt != BI) {
- assert (!isa<DbgInfoIntrinsic>(CondIt) && "Hey do not forget debug info!");
+ while (isa<DbgInfoIntrinsic>(CondIt)) ++CondIt;
+
+ if (&*CondIt != BI)
return false;
- }
// Cond is known to be a compare or binary operator. Check to make sure that
// neither operand is a potentially-trapping constant expression.
if (CE->canTrap())
return false;
-
// Finally, don't infinitely unroll conditional loops.
BasicBlock *TrueDest = BI->getSuccessor(0);
BasicBlock *FalseDest = BI->getSuccessor(1);
if (TrueDest == BB || FalseDest == BB)
return false;
-
+
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
BasicBlock *PredBlock = *PI;
BranchInst *PBI = dyn_cast<BranchInst>(PredBlock->getTerminator());
// Check that we have two conditional branches. If there is a PHI node in
// the common successor, verify that the same value flows in from both
// blocks.
- if (PBI == 0 || PBI->isUnconditional() ||
- !SafeToMergeTerminators(BI, PBI))
+ if (PBI == 0 || PBI->isUnconditional() || !SafeToMergeTerminators(BI, PBI))
continue;
+ // Determine if the two branches share a common destination.
+ Instruction::BinaryOps Opc;
+ bool InvertPredCond = false;
+
+ if (PBI->getSuccessor(0) == TrueDest)
+ Opc = Instruction::Or;
+ else if (PBI->getSuccessor(1) == FalseDest)
+ Opc = Instruction::And;
+ else if (PBI->getSuccessor(0) == FalseDest)
+ Opc = Instruction::And, InvertPredCond = true;
+ else if (PBI->getSuccessor(1) == TrueDest)
+ Opc = Instruction::Or, InvertPredCond = true;
+ else
+ continue;
+
// Ensure that any values used in the bonus instruction are also used
// by the terminator of the predecessor. This means that those values
// must already have been resolved, so we won't be inhibiting the
if (!UsedValues.empty()) return false;
}
-
- Instruction::BinaryOps Opc;
- bool InvertPredCond = false;
-
- if (PBI->getSuccessor(0) == TrueDest)
- Opc = Instruction::Or;
- else if (PBI->getSuccessor(1) == FalseDest)
- Opc = Instruction::And;
- else if (PBI->getSuccessor(0) == FalseDest)
- Opc = Instruction::And, InvertPredCond = true;
- else if (PBI->getSuccessor(1) == TrueDest)
- Opc = Instruction::Or, InvertPredCond = true;
- else
- continue;
DEBUG(dbgs() << "FOLDING BRANCH TO COMMON DEST:\n" << *PBI << *BB);
-
+ IRBuilder<> Builder(PBI);
+
// If we need to invert the condition in the pred block to match, do so now.
if (InvertPredCond) {
Value *NewCond = PBI->getCondition();
CmpInst *CI = cast<CmpInst>(NewCond);
CI->setPredicate(CI->getInversePredicate());
} else {
- NewCond = BinaryOperator::CreateNot(NewCond,
- PBI->getCondition()->getName()+".not", PBI);
+ NewCond = Builder.CreateNot(NewCond,
+ PBI->getCondition()->getName()+".not");
}
PBI->setCondition(NewCond);
New->takeName(Cond);
Cond->setName(New->getName()+".old");
- Value *NewCond = BinaryOperator::Create(Opc, PBI->getCondition(),
- New, "or.cond", PBI);
+ Instruction *NewCond =
+ cast<Instruction>(Builder.CreateBinOp(Opc, PBI->getCondition(),
+ New, "or.cond"));
PBI->setCondition(NewCond);
if (PBI->getSuccessor(0) == BB) {
AddPredecessorToBlock(TrueDest, PredBlock, BB);
AddPredecessorToBlock(FalseDest, PredBlock, BB);
PBI->setSuccessor(1, FalseDest);
}
+
+ // Copy any debug value intrinsics into the end of PredBlock.
