#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/STLExtras.h"
#include <algorithm>
-#include <functional>
#include <set>
#include <map>
using namespace llvm;
class SimplifyCFGOpt {
const TargetData *const TD;
- ConstantInt *GetConstantInt(Value *V);
- Value *GatherConstantSetEQs(Value *V, std::vector<ConstantInt*> &Values);
- Value *GatherConstantSetNEs(Value *V, std::vector<ConstantInt*> &Values);
- bool GatherValueComparisons(Instruction *Cond, Value *&CompVal,
- std::vector<ConstantInt*> &Values);
Value *isValueEqualityComparison(TerminatorInst *TI);
BasicBlock *GetValueEqualityComparisonCases(TerminatorInst *TI,
std::vector<std::pair<ConstantInt*, BasicBlock*> > &Cases);
BasicBlock *Pred);
bool FoldValueComparisonIntoPredecessors(TerminatorInst *TI);
+ bool SimplifyReturn(ReturnInst *RI);
+ bool SimplifyUnwind(UnwindInst *UI);
+ bool SimplifyUnreachable(UnreachableInst *UI);
+ bool SimplifySwitch(SwitchInst *SI);
+ bool SimplifyIndirectBr(IndirectBrInst *IBI);
+ bool SimplifyUncondBranch(BranchInst *BI);
+ bool SimplifyCondBranch(BranchInst *BI);
+
public:
explicit SimplifyCFGOpt(const TargetData *td) : TD(td) {}
bool run(BasicBlock *BB);
/// GetConstantInt - Extract ConstantInt from value, looking through IntToPtr
/// and PointerNullValue. Return NULL if value is not a constant int.
-ConstantInt *SimplifyCFGOpt::GetConstantInt(Value *V) {
+static ConstantInt *GetConstantInt(Value *V, const TargetData *TD) {
// Normal constant int.
ConstantInt *CI = dyn_cast<ConstantInt>(V);
if (CI || !TD || !isa<Constant>(V) || !V->getType()->isPointerTy())
return 0;
}
-/// GatherConstantSetEQs - Given a potentially 'or'd together collection of
-/// icmp_eq instructions that compare a value against a constant, return the
-/// value being compared, and stick the constant into the Values vector.
-Value *SimplifyCFGOpt::
-GatherConstantSetEQs(Value *V, std::vector<ConstantInt*> &Values) {
- if (Instruction *Inst = dyn_cast<Instruction>(V)) {
- if (Inst->getOpcode() == Instruction::ICmp &&
- cast<ICmpInst>(Inst)->getPredicate() == ICmpInst::ICMP_EQ) {
- if (ConstantInt *C = GetConstantInt(Inst->getOperand(1))) {
- Values.push_back(C);
- return Inst->getOperand(0);
- } else if (ConstantInt *C = GetConstantInt(Inst->getOperand(0))) {
- Values.push_back(C);
- return Inst->getOperand(1);
+/// GatherConstantCompares - Given a potentially 'or'd or 'and'd together
+/// collection of icmp eq/ne instructions that compare a value against a
+/// constant, return the value being compared, and stick the constant into the
+/// Values vector.
+static Value *
+GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra,
+ const TargetData *TD, bool isEQ) {
+ 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)) {
+ Vals.push_back(C);
+ return I->getOperand(0);
}
- } else if (Inst->getOpcode() == Instruction::Or) {
- if (Value *LHS = GatherConstantSetEQs(Inst->getOperand(0), Values))
- if (Value *RHS = GatherConstantSetEQs(Inst->getOperand(1), Values))
- if (LHS == RHS)
- return LHS;
- }
+ return 0;
}
- return 0;
-}
+
+ // Otherwise, we can only handle an | or &, depending on isEQ.
+ if (I->getOpcode() != (isEQ ? Instruction::Or : Instruction::And))
+ return 0;
+
+ unsigned NumValsBeforeLHS = Vals.size();
+ if (Value *LHS = GatherConstantCompares(I->getOperand(0), Vals, Extra, TD,
+ isEQ)) {
+ unsigned NumVals = Vals.size();
+ if (Value *RHS = GatherConstantCompares(I->getOperand(1), Vals, Extra, TD,
+ isEQ)) {
+ if (LHS == RHS)
+ return LHS;
+ }
+ Vals.resize(NumVals);
-/// GatherConstantSetNEs - Given a potentially 'and'd together collection of
-/// setne instructions that compare a value against a constant, return the value
-/// being compared, and stick the constant into the Values vector.
-Value *SimplifyCFGOpt::
-GatherConstantSetNEs(Value *V, std::vector<ConstantInt*> &Values) {
- if (Instruction *Inst = dyn_cast<Instruction>(V)) {
- if (Inst->getOpcode() == Instruction::ICmp &&
- cast<ICmpInst>(Inst)->getPredicate() == ICmpInst::ICMP_NE) {
- if (ConstantInt *C = GetConstantInt(Inst->getOperand(1))) {
- Values.push_back(C);
- return Inst->getOperand(0);
- } else if (ConstantInt *C = GetConstantInt(Inst->getOperand(0))) {
- Values.push_back(C);
- return Inst->getOperand(1);
- }
- } else if (Inst->getOpcode() == Instruction::And) {
- if (Value *LHS = GatherConstantSetNEs(Inst->getOperand(0), Values))
- if (Value *RHS = GatherConstantSetNEs(Inst->getOperand(1), Values))
- if (LHS == RHS)
- return LHS;
+ // The RHS of the or/and can't be folded in and we haven't used "Extra" yet,
+ // set it and return success.
+ if (Extra == 0 || Extra == I->getOperand(1)) {
+ Extra = I->getOperand(1);
+ return LHS;
}
+
+ Vals.resize(NumValsBeforeLHS);
+ return 0;
}
- return 0;
-}
-
-/// GatherValueComparisons - If the specified Cond is an 'and' or 'or' of a
-/// bunch of comparisons of one value against constants, return the value and
-/// the constants being compared.
-bool SimplifyCFGOpt::GatherValueComparisons(Instruction *Cond, Value *&CompVal,
- std::vector<ConstantInt*> &Values) {
- if (Cond->getOpcode() == Instruction::Or) {
- CompVal = GatherConstantSetEQs(Cond, Values);
-
- // Return true to indicate that the condition is true if the CompVal is
- // equal to one of the constants.
- return true;
- } else if (Cond->getOpcode() == Instruction::And) {
- CompVal = GatherConstantSetNEs(Cond, Values);
-
- // Return false to indicate that the condition is false if the CompVal is
- // equal to one of the constants.
- return false;
+
+ // If the LHS can't be folded in, but Extra is available and RHS can, try to
+ // use LHS as Extra.
+ if (Extra == 0 || Extra == I->getOperand(0)) {
+ Extra = I->getOperand(0);
+ if (Value *RHS = GatherConstantCompares(I->getOperand(1), Vals, Extra, TD,
+ isEQ))
+ return RHS;
+ Vals.resize(NumValsBeforeLHS);
+ Extra = 0;
}
- return false;
+
+ return 0;
}
-
+
static void EraseTerminatorInstAndDCECond(TerminatorInst *TI) {
Instruction* Cond = 0;
if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
} else if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
if (BI->isConditional())
Cond = dyn_cast<Instruction>(BI->getCondition());
+ } else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(TI)) {
+ Cond = dyn_cast<Instruction>(IBI->getAddress());
}
TI->eraseFromParent();
if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition()))
if ((ICI->getPredicate() == ICmpInst::ICMP_EQ ||
ICI->getPredicate() == ICmpInst::ICMP_NE) &&
- GetConstantInt(ICI->getOperand(1)))
+ GetConstantInt(ICI->getOperand(1), TD))
CV = ICI->getOperand(0);
// Unwrap any lossless ptrtoint cast.
