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BranchFusion.cpp
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BranchFusion.cpp
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//===- BranchFusion.cpp - A branch fusion pass ----------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar/BranchFusion.h"
#include "llvm/Transforms/IPO/FunctionMerging.h"
#include "llvm/ADT/PtrToRefUtils.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SequenceAlignment.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/InitializePasses.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/ModuleSlotTracker.h"
#include "llvm/IR/Verifier.h"
#include <llvm/IR/IRBuilder.h>
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/PostDominators.h"
#include "llvm/Transforms/Scalar.h"
//#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/BreadthFirstIterator.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/Utils/Local.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/InstCombine/InstCombine.h"
#include "llvm/Transforms/Utils/FunctionComparator.h"
#include "llvm/Transforms/Utils/Mem2Reg.h"
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
#include <algorithm>
#include <list>
#include <limits.h>
#include <functional>
#include <queue>
#include <vector>
#include <algorithm>
#include <stdlib.h>
#include <time.h>
#define DEBUG_TYPE "brfusion"
using namespace llvm;
static cl::opt<bool> Debug("brfusion-debug", cl::init(false), cl::Hidden,
cl::desc("Enable debug information"));
static cl::opt<bool>
EnableSOA("brfusion-soa", cl::init(true), cl::Hidden,
cl::desc("Enable the state-of-the-art brfusion technique"));
static cl::opt<bool>
ForceAll("brfusion-force", cl::init(false), cl::Hidden,
cl::desc("Force all valid branch fusion transformations found"));
static cl::opt<int> TraversalStrategy(
"brfusion-traversal", cl::init(0), cl::Hidden,
cl::desc("Select which traversal strategy: 0:rpo 1:po 2:dominated-first"));
static cl::opt<int> ReductionThreshold(
"brfusion-threshold", cl::init(2), cl::Hidden,
cl::desc("Select which traversal strategy: 0:rpo 1:po 2:dominated-first"));
static cl::opt<bool>
WriteDotFile("brfusion-dot", cl::init(false), cl::Hidden,
cl::desc("Write .dot files of the successful branch fusion"));
static cl::opt<bool> UseCostInFingerprint(
"brfusion-fingerprint-cost", cl::init(true), cl::Hidden,
cl::desc("Use instruction cost as part of the fingerprint"));
static std::string GetValueName(const Value *V) {
if (V) {
std::string name;
raw_string_ostream namestream(name);
V->printAsOperand(namestream, false);
return namestream.str();
} else
return "[null]";
}
class BranchFusion {
unsigned CountChanges;
bool merge(Function &F, BranchInst *BI, DominatorTree &DT,
TargetTransformInfo &TTI, std::list<BranchInst *> &ListBIs,
std::unordered_set<std::string> &PreviousBlocks);
public:
BranchFusion() : CountChanges(0) {}
bool runImpl(Function &F);
};
PreservedAnalyses BranchFusionPass::run(Function &F,
FunctionAnalysisManager &AM) {