+ for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
+ if (isa<DbgInfoIntrinsic>(*I))
+ I->clone()->insertBefore(PBI);
+
return true;
}
return false;
// in the constant and simplify the block result. Subsequent passes of
// simplifycfg will thread the block.
if (BlockIsSimpleEnoughToThreadThrough(BB)) {
+ pred_iterator PB = pred_begin(BB), PE = pred_end(BB);
PHINode *NewPN = PHINode::Create(Type::getInt1Ty(BB->getContext()),
+ std::distance(PB, PE),
BI->getCondition()->getName() + ".pr",
BB->begin());
// Okay, we're going to insert the PHI node. Since PBI is not the only
// predecessor, compute the PHI'd conditional value for all of the preds.
// Any predecessor where the condition is not computable we keep symbolic.
- for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
+ for (pred_iterator PI = PB; PI != PE; ++PI) {
BasicBlock *P = *PI;
if ((PBI = dyn_cast<BranchInst>(P->getTerminator())) &&
PBI != BI && PBI->isConditional() &&
}
DEBUG(dbgs() << *PBI->getParent()->getParent());
-
+
// BI may have other predecessors. Because of this, we leave
// it alone, but modify PBI.
// Make sure we get to CommonDest on True&True directions.
Value *PBICond = PBI->getCondition();
+ IRBuilder<true, NoFolder> Builder(PBI);
if (PBIOp)
- PBICond = BinaryOperator::CreateNot(PBICond,
- PBICond->getName()+".not",
- PBI);
+ PBICond = Builder.CreateNot(PBICond, PBICond->getName()+".not");
+
Value *BICond = BI->getCondition();
if (BIOp)
- BICond = BinaryOperator::CreateNot(BICond,
- BICond->getName()+".not",
- PBI);
+ BICond = Builder.CreateNot(BICond, BICond->getName()+".not");
+
// Merge the conditions.
- Value *Cond = BinaryOperator::CreateOr(PBICond, BICond, "brmerge", PBI);
+ Value *Cond = Builder.CreateOr(PBICond, BICond, "brmerge");
// Modify PBI to branch on the new condition to the new dests.
PBI->setCondition(Cond);
Value *PBIV = PN->getIncomingValue(PBBIdx);
if (BIV != PBIV) {
// Insert a select in PBI to pick the right value.
- Value *NV = SelectInst::Create(PBICond, PBIV, BIV,
- PBIV->getName()+".mux", PBI);
+ Value *NV = cast<SelectInst>
+ (Builder.CreateSelect(PBICond, PBIV, BIV, PBIV->getName()+".mux"));
PN->setIncomingValue(PBBIdx, NV);
}
}
return true;
}
-// SimplifyIndirectBrOnSelect - Replaces
-// (indirectbr (select cond, blockaddress(@fn, BlockA),
-// blockaddress(@fn, BlockB)))
-// with
-// (br cond, BlockA, BlockB).
-static bool SimplifyIndirectBrOnSelect(IndirectBrInst *IBI, SelectInst *SI) {
- // Check that both operands of the select are block addresses.
- BlockAddress *TBA = dyn_cast<BlockAddress>(SI->getTrueValue());
- BlockAddress *FBA = dyn_cast<BlockAddress>(SI->getFalseValue());
- if (!TBA || !FBA)
- return false;
-
- // Extract the actual blocks.
- BasicBlock *TrueBB = TBA->getBasicBlock();
- BasicBlock *FalseBB = FBA->getBasicBlock();
-
+// SimplifyTerminatorOnSelect - Simplifies a terminator by replacing it with a
+// branch to TrueBB if Cond is true or to FalseBB if Cond is false.
+// Takes care of updating the successors and removing the old terminator.
+// Also makes sure not to introduce new successors by assuming that edges to
+// non-successor TrueBBs and FalseBBs aren't reachable.