BranchInst *BI = cast<BranchInst>(TI);
ICmpInst *ICI = cast<ICmpInst>(BI->getCondition());
- Cases.push_back(std::make_pair(GetConstantInt(ICI->getOperand(1)),
+ Cases.push_back(std::make_pair(GetConstantInt(ICI->getOperand(1), TD),
BI->getSuccessor(ICI->getPredicate() ==
ICmpInst::ICMP_NE)));
return BI->getSuccessor(ICI->getPredicate() == ICmpInst::ICMP_EQ);
}
// Otherwise, just sort both lists and compare element by element.
- std::sort(V1->begin(), V1->end());
- std::sort(V2->begin(), V2->end());
+ array_pod_sort(V1->begin(), V1->end());
+ array_pod_sort(V2->begin(), V2->end());
unsigned i1 = 0, i2 = 0, e1 = V1->size(), e2 = V2->size();
while (i1 != e1 && i2 != e2) {
if ((*V1)[i1].first == (*V2)[i2].first)
// If we are here, we know that the value is none of those cases listed in
// PredCases. If there are any cases in ThisCases that are in PredCases, we
// can simplify TI.
- if (ValuesOverlap(PredCases, ThisCases)) {
- if (isa<BranchInst>(TI)) {
- // Okay, one of the successors of this condbr is dead. Convert it to a
- // uncond br.
- assert(ThisCases.size() == 1 && "Branch can only have one case!");
- // Insert the new branch.
- Instruction *NI = BranchInst::Create(ThisDef, TI);
- (void) NI;
-
- // Remove PHI node entries for the dead edge.
- ThisCases[0].second->removePredecessor(TI->getParent());
-
- DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
- << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n");
-
- EraseTerminatorInstAndDCECond(TI);
- return true;
-
- } else {
- SwitchInst *SI = cast<SwitchInst>(TI);
- // Okay, TI has cases that are statically dead, prune them away.
- SmallPtrSet<Constant*, 16> DeadCases;
- for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
- DeadCases.insert(PredCases[i].first);
+ if (!ValuesOverlap(PredCases, ThisCases))
+ return false;
+
+ if (isa<BranchInst>(TI)) {
+ // Okay, one of the successors of this condbr is dead. Convert it to a
+ // uncond br.
+ assert(ThisCases.size() == 1 && "Branch can only have one case!");
+ // Insert the new branch.
+ Instruction *NI = BranchInst::Create(ThisDef, TI);
+ (void) NI;
- DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
- << "Through successor TI: " << *TI);
+ // Remove PHI node entries for the dead edge.
+ ThisCases[0].second->removePredecessor(TI->getParent());
- for (unsigned i = SI->getNumCases()-1; i != 0; --i)
- if (DeadCases.count(SI->getCaseValue(i))) {
- SI->getSuccessor(i)->removePredecessor(TI->getParent());
- SI->removeCase(i);
- }
+ DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
+ << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n");
- DEBUG(dbgs() << "Leaving: " << *TI << "\n");
- return true;
- }
+ EraseTerminatorInstAndDCECond(TI);
+ return true;
}
-
- } else {
- // Otherwise, TI's block must correspond to some matched value. Find out
- // which value (or set of values) this is.
- ConstantInt *TIV = 0;
- BasicBlock *TIBB = TI->getParent();
+
+ SwitchInst *SI = cast<SwitchInst>(TI);
+ // Okay, TI has cases that are statically dead, prune them away.
+ SmallPtrSet<Constant*, 16> DeadCases;
for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
- if (PredCases[i].second == TIBB) {
- if (TIV == 0)
- TIV = PredCases[i].first;
- else
- return false; // Cannot handle multiple values coming to this block.
- }
- assert(TIV && "No edge from pred to succ?");
-
- // Okay, we found the one constant that our value can be if we get into TI's
- // BB. Find out which successor will unconditionally be branched to.
- BasicBlock *TheRealDest = 0;
- for (unsigned i = 0, e = ThisCases.size(); i != e; ++i)
- if (ThisCases[i].first == TIV) {
- TheRealDest = ThisCases[i].second;
- break;
+ DeadCases.insert(PredCases[i].first);
+
+ DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
+ << "Through successor TI: " << *TI);
+
+ for (unsigned i = SI->getNumCases()-1; i != 0; --i)
+ if (DeadCases.count(SI->getCaseValue(i))) {
+ SI->getSuccessor(i)->removePredecessor(TI->getParent());
+ SI->removeCase(i);
}
- // If not handled by any explicit cases, it is handled by the default case.
- if (TheRealDest == 0) TheRealDest = ThisDef;
+ DEBUG(dbgs() << "Leaving: " << *TI << "\n");
+ return true;
+ }
+
+ // Otherwise, TI's block must correspond to some matched value. Find out
+ // which value (or set of values) this is.
+ ConstantInt *TIV = 0;
+ BasicBlock *TIBB = TI->getParent();
+ for (unsigned i = 0, e = PredCases.size(); i != e; ++i)
+ if (PredCases[i].second == TIBB) {
+ if (TIV != 0)
+ return false; // Cannot handle multiple values coming to this block.
+ TIV = PredCases[i].first;
+ }
+ assert(TIV && "No edge from pred to succ?");
+
+ // Okay, we found the one constant that our value can be if we get into TI's
+ // BB. Find out which successor will unconditionally be branched to.
+ BasicBlock *TheRealDest = 0;
+ for (unsigned i = 0, e = ThisCases.size(); i != e; ++i)
+ if (ThisCases[i].first == TIV) {
+ TheRealDest = ThisCases[i].second;
+ break;
+ }
- // Remove PHI node entries for dead edges.
- BasicBlock *CheckEdge = TheRealDest;
- for (succ_iterator SI = succ_begin(TIBB), e = succ_end(TIBB); SI != e; ++SI)
- if (*SI != CheckEdge)
- (*SI)->removePredecessor(TIBB);
- else
- CheckEdge = 0;
+ // If not handled by any explicit cases, it is handled by the default case.
+ if (TheRealDest == 0) TheRealDest = ThisDef;
- // Insert the new branch.
- Instruction *NI = BranchInst::Create(TheRealDest, TI);
- (void) NI;
+ // Remove PHI node entries for dead edges.
+ BasicBlock *CheckEdge = TheRealDest;
+ for (succ_iterator SI = succ_begin(TIBB), e = succ_end(TIBB); SI != e; ++SI)
+ if (*SI != CheckEdge)
+ (*SI)->removePredecessor(TIBB);
+ else
+ CheckEdge = 0;
- DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
- << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n");
+ // Insert the new branch.
+ Instruction *NI = BranchInst::Create(TheRealDest, TI);
+ (void) NI;
- EraseTerminatorInstAndDCECond(TI);
- return true;
- }
- return false;
+ DEBUG(dbgs() << "Threading pred instr: " << *Pred->getTerminator()
+ << "Through successor TI: " << *TI << "Leaving: " << *NI << "\n");
+
+ EraseTerminatorInstAndDCECond(TI);
+ return true;
}
namespace {
};
}
+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());
+}
+
/// 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
(PN = dyn_cast<PHINode>(BBI)); ++BBI) {
Value *BB1V = PN->getIncomingValueForBlock(BB1);
Value *BB2V = PN->getIncomingValueForBlock(BB2);
- if (BB1V != BB2V) {
- // 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);
- // 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)
- PN->setIncomingValue(i, SI);
- }
+ if (BB1V == BB2V) continue;
+
+ // 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);
+ // 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)
+ PN->setIncomingValue(i, SI);
}
}
BBI != BBE; ++BBI) {
Instruction *I = BBI;
// Skip debug info.
- if (isa<DbgInfoIntrinsic>(I)) continue;
- if (I == Term) break;
+ if (isa<DbgInfoIntrinsic>(I)) continue;
+ if (I == Term) break;
- if (!HInst)
- HInst = I;
- else
+ if (HInst)
return false;
+ HInst = I;
}
if (!HInst)
return false;
// Be conservative for now. FP select instruction can often be expensive.