// auto &FAM =
// AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
// std::function<TargetTransformInfo *(Function &)> GTTI =
// [&FAM](Function &F) -> TargetTransformInfo * {
// return &FAM.getResult<TargetIRAnalysis>(F);
// };
BranchFusion BF;
if (BF.runImpl(F)) //, GTTI))
return PreservedAnalyses::none();
return PreservedAnalyses::all();
}
class BranchFusionLegacyPass : public FunctionPass {
public:
static char ID;
BranchFusionLegacyPass() : FunctionPass(ID) {
initializeBranchFusionLegacyPassPass(*PassRegistry::getPassRegistry());
}
bool runOnFunction(Function &F) override {
BranchFusion BF;
return BF.runImpl(F);
}
/*
bool runOnFunction(Function &F) override {
return false;
//FunctionMerging FM;
//return FM.runImpl(M, GTTI);
}
*/
void getAnalysisUsage(AnalysisUsage &AU) const override {
// AU.addRequired<TargetTransformInfoWrapperPass>();
// ModulePass::getAnalysisUsage(AU);
}
};
class SEMERegion {
private:
BasicBlock *Entry;
std::vector<BasicBlock *> Blocks;
std::vector<BasicBlock *> Exits;
void collectDominatedRegion(BasicBlock *BB, DominatorTree &DT,
std::set<Value *> &Visited);
public:
using iterator =
PtrToRefIterator<BasicBlock, std::vector<BasicBlock *>::iterator>;
SEMERegion(BasicBlock *Entry, DominatorTree &DT) : Entry(Entry) {
std::set<Value *> Visited;
collectDominatedRegion(Entry, DT, Visited);
}
const BasicBlock &getEntryBlock() const { return *Entry; }
BasicBlock &getEntryBlock() { return *Entry; }
bool contains(BasicBlock *BB) {
return std::find(Blocks.begin(), Blocks.end(), BB) != Blocks.end();
}
bool isExitBlock(BasicBlock *BB) {
return std::find(Exits.begin(), Exits.end(), BB) != Exits.end();
}
iterator begin() { return iterator(Blocks.begin()); }
iterator end() { return iterator(Blocks.end()); }
iterator exit_begin() { return iterator(Exits.begin()); }
iterator exit_end() { return iterator(Exits.end()); }
iterator_range<iterator> exits() {
return make_range<iterator>(exit_begin(), exit_end());
}
size_t size() { return Blocks.size(); }
size_t getNumExitBlocks() { return Exits.size(); }
BasicBlock *getUniqueExitBlock() {
if (Exits.size() == 1)
return *Exits.begin();
else
return nullptr;
}
};
void SEMERegion::collectDominatedRegion(BasicBlock *BB, DominatorTree &DT,
std::set<Value *> &Visited) {
if (DT.dominates(Entry, BB)) {
// errs() << Entry->getName() << " dominate " << BB->getName() << "\n";
if (Visited.find(BB) != Visited.end())
return;
Visited.insert(BB);
Blocks.push_back(BB);
for (auto BBIt = succ_begin(BB), EndIt = succ_end(BB); BBIt != EndIt;
BBIt++) {
collectDominatedRegion(*BBIt, DT, Visited);
}
} else {
Exits.push_back(BB);
// errs() << Entry->getName() << " NOT dominate " << BB->getName() << "\n";
}
}
struct MatchingBlocks {
BasicBlock *Blocks[2];
std::map<Instruction *, Instruction *> MatchingInsts;
MatchingBlocks() { Blocks[0] = Blocks[1] = nullptr; }
MatchingBlocks(BasicBlock *BB0, BasicBlock *BB1) {
Blocks[0] = BB0;
Blocks[1] = BB1;
}
BasicBlock *operator[](size_t i) { return Blocks[i]; }
