#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
#include "llvm/Constants.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/LLVMContext.h"
#include "llvm/Pass.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
using namespace llvm;
namespace {
class LowerSwitch : public FunctionPass {
public:
static char ID; LowerSwitch() : FunctionPass(ID) {
initializeLowerSwitchPass(*PassRegistry::getPassRegistry());
}
virtual bool runOnFunction(Function &F);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addPreserved<UnifyFunctionExitNodes>();
AU.addPreserved("mem2reg");
AU.addPreservedID(LowerInvokePassID);
}
struct CaseRange {
Constant* Low;
Constant* High;
BasicBlock* BB;
CaseRange(Constant *low = 0, Constant *high = 0, BasicBlock *bb = 0) :
Low(low), High(high), BB(bb) { }
};
typedef std::vector<CaseRange> CaseVector;
typedef std::vector<CaseRange>::iterator CaseItr;
private:
void processSwitchInst(SwitchInst *SI);
BasicBlock* switchConvert(CaseItr Begin, CaseItr End, Value* Val,
BasicBlock* OrigBlock, BasicBlock* Default);
BasicBlock* newLeafBlock(CaseRange& Leaf, Value* Val,
BasicBlock* OrigBlock, BasicBlock* Default);
unsigned Clusterify(CaseVector& Cases, SwitchInst *SI);
};
}
char LowerSwitch::ID = 0;
INITIALIZE_PASS(LowerSwitch, "lowerswitch",
"Lower SwitchInst's to branches", false, false)
char &llvm::LowerSwitchID = LowerSwitch::ID;
FunctionPass *llvm::createLowerSwitchPass() {
return new LowerSwitch();
}
bool LowerSwitch::runOnFunction(Function &F) {
bool Changed = false;
for (Function::iterator I = F.begin(), E = F.end(); I != E; ) {
BasicBlock *Cur = I++;
if (SwitchInst *SI = dyn_cast<SwitchInst>(Cur->getTerminator())) {
Changed = true;
processSwitchInst(SI);
}
}
return Changed;
}
static raw_ostream& operator<<(raw_ostream &O,
const LowerSwitch::CaseVector &C)
LLVM_ATTRIBUTE_USED;
static raw_ostream& operator<<(raw_ostream &O,
const LowerSwitch::CaseVector &C) {
O << "[";
for (LowerSwitch::CaseVector::const_iterator B = C.begin(),
E = C.end(); B != E; ) {
O << *B->Low << " -" << *B->High;
if (++B != E) O << ", ";
}
return O << "]";
}
BasicBlock* LowerSwitch::switchConvert(CaseItr Begin, CaseItr End,
Value* Val, BasicBlock* OrigBlock,
BasicBlock* Default)
{
unsigned Size = End - Begin;
if (Size == 1)
return newLeafBlock(*Begin, Val, OrigBlock, Default);
unsigned Mid = Size / 2;
std::vector<CaseRange> LHS(Begin, Begin + Mid);
DEBUG(dbgs() << "LHS: " << LHS << "\n");
std::vector<CaseRange> RHS(Begin + Mid, End);
DEBUG(dbgs() << "RHS: " << RHS << "\n");
CaseRange& Pivot = *(Begin + Mid);
DEBUG(dbgs() << "Pivot ==> "
<< cast<ConstantInt>(Pivot.Low)->getValue() << " -"
<< cast<ConstantInt>(Pivot.High)->getValue() << "\n");
BasicBlock* LBranch = switchConvert(LHS.begin(), LHS.end(), Val,
OrigBlock, Default);
BasicBlock* RBranch = switchConvert(RHS.begin(), RHS.end(), Val,
OrigBlock, Default);
Function* F = OrigBlock->getParent();
BasicBlock* NewNode = BasicBlock::Create(Val->getContext(), "NodeBlock");
Function::iterator FI = OrigBlock;
F->getBasicBlockList().insert(++FI, NewNode);
ICmpInst* Comp = new ICmpInst(ICmpInst::ICMP_ULT,
Val, Pivot.Low, "Pivot");
NewNode->getInstList().push_back(Comp);
BranchInst::Create(LBranch, RBranch, Comp, NewNode);
return NewNode;
}
BasicBlock* LowerSwitch::newLeafBlock(CaseRange& Leaf, Value* Val,
BasicBlock* OrigBlock,
BasicBlock* Default)
{