Value *BrCond = BI->getCondition();
- if (isa<Instruction>(BrCond) &&
- cast<Instruction>(BrCond)->getOpcode() == Instruction::FCmp)
+ if (isa<FCmpInst>(BrCond))
return false;
// If BB1 is actually on the false edge of the conditional branch, remember
for(Value::use_iterator UI = BrCond->use_begin(), UE = BrCond->use_end();
UI != UE; ++UI) {
Instruction *Use = cast<Instruction>(*UI);
- if (BB1Insns.count(Use)) {
- // If BrCond uses the instruction that place it just before
- // branch instruction.
- InsertPos = BI;
- break;
- }
+ if (!BB1Insns.count(Use)) continue;
+
+ // If BrCond uses the instruction that place it just before
+ // branch instruction.
+ InsertPos = BI;
+ break;
}
} else
InsertPos = BI;
for (unsigned i = 0, e = PHIUses.size(); i != e; ++i) {
PHINode *PN = PHIUses[i];
for (unsigned j = 0, ee = PN->getNumIncomingValues(); j != ee; ++j)
- if (PN->getIncomingBlock(j) == BB1 ||
- PN->getIncomingBlock(j) == BIParent)
+ if (PN->getIncomingBlock(j) == BB1 || PN->getIncomingBlock(j) == BIParent)
PN->setIncomingValue(j, SI);
}
// 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) {
- ConstantInt *CB;
- if ((CB = dyn_cast<ConstantInt>(PN->getIncomingValue(i))) &&
- CB->getType()->isIntegerTy(1)) {
- // Okay, we now know that all edges from PredBB should be revectored to
- // branch to RealDest.
- BasicBlock *PredBB = PN->getIncomingBlock(i);
- BasicBlock *RealDest = BI->getSuccessor(!CB->getZExtValue());
+ ConstantInt *CB = dyn_cast<ConstantInt>(PN->getIncomingValue(i));
+ if (CB == 0 || !CB->getType()->isIntegerTy(1)) continue;
+
+ // Okay, we now know that all edges from PredBB should be revectored to
+ // branch to RealDest.
+ BasicBlock *PredBB = PN->getIncomingBlock(i);
+ BasicBlock *RealDest = BI->getSuccessor(!CB->getZExtValue());
+
+ if (RealDest == BB) continue; // Skip self loops.
+
+ // The dest block might have PHI nodes, other predecessors and other
+ // difficult cases. Instead of being smart about this, just insert a new
+ // block that jumps to the destination block, effectively splitting
+ // the edge we are about to create.
+ BasicBlock *EdgeBB = BasicBlock::Create(BB->getContext(),
+ RealDest->getName()+".critedge",
+ RealDest->getParent(), RealDest);
+ BranchInst::Create(RealDest, EdgeBB);
+ PHINode *PN;
+ for (BasicBlock::iterator BBI = RealDest->begin();
+ (PN = dyn_cast<PHINode>(BBI)); ++BBI) {
+ Value *V = PN->getIncomingValueForBlock(BB);
+ PN->addIncoming(V, EdgeBB);
+ }
+
+ // BB may have instructions that are being threaded over. Clone these
+ // instructions into EdgeBB. We know that there will be no uses of the
+ // cloned instructions outside of EdgeBB.
+ BasicBlock::iterator InsertPt = EdgeBB->begin();
+ DenseMap<Value*, Value*> TranslateMap; // Track translated values.
+ for (BasicBlock::iterator BBI = BB->begin(); &*BBI != BI; ++BBI) {
+ if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
+ TranslateMap[PN] = PN->getIncomingValueForBlock(PredBB);
+ continue;
+ }
+ // Clone the instruction.
+ Instruction *N = BBI->clone();
+ if (BBI->hasName()) N->setName(BBI->getName()+".c");
- if (RealDest == BB) continue; // Skip self loops.
+ // Update operands due to translation.
+ for (User::op_iterator i = N->op_begin(), e = N->op_end();
+ i != e; ++i) {
+ DenseMap<Value*, Value*>::iterator PI = TranslateMap.find(*i);
+ if (PI != TranslateMap.end())
+ *i = PI->second;
+ }
- // The dest block might have PHI nodes, other predecessors and other
- // difficult cases. Instead of being smart about this, just insert a new
- // block that jumps to the destination block, effectively splitting
- // the edge we are about to create.
- BasicBlock *EdgeBB = BasicBlock::Create(BB->getContext(),
- RealDest->getName()+".critedge",
- RealDest->getParent(), RealDest);
- BranchInst::Create(RealDest, EdgeBB);
- PHINode *PN;
- for (BasicBlock::iterator BBI = RealDest->begin();
- (PN = dyn_cast<PHINode>(BBI)); ++BBI) {
- Value *V = PN->getIncomingValueForBlock(BB);
- PN->addIncoming(V, EdgeBB);
+ // Check for trivial simplification.
+ if (Constant *C = ConstantFoldInstruction(N)) {
+ TranslateMap[BBI] = C;
+ delete N; // Constant folded away, don't need actual inst
+ } else {
+ // Insert the new instruction into its new home.
+ EdgeBB->getInstList().insert(InsertPt, N);
+ if (!BBI->use_empty())
+ TranslateMap[BBI] = N;
}
+ }
- // BB may have instructions that are being threaded over. Clone these
- // instructions into EdgeBB. We know that there will be no uses of the
- // cloned instructions outside of EdgeBB.
- BasicBlock::iterator InsertPt = EdgeBB->begin();
- std::map<Value*, Value*> TranslateMap; // Track translated values.
- for (BasicBlock::iterator BBI = BB->begin(); &*BBI != BI; ++BBI) {
- if (PHINode *PN = dyn_cast<PHINode>(BBI)) {
- TranslateMap[PN] = PN->getIncomingValueForBlock(PredBB);
- } else {
- // Clone the instruction.
- Instruction *N = BBI->clone();
- if (BBI->hasName()) N->setName(BBI->getName()+".c");
-
- // Update operands due to translation.
- for (User::op_iterator i = N->op_begin(), e = N->op_end();
- i != e; ++i) {
- std::map<Value*, Value*>::iterator PI =
- TranslateMap.find(*i);
- if (PI != TranslateMap.end())
- *i = PI->second;
- }
-
- // Check for trivial simplification.
- if (Constant *C = ConstantFoldInstruction(N)) {
- TranslateMap[BBI] = C;
- delete N; // Constant folded away, don't need actual inst
- } else {
- // Insert the new instruction into its new home.
- EdgeBB->getInstList().insert(InsertPt, N);
- if (!BBI->use_empty())
- TranslateMap[BBI] = N;
- }
- }
+ // Loop over all of the edges from PredBB to BB, changing them to branch
+ // to EdgeBB instead.
+ TerminatorInst *PredBBTI = PredBB->getTerminator();
+ for (unsigned i = 0, e = PredBBTI->getNumSuccessors(); i != e; ++i)
+ if (PredBBTI->getSuccessor(i) == BB) {
+ BB->removePredecessor(PredBB);
+ PredBBTI->setSuccessor(i, EdgeBB);
}
-
- // Loop over all of the edges from PredBB to BB, changing them to branch
- // to EdgeBB instead.
- TerminatorInst *PredBBTI = PredBB->getTerminator();
- for (unsigned i = 0, e = PredBBTI->getNumSuccessors(); i != e; ++i)
- if (PredBBTI->getSuccessor(i) == BB) {
- BB->removePredecessor(PredBB);
- PredBBTI->setSuccessor(i, EdgeBB);
- }
-
- // Recurse, simplifying any other constants.
- return FoldCondBranchOnPHI(BI) | true;
- }
+
+ // Recurse, simplifying any other constants.