void setMatchingPair(Instruction *I1, Instruction *I2) {
MatchingInsts[I1] = I2;
MatchingInsts[I2] = I1;
}
bool isMatchingPair(Instruction *I1, Instruction *I2) {
if (MatchingInsts.find(I1) == MatchingInsts.end())
return false;
return (MatchingInsts[I1] == I2);
}
Instruction *getMatchingInstruction(Instruction *I) {
if (MatchingInsts.find(I) == MatchingInsts.end())
return nullptr;
return MatchingInsts[I];
}
};
class DotPrinter {
public:
std::string Str;
raw_string_ostream OS;
BranchInst *BI;
SEMERegion &LeftR;
SEMERegion &RightR;
ModuleSlotTracker MST;
DotPrinter(Function &F, BranchInst *BI, SEMERegion &LeftR, SEMERegion &RightR, AlignedSequence<Value *> &AlignedInsts) : OS(Str), BI(BI), LeftR(LeftR), RightR(RightR), MST(F.getParent()) {
std::map<BasicBlock *, std::string> BB2Id;
std::map<BasicBlock *, std::string> PortPrefix;
write("digraph {\n");
std::set<BasicBlock *> Visited;
unsigned NId = 0;
MatchingBlocks MB;
int ClosedMB = 0;
for (auto &Entry : AlignedInsts) {
if (Entry.get(0)) {
if (isa<BasicBlock>(Entry.get(0)))
MB.Blocks[0] = dyn_cast<BasicBlock>(Entry.get(0));
else if (Instruction *I = dyn_cast<Instruction>(Entry.get(0))) {
if (I->isTerminator()) ClosedMB = ClosedMB | 1;
}
}
if (Entry.get(1)) {
if (isa<BasicBlock>(Entry.get(1)))
MB.Blocks[1] = dyn_cast<BasicBlock>(Entry.get(1));
else if (Instruction *I = dyn_cast<Instruction>(Entry.get(1))) {
if (I->isTerminator()) ClosedMB = ClosedMB | 2;
}
}
if (Entry.match()) {
Instruction *I1 = dyn_cast<Instruction>(Entry.get(0));
Instruction *I2 = dyn_cast<Instruction>(Entry.get(1));
if (I1 && I2) MB.setMatchingPair(I1,I2);
}
if (ClosedMB==3) {
if (MB.MatchingInsts.size()) {
BasicBlock *BB1 = MB[0];
BasicBlock *BB2 = MB[1];
std::string Name = std::string("m_bb")+std::to_string(NId);
writeNodePair(MB, Name);
NId++;
Visited.insert(BB1);
Visited.insert(BB2);
BB2Id[BB1] = Name;
BB2Id[BB2] = Name;
PortPrefix[BB1] = "f1";
PortPrefix[BB2] = "f2";
}
ClosedMB = 0;
MB.MatchingInsts.clear();
}
}
NId = 0;
for (BasicBlock &BB : F) {
if (Visited.count(&BB)) continue;
std::string Name = std::string("f_bb")+std::to_string(NId);
writeNode(BB, Name,"f");
NId++;
Visited.insert(&BB);
BB2Id[&BB] = Name;
PortPrefix[&BB] = "f";
}
Visited.clear();
for (BasicBlock &BB : F) {
if (Visited.count(&BB)) continue;
auto *TI = BB.getTerminator();
BranchInst *Br = dyn_cast<BranchInst>(TI);
for (unsigned i = 0; i<TI->getNumSuccessors(); i++) {
write(BB2Id[&BB]+std::string(":")+PortPrefix[&BB]);
if (Br && Br->isConditional()) { if (i==0) write("T"); else write("F"); }
write(" -> ");
std::string NodeAddr = BB2Id[TI->getSuccessor(i)]+std::string(":")+PortPrefix[TI->getSuccessor(i)];
write(NodeAddr);
write("\n");
}
Visited.insert(&BB);
}
write("}\n");
}
void write(std::string s) {
Str += s;
}
void write(const char *s) {
Str += s;
}
void writeBlockEntry(BasicBlock &BB) {
write(BB.getName().str());
write(":");
}
void write(Instruction &I) {
I.print(OS, MST, false);
}
void writeNode(BasicBlock &BB, std::string Name, std::string Port) {
