mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-12-15 20:29:48 +00:00
495e547ef9
Follow up from r222926. Also handle multiple destinations from merged cases on multiple and subsequent phi instructions. rdar://problem/19106978 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@223135 91177308-0d34-0410-b5e6-96231b3b80d8
449 lines
17 KiB
C++
449 lines
17 KiB
C++
//===- LowerSwitch.cpp - Eliminate Switch instructions --------------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// The LowerSwitch transformation rewrites switch instructions with a sequence
|
|
// of branches, which allows targets to get away with not implementing the
|
|
// switch instruction until it is convenient.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Transforms/Scalar.h"
|
|
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
|
|
#include "llvm/ADT/STLExtras.h"
|
|
#include "llvm/IR/Constants.h"
|
|
#include "llvm/IR/Function.h"
|
|
#include "llvm/IR/Instructions.h"
|
|
#include "llvm/IR/LLVMContext.h"
|
|
#include "llvm/IR/CFG.h"
|
|
#include "llvm/Pass.h"
|
|
#include "llvm/Support/Compiler.h"
|
|
#include "llvm/Support/Debug.h"
|
|
#include "llvm/Support/raw_ostream.h"
|
|
#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
|
|
#include <algorithm>
|
|
using namespace llvm;
|
|
|
|
#define DEBUG_TYPE "lower-switch"
|
|
|
|
namespace {
|
|
/// LowerSwitch Pass - Replace all SwitchInst instructions with chained branch
|
|
/// instructions.
|
|
class LowerSwitch : public FunctionPass {
|
|
public:
|
|
static char ID; // Pass identification, replacement for typeid
|
|
LowerSwitch() : FunctionPass(ID) {
|
|
initializeLowerSwitchPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
bool runOnFunction(Function &F) override;
|
|
|
|
void getAnalysisUsage(AnalysisUsage &AU) const override {
|
|
// This is a cluster of orthogonal Transforms
|
|
AU.addPreserved<UnifyFunctionExitNodes>();
|
|
AU.addPreserved("mem2reg");
|
|
AU.addPreservedID(LowerInvokePassID);
|
|
}
|
|
|
|
struct CaseRange {
|
|
Constant* Low;
|
|
Constant* High;
|
|
BasicBlock* BB;
|
|
|
|
CaseRange(Constant *low = nullptr, Constant *high = nullptr,
|
|
BasicBlock *bb = nullptr) :
|
|
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,
|
|
ConstantInt *LowerBound, ConstantInt *UpperBound,
|
|
Value *Val, BasicBlock *Predecessor,
|
|
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());
|
|
}
|
|
};
|
|
}
|
|
|
|
char LowerSwitch::ID = 0;
|
|
INITIALIZE_PASS(LowerSwitch, "lowerswitch",
|
|
"Lower SwitchInst's to branches", false, false)
|
|
|
|
// Publicly exposed interface to pass...
|
|
char &llvm::LowerSwitchID = LowerSwitch::ID;
|
|
// 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 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 << "]";
|
|
}
|
|
|
|
// \brief Update the first occurrence of the "switch statement" BB in the PHI
|
|
// node with the "new" BB. The other occurrences will:
|
|
//
|
|
// 1) Be updated by subsequent calls to this function. Switch statements may
|
|
// have more than one outcoming edge into the same BB if they all have the same
|
|
// value. When the switch statement is converted these incoming edges are now
|
|
// coming from multiple BBs.
|
|
// 2) Removed if subsequent incoming values now share the same case, i.e.,
|
|
// multiple outcome edges are condensed into one. This is necessary to keep the
|
|
// number of phi values equal to the number of branches to SuccBB.
|
|
static void fixPhis(BasicBlock *SuccBB, BasicBlock *OrigBB, BasicBlock *NewBB,
|
|
unsigned NumMergedCases) {
|
|
for (BasicBlock::iterator I = SuccBB->begin(), IE = SuccBB->getFirstNonPHI();
|
|
I != IE; ++I) {
|
|
PHINode *PN = cast<PHINode>(I);
|
|
|
|
// Only update the first occurence.
|
|
unsigned Idx = 0, E = PN->getNumIncomingValues();
|
|
unsigned LocalNumMergedCases = NumMergedCases;
|
|
for (; Idx != E; ++Idx) {
|
|
if (PN->getIncomingBlock(Idx) == OrigBB) {
|
|
PN->setIncomingBlock(Idx, NewBB);
|
|
break;
|
|
}
|
|
}
|
|
|
|
// Remove additional occurences coming from condensed cases and keep the
|
|
// number of incoming values equal to the number of branches to SuccBB.