+ return FoldCondBranchOnPHI(BI) | true;
}
return false;
// Move all 'aggressive' instructions, which are defined in the
// conditional parts of the if's up to the dominating block.
- if (IfBlock1) {
+ if (IfBlock1)
DomBlock->getInstList().splice(DomBlock->getTerminator(),
- IfBlock1->getInstList(),
- IfBlock1->begin(),
+ IfBlock1->getInstList(), IfBlock1->begin(),
IfBlock1->getTerminator());
- }
- if (IfBlock2) {
+ if (IfBlock2)
DomBlock->getInstList().splice(DomBlock->getTerminator(),
- IfBlock2->getInstList(),
- IfBlock2->begin(),
+ IfBlock2->getInstList(), IfBlock2->begin(),
IfBlock2->getTerminator());
- }
while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
// Change the PHI node into a select instruction.
- Value *TrueVal =
- PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse);
- Value *FalseVal =
- PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue);
+ Value *TrueVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse);
+ Value *FalseVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue);
Value *NV = SelectInst::Create(IfCond, TrueVal, FalseVal, "", AfterPHIIt);
PN->replaceAllUsesWith(NV);
return true;
}
-/// isTerminatorFirstRelevantInsn - Return true if Term is very first
-/// instruction ignoring Phi nodes and dbg intrinsics.
-static bool isTerminatorFirstRelevantInsn(BasicBlock *BB, Instruction *Term) {
- BasicBlock::iterator BBI = Term;
- while (BBI != BB->begin()) {
- --BBI;
- if (!isa<DbgInfoIntrinsic>(BBI))
- break;
- }
-
- if (isa<PHINode>(BBI) || &*BBI == Term || isa<DbgInfoIntrinsic>(BBI))
- return true;
- return false;
-}
-
/// 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.
// Check to ensure both blocks are empty (just a return) or optionally empty
// with PHI nodes. If there are other instructions, merging would cause extra
// computation on one path or the other.
- if (!isTerminatorFirstRelevantInsn(TrueSucc, TrueRet))
+ if (!TrueSucc->getFirstNonPHIOrDbg()->isTerminator())
return false;
- if (!isTerminatorFirstRelevantInsn(FalseSucc, FalseRet))
+ if (!FalseSucc->getFirstNonPHIOrDbg()->isTerminator())
return false;
// Okay, we found a branch that is going to two return nodes. If
// must be at the front of the block.
BasicBlock::iterator FrontIt = BB->front();
// Ignore dbg intrinsics.
- while(isa<DbgInfoIntrinsic>(FrontIt))
+ while (isa<DbgInfoIntrinsic>(FrontIt))
++FrontIt;
// Allow a single instruction to be hoisted in addition to the compare
UsedValues.erase(Pair.first);
if (UsedValues.empty()) break;
- if (Instruction* I = dyn_cast<Instruction>(Pair.first)) {
+ if (Instruction *I = dyn_cast<Instruction>(Pair.first)) {
for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end();
OI != OE; ++OI)
Worklist.push_back(std::make_pair(OI->get(), Pair.second+1));
// If we need to invert the condition in the pred block to match, do so now.
if (InvertPredCond) {
- Value *NewCond =
- BinaryOperator::CreateNot(PBI->getCondition(),
+ Value *NewCond = PBI->getCondition();
+
+ if (NewCond->hasOneUse() && isa<CmpInst>(NewCond)) {
+ CmpInst *CI = cast<CmpInst>(NewCond);
+ CI->setPredicate(CI->getInversePredicate());
+ } else {
+ NewCond = BinaryOperator::CreateNot(NewCond,
PBI->getCondition()->getName()+".not", PBI);
+ }
+
PBI->setCondition(NewCond);
BasicBlock *OldTrue = PBI->getSuccessor(0);
BasicBlock *OldFalse = PBI->getSuccessor(1);
AddPredecessorToBlock(FalseDest, PredBlock, BB);
PBI->setSuccessor(1, FalseDest);
}
- return true;
+ return SimplifyCFG(PBI->getParent()) | true;
}
return false;
}
return true;
}
-bool SimplifyCFGOpt::run(BasicBlock *BB) {
- bool Changed = false;
- Function *M = BB->getParent();
+// 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;
- assert(BB && BB->getParent() && "Block not embedded in function!");
- assert(BB->getTerminator() && "Degenerate basic block encountered!");
- assert(&BB->getParent()->getEntryBlock() != BB &&
- "Can't Simplify entry block!");
+ // Extract the actual blocks.
+ BasicBlock *TrueBB = TBA->getBasicBlock();
+ BasicBlock *FalseBB = FBA->getBasicBlock();
+
+ // 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
+ // successor.
+ BasicBlock *KeepEdge1 = TrueBB;
+ 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);
+ // 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());
+ }
- // Remove basic blocks that have no predecessors... or that just have themself
- // as a predecessor. These are unreachable.
- if (pred_begin(BB) == pred_end(BB) || BB->getSinglePredecessor() == BB) {
- DEBUG(dbgs() << "Removing BB: \n" << *BB);
- DeleteDeadBlock(BB);
- return true;
+ // 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);
+ 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);
+ } else if (KeepEdge1 && (KeepEdge2 || TrueBB == FalseBB)) {
+ // Neither of the selected blocks were successors, so this
+ // indirectbr must be unreachable.
+ new UnreachableInst(IBI->getContext(), IBI);
+ } 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);
+ else
+ // Only FalseBB was found.
+ BranchInst::Create(FalseBB, IBI);
}
- // Check to see if we can constant propagate this terminator instruction
- // away...
- Changed |= ConstantFoldTerminator(BB);
+ EraseTerminatorInstAndDCECond(IBI);
+ return true;
+}
- // Check for and eliminate duplicate PHI nodes in this block.
- Changed |= EliminateDuplicatePHINodes(BB);
+/// 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
+/// pattern that occurs when "A == 1 || A == 2 || A == 3" gets simplified. In
+/// this case, we merge the first two "or's of icmp" into a switch, but then the
+/// default value goes to an uncond block with a seteq in it, we get something
+/// like:
+///
+/// switch i8 %A, label %DEFAULT [ i8 1, label %end i8 2, label %end ]
+/// DEFAULT:
+/// %tmp = icmp eq i8 %A, 92
+/// br label %end
+/// end:
+/// ... = phi i1 [ true, %entry ], [ %tmp, %DEFAULT ], [ true, %entry ]
+///
+/// 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) {
+ 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;
+
+ Value *V = ICI->getOperand(0);
+ ConstantInt *Cst = cast<ConstantInt>(ICI->getOperand(1));
+
+ // The pattern we're looking for is where our only predecessor is a switch on
+ // 'V' and this block is the default case for the switch. In this case we can
+ // fold the compared value into the switch to simplify things.
+ BasicBlock *Pred = BB->getSinglePredecessor();
+ if (Pred == 0 || !isa<SwitchInst>(Pred->getTerminator())) return false;
+
+ SwitchInst *SI = cast<SwitchInst>(Pred->getTerminator());
+ if (SI->getCondition() != V)
+ return false;
+
+ // If BB is reachable on a non-default case, then we simply know the value of
+ // V in this block. Substitute it and constant fold the icmp instruction
+ // away.
+ if (SI->getDefaultDest() != BB) {
+ ConstantInt *VVal = SI->findCaseDest(BB);
+ assert(VVal && "Should have a unique destination value");
+ ICI->setOperand(0, VVal);
+
+ if (Constant *C = ConstantFoldInstruction(ICI)) {
+ ICI->replaceAllUsesWith(C);
+ ICI->eraseFromParent();
+ }
+ // BB is now empty, so it is likely to simplify away.
+ return SimplifyCFG(BB) | true;
+ }
+
+ // Ok, the block is reachable from the default dest. If the constant we're
+ // comparing exists in one of the other edges, then we can constant fold ICI
+ // and zap it.
