mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-19 19:29:31 +00:00
can collide with system defined names. Windows defines _BB, for example. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35066 91177308-0d34-0410-b5e6-96231b3b80d8
319 lines
11 KiB
C++
319 lines
11 KiB
C++
//===- LowerSwitch.cpp - Eliminate Switch instructions --------------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file was developed by the LLVM research group and is distributed under
|
|
// the University of Illinois Open Source License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// The LowerSwitch transformation rewrites switch statements with a sequence of
|
|
// branches, which allows targets to get away with not implementing the switch
|
|
// statement until it is convenient.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#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/Pass.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/Support/Compiler.h"
|
|
#include <algorithm>
|
|
using namespace llvm;
|
|
|
|
namespace {
|
|
/// LowerSwitch Pass - Replace all SwitchInst instructions with chained branch
|
|
/// instructions. Note that this cannot be a BasicBlock pass because it
|
|
/// modifies the CFG!
|
|
class VISIBILITY_HIDDEN LowerSwitch : public FunctionPass {
|
|
public:
|
|
virtual bool runOnFunction(Function &F);
|
|
|
|
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
|
|
// This is a cluster of orthogonal Transforms
|
|
AU.addPreserved<UnifyFunctionExitNodes>();
|
|
AU.addPreservedID(PromoteMemoryToRegisterID);
|
|
AU.addPreservedID(LowerSelectID);
|
|
AU.addPreservedID(LowerInvokePassID);
|
|
AU.addPreservedID(LowerAllocationsID);
|
|
}
|
|
|
|
struct CaseRange {
|
|
Constant* Low;
|
|
Constant* High;
|
|
BasicBlock* BB;
|
|
|
|
CaseRange() : Low(0), High(0), BB(0) { }
|
|
CaseRange(Constant* low, Constant* high, BasicBlock* bb) :
|
|
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);
|
|
};
|
|
|
|
/// The comparison function for sorting the switch case values in the vector.
|
|
/// WARNING: Case ranges should be disjoint!
|
|
struct CaseCmp {
|
|
bool operator () (const LowerSwitch::CaseRange& C1,
|
|
const LowerSwitch::CaseRange& C2) {
|
|
|
|
const ConstantInt* CI1 = cast<const ConstantInt>(C1.Low);
|
|
const ConstantInt* CI2 = cast<const ConstantInt>(C2.High);
|
|
return CI1->getValue().slt(CI2->getValue());
|
|
}
|
|
};
|
|
|
|
RegisterPass<LowerSwitch>
|
|
X("lowerswitch", "Lower SwitchInst's to branches");
|
|
}
|
|
|
|
// Publically exposed interface to pass...
|
|
const PassInfo *llvm::LowerSwitchID = X.getPassInfo();
|
|
// createLowerSwitchPass - Interface to this file...
|
|
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++; // Advance over block so we don't traverse new blocks
|
|
|
|
if (SwitchInst *SI = dyn_cast<SwitchInst>(Cur->getTerminator())) {
|
|
Changed = true;
|
|
processSwitchInst(SI);
|
|
}
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
// operator<< - Used for debugging purposes.
|
|
//
|
|
static std::ostream& operator<<(std::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 << "]";
|
|
}
|
|
|
|
static OStream& operator<<(OStream &O, const LowerSwitch::CaseVector &C) {
|
|
if (O.stream()) *O.stream() << C;
|
|
return O;
|
|
}
|
|
|
|
// switchConvert - Convert the switch statement into a binary lookup of
|
|
// the case values. The function recursively builds this tree.
|
|
//
|
|
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);
|
|
DOUT << "LHS: " << LHS << "\n";
|
|
std::vector<CaseRange> RHS(Begin + Mid, End);
|
|
DOUT << "RHS: " << RHS << "\n";
|
|
|
|
CaseRange& Pivot = *(Begin + Mid);
|
|
DEBUG( DOUT << "Pivot ==> "
|
|
<< cast<ConstantInt>(Pivot.Low)->getValue().toStringSigned(10)
|
|
<< " -"
|
|
<< cast<ConstantInt>(Pivot.High)->getValue().toStringSigned(10)
|
|
<< "\n");
|
|
|
|
BasicBlock* LBranch = switchConvert(LHS.begin(), LHS.end(), Val,
|
|
OrigBlock, Default);
|
|
BasicBlock* RBranch = switchConvert(RHS.begin(), RHS.end(), Val,
|
|
OrigBlock, Default);
|
|
|
|
// Create a new node that checks if the value is < pivot. Go to the
|
|
// left branch if it is and right branch if not.
|
|
Function* F = OrigBlock->getParent();
|
|
BasicBlock* NewNode = new BasicBlock("NodeBlock");
|
|
F->getBasicBlockList().insert(OrigBlock->getNext(), NewNode);
|
|
|
|
ICmpInst* Comp = new ICmpInst(ICmpInst::ICMP_SLT, Val, Pivot.Low, "Pivot");
|
|
NewNode->getInstList().push_back(Comp);
|
|
new BranchInst(LBranch, RBranch, Comp, NewNode);
|
|
return NewNode;
|
|
}
|
|
|
|
// newLeafBlock - Create a new leaf block for the binary lookup tree. It
|
|
// checks if the switch's value == the case's value. If not, then it
|
|
// jumps to the default branch. At this point in the tree, the value
|
|
// can't be another valid case value, so the jump to the "default" branch
|
|
// is warranted.
|
|
//
|
|
BasicBlock* LowerSwitch::newLeafBlock(CaseRange& Leaf, Value* Val,
|
|
BasicBlock* OrigBlock,
|
|
BasicBlock* Default)
|
|
{
|
|
Function* F = OrigBlock->getParent();
|
|
BasicBlock* NewLeaf = new BasicBlock("LeafBlock");
|
|
F->getBasicBlockList().insert(OrigBlock->getNext(), NewLeaf);
|
|
|
|
// 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.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);
|
|
}
|
|
|
|
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.
|
|
//
|
|
void LowerSwitch::processSwitchInst(SwitchInst *SI) {
|
|
BasicBlock *CurBlock = SI->getParent();
|
|
BasicBlock *OrigBlock = CurBlock;
|
|
Function *F = CurBlock->getParent();
|
|
Value *Val = SI->getOperand(0); // The value we are switching on...
|
|
BasicBlock* Default = SI->getDefaultDest();
|
|
|
|
// If there is only the default destination, don't bother with the code below.
|
|
if (SI->getNumOperands() == 2) {
|
|
new BranchInst(SI->getDefaultDest(), CurBlock);
|
|
CurBlock->getInstList().erase(SI);
|
|
return;
|
|
}
|
|
|
|
// Create a new, empty default block so that the new hierarchy of
|
|
// if-then statements go to this and the PHI nodes are happy.
|
|
BasicBlock* NewDefault = new BasicBlock("NewDefault");
|
|
F->getBasicBlockList().insert(Default, NewDefault);
|
|
|
|
new BranchInst(Default, NewDefault);
|
|
|
|
// If there is an entry in any PHI nodes for the default edge, make sure
|
|
// to update them as well.
|
|
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);
|
|
}
|
|
|
|
// Prepare cases vector.
|
|
CaseVector Cases;
|
|
unsigned numCmps = Clusterify(Cases, SI);
|
|
|
|
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);
|
|
|
|
// Branch to our shiny new if-then stuff...
|
|
new BranchInst(SwitchBlock, OrigBlock);
|
|
|
|
// We are now done with the switch instruction, delete it.
|
|
CurBlock->getInstList().erase(SI);
|
|
}
|