bool HasCondBr = false;
if (BranchInst *Br = dyn_cast<BranchInst>(BB.getTerminator())) {
HasCondBr = Br->isConditional();
}
write(Name);
write(" [shape = none, ");
if (LeftR.contains(&BB))
write(" xlabel=\"L\", ");
else if (RightR.contains(&BB))
write(" xlabel=\"R\", ");
write("label = <<table ");
if (LeftR.contains(&BB))
write(" bgcolor=\"LightYellow\" ");
else if (RightR.contains(&BB))
write(" bgcolor=\"LightCyan\" ");
write(" border=\"0\" cellspacing=\"0\">\n");
if (HasCondBr)
write(std::string("<tr><td port=\"")+Port+"\" border=\"1\" colspan=\"2\">");
else
write(std::string("<tr><td port=\"")+Port+"\" border=\"1\">");
writeBlockInnerTable(BB);
write("</td></tr>\n");
if (HasCondBr)
write(std::string("<tr><td border=\"1\" port=\"")+Port+std::string("T\">T</td><td border=\"1\" port=\"")+Port+"F\">F</td></tr>\n");
write("</table>> ]\n");
}
void writeNodePair(MatchingBlocks &MB, std::string Name) {
BasicBlock *BB1 = MB[0];
BasicBlock *BB2 = MB[1];
bool HasCondBr1 = false;
if (BranchInst *Br = dyn_cast<BranchInst>(BB1->getTerminator())) {
HasCondBr1 = Br->isConditional();
}
bool HasCondBr2 = false;
if (BranchInst *Br = dyn_cast<BranchInst>(BB2->getTerminator())) {
HasCondBr2 = Br->isConditional();
}
write(Name);
write(" [shape = none, label = <<table border=\"0\" cellspacing=\"0\">\n");
auto It1 = BB1->begin();
auto It2 = BB2->begin();
write("<tr><td port=\"f1\" border=\"1\" colspan=\"2\">");
write("<table bgcolor=\"LightYellow\" border=\"0\">\n");
write("<tr><td align=\"left\">");
writeBlockEntry(*BB1);
write("</td></tr>\n");
while (It1!=BB1->end() && It2!=BB2->end()) {
if (It1==BB1->end()) {
write("<tr><td bgcolor=\"#e8765c70\" align=\"left\"> </td></tr>\n");
It2++;
} else {
Instruction *MI = MB.getMatchingInstruction(&*It1);
if (MI) {
while (MI!=(&*It2)) {
write("<tr><td bgcolor=\"#e8765c70\" align=\"left\"> </td></tr>\n");
It2++;
}
write("<tr><td bgcolor=\"lightgreen\" align=\"left\">");
write(*It1);
write("</td></tr>\n");
It2++;
} else {
write("<tr><td bgcolor=\"#e8765c70\" align=\"left\">");
write(*It1);
write("</td></tr>\n");
}
It1++;
}
}
write("</table>\n");
write("</td>\n");
It1 = BB1->begin();
It2 = BB2->begin();
write("<td port=\"f2\" border=\"1\" colspan=\"2\">");
write("<table bgcolor=\"LightCyan\" border=\"0\">\n");
write("<tr><td align=\"left\">");
writeBlockEntry(*BB2);
write("</td></tr>\n");
while (It1!=BB1->end() && It2!=BB2->end()) {
if (It2==BB2->end()) {
write("<tr><td bgcolor=\"#e8765c70\" align=\"left\"> </td></tr>\n");
It1++;
} else {
Instruction *MI = MB.getMatchingInstruction(&*It2);
if (MB.isMatchingPair(&*It1,&*It2)) {
write("<tr><td bgcolor=\"lightgreen\" align=\"left\">");
write(*It2);
write("</td></tr>\n");
It1++;
} else {
while (It1!=BB1->end() && MB.getMatchingInstruction(&*It1)==nullptr) {
write("<tr><td bgcolor=\"#e8765c70\" align=\"left\"> </td></tr>\n");
It1++;
}
write("<tr><td bgcolor=\"#e8765c70\" align=\"left\">");
write(*It2);
write("</td></tr>\n");
}
It2++;
}
}
write("</table>\n");