+ if (SI->findCaseValue(Cst) != 0) {
+ Value *V;
+ if (ICI->getPredicate() == ICmpInst::ICMP_EQ)
+ V = ConstantInt::getFalse(BB->getContext());
+ else
+ V = ConstantInt::getTrue(BB->getContext());
+
+ ICI->replaceAllUsesWith(V);
+ ICI->eraseFromParent();
+ // BB is now empty, so it is likely to simplify away.
+ return SimplifyCFG(BB) | true;
+ }
+
+ // The use of the icmp has to be in the 'end' block, by the only PHI node in
+ // the block.
+ BasicBlock *SuccBlock = BB->getTerminator()->getSuccessor(0);
+ PHINode *PHIUse = dyn_cast<PHINode>(ICI->use_back());
+ if (PHIUse == 0 || PHIUse != &SuccBlock->front() ||
+ isa<PHINode>(++BasicBlock::iterator(PHIUse)))
+ return false;
- // 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);
+ // If the icmp is a SETEQ, then the default dest gets false, the new edge gets
+ // true in the PHI.
+ Constant *DefaultCst = ConstantInt::getTrue(BB->getContext());
+ Constant *NewCst = ConstantInt::getFalse(BB->getContext());
- // If this is a returning block with only PHI nodes in it, fold the return
- // instruction into any unconditional branch predecessors.
- //
- // If any predecessor is a conditional branch that just selects among
- // different return values, fold the replace the branch/return with a select
- // and return.
- if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
- if (isTerminatorFirstRelevantInsn(BB, BB->getTerminator())) {
- // Find predecessors that end with branches.
- SmallVector<BasicBlock*, 8> UncondBranchPreds;
- SmallVector<BranchInst*, 8> CondBranchPreds;
- for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
- BasicBlock *P = *PI;
- TerminatorInst *PTI = P->getTerminator();
- if (BranchInst *BI = dyn_cast<BranchInst>(PTI)) {
- if (BI->isUnconditional())
- UncondBranchPreds.push_back(P);
- else
- CondBranchPreds.push_back(BI);
- }
- }
+ if (ICI->getPredicate() == ICmpInst::ICMP_EQ)
+ std::swap(DefaultCst, NewCst);
- // If we found some, do the transformation!
- if (!UncondBranchPreds.empty()) {
- 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);
- Pred->getInstList().erase(UncondBranch);
- }
+ // Replace ICI (which is used by the PHI for the default value) with true or
+ // false depending on if it is EQ or NE.
+ ICI->replaceAllUsesWith(DefaultCst);
+ ICI->eraseFromParent();
- // If we eliminated all predecessors of the block, delete the block now.
- if (pred_begin(BB) == pred_end(BB))
- // We know there are no successors, so just nuke the block.
- M->getBasicBlockList().erase(BB);
+ // Okay, the switch goes to this block on a default value. Add an edge from
+ // the switch to the merge point on the compared value.
+ BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "switch.edge",
+ BB->getParent(), BB);
+ SI->addCase(Cst, NewBB);
+
+ // NewBB branches to the phi block, add the uncond branch and the phi entry.
+ BranchInst::Create(SuccBlock, NewBB);
+ PHIUse->addIncoming(NewCst, NewBB);
+ return true;
+}
- 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) {
+ Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
+ if (Cond == 0) return false;
+
+
+ // Change br (X == 0 | X == 1), T, F into a switch instruction.
+ // If this is a bunch of seteq's or'd together, or if it's a bunch of
+ // 'setne's and'ed together, collect them.
+ Value *CompVal = 0;
+ std::vector<ConstantInt*> Values;
+ bool TrueWhenEqual = true;
+ Value *ExtraCase = 0;
+
+ if (Cond->getOpcode() == Instruction::Or) {
+ CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, true);
+ } else if (Cond->getOpcode() == Instruction::And) {
+ CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, false);
+ TrueWhenEqual = false;
+ }
+
+ // If we didn't have a multiply compared value, fail.
+ if (CompVal == 0) return false;
- // Check out all of the conditional branches going to this return
- // instruction. If any of them just select between returns, change the
- // branch itself into a select/return pair.
- while (!CondBranchPreds.empty()) {
- BranchInst *BI = CondBranchPreds.pop_back_val();
-
- // 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))
- return true;
- }
- }
- } else if (isa<UnwindInst>(BB->begin())) {
- // 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.
- //
- SmallVector<BasicBlock*, 8> Preds(pred_begin(BB), pred_end(BB));
- while (!Preds.empty()) {
- BasicBlock *Pred = Preds.back();
- if (InvokeInst *II = dyn_cast<InvokeInst>(Pred->getTerminator()))
- if (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);
- 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);
- CI->setCallingConv(II->getCallingConv());
- CI->setAttributes(II->getAttributes());
- // If the invoke produced a value, the Call now does instead.
- II->replaceAllUsesWith(CI);
- delete II;
- Changed = true;
- }
+ // 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);
+ Values.erase(std::unique(Values.begin(), Values.end()), Values.end());
+
+ // If Extra was used, we require at least two switch values to do the
+ // transformation. A switch with one value is just an cond branch.
+ if (ExtraCase && Values.size() < 2) return false;
+
+ // Figure out which block is which destination.
+ BasicBlock *DefaultBB = BI->getSuccessor(1);
+ BasicBlock *EdgeBB = BI->getSuccessor(0);
+ if (!TrueWhenEqual) std::swap(DefaultBB, EdgeBB);
+
+ BasicBlock *BB = BI->getParent();
+
+ // If there are any extra values that couldn't be folded into the switch
+ // then we evaluate them with an explicit branch first. Split the block
+ // right before the condbr to handle it.
+ if (ExtraCase) {
+ BasicBlock *NewBB = BB->splitBasicBlock(BI, "switch.early.test");
+ // Remove the uncond branch added to the old block.
+ TerminatorInst *OldTI = BB->getTerminator();
+
+ BranchInst::Create(EdgeBB, NewBB, ExtraCase, OldTI);
+ OldTI->eraseFromParent();
+
+ // If there are PHI nodes in EdgeBB, then we need to add a new entry to them
+ // for the edge we just added.
+ for (BasicBlock::iterator I = EdgeBB->begin(); isa<PHINode>(I); ++I) {
+ PHINode *PN = cast<PHINode>(I);
+ PN->addIncoming(PN->getIncomingValueForBlock(NewBB), BB);
+ }
+ BB = NewBB;
+ }
+
+ // 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);
+ }
+
+ // Create the new switch instruction now.
+ SwitchInst *New = SwitchInst::Create(CompVal, DefaultBB, Values.size(), BI);
+
+ // Add all of the 'cases' to the switch instruction.
+ for (unsigned i = 0, e = Values.size(); i != e; ++i)
+ New->addCase(Values[i], EdgeBB);
+
+ // We added edges from PI to the EdgeBB. As such, if there were any
+ // PHI nodes in EdgeBB, they need entries to be added corresponding to
+ // the number of edges added.
+ for (BasicBlock::iterator BBI = EdgeBB->begin();
+ isa<PHINode>(BBI); ++BBI) {
+ PHINode *PN = cast<PHINode>(BBI);
+ Value *InVal = PN->getIncomingValueForBlock(BB);
+ for (unsigned i = 0, e = Values.size()-1; i != e; ++i)
+ PN->addIncoming(InVal, BB);
+ }
+
+ // Erase the old branch instruction.
+ EraseTerminatorInstAndDCECond(BI);
+ return true;
+}
- Preds.pop_back();
+bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI) {
+ BasicBlock *BB = RI->getParent();
+ if (!BB->getFirstNonPHIOrDbg()->isTerminator()) return false;
+
+ // Find predecessors that end with branches.