+static bool SimplifyTerminatorOnSelect(TerminatorInst *OldTerm, Value *Cond,
+ BasicBlock *TrueBB, BasicBlock *FalseBB){
// Remove any superfluous successor edges from the CFG.
// First, figure out which successors to preserve.
// If TrueBB and FalseBB are equal, only try to preserve one copy of that
BasicBlock *KeepEdge2 = TrueBB != FalseBB ? FalseBB : 0;
// Then remove the rest.
- for (unsigned I = 0, E = IBI->getNumSuccessors(); I != E; ++I) {
- BasicBlock *Succ = IBI->getSuccessor(I);
+ for (unsigned I = 0, E = OldTerm->getNumSuccessors(); I != E; ++I) {
+ BasicBlock *Succ = OldTerm->getSuccessor(I);
// Make sure only to keep exactly one copy of each edge.
if (Succ == KeepEdge1)
KeepEdge1 = 0;
else if (Succ == KeepEdge2)
KeepEdge2 = 0;
else
- Succ->removePredecessor(IBI->getParent());
+ Succ->removePredecessor(OldTerm->getParent());
}
+ IRBuilder<> Builder(OldTerm);
+ Builder.SetCurrentDebugLocation(OldTerm->getDebugLoc());
+
// Insert an appropriate new terminator.
if ((KeepEdge1 == 0) && (KeepEdge2 == 0)) {
if (TrueBB == FalseBB)
// We were only looking for one successor, and it was present.
// Create an unconditional branch to it.
- BranchInst::Create(TrueBB, IBI);
+ Builder.CreateBr(TrueBB);
else
// We found both of the successors we were looking for.
// Create a conditional branch sharing the condition of the select.
- BranchInst::Create(TrueBB, FalseBB, SI->getCondition(), IBI);
+ Builder.CreateCondBr(Cond, TrueBB, FalseBB);
} else if (KeepEdge1 && (KeepEdge2 || TrueBB == FalseBB)) {
// Neither of the selected blocks were successors, so this
- // indirectbr must be unreachable.
- new UnreachableInst(IBI->getContext(), IBI);
+ // terminator must be unreachable.
+ new UnreachableInst(OldTerm->getContext(), OldTerm);
} else {
// One of the selected values was a successor, but the other wasn't.
// Insert an unconditional branch to the one that was found;
// the edge to the one that wasn't must be unreachable.
if (KeepEdge1 == 0)
// Only TrueBB was found.
- BranchInst::Create(TrueBB, IBI);
+ Builder.CreateBr(TrueBB);
else
// Only FalseBB was found.
- BranchInst::Create(FalseBB, IBI);
+ Builder.CreateBr(FalseBB);
}
- EraseTerminatorInstAndDCECond(IBI);
+ EraseTerminatorInstAndDCECond(OldTerm);
return true;
}
+// SimplifySwitchOnSelect - Replaces
+// (switch (select cond, X, Y)) on constant X, Y
+// with a branch - conditional if X and Y lead to distinct BBs,
+// unconditional otherwise.
+static bool SimplifySwitchOnSelect(SwitchInst *SI, SelectInst *Select) {
+ // Check for constant integer values in the select.
+ ConstantInt *TrueVal = dyn_cast<ConstantInt>(Select->getTrueValue());
+ ConstantInt *FalseVal = dyn_cast<ConstantInt>(Select->getFalseValue());
+ if (!TrueVal || !FalseVal)
+ return false;
+
+ // Find the relevant condition and destinations.
+ Value *Condition = Select->getCondition();
+ BasicBlock *TrueBB = SI->getSuccessor(SI->findCaseValue(TrueVal));
+ BasicBlock *FalseBB = SI->getSuccessor(SI->findCaseValue(FalseVal));
+
+ // Perform the actual simplification.
+ return SimplifyTerminatorOnSelect(SI, Condition, TrueBB, FalseBB);
+}
+
+// SimplifyIndirectBrOnSelect - Replaces
+// (indirectbr (select cond, blockaddress(@fn, BlockA),
+// blockaddress(@fn, BlockB)))
+// with
+// (br cond, BlockA, BlockB).
