mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-20 11:29:24 +00:00
Patch contributed by Paolo Invernizzi. Thanks Paolo! git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16368 91177308-0d34-0410-b5e6-96231b3b80d8
223 lines
8.0 KiB
C++
223 lines
8.0 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/Constants.h"
|
|
#include "llvm/Function.h"
|
|
#include "llvm/Instructions.h"
|
|
#include "llvm/Pass.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/ADT/Statistic.h"
|
|
#include <algorithm>
|
|
using namespace llvm;
|
|
|
|
namespace {
|
|
Statistic<> NumLowered("lowerswitch", "Number of SwitchInst's replaced");
|
|
|
|
/// LowerSwitch Pass - Replace all SwitchInst instructions with chained branch
|
|
/// instructions. Note that this cannot be a BasicBlock pass because it
|
|
/// modifies the CFG!
|
|
class LowerSwitch : public FunctionPass {
|
|
public:
|
|
bool runOnFunction(Function &F);
|
|
typedef std::pair<Constant*, BasicBlock*> Case;
|
|
typedef std::vector<Case>::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* OrigBlock, BasicBlock* Default);
|
|
};
|
|
|
|
/// The comparison function for sorting the switch case values in the vector.
|
|
struct CaseCmp {
|
|
bool operator () (const LowerSwitch::Case& C1,
|
|
const LowerSwitch::Case& C2) {
|
|
if (const ConstantUInt* U1 = dyn_cast<const ConstantUInt>(C1.first))
|
|
return U1->getValue() < cast<const ConstantUInt>(C2.first)->getValue();
|
|
|
|
const ConstantSInt* S1 = dyn_cast<const ConstantSInt>(C1.first);
|
|
return S1->getValue() < cast<const ConstantSInt>(C2.first)->getValue();
|
|
}
|
|
};
|
|
|
|
RegisterOpt<LowerSwitch>
|
|
X("lowerswitch", "Lower SwitchInst's to branches");
|
|
}
|
|
|
|
// 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.
|
|
//
|
|
std::ostream& operator<<(std::ostream &O,
|
|
const std::vector<LowerSwitch::Case> &C) {
|
|
O << "[";
|
|
|
|
for (std::vector<LowerSwitch::Case>::const_iterator B = C.begin(),
|
|
E = C.end(); B != E; ) {
|
|
O << *B->first;
|
|
if (++B != E) O << ", ";
|
|
}
|
|
|
|
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<Case> LHS(Begin, Begin + Mid);
|
|
DEBUG(std::cerr << "LHS: " << LHS << "\n");
|
|
std::vector<Case> RHS(Begin + Mid, End);
|
|
DEBUG(std::cerr << "RHS: " << RHS << "\n");
|
|
|
|
Case& Pivot = *(Begin + Mid);
|
|
DEBUG(std::cerr << "Pivot ==> "
|
|
<< (int64_t)cast<ConstantInt>(Pivot.first)->getRawValue()
|
|
<< "\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);
|
|
|
|
SetCondInst* Comp = new SetCondInst(Instruction::SetLT, Val, Pivot.first,
|
|
"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(Case& Leaf, Value* Val,
|
|
BasicBlock* OrigBlock,
|
|
BasicBlock* Default)
|
|
{
|
|
Function* F = OrigBlock->getParent();
|
|
BasicBlock* NewLeaf = new BasicBlock("LeafBlock");
|
|
F->getBasicBlockList().insert(OrigBlock->getNext(), NewLeaf);
|
|
|
|
// Make the seteq instruction...
|
|
SetCondInst* Comp = new SetCondInst(Instruction::SetEQ, Val,
|
|
Leaf.first, "SwitchLeaf");
|
|
NewLeaf->getInstList().push_back(Comp);
|
|
|
|
// Make the conditional branch...
|
|
BasicBlock* Succ = Leaf.second;
|
|
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);
|
|
int BlockIdx = PN->getBasicBlockIndex(OrigBlock);
|
|
assert(BlockIdx != -1 && "Switch didn't go to this successor??");
|
|
PN->setIncomingBlock((unsigned)BlockIdx, NewLeaf);
|
|
}
|
|
|
|
return NewLeaf;
|
|
}
|
|
|
|
// 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);
|
|
}
|
|
|
|
std::vector<Case> Cases;
|
|
|
|
// 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());
|
|
DEBUG(std::cerr << "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);
|
|
}
|