|
|
for (++Idx; LocalNumMergedCases > 0 && Idx < E; ++Idx)
|
|
if (PN->getIncomingBlock(Idx) == OrigBB) {
|
|
PN->removeIncomingValue(Idx);
|
|
LocalNumMergedCases--;
|
|
}
|
|
}
|
|
}
|
|
|
|
// switchConvert - Convert the switch statement into a binary lookup of
|
|
// the case values. The function recursively builds this tree.
|
|
// LowerBound and UpperBound are used to keep track of the bounds for Val
|
|
// that have already been checked by a block emitted by one of the previous
|
|
// calls to switchConvert in the call stack.
|
|
BasicBlock *LowerSwitch::switchConvert(CaseItr Begin, CaseItr End,
|
|
ConstantInt *LowerBound,
|
|
ConstantInt *UpperBound, Value *Val,
|
|
BasicBlock *Predecessor,
|
|
BasicBlock *OrigBlock,
|
|
BasicBlock *Default) {
|
|
unsigned Size = End - Begin;
|
|
|
|
if (Size == 1) {
|
|
// Check if the Case Range is perfectly squeezed in between
|
|
// already checked Upper and Lower bounds. If it is then we can avoid
|
|
// emitting the code that checks if the value actually falls in the range
|
|
// because the bounds already tell us so.
|
|
if (Begin->Low == LowerBound && Begin->High == UpperBound) {
|
|
unsigned NumMergedCases = 0;
|
|
if (LowerBound && UpperBound)
|
|
NumMergedCases =
|
|
UpperBound->getSExtValue() - LowerBound->getSExtValue();
|
|
fixPhis(Begin->BB, OrigBlock, Predecessor, NumMergedCases);
|
|
return Begin->BB;
|
|
}
|
|
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");
|
|
|
|
// NewLowerBound here should never be the integer minimal value.
|
|
// This is because it is computed from a case range that is never
|
|
// the smallest, so there is always a case range that has at least
|
|
// a smaller value.
|
|
ConstantInt *NewLowerBound = cast<ConstantInt>(Pivot.Low);
|
|
ConstantInt *NewUpperBound;
|
|
|
|
// If we don't have a Default block then it means that we can never
|
|
// have a value outside of a case range, so set the UpperBound to the highest
|
|
// value in the LHS part of the case ranges.
|
|
if (Default != nullptr) {
|
|
// Because NewLowerBound is never the smallest representable integer
|
|
// it is safe here to subtract one.
|
|
NewUpperBound = ConstantInt::get(NewLowerBound->getContext(),
|
|
NewLowerBound->getValue() - 1);
|
|
} else {
|
|
CaseItr LastLHS = LHS.begin() + LHS.size() - 1;
|
|
NewUpperBound = cast<ConstantInt>(LastLHS->High);
|
|
}
|
|
|
|
DEBUG(dbgs() << "LHS Bounds ==> ";
|
|
if (LowerBound) {
|
|
dbgs() << cast<ConstantInt>(LowerBound)->getSExtValue();
|
|
} else {
|
|
dbgs() << "NONE";
|
|
}
|
|
dbgs() << " - " << NewUpperBound->getSExtValue() << "\n";
|
|
dbgs() << "RHS Bounds ==> ";
|
|
dbgs() << NewLowerBound->getSExtValue() << " - ";
|
|
if (UpperBound) {
|
|
dbgs() << cast<ConstantInt>(UpperBound)->getSExtValue() << "\n";
|
|
} else {
|
|
dbgs() << "NONE\n";
|
|
});
|
|
|
|
// 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 = BasicBlock::Create(Val->getContext(), "NodeBlock");
|
|
|
|
ICmpInst* Comp = new ICmpInst(ICmpInst::ICMP_SLT,
|
|
Val, Pivot.Low, "Pivot");
|
|
|
|
BasicBlock *LBranch = switchConvert(LHS.begin(), LHS.end(), LowerBound,
|
|
NewUpperBound, Val, NewNode, OrigBlock,
|
|
Default);
|
|
BasicBlock *RBranch = switchConvert(RHS.begin(), RHS.end(), NewLowerBound,
|
|
UpperBound, Val, NewNode, OrigBlock,
|
|
Default);
|
|
|
|
Function::iterator FI = OrigBlock;
|
|
F->getBasicBlockList().insert(++FI, NewNode);
|
|
NewNode->getInstList().push_back(Comp);
|
|
|
|
BranchInst::Create(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 = BasicBlock::Create(Val->getContext(), "LeafBlock");
|
|
Function::iterator FI = OrigBlock;
|
|
F->getBasicBlockList().insert(++FI, NewLeaf);
|
|
|
|
// Emit comparison
|
|
ICmpInst* Comp = nullptr;
|
|
if (Leaf.Low == Leaf.High) {
|
|
// Make the seteq instruction...