+static bool SimplifyIndirectBrOnSelect(IndirectBrInst *IBI, SelectInst *SI) {
+ // Check that both operands of the select are block addresses.
+ BlockAddress *TBA = dyn_cast<BlockAddress>(SI->getTrueValue());
+ BlockAddress *FBA = dyn_cast<BlockAddress>(SI->getFalseValue());
+ if (!TBA || !FBA)
+ return false;
+
+ // Extract the actual blocks.
+ BasicBlock *TrueBB = TBA->getBasicBlock();
+ BasicBlock *FalseBB = FBA->getBasicBlock();
+
+ // Perform the actual simplification.
+ return SimplifyTerminatorOnSelect(IBI, SI->getCondition(), TrueBB, FalseBB);
+}
+
/// TryToSimplifyUncondBranchWithICmpInIt - This is called when we find an icmp
/// instruction (a seteq/setne with a constant) as the only instruction in a
/// block that ends with an uncond branch. We are looking for a very specific
/// 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) {
+ const TargetData *TD,
+ IRBuilder<> &Builder) {
BasicBlock *BB = ICI->getParent();
+
// If the block has any PHIs in it or the icmp has multiple uses, it is too
// complex.
if (isa<PHINode>(BB->begin()) || !ICI->hasOneUse()) return false;
SI->addCase(Cst, NewBB);
// NewBB branches to the phi block, add the uncond branch and the phi entry.
- BranchInst::Create(SuccBlock, NewBB);
+ Builder.SetInsertPoint(NewBB);
+ Builder.SetCurrentDebugLocation(SI->getDebugLoc());
+ Builder.CreateBr(SuccBlock);
PHIUse->addIncoming(NewCst, NewBB);
return true;
}
/// 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 TargetData *TD,
+ IRBuilder<> &Builder) {
Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
if (Cond == 0) return false;
std::vector<ConstantInt*> Values;
bool TrueWhenEqual = true;
Value *ExtraCase = 0;
+ unsigned UsedICmps = 0;
if (Cond->getOpcode() == Instruction::Or) {
- CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, true);
+ CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, true,
+ UsedICmps);
} else if (Cond->getOpcode() == Instruction::And) {
- CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, false);
+ CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, false,
+ UsedICmps);
TrueWhenEqual = false;
}
// If we didn't have a multiply compared value, fail.
if (CompVal == 0) return false;
+ // Avoid turning single icmps into a switch.
+ if (UsedICmps <= 1)
+ return false;
+
// There might be duplicate constants in the list, which the switch
// instruction can't handle, remove them now.
array_pod_sort(Values.begin(), Values.end(), ConstantIntSortPredicate);
BasicBlock *NewBB = BB->splitBasicBlock(BI, "switch.early.test");
// Remove the uncond branch added to the old block.
TerminatorInst *OldTI = BB->getTerminator();
-
+ Builder.SetInsertPoint(OldTI);
+
if (TrueWhenEqual)
- BranchInst::Create(EdgeBB, NewBB, ExtraCase, OldTI);
+ Builder.CreateCondBr(ExtraCase, EdgeBB, NewBB);
else
- BranchInst::Create(NewBB, EdgeBB, ExtraCase, OldTI);
+ Builder.CreateCondBr(ExtraCase, NewBB, EdgeBB);
OldTI->eraseFromParent();
<< "\nEXTRABB = " << *BB);
BB = NewBB;
}
-
+
+ Builder.SetInsertPoint(BI);
// Convert pointer to int before we switch.
if (CompVal->getType()->isPointerTy()) {
assert(TD && "Cannot switch on pointer without TargetData");
- CompVal = new PtrToIntInst(CompVal,
- TD->getIntPtrType(CompVal->getContext()),
- "magicptr", BI);
+ CompVal = Builder.CreatePtrToInt(CompVal,
+ TD->getIntPtrType(CompVal->getContext()),
+ "magicptr");
}
// Create the new switch instruction now.