write("</td></tr>\n");
if (HasCondBr1 || HasCondBr2) {
write("<tr>");
if (HasCondBr1)
write("<td border=\"1\" port=\"f1T\">T</td><td border=\"1\" port=\"f1F\">F</td>\n");
else
write("<td border=\"0\" colspan=\"2\"> </td>\n");
if (HasCondBr2)
write("<td border=\"1\" port=\"f2T\">T</td><td border=\"1\" port=\"f2F\">F</td>\n");
else
write("<td border=\"0\" colspan=\"2\"> </td>\n");
write("</tr>\n");
}
write("</table>> ]\n");
}
void writeBlockInnerTable(BasicBlock &BB) {
write("<table border=\"0\">\n");
write("<tr><td align=\"left\">");
writeBlockEntry(BB);
write("</td></tr>\n");
for (Instruction &I: BB) {
if (&I == this->BI) {
write("<tr><td bgcolor=\"yellow\" align=\"left\">");
}else
write("<tr><td align=\"left\">");
write(I);
write("</td></tr>\n");
}
write("</table>\n");
}
};
bool BranchFusion::merge(Function &F, BranchInst *BI, DominatorTree &DT,
TargetTransformInfo &TTI, std::list<BranchInst *> &ListBIs,
std::unordered_set<std::string> &PreviousBlocks) {
// Check the instruction is not deleted
// This should not happen (we remove instructions we delete from ListBIs)
// but apparently some other piece of code might remove branches
if (BI->getParent() == nullptr)
return false;
if (Debug) {
errs() << "Original version\n";
F.dump();
errs() << "Select branch for merging\n";
BI->dump();
}
BasicBlock *BBT = BI->getSuccessor(0);
BasicBlock *BBF = BI->getSuccessor(1);
Value *BrCond = BI->getCondition();
SEMERegion LeftR(BBT, DT);
SEMERegion RightR(BBF, DT);
int SizeLeft = 0;
int SizeRight = 0;
if (Debug) {
errs() << "Select branch for merging\n";
BI->dump();
errs() << "LEFT REGION:\n";
for (BasicBlock &BB : LeftR) BB.dump();
errs() << "RIGHT REGION:\n";
for (BasicBlock &BB : RightR) BB.dump();
}
std::set<BasicBlock *> KnownBBs;
for (BasicBlock &BB : LeftR) {
KnownBBs.insert(&BB);
//predecessors must be within the same region or be the entry block
for (auto It = pred_begin(&BB), E = pred_end(&BB); It != E; It++) {
BasicBlock *PredBB = *It;
if (!LeftR.contains(PredBB) && PredBB != BI->getParent()) {
return false;
}
}
for (Instruction &I : BB) {
auto cost = TTI.getInstructionCost(
&I, TargetTransformInfo::TargetCostKind::TCK_CodeSize);
SizeLeft += cost.getValue().getValue();
}
}
for (BasicBlock &BB : RightR) {
KnownBBs.insert(&BB);
//predecessors must be within the same region or be the entry block
for (auto It = pred_begin(&BB), E = pred_end(&BB); It != E; It++) {
BasicBlock *PredBB = *It;
if (!RightR.contains(PredBB) && PredBB != BI->getParent()) {
return false;
}
}
for (Instruction &I : BB) {
auto cost = TTI.getInstructionCost(
&I, TargetTransformInfo::TargetCostKind::TCK_CodeSize);
SizeRight += cost.getValue().getValue();
}
}
//TODO: fix issue with PHI-node assignment from Function Merging
if (BI->getSuccessor(0)->getUniquePredecessor()!=BI->getParent() ||
BI->getSuccessor(1)->getUniquePredecessor()!=BI->getParent()) {
return false;
}
//TODO: handle landingpad on exit blocks. This might break the link between the invoke and the landingpad.