|
|
Comp = new ICmpInst(*NewLeaf, ICmpInst::ICMP_EQ, Val,
|
|
Leaf.Low, "SwitchLeaf");
|
|
} else {
|
|
// Make range comparison
|
|
if (cast<ConstantInt>(Leaf.Low)->isMinValue(true /*isSigned*/)) {
|
|
// Val >= Min && Val <= Hi --> Val <= Hi
|
|
Comp = new ICmpInst(*NewLeaf, ICmpInst::ICMP_SLE, Val, Leaf.High,
|
|
"SwitchLeaf");
|
|
} else if (cast<ConstantInt>(Leaf.Low)->isZero()) {
|
|
// Val >= 0 && Val <= Hi --> Val <=u Hi
|
|
Comp = new ICmpInst(*NewLeaf, ICmpInst::ICMP_ULE, Val, Leaf.High,
|
|
"SwitchLeaf");
|
|
} 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(*NewLeaf, ICmpInst::ICMP_ULE, Add, UpperBound,
|
|
"SwitchLeaf");
|
|
}
|
|
}
|
|
|
|
// Make the conditional branch...
|
|
BasicBlock* Succ = Leaf.BB;
|
|
BranchInst::Create(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 (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); i != e; ++i)
|
|
Cases.push_back(CaseRange(i.getCaseValue(), i.getCaseValue(),
|
|
i.getCaseSuccessor()));
|
|
|
|
std::sort(Cases.begin(), Cases.end(), CaseCmp());
|
|
|
|
// Merge case into clusters
|
|
if (Cases.size()>=2)
|
|
for (CaseItr I = Cases.begin(), J = std::next(Cases.begin());
|
|
J != Cases.end();) {
|
|
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->getCondition(); // 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->getNumCases()) {
|
|
BranchInst::Create(SI->getDefaultDest(), CurBlock);
|
|
CurBlock->getInstList().erase(SI);
|
|
return;
|
|
}
|
|
|
|
const bool DefaultIsUnreachable =
|
|
Default->size() == 1 && isa<UnreachableInst>(Default->getTerminator());
|
|
// Create a new, empty default block so that the new hierarchy of
|
|
// if-then statements go to this and the PHI nodes are happy.
|
|
// if the default block is set as an unreachable we avoid creating one
|
|
// because will never be a valid target.
|
|
BasicBlock *NewDefault = nullptr;
|
|
if (!DefaultIsUnreachable) {
|
|
NewDefault = BasicBlock::Create(SI->getContext(), "NewDefault");
|
|
F->getBasicBlockList().insert(Default, NewDefault);
|
|
|
|
BranchInst::Create(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);
|
|
|
|
DEBUG(dbgs() << "Clusterify finished. Total clusters: " << Cases.size()
|
|
<< ". Total compares: " << numCmps << "\n");
|
|
DEBUG(dbgs() << "Cases: " << Cases << "\n");
|
|
(void)numCmps;
|
|
|
|
ConstantInt *UpperBound = nullptr;
|
|
ConstantInt *LowerBound = nullptr;
|
|
|
|
// Optimize the condition where Default is an unreachable block. In this case
|
|
// we can make the bounds tightly fitted around the case value ranges,
|
|
// because we know that the value passed to the switch should always be
|
|
// exactly one of the case values.
|
|
if (DefaultIsUnreachable) {
|
|
CaseItr LastCase = Cases.begin() + Cases.size() - 1;
|
|
UpperBound = cast<ConstantInt>(LastCase->High);
|
|
LowerBound = cast<ConstantInt>(Cases.begin()->Low);
|
|
}
|
|
BasicBlock *SwitchBlock =
|
|
switchConvert(Cases.begin(), Cases.end(), LowerBound, UpperBound, Val,
|
|
OrigBlock, OrigBlock, NewDefault);
|
|
|
|
// Branch to our shiny new if-then stuff...
|
|
BranchInst::Create(SwitchBlock, OrigBlock);
|
|
|
|
// We are now done with the switch instruction, delete it.
|
|
CurBlock->getInstList().erase(SI);
|
|
|
|
pred_iterator PI = pred_begin(Default), E = pred_end(Default);
|
|
// If the Default block has no more predecessors just remove it
|
|
if (PI == E) {
|
|
DeleteDeadBlock(Default);
|
|
}
|
|
}
|