- SwitchInst *New = SwitchInst::Create(CompVal, DefaultBB, Values.size(), BI);
-
+ SwitchInst *New = Builder.CreateSwitch(CompVal, DefaultBB, Values.size());
+
// Add all of the 'cases' to the switch instruction.
for (unsigned i = 0, e = Values.size(); i != e; ++i)
New->addCase(Values[i], EdgeBB);
return true;
}
-bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI) {
+bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder) {
BasicBlock *BB = RI->getParent();
if (!BB->getFirstNonPHIOrDbg()->isTerminator()) return false;
}
// If we found some, do the transformation!
- if (!UncondBranchPreds.empty()) {
+ if (!UncondBranchPreds.empty() && DupRet) {
while (!UncondBranchPreds.empty()) {
BasicBlock *Pred = UncondBranchPreds.pop_back_val();
DEBUG(dbgs() << "FOLDING: " << *BB
<< "INTO UNCOND BRANCH PRED: " << *Pred);
- Instruction *UncondBranch = Pred->getTerminator();
- // Clone the return and add it to the end of the predecessor.
- Instruction *NewRet = RI->clone();
- Pred->getInstList().push_back(NewRet);
-
- // If the return instruction returns a value, and if the value was a
- // PHI node in "BB", propagate the right value into the return.
- for (User::op_iterator i = NewRet->op_begin(), e = NewRet->op_end();
- i != e; ++i)
- if (PHINode *PN = dyn_cast<PHINode>(*i))
- if (PN->getParent() == BB)
- *i = PN->getIncomingValueForBlock(Pred);
-
- // Update any PHI nodes in the returning block to realize that we no
- // longer branch to them.
- BB->removePredecessor(Pred);
- UncondBranch->eraseFromParent();
+ (void)FoldReturnIntoUncondBranch(RI, BB, Pred);
}
// If we eliminated all predecessors of the block, delete the block now.
// Check to see if the non-BB successor is also a return block.
if (isa<ReturnInst>(BI->getSuccessor(0)->getTerminator()) &&
isa<ReturnInst>(BI->getSuccessor(1)->getTerminator()) &&
- SimplifyCondBranchToTwoReturns(BI))
+ SimplifyCondBranchToTwoReturns(BI, Builder))
return true;
}
return false;
}
-bool SimplifyCFGOpt::SimplifyUnwind(UnwindInst *UI) {
+bool SimplifyCFGOpt::SimplifyUnwind(UnwindInst *UI, IRBuilder<> &Builder) {
// Check to see if the first instruction in this block is just an unwind.
// If so, replace any invoke instructions which use this as an exception
// destination with call instructions.
if (II && II->getUnwindDest() == BB) {
// Insert a new branch instruction before the invoke, because this
// is now a fall through.
- BranchInst *BI = BranchInst::Create(II->getNormalDest(), II);
+ Builder.SetInsertPoint(II);
+ BranchInst *BI = Builder.CreateBr(II->getNormalDest());
Pred->getInstList().remove(II); // Take out of symbol table
// Insert the call now.
SmallVector<Value*,8> Args(II->op_begin(), II->op_end()-3);
- CallInst *CI = CallInst::Create(II->getCalledValue(),
- Args.begin(), Args.end(),
- II->getName(), BI);
+ Builder.SetInsertPoint(BI);
+ CallInst *CI = Builder.CreateCall(II->getCalledValue(),
+ Args.begin(), Args.end(),
+ II->getName());
CI->setCallingConv(II->getCallingConv());
CI->setAttributes(II->getAttributes());
// If the invoke produced a value, the Call now does instead.