Function* F = OrigBlock->getParent();
BasicBlock* NewLeaf = BasicBlock::Create(Val->getContext(), "LeafBlock");
Function::iterator FI = OrigBlock;
F->getBasicBlockList().insert(++FI, NewLeaf);
ICmpInst* Comp = NULL;
if (Leaf.Low == Leaf.High) {
Comp = new ICmpInst(*NewLeaf, ICmpInst::ICMP_EQ, Val,
Leaf.Low, "SwitchLeaf");
} else {
if (cast<ConstantInt>(Leaf.Low)->isMinValue(true )) {
Comp = new ICmpInst(*NewLeaf, ICmpInst::ICMP_SLE, Val, Leaf.High,
"SwitchLeaf");
} else if (cast<ConstantInt>(Leaf.Low)->isZero()) {
Comp = new ICmpInst(*NewLeaf, ICmpInst::ICMP_ULE, Val, Leaf.High,
"SwitchLeaf");
} else {
Constant* NegLo = ConstantExpr::getNeg(Leaf.Low);
Instruction* Add = BinaryOperator::CreateAdd(Val, NegLo,
Val->getName()+".off",
NewLeaf);
Constant *UpperBound = ConstantExpr::getAdd(NegLo, Leaf.High);
Comp = new ICmpInst(*NewLeaf, ICmpInst::ICMP_ULE, Add, UpperBound,
"SwitchLeaf");
}
}
BasicBlock* Succ = Leaf.BB;
BranchInst::Create(Succ, Default, Comp, NewLeaf);
for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
PHINode* PN = cast<PHINode>(I);
uint64_t Range = cast<ConstantInt>(Leaf.High)->getSExtValue() -
cast<ConstantInt>(Leaf.Low)->getSExtValue();
for (uint64_t j = 0; j < Range; ++j) {
PN->removeIncomingValue(OrigBlock);
}
int BlockIdx = PN->getBasicBlockIndex(OrigBlock);
assert(BlockIdx != -1 && "Switch didn't go to this successor??");
PN->setIncomingBlock((unsigned)BlockIdx, NewLeaf);
}
return NewLeaf;
}
unsigned LowerSwitch::Clusterify(CaseVector& Cases, SwitchInst *SI) {
IntegersSubsetToBB TheClusterifier;
for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
i != e; ++i) {
BasicBlock *SuccBB = i.getCaseSuccessor();
IntegersSubset CaseRanges = i.getCaseValueEx();
TheClusterifier.add(CaseRanges, SuccBB);
}
TheClusterifier.optimize();
size_t numCmps = 0;
for (IntegersSubsetToBB::RangeIterator i = TheClusterifier.begin(),
e = TheClusterifier.end(); i != e; ++i, ++numCmps) {
IntegersSubsetToBB::Cluster &C = *i;
Cases.push_back(CaseRange(C.first.getLow().toConstantInt(),
C.first.getHigh().toConstantInt(), C.second));
if (C.first.isSingleNumber())
++numCmps;
}
return numCmps;
}
void LowerSwitch::processSwitchInst(SwitchInst *SI) {
BasicBlock *CurBlock = SI->getParent();
BasicBlock *OrigBlock = CurBlock;
Function *F = CurBlock->getParent();
Value *Val = SI->getCondition(); BasicBlock* Default = SI->getDefaultDest();
if (!SI->getNumCases()) {
BranchInst::Create(SI->getDefaultDest(), CurBlock);
CurBlock->getInstList().erase(SI);
return;
}
BasicBlock* NewDefault = BasicBlock::Create(SI->getContext(), "NewDefault");
F->getBasicBlockList().insert(Default, NewDefault);
BranchInst::Create(Default, NewDefault);
for (BasicBlock::iterator I = Default->begin(); isa<PHINode>(I); ++I) {
PHINode *PN = cast<PHINode>(I);
int BlockIdx = PN->getBasicBlockIndex(OrigBlock);
assert(BlockIdx != -1 && "Switch didn't go to this successor??");
PN->setIncomingBlock((unsigned)BlockIdx, NewDefault);
}
CaseVector Cases;
unsigned numCmps = Clusterify(Cases, SI);
DEBUG(dbgs() << "Clusterify finished. Total clusters: " << Cases.size()
<< ". Total compares: " << numCmps << "\n");
DEBUG(dbgs() << "Cases: " << Cases << "\n");
(void)numCmps;
BasicBlock* SwitchBlock = switchConvert(Cases.begin(), Cases.end(), Val,
OrigBlock, NewDefault);
BranchInst::Create(SwitchBlock, OrigBlock);
CurBlock->getInstList().erase(SI);
}