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Use range tests in LowerSwitch, where possible

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35057 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Anton Korobeynikov 2007-03-10 16:46:28 +00:00
parent 3400e6af6b
commit e2ff29c17c
2 changed files with 164 additions and 31 deletions
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145
lib/Transforms/Utils/LowerSwitch.cpp
View File

@ -40,26 +40,38 @@ namespace {
AU.addPreservedID(LowerInvokePassID);
AU.addPreservedID(LowerAllocationsID);
}
typedef std::pair<Constant*, BasicBlock*> Case;
typedef std::vector<Case>::iterator CaseItr;
struct CaseRange {
Constant* Low;
Constant* High;
BasicBlock* BB;
CaseRange(Constant* _Low = NULL, Constant* _High = NULL,
BasicBlock* _BB = NULL):
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(Case& Leaf, Value* Val,
BasicBlock* newLeafBlock(CaseRange& Leaf, Value* Val,
BasicBlock* OrigBlock, BasicBlock* Default);
unsigned Clusterify(CaseVector& Cases, SwitchInst *SI);
};
/// The comparison function for sorting the switch case values in the vector.
/// WARNING: Case ranges should be disjoint!
struct CaseCmp {
bool operator () (const LowerSwitch::Case& C1,
const LowerSwitch::Case& C2) {
bool operator () (const LowerSwitch::CaseRange& C1,
const LowerSwitch::CaseRange& C2) {
const ConstantInt* CI1 = cast<const ConstantInt>(C1.first);
const ConstantInt* CI2 = cast<const ConstantInt>(C2.first);
return CI1->getValue().ult(CI2->getValue());
const ConstantInt* CI1 = cast<const ConstantInt>(C1.Low);
const ConstantInt* CI2 = cast<const ConstantInt>(C2.High);
return CI1->getValue().slt(CI2->getValue());
}
};
@ -91,19 +103,20 @@ bool LowerSwitch::runOnFunction(Function &F) {
// operator<< - Used for debugging purposes.
//
std::ostream& operator<<(std::ostream &O,
const std::vector<LowerSwitch::Case> &C) {
static std::ostream& operator<<(std::ostream &O,
const LowerSwitch::CaseVector &C) {
O << "[";
for (std::vector<LowerSwitch::Case>::const_iterator B = C.begin(),
for (LowerSwitch::CaseVector::const_iterator B = C.begin(),
E = C.end(); B != E; ) {
O << *B->first;
O << *B->Low << " -" << *B->High;
if (++B != E) O << ", ";
}
return O << "]";
}
OStream& operator<<(OStream &O, const std::vector<LowerSwitch::Case> &C) {
static OStream& operator<<(OStream &O, const LowerSwitch::CaseVector &C) {
if (O.stream()) *O.stream() << C;
return O;
}
@ -121,14 +134,16 @@ BasicBlock* LowerSwitch::switchConvert(CaseItr Begin, CaseItr End,
return newLeafBlock(*Begin, Val, OrigBlock, Default);
unsigned Mid = Size / 2;
std::vector<Case> LHS(Begin, Begin + Mid);
std::vector<CaseRange> LHS(Begin, Begin + Mid);
DOUT << "LHS: " << LHS << "\n";
std::vector<Case> RHS(Begin + Mid, End);
std::vector<CaseRange> RHS(Begin + Mid, End);
DOUT << "RHS: " << RHS << "\n";
Case& Pivot = *(Begin + Mid);
CaseRange& Pivot = *(Begin + Mid);
DEBUG( DOUT << "Pivot ==> "
<< cast<ConstantInt>(Pivot.first)->getValue().toStringSigned(10)
<< cast<ConstantInt>(Pivot.Low)->getValue().toStringSigned(10)
<< " -"
<< cast<ConstantInt>(Pivot.High)->getValue().toStringSigned(10)
<< "\n");
BasicBlock* LBranch = switchConvert(LHS.begin(), LHS.end(), Val,
@ -142,7 +157,7 @@ BasicBlock* LowerSwitch::switchConvert(CaseItr Begin, CaseItr End,
BasicBlock* NewNode = new BasicBlock("NodeBlock");
F->getBasicBlockList().insert(OrigBlock->getNext(), NewNode);
ICmpInst* Comp = new ICmpInst(ICmpInst::ICMP_ULT, Val, Pivot.first, "Pivot");
ICmpInst* Comp = new ICmpInst(ICmpInst::ICMP_SLT, Val, Pivot.Low, "Pivot");
NewNode->getInstList().push_back(Comp);
new BranchInst(LBranch, RBranch, Comp, NewNode);
return NewNode;
@ -154,7 +169,7 @@ BasicBlock* LowerSwitch::switchConvert(CaseItr Begin, CaseItr End,
// can't be another valid case value, so the jump to the "default" branch
// is warranted.
//
BasicBlock* LowerSwitch::newLeafBlock(Case& Leaf, Value* Val,
BasicBlock* LowerSwitch::newLeafBlock(CaseRange& Leaf, Value* Val,
BasicBlock* OrigBlock,
BasicBlock* Default)
{
@ -162,19 +177,49 @@ BasicBlock* LowerSwitch::newLeafBlock(Case& Leaf, Value* Val,
BasicBlock* NewLeaf = new BasicBlock("LeafBlock");
F->getBasicBlockList().insert(OrigBlock->getNext(), NewLeaf);
// Make the seteq instruction...
ICmpInst* Comp = new ICmpInst(ICmpInst::ICMP_EQ, Val,
Leaf.first, "SwitchLeaf");
NewLeaf->getInstList().push_back(Comp);
// Emit comparison
ICmpInst* Comp = NULL;
if (Leaf.Low == Leaf.High) {
// Make the seteq instruction...
Comp = new ICmpInst(ICmpInst::ICMP_EQ, Val, Leaf.Low,
"SwitchLeaf", NewLeaf);
} else {
// Make range comparison
if (cast<ConstantInt>(Leaf.Low)->isMinValue(true /*isSigned*/)) {
// Val >= Min && Val <= Hi --> Val <= Hi
Comp = new ICmpInst(ICmpInst::ICMP_SLE, Val, Leaf.High,
"SwitchLeaf", NewLeaf);
} else if (cast<ConstantInt>(Leaf.Low)->isZero()) {
// Val >= 0 && Val <= Hi --> Val <=u Hi
Comp = new ICmpInst(ICmpInst::ICMP_ULE, Val, Leaf.High,
"SwitchLeaf", NewLeaf);
} else {
// Emit V-Lo <=u Hi-Lo
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(ICmpInst::ICMP_ULE, Add, UpperBound,
"SwitchLeaf", NewLeaf);
}
}
// Make the conditional branch...
BasicBlock* Succ = Leaf.second;
BasicBlock* Succ = Leaf.BB;
new BranchInst(Succ, Default, Comp, NewLeaf);
// If there were any PHI nodes in this successor, rewrite one entry
// from OrigBlock to come from NewLeaf.
for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
PHINode* PN = cast<PHINode>(I);
// Remove all but one incoming entries from the cluster
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);
@ -183,6 +228,44 @@ BasicBlock* LowerSwitch::newLeafBlock(Case& Leaf, Value* Val,
return NewLeaf;
}
// Clusterify - Transform simple list of Cases into list of CaseRange's
unsigned LowerSwitch::Clusterify(CaseVector& Cases, SwitchInst *SI) {
unsigned numCmps = 0;
// Start with "simple" cases
for (unsigned i = 1; i < SI->getNumSuccessors(); ++i)
Cases.push_back(CaseRange(SI->getSuccessorValue(i),
SI->getSuccessorValue(i),
SI->getSuccessor(i)));
sort(Cases.begin(), Cases.end(), CaseCmp());
// Merge case into clusters
if (Cases.size()>=2)
for (CaseItr I=Cases.begin(), J=++(Cases.begin()), E=Cases.end(); J!=E; ) {
int64_t nextValue = cast<ConstantInt>(J->Low)->getSExtValue();
int64_t currentValue = cast<ConstantInt>(I->High)->getSExtValue();
BasicBlock* nextBB = J->BB;
BasicBlock* currentBB = I->BB;
// If the two neighboring cases go to the same destination, merge them
// into a single case.
if ((nextValue-currentValue==1) && (currentBB == nextBB)) {
I->High = J->High;
J = Cases.erase(J);
} else {
I = J++;
}
}
for (CaseItr I=Cases.begin(), E=Cases.end(); I!=E; ++I, ++numCmps) {
if (I->Low != I->High)
// A range counts double, since it requires two compares.
++numCmps;
}
return numCmps;
}
// processSwitchInst - Replace the specified switch instruction with a sequence
// of chained if-then insts in a balanced binary search.
//
@ -216,14 +299,14 @@ void LowerSwitch::processSwitchInst(SwitchInst *SI) {
PN->setIncomingBlock((unsigned)BlockIdx, NewDefault);
}
std::vector<Case> Cases;
// Prepare cases vector.
CaseVector Cases;
unsigned numCmps = Clusterify(Cases, SI);
// Expand comparisons for all of the non-default cases...
for (unsigned i = 1; i < SI->getNumSuccessors(); ++i)
Cases.push_back(Case(SI->getSuccessorValue(i), SI->getSuccessor(i)));
std::sort(Cases.begin(), Cases.end(), CaseCmp());
DOUT << "Clusterify finished. Total clusters: " << Cases.size()
<< ". Total compares: " << numCmps << "\n";
DOUT << "Cases: " << Cases << "\n";
BasicBlock* SwitchBlock = switchConvert(Cases.begin(), Cases.end(), Val,
OrigBlock, NewDefault);