if (LI->isVolatile())
break;
- // Delete this instruction
+ // Delete this instruction (any uses are guaranteed to be dead)
+ if (!BBI->use_empty())
+ BBI->replaceAllUsesWith(UndefValue::get(BBI->getType()));
BBI->eraseFromParent();
Changed = true;
}
SmallVector<BasicBlock*, 8> Preds(pred_begin(BB), pred_end(BB));
for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
TerminatorInst *TI = Preds[i]->getTerminator();
-
+ IRBuilder<> Builder(TI);
if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (BI->isUnconditional()) {
if (BI->getSuccessor(0) == BB) {
}
} else {
if (BI->getSuccessor(0) == BB) {
- BranchInst::Create(BI->getSuccessor(1), BI);
+ Builder.CreateBr(BI->getSuccessor(1));
EraseTerminatorInstAndDCECond(BI);
} else if (BI->getSuccessor(1) == BB) {
- BranchInst::Create(BI->getSuccessor(0), BI);
+ Builder.CreateBr(BI->getSuccessor(0));
EraseTerminatorInstAndDCECond(BI);
Changed = true;
}
// If the default value is unreachable, figure out the most popular
// destination and make it the default.
if (SI->getSuccessor(0) == BB) {
- std::map<BasicBlock*, unsigned> Popularity;
- for (unsigned i = 1, e = SI->getNumCases(); i != e; ++i)
- Popularity[SI->getSuccessor(i)]++;
-
+ std::map<BasicBlock*, std::pair<unsigned, unsigned> > Popularity;
+ for (unsigned i = 1, e = SI->getNumCases(); i != e; ++i) {
+ std::pair<unsigned, unsigned>& entry =
+ Popularity[SI->getSuccessor(i)];
+ if (entry.first == 0) {
+ entry.first = 1;
+ entry.second = i;
+ } else {
+ entry.first++;
+ }
+ }
+
// Find the most popular block.
unsigned MaxPop = 0;
+ unsigned MaxIndex = 0;
BasicBlock *MaxBlock = 0;
- for (std::map<BasicBlock*, unsigned>::iterator
+ for (std::map<BasicBlock*, std::pair<unsigned, unsigned> >::iterator
I = Popularity.begin(), E = Popularity.end(); I != E; ++I) {
- if (I->second > MaxPop) {
- MaxPop = I->second;
+ if (I->second.first > MaxPop ||
+ (I->second.first == MaxPop && MaxIndex > I->second.second)) {
+ MaxPop = I->second.first;
+ MaxIndex = I->second.second;
MaxBlock = I->first;
}
}
if (II->getUnwindDest() == BB) {
// Convert the invoke to a call instruction. This would be a good
// place to note that the call does not throw though.
- BranchInst *BI = BranchInst::Create(II->getNormalDest(), II);
+ BranchInst *BI = Builder.CreateBr(II->getNormalDest());
II->removeFromParent(); // Take out of symbol table
// Insert the call now...
SmallVector<Value*, 8> Args(II->op_begin(), II->op_end()-3);
- CallInst *CI = CallInst::Create(II->getCalledValue(),
- Args.begin(), Args.end(),
- II->getName(), BI);
+ Builder.SetInsertPoint(BI);
+ CallInst *CI = Builder.CreateCall(II->getCalledValue(),
+ Args.begin(), Args.end(),
+ II->getName());
CI->setCallingConv(II->getCallingConv());
CI->setAttributes(II->getAttributes());
// If the invoke produced a value, the call does now instead.
return Changed;
}
+/// TurnSwitchRangeIntoICmp - Turns a switch with that contains only a
+/// integer range comparison into a sub, an icmp and a branch.
+static bool TurnSwitchRangeIntoICmp(SwitchInst *SI, IRBuilder<> &Builder) {
+ assert(SI->getNumCases() > 2 && "Degenerate switch?");
+
+ // Make sure all cases point to the same destination and gather the values.