+ SmallVector<BasicBlock*, 8> UncondBranchPreds;
+ SmallVector<BranchInst*, 8> CondBranchPreds;
+ for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
+ BasicBlock *P = *PI;
+ TerminatorInst *PTI = P->getTerminator();
+ if (BranchInst *BI = dyn_cast<BranchInst>(PTI)) {
+ if (BI->isUnconditional())
+ UncondBranchPreds.push_back(P);
+ else
+ CondBranchPreds.push_back(BI);
}
-
- // If this block is now dead, remove it.
- if (pred_begin(BB) == pred_end(BB)) {
+ }
+
+ // If we found some, do the transformation!
+ if (!UncondBranchPreds.empty()) {
+ 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);
+ Pred->getInstList().erase(UncondBranch);
+ }
+
+ // If we eliminated all predecessors of the block, delete the block now.
+ if (pred_begin(BB) == pred_end(BB))
// We know there are no successors, so just nuke the block.
- M->getBasicBlockList().erase(BB);
+ BB->eraseFromParent();
+
+ return true;
+ }
+
+ // Check out all of the conditional branches going to this return
+ // instruction. If any of them just select between returns, change the
+ // branch itself into a select/return pair.
+ while (!CondBranchPreds.empty()) {
+ BranchInst *BI = CondBranchPreds.pop_back_val();
+
+ // 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))
return true;
- }
+ }
+ return false;
+}
- } else if (SwitchInst *SI = dyn_cast<SwitchInst>(BB->getTerminator())) {
- 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))
- return SimplifyCFG(BB) || 1;
-
- // 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))
- return SimplifyCFG(BB) || 1;
- }
- } else if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator())) {
- if (BI->isUnconditional()) {
- BasicBlock::iterator BBI = BB->getFirstNonPHI();
+bool SimplifyCFGOpt::SimplifyUnwind(UnwindInst *UI) {
+ // 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.
+ BasicBlock *BB = UI->getParent();
+ if (!BB->getFirstNonPHIOrDbg()->isTerminator()) return false;
- // Ignore dbg intrinsics.
- while (isa<DbgInfoIntrinsic>(BBI))
- ++BBI;
- if (BBI->isTerminator()) // Terminator is the only non-phi instruction!
- if (TryToSimplifyUncondBranchFromEmptyBlock(BB))
- return true;
+ bool Changed = false;
+ SmallVector<BasicBlock*, 8> Preds(pred_begin(BB), pred_end(BB));
+ while (!Preds.empty()) {
+ BasicBlock *Pred = Preds.back();
+ InvokeInst *II = dyn_cast<InvokeInst>(Pred->getTerminator());
+ 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);
+ Pred->getInstList().remove(II); // Take out of symbol table
- } else { // Conditional branch
- if (isValueEqualityComparison(BI)) {
- // 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(BI, OnlyPred))
- return SimplifyCFG(BB) | true;
-
- // This block must be empty, except for the setcond inst, if it exists.
- // Ignore dbg intrinsics.
- BasicBlock::iterator I = BB->begin();
- // Ignore dbg intrinsics.
- while (isa<DbgInfoIntrinsic>(I))
- ++I;
- if (&*I == BI) {
- if (FoldValueComparisonIntoPredecessors(BI))
- return SimplifyCFG(BB) | true;
- } else if (&*I == cast<Instruction>(BI->getCondition())){
- ++I;
- // Ignore dbg intrinsics.
- while (isa<DbgInfoIntrinsic>(I))
- ++I;
- if(&*I == BI) {
- if (FoldValueComparisonIntoPredecessors(BI))
- return SimplifyCFG(BB) | true;
- }
- }
- }
-
- // If this is a branch on a phi node in the current block, thread control
- // through this block if any PHI node entries are constants.
- if (PHINode *PN = dyn_cast<PHINode>(BI->getCondition()))
- if (PN->getParent() == BI->getParent())
- if (FoldCondBranchOnPHI(BI))
- return SimplifyCFG(BB) | true;
-
- // 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.
- if (FoldBranchToCommonDest(BI))
- return SimplifyCFG(BB) | 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;
- }
- } else if (isa<UnreachableInst>(BB->getTerminator())) {
- // If there are any instructions immediately before the unreachable that can
- // be removed, do so.
- Instruction *Unreachable = BB->getTerminator();
- while (Unreachable != BB->begin()) {
- BasicBlock::iterator BBI = Unreachable;
- --BBI;
- // Do not delete instructions that can have side effects, like calls
- // (which may never return) and volatile loads and stores.
- if (isa<CallInst>(BBI) && !isa<DbgInfoIntrinsic>(BBI)) break;
-
- if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
- if (SI->isVolatile())
- break;
-
- if (LoadInst *LI = dyn_cast<LoadInst>(BBI))
- if (LI->isVolatile())
- break;
-
- // Delete this instruction
- BB->getInstList().erase(BBI);
+ // 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);
+ CI->setCallingConv(II->getCallingConv());
+ CI->setAttributes(II->getAttributes());
+ // If the invoke produced a value, the Call now does instead.
+ II->replaceAllUsesWith(CI);
+ delete II;
Changed = true;
}
+
+ Preds.pop_back();
+ }
+
+ // If this block is now dead (and isn't the entry block), remove it.
+ if (pred_begin(BB) == pred_end(BB) &&
+ BB != &BB->getParent()->getEntryBlock()) {
+ // We know there are no successors, so just nuke the block.
+ BB->eraseFromParent();
+ return true;
+ }
+
+ return Changed;
+}
- // If the unreachable instruction is the first in the block, take a gander
- // at all of the predecessors of this instruction, and simplify them.
- if (&BB->front() == Unreachable) {
- 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();
-
- if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
- if (BI->isUnconditional()) {
- if (BI->getSuccessor(0) == BB) {
- new UnreachableInst(TI->getContext(), TI);
- TI->eraseFromParent();
- Changed = true;
- }
- } else {
- if (BI->getSuccessor(0) == BB) {
- BranchInst::Create(BI->getSuccessor(1), BI);
- EraseTerminatorInstAndDCECond(BI);
- } else if (BI->getSuccessor(1) == BB) {
- BranchInst::Create(BI->getSuccessor(0), BI);
- EraseTerminatorInstAndDCECond(BI);
- Changed = true;
- }
+bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) {
+ BasicBlock *BB = UI->getParent();
+
+ bool Changed = false;
+
+ // If there are any instructions immediately before the unreachable that can
+ // be removed, do so.
+ while (UI != BB->begin()) {
+ BasicBlock::iterator BBI = UI;
+ --BBI;
+ // Do not delete instructions that can have side effects, like calls
+ // (which may never return) and volatile loads and stores.
+ if (isa<CallInst>(BBI) && !isa<DbgInfoIntrinsic>(BBI)) break;
+
+ if (StoreInst *SI = dyn_cast<StoreInst>(BBI))
+ if (SI->isVolatile())
+ break;
+
+ if (LoadInst *LI = dyn_cast<LoadInst>(BBI))
+ if (LI->isVolatile())
+ break;
+
+ // Delete this instruction
+ BB->getInstList().erase(BBI);
+ Changed = true;
+ }
+
+ // If the unreachable instruction is the first in the block, take a gander
+ // at all of the predecessors of this instruction, and simplify them.
+ if (&BB->front() != UI) return Changed;
+
+ 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();
+
+ if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
+ if (BI->isUnconditional()) {
+ if (BI->getSuccessor(0) == BB) {
+ new UnreachableInst(TI->getContext(), TI);
+ TI->eraseFromParent();
+ Changed = true;
+ }
+ } else {
+ if (BI->getSuccessor(0) == BB) {
+ BranchInst::Create(BI->getSuccessor(1), BI);
+ EraseTerminatorInstAndDCECond(BI);
+ } else if (BI->getSuccessor(1) == BB) {
+ BranchInst::Create(BI->getSuccessor(0), BI);
+ EraseTerminatorInstAndDCECond(BI);
+ Changed = true;
+ }
+ }
+ } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
+ for (unsigned i = 1, e = SI->getNumCases(); i != e; ++i)
+ if (SI->getSuccessor(i) == BB) {
+ BB->removePredecessor(SI->getParent());
+ SI->removeCase(i);
+ --i; --e;
+ 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)]++;
+
+ // Find the most popular block.