50
test/Transforms/LowerSwitch/feature.ll Normal file
View File

@ -0,0 +1,50 @@
; RUN: llvm-as %s -o - | opt -lowerswitch | llvm-dis | grep slt | wc -l | grep 10 &&
; RUN: llvm-as %s -o - | opt -lowerswitch | llvm-dis | grep ule | wc -l | grep 3 &&
; RUN: llvm-as %s -o - | opt -lowerswitch | llvm-dis | grep eq | wc -l | grep 9
define i32 @main(i32 %tmp158) {
entry:
switch i32 %tmp158, label %bb336 [
i32 -2, label %bb338
i32 -3, label %bb338
i32 -4, label %bb338
i32 -5, label %bb338
i32 -6, label %bb338
i32 0, label %bb338
i32 1, label %bb338
i32 2, label %bb338
i32 3, label %bb338
i32 4, label %bb338
i32 5, label %bb338
i32 6, label %bb338
i32 7, label %bb
i32 8, label %bb338
i32 9, label %bb322
i32 10, label %bb324
i32 11, label %bb326
i32 12, label %bb328
i32 13, label %bb330
i32 14, label %bb332
i32 15, label %bb334
]
bb:
ret i32 2
bb322:
ret i32 3
bb324:
ret i32 4
bb326:
ret i32 5
bb328:
ret i32 6
bb330:
ret i32 7
bb332:
ret i32 8
bb334:
ret i32 9
bb336:
ret i32 10
bb338:
ret i32 11
}