+ SmallVector<ConstantInt *, 16> Cases;
+ Cases.push_back(SI->getCaseValue(1));
+ for (unsigned I = 2, E = SI->getNumCases(); I != E; ++I) {
+ if (SI->getSuccessor(I-1) != SI->getSuccessor(I))
+ return false;
+ Cases.push_back(SI->getCaseValue(I));
+ }
+ assert(Cases.size() == SI->getNumCases()-1 && "Not all cases gathered");
-bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI) {
+ // Sort the case values, then check if they form a range we can transform.
+ array_pod_sort(Cases.begin(), Cases.end(), ConstantIntSortPredicate);
+ for (unsigned I = 1, E = Cases.size(); I != E; ++I) {
+ if (Cases[I-1]->getValue() != Cases[I]->getValue()+1)
+ return false;
+ }
+
+ Constant *Offset = ConstantExpr::getNeg(Cases.back());
+ Constant *NumCases = ConstantInt::get(Offset->getType(), SI->getNumCases()-1);
+
+ Value *Sub = SI->getCondition();
+ if (!Offset->isNullValue())
+ Sub = Builder.CreateAdd(Sub, Offset, Sub->getName()+".off");
+ Value *Cmp = Builder.CreateICmpULT(Sub, NumCases, "switch");
+ Builder.CreateCondBr(Cmp, SI->getSuccessor(1), SI->getDefaultDest());
+
+ // Prune obsolete incoming values off the successor's PHI nodes.
+ for (BasicBlock::iterator BBI = SI->getSuccessor(1)->begin();
+ isa<PHINode>(BBI); ++BBI) {
+ for (unsigned I = 0, E = SI->getNumCases()-2; I != E; ++I)
+ cast<PHINode>(BBI)->removeIncomingValue(SI->getParent());
+ }
+ SI->eraseFromParent();
+
+ return true;
+}
+
+/// EliminateDeadSwitchCases - Compute masked bits for the condition of a switch
+/// and use it to remove dead cases.
+static bool EliminateDeadSwitchCases(SwitchInst *SI) {
+ Value *Cond = SI->getCondition();
+ unsigned Bits = cast<IntegerType>(Cond->getType())->getBitWidth();
+ APInt KnownZero(Bits, 0), KnownOne(Bits, 0);
+ ComputeMaskedBits(Cond, APInt::getAllOnesValue(Bits), KnownZero, KnownOne);
+
+ // Gather dead cases.
+ SmallVector<ConstantInt*, 8> DeadCases;
+ for (unsigned I = 1, E = SI->getNumCases(); I != E; ++I) {
+ if ((SI->getCaseValue(I)->getValue() & KnownZero) != 0 ||
+ (SI->getCaseValue(I)->getValue() & KnownOne) != KnownOne) {
+ DeadCases.push_back(SI->getCaseValue(I));
+ DEBUG(dbgs() << "SimplifyCFG: switch case '"
+ << SI->getCaseValue(I)->getValue() << "' is dead.\n");
+ }
+ }
+
+ // Remove dead cases from the switch.
+ for (unsigned I = 0, E = DeadCases.size(); I != E; ++I) {
+ unsigned Case = SI->findCaseValue(DeadCases[I]);
+ // Prune unused values from PHI nodes.
+ SI->getSuccessor(Case)->removePredecessor(SI->getParent());
+ SI->removeCase(Case);
+ }
+
+ return !DeadCases.empty();
+}
+
+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;
// 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))
+ if (SimplifyEqualityComparisonWithOnlyPredecessor(SI, OnlyPred, Builder))
return SimplifyCFG(BB) | true;
-
+
+ Value *Cond = SI->getCondition();
+ if (SelectInst *Select = dyn_cast<SelectInst>(Cond))
+ if (SimplifySwitchOnSelect(SI, Select))
+ 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();
while (isa<DbgInfoIntrinsic>(BBI))
++BBI;
if (SI == &*BBI)
- if (FoldValueComparisonIntoPredecessors(SI))
+ if (FoldValueComparisonIntoPredecessors(SI, Builder))
return SimplifyCFG(BB) | true;
-
+
+ // Try to transform the switch into an icmp and a branch.