+ unsigned MaxPop = 0;
+ BasicBlock *MaxBlock = 0;
+ for (std::map<BasicBlock*, unsigned>::iterator
+ I = Popularity.begin(), E = Popularity.end(); I != E; ++I) {
+ if (I->second > MaxPop) {
+ MaxPop = I->second;
+ MaxBlock = I->first;
}
- } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
+ }
+ if (MaxBlock) {
+ // Make this the new default, allowing us to delete any explicit
+ // edges to it.
+ SI->setSuccessor(0, MaxBlock);
+ Changed = true;
+
+ // If MaxBlock has phinodes in it, remove MaxPop-1 entries from
+ // it.
+ if (isa<PHINode>(MaxBlock->begin()))
+ for (unsigned i = 0; i != MaxPop-1; ++i)
+ MaxBlock->removePredecessor(SI->getParent());
+
for (unsigned i = 1, e = SI->getNumCases(); i != e; ++i)
- if (SI->getSuccessor(i) == BB) {
- BB->removePredecessor(SI->getParent());
+ if (SI->getSuccessor(i) == MaxBlock) {
SI->removeCase(i);
--i; --e;
- 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)]++;
-
- // Find the most popular block.
- unsigned MaxPop = 0;
- BasicBlock *MaxBlock = 0;
- for (std::map<BasicBlock*, unsigned>::iterator
- I = Popularity.begin(), E = Popularity.end(); I != E; ++I) {
- if (I->second > MaxPop) {
- MaxPop = I->second;
- MaxBlock = I->first;
- }
- }
- if (MaxBlock) {
- // Make this the new default, allowing us to delete any explicit
- // edges to it.
- SI->setSuccessor(0, MaxBlock);
- Changed = true;
-
- // If MaxBlock has phinodes in it, remove MaxPop-1 entries from
- // it.
- if (isa<PHINode>(MaxBlock->begin()))
- for (unsigned i = 0; i != MaxPop-1; ++i)
- MaxBlock->removePredecessor(SI->getParent());
-
- for (unsigned i = 1, e = SI->getNumCases(); i != e; ++i)
- if (SI->getSuccessor(i) == MaxBlock) {
- SI->removeCase(i);
- --i; --e;
- }
}
- }
- } else if (InvokeInst *II = dyn_cast<InvokeInst>(TI)) {
- 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);
- 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);
- CI->setCallingConv(II->getCallingConv());
- CI->setAttributes(II->getAttributes());
- // If the invoke produced a value, the call does now instead.
- II->replaceAllUsesWith(CI);
- delete II;
- Changed = true;
- }
}
}
-
- // If this block is now dead, remove it.
- if (pred_begin(BB) == pred_end(BB)) {
- // We know there are no successors, so just nuke the block.
- M->getBasicBlockList().erase(BB);
- return true;
+ } else if (InvokeInst *II = dyn_cast<InvokeInst>(TI)) {
+ 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);
+ 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);
+ CI->setCallingConv(II->getCallingConv());
+ CI->setAttributes(II->getAttributes());
+ // If the invoke produced a value, the call does now instead.
+ II->replaceAllUsesWith(CI);
+ delete II;
+ Changed = true;
}
}
}
+
+ // If this block is now dead, remove it.
+ if (pred_begin(BB) == pred_end(BB) &&
+ BB != &BB->getParent()->getEntryBlock()) {
+ // We know there are no successors, so just nuke the block.
+ BB->eraseFromParent();
+ return true;
+ }
- // Merge basic blocks into their predecessor if there is only one distinct
- // pred, and if there is only one distinct successor of the predecessor, and
- // if there are no PHI nodes.
- //
- if (MergeBlockIntoPredecessor(BB))
+ return Changed;
+}
+
+
+bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI) {
+ // 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))
+ 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))
+ return SimplifyCFG(BB) | true;
+
+ return false;
+}
+
+bool SimplifyCFGOpt::SimplifyIndirectBr(IndirectBrInst *IBI) {
+ BasicBlock *BB = IBI->getParent();
+ bool Changed = false;
+
+ // Eliminate redundant destinations.
+ SmallPtrSet<Value *, 8> Succs;
+ for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) {
+ BasicBlock *Dest = IBI->getDestination(i);
+ if (!Dest->hasAddressTaken() || !Succs.insert(Dest)) {
+ Dest->removePredecessor(BB);
+ IBI->removeDestination(i);
+ --i; --e;
+ Changed = true;
+ }
+ }
+
+ if (IBI->getNumDestinations() == 0) {
+ // If the indirectbr has no successors, change it to unreachable.
+ new UnreachableInst(IBI->getContext(), IBI);
+ EraseTerminatorInstAndDCECond(IBI);
+ return true;
+ }
+
+ if (IBI->getNumDestinations() == 1) {
+ // If the indirectbr has one successor, change it to a direct branch.
+ BranchInst::Create(IBI->getDestination(0), IBI);
+ EraseTerminatorInstAndDCECond(IBI);
return true;
+ }
+
+ if (SelectInst *SI = dyn_cast<SelectInst>(IBI->getAddress())) {
+ if (SimplifyIndirectBrOnSelect(IBI, SI))
+ return SimplifyCFG(BB) | true;
+ }
+ return Changed;
+}
- // Otherwise, if this block only has a single predecessor, and if that block
- // is a conditional branch, see if we can hoist any code from this block up
- // into our predecessor.
- pred_iterator PI(pred_begin(BB)), PE(pred_end(BB));
- BasicBlock *OnlyPred = *PI++;
- for (; PI != PE; ++PI) // Search all predecessors, see if they are all same
- if (*PI != OnlyPred) {
- OnlyPred = 0; // There are multiple different predecessors...
- break;
+bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI) {
+ BasicBlock *BB = BI->getParent();
+
+ // If the Terminator is the only non-phi instruction, simplify the block.
+ BasicBlock::iterator I = BB->getFirstNonPHIOrDbg();
+ if (I->isTerminator() && BB != &BB->getParent()->getEntryBlock() &&
+ TryToSimplifyUncondBranchFromEmptyBlock(BB))
+ return true;
+
+ // If the only instruction in the block is a seteq/setne comparison
+ // against a constant, try to simplify the block.
+ if (ICmpInst *ICI = dyn_cast<ICmpInst>(I))
+ if (ICI->isEquality() && isa<ConstantInt>(ICI->getOperand(1))) {
+ for (++I; isa<DbgInfoIntrinsic>(I); ++I)
+ ;
+ if (I->isTerminator() && TryToSimplifyUncondBranchWithICmpInIt(ICI))
+ return true;
}
- if (OnlyPred)
- if (BranchInst *BI = dyn_cast<BranchInst>(OnlyPred->getTerminator()))
- if (BI->isConditional()) {
- // Get the other block.
- BasicBlock *OtherBB = BI->getSuccessor(BI->getSuccessor(0) == BB);
- PI = pred_begin(OtherBB);
- ++PI;
-
- if (PI == pred_end(OtherBB)) {
- // We have a conditional branch to two blocks that are only reachable
- // from the condbr. We know that the condbr dominates the two blocks,
- // so see if there is any identical code in the "then" and "else"
- // blocks. If so, we can hoist it up to the branching block.
- Changed |= HoistThenElseCodeToIf(BI);
- } else {
- BasicBlock* OnlySucc = NULL;
- for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB);
- SI != SE; ++SI) {
- if (!OnlySucc)
- OnlySucc = *SI;
- else if (*SI != OnlySucc) {
- OnlySucc = 0; // There are multiple distinct successors!