+ if (TurnSwitchRangeIntoICmp(SI, Builder))
+ return SimplifyCFG(BB) | true;
+
+ // Remove unreachable cases.
+ if (EliminateDeadSwitchCases(SI))
+ return SimplifyCFG(BB) | true;
+
return false;
}
return Changed;
}
-bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI) {
+bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder){
BasicBlock *BB = BI->getParent();
// If the Terminator is the only non-phi instruction, simplify the block.
if (ICI->isEquality() && isa<ConstantInt>(ICI->getOperand(1))) {
for (++I; isa<DbgInfoIntrinsic>(I); ++I)
;
- if (I->isTerminator() && TryToSimplifyUncondBranchWithICmpInIt(ICI, TD))
+ if (I->isTerminator()
+ && TryToSimplifyUncondBranchWithICmpInIt(ICI, TD, Builder))
return true;
}
}
-bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI) {
+bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) {
BasicBlock *BB = BI->getParent();
// Conditional branch
// see if that predecessor totally determines the outcome of this
// switch.
if (BasicBlock *OnlyPred = BB->getSinglePredecessor())
- if (SimplifyEqualityComparisonWithOnlyPredecessor(BI, OnlyPred))
+ if (SimplifyEqualityComparisonWithOnlyPredecessor(BI, OnlyPred, Builder))
return SimplifyCFG(BB) | true;
// This block must be empty, except for the setcond inst, if it exists.
while (isa<DbgInfoIntrinsic>(I))
++I;
if (&*I == BI) {
- if (FoldValueComparisonIntoPredecessors(BI))
+ if (FoldValueComparisonIntoPredecessors(BI, Builder))
return SimplifyCFG(BB) | true;
} else if (&*I == cast<Instruction>(BI->getCondition())){
++I;
// Ignore dbg intrinsics.
while (isa<DbgInfoIntrinsic>(I))
++I;
- if (&*I == BI && FoldValueComparisonIntoPredecessors(BI))
+ if (&*I == BI && FoldValueComparisonIntoPredecessors(BI, Builder))
return SimplifyCFG(BB) | true;
}
}
// Try to turn "br (X == 0 | X == 1), T, F" into a switch instruction.
- if (SimplifyBranchOnICmpChain(BI, TD))
+ if (SimplifyBranchOnICmpChain(BI, TD, Builder))
return true;
// We have a conditional branch to two blocks that are only reachable
if (MergeBlockIntoPredecessor(BB))
return true;
+ IRBuilder<> Builder(BB);
+
// If there is a trivial two-entry PHI node in this basic block, and we can
// eliminate it, do so now.
if (PHINode *PN = dyn_cast<PHINode>(BB->begin()))
if (PN->getNumIncomingValues() == 2)
Changed |= FoldTwoEntryPHINode(PN, TD);
+ Builder.SetInsertPoint(BB->getTerminator());
if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator())) {
if (BI->isUnconditional()) {
- if (SimplifyUncondBranch(BI)) return true;
+ if (SimplifyUncondBranch(BI, Builder)) return true;
} else {
- if (SimplifyCondBranch(BI)) return true;
+ if (SimplifyCondBranch(BI, Builder)) return true;
}
} else if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
- if (SimplifyReturn(RI)) return true;
+ if (SimplifyReturn(RI, Builder)) return true;
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(BB->getTerminator())) {
- if (SimplifySwitch(SI)) return true;
+ if (SimplifySwitch(SI, Builder)) return true;
} else if (UnreachableInst *UI =
dyn_cast<UnreachableInst>(BB->getTerminator())) {
if (SimplifyUnreachable(UI)) return true;
} else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
- if (SimplifyUnwind(UI)) return true;
+ if (SimplifyUnwind(UI, Builder)) return true;
} else if (IndirectBrInst *IBI =
dyn_cast<IndirectBrInst>(BB->getTerminator())) {
if (SimplifyIndirectBr(IBI)) return true;
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