- break;
- }
- }
+ return false;
+}
- if (OnlySucc == OtherBB) {
- // If BB's only successor is the other successor of the predecessor,
- // i.e. a triangle, see if we can hoist any code from this block up
- // to the "if" block.
- Changed |= SpeculativelyExecuteBB(BI, BB);
- }
- }
- }
+bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI) {
+ BasicBlock *BB = BI->getParent();
+
+ // Conditional branch
+ if (isValueEqualityComparison(BI)) {
+ // 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(BI, OnlyPred))
+ return SimplifyCFG(BB) | true;
+
+ // This block must be empty, except for the setcond inst, if it exists.
+ // Ignore dbg intrinsics.
+ BasicBlock::iterator I = BB->begin();
+ // Ignore dbg intrinsics.
+ while (isa<DbgInfoIntrinsic>(I))
+ ++I;
+ if (&*I == BI) {
+ if (FoldValueComparisonIntoPredecessors(BI))
+ 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))
+ return SimplifyCFG(BB) | true;
+ }
+ }
+
+ // Try to turn "br (X == 0 | X == 1), T, F" into a switch instruction.
+ if (SimplifyBranchOnICmpChain(BI, TD))
+ return 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
+ // there is any identical code in the "then" and "else" blocks. If so, we
+ // can hoist it up to the branching block.
+ if (BI->getSuccessor(0)->getSinglePredecessor() != 0) {
+ if (BI->getSuccessor(1)->getSinglePredecessor() != 0) {
+ if (HoistThenElseCodeToIf(BI))
+ return SimplifyCFG(BB) | true;
+ } else {
+ // If Successor #1 has multiple preds, we may be able to conditionally
+ // execute Successor #0 if it branches to successor #1.
+ TerminatorInst *Succ0TI = BI->getSuccessor(0)->getTerminator();
+ if (Succ0TI->getNumSuccessors() == 1 &&
+ Succ0TI->getSuccessor(0) == BI->getSuccessor(1))
+ if (SpeculativelyExecuteBB(BI, BI->getSuccessor(0)))
+ return SimplifyCFG(BB) | true;
+ }
+ } else if (BI->getSuccessor(1)->getSinglePredecessor() != 0) {
+ // If Successor #0 has multiple preds, we may be able to conditionally
+ // execute Successor #1 if it branches to successor #0.
+ TerminatorInst *Succ1TI = BI->getSuccessor(1)->getTerminator();
+ if (Succ1TI->getNumSuccessors() == 1 &&
+ Succ1TI->getSuccessor(0) == BI->getSuccessor(0))
+ if (SpeculativelyExecuteBB(BI, BI->getSuccessor(1)))
+ return SimplifyCFG(BB) | true;
+ }
+
+ // If this is a branch on a phi node in the current block, thread control
+ // through this block if any PHI node entries are constants.
+ if (PHINode *PN = dyn_cast<PHINode>(BI->getCondition()))
+ if (PN->getParent() == BI->getParent())
+ if (FoldCondBranchOnPHI(BI))
+ return SimplifyCFG(BB) | true;
+
+ // 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.
+ if (FoldBranchToCommonDest(BI))
+ return SimplifyCFG(BB) | true;
+
+ // Scan predecessor blocks for conditional branches.
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
- if (BranchInst *BI = dyn_cast<BranchInst>((*PI)->getTerminator()))
- // Change br (X == 0 | X == 1), T, F into a switch instruction.
- if (BI->isConditional() && isa<Instruction>(BI->getCondition())) {
- Instruction *Cond = cast<Instruction>(BI->getCondition());
- // If this is a bunch of seteq's or'd together, or if it's a bunch of
- // 'setne's and'ed together, collect them.
- Value *CompVal = 0;
- std::vector<ConstantInt*> Values;
- bool TrueWhenEqual = GatherValueComparisons(Cond, CompVal, Values);
- if (CompVal) {
- // There might be duplicate constants in the list, which the switch
- // instruction can't handle, remove them now.
- std::sort(Values.begin(), Values.end(), ConstantIntOrdering());
- Values.erase(std::unique(Values.begin(), Values.end()), Values.end());
-
- // Figure out which block is which destination.
- BasicBlock *DefaultBB = BI->getSuccessor(1);
- BasicBlock *EdgeBB = BI->getSuccessor(0);
- if (!TrueWhenEqual) std::swap(DefaultBB, EdgeBB);
-
- // 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);
- }
+ if (BranchInst *PBI = dyn_cast<BranchInst>((*PI)->getTerminator()))
+ if (PBI != BI && PBI->isConditional())
+ if (SimplifyCondBranchToCondBranch(PBI, BI))
+ return SimplifyCFG(BB) | true;
- // Create the new switch instruction now.
- SwitchInst *New = SwitchInst::Create(CompVal, DefaultBB,
- Values.size(), BI);
-
- // Add all of the 'cases' to the switch instruction.
- for (unsigned i = 0, e = Values.size(); i != e; ++i)
- New->addCase(Values[i], EdgeBB);
-
- // We added edges from PI to the EdgeBB. As such, if there were any
- // PHI nodes in EdgeBB, they need entries to be added corresponding to
- // the number of edges added.
- for (BasicBlock::iterator BBI = EdgeBB->begin();
- isa<PHINode>(BBI); ++BBI) {
- PHINode *PN = cast<PHINode>(BBI);
- Value *InVal = PN->getIncomingValueForBlock(*PI);
- for (unsigned i = 0, e = Values.size()-1; i != e; ++i)
- PN->addIncoming(InVal, *PI);
- }
+ return false;
+}
- // Erase the old branch instruction.
- EraseTerminatorInstAndDCECond(BI);
- return true;
- }
- }
+bool SimplifyCFGOpt::run(BasicBlock *BB) {
+ bool Changed = false;
+ Function *Fn = BB->getParent();
+
+ assert(BB && Fn && "Block not embedded in function!");
+ assert(BB->getTerminator() && "Degenerate basic block encountered!");
+
+ // Remove basic blocks that have no predecessors (except the entry block)...
+ // or that just have themself as a predecessor. These are unreachable.
+ if ((pred_begin(BB) == pred_end(BB) && BB != &Fn->getEntryBlock()) ||
+ BB->getSinglePredecessor() == BB) {
+ DEBUG(dbgs() << "Removing BB: \n" << *BB);
+ DeleteDeadBlock(BB);
+ return true;
+ }
+
+ // Check to see if we can constant propagate this terminator instruction
+ // away...
+ Changed |= ConstantFoldTerminator(BB);
+
+ // Check for and eliminate duplicate PHI nodes in this block.
+ Changed |= EliminateDuplicatePHINodes(BB);
+
+ // Merge basic blocks into their predecessor if there is only one distinct
+ // pred, and if there is only one distinct successor of the predecessor, and
+ // if there are no PHI nodes.
+ //
+ if (MergeBlockIntoPredecessor(BB))
+ return true;
+
+ // 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);
+
+ if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator())) {
+ if (BI->isUnconditional()) {
+ if (SimplifyUncondBranch(BI)) return true;
+ } else {
+ if (SimplifyCondBranch(BI))
+ return true;
+ }
+ } else if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
+ if (SimplifyReturn(RI)) return true;
+ } else if (SwitchInst *SI = dyn_cast<SwitchInst>(BB->getTerminator())) {
+ if (SimplifySwitch(SI)) 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;
+ } else if (IndirectBrInst *IBI =
+ dyn_cast<IndirectBrInst>(BB->getTerminator())) {
+ if (SimplifyIndirectBr(IBI)) return true;
+ }
return Changed;
}
/// eliminates unreachable basic blocks, and does other "peephole" optimization
/// of the CFG. It returns true if a modification was made.
///
-/// WARNING: The entry node of a function may not be simplified.
-///
bool llvm::SimplifyCFG(BasicBlock *BB, const TargetData *TD) {
return SimplifyCFGOpt(TD).run(BB);
}
projects / oota-llvm.git / blobdiff