for (BasicBlock &BB : LeftR.exits()) {
//errs() << "Left Exit: " << BB.getName().str() << "\n";
if (BB.isLandingPad()) return false;
}
for (BasicBlock &BB : RightR.exits()) {
//errs() << "Right Exit: " << BB.getName().str() << "\n";
if (BB.isLandingPad()) return false;
}
bool IsSingleExit = LeftR.getNumExitBlocks() == 1 &&
RightR.getNumExitBlocks() == 1 &&
LeftR.getUniqueExitBlock() == RightR.getUniqueExitBlock();
if (EnableSOA) {
bool IsSOA = LeftR.size() == 1 && RightR.size() == 1 && IsSingleExit;
if (!IsSOA) {
errs() << "Skipping NOT SOA\n";
return false;
}
errs() << "Processing SOA-valid Branch\n";
}
// if (!IsSingleExit) return false;
/* fixed:
for (BasicBlock *BB : KnownBBs) {
for (auto It = pred_begin(BB), E = pred_end(BB); It != E; It++) {
BasicBlock *PredBB = *It;
if (!KnownBBs.count(PredBB) && PredBB != BI->getParent()) {
return false;
}
}
}*/
AlignmentStats TotalAlignmentStats;
AlignedSequence<Value *> AlignedInsts =
FunctionMerger::alignBlocks(LeftR, RightR, TotalAlignmentStats, (UseCostInFingerprint?(&TTI):nullptr) );
int CountMatchUsefullInsts = 0;
for (auto &Entry : AlignedInsts) {
if (Debug) {
errs() << "-----------------------------------------------------\n";
if (Entry.get(0)) {
if (isa<BasicBlock>(Entry.get(0)))
errs() << Entry.get(0)->getName() << "\n";
else
Entry.get(0)->dump();
} else
errs() << "\t-\n";
if (Entry.get(1)) {
if (isa<BasicBlock>(Entry.get(1)))
errs() << Entry.get(1)->getName() << "\n";
else
Entry.get(1)->dump();
} else {
errs() << "\t-\n";
}
}
if (Entry.match()) {
if (isa<BinaryOperator>(Entry.get(0)))
CountMatchUsefullInsts++;
if (isa<CallInst>(Entry.get(0)))
CountMatchUsefullInsts++;
if (isa<InvokeInst>(Entry.get(0)))
CountMatchUsefullInsts++;
if (isa<CmpInst>(Entry.get(0)))
CountMatchUsefullInsts++;
if (isa<CastInst>(Entry.get(0)))
CountMatchUsefullInsts++;
// if (isa<StoreInst>(Pair.first))
// CountMatchUsefullInsts++;
}
}
std::string DotStr;
if (WriteDotFile && (EnableHyFMNW || EnableHyFMPA)) {
DotPrinter DP(F, BI, LeftR, RightR, AlignedInsts);
DotStr = DP.Str;
}
LLVMContext &Context = F.getContext();
const DataLayout *DL = &F.getParent()->getDataLayout();
Type *IntPtrTy = DL->getIntPtrType(Context);
ValueToValueMapTy VMap;
// initialize VMap
for (Argument &Arg : F.args()) {
VMap[&Arg] = &Arg;
}
for (BasicBlock &BB : F) {
if (KnownBBs.count(&BB))
continue;
VMap[&BB] = &BB;
for (Instruction &I : BB) {
VMap[&I] = &I;
}
}
FunctionMergingOptions Options = FunctionMergingOptions()
.enableUnifiedReturnTypes(false)
.matchOnlyIdenticalTypes(true);
BasicBlock *EntryBB = BasicBlock::Create(Context, "", &F);
FunctionMerger::SALSSACodeGen CG(LeftR, RightR);
CG.setFunctionIdentifier(BrCond)
.setEntryPoints(BBT, BBF)
.setReturnTypes(F.getReturnType(), F.getReturnType())
.setMergedFunction(&F)
.setMergedEntryPoint(EntryBB)
.setMergedReturnType(F.getReturnType(), false)
.setContext(&Context)
.setIntPtrType(IntPtrTy);
if (!CG.generate(AlignedInsts, VMap, Options)) {
errs() << "ERROR: Failed to generate the fused branches!\n";
if (Debug) {
errs() << "Destroying generated code\n";
F.dump();
}
CG.destroyGeneratedCode();
if (Debug) {
errs() << "Generated code destroyed\n";
}
EntryBB->eraseFromParent();
if (Debug) {
errs() << "Branch fusion reversed\n";
F.dump();
}
for (BasicBlock &BB : F) {
if (!PreviousBlocks.count(BB.getName().str())) {
errs() << "ERROR: Basic Block kept hanging by rollback: " << BB.getName().str() << "\n";
}
}
return false;
}
/*
Update PHI nodes in the exit blocks from both left and right SEME regions.
*/
std::map<PHINode *, PHINode *> ReplacedPHIs;
auto ProcessPHIs = [&](auto ExitSet,
std::set<BasicBlock *> &VisitedBB) -> bool {
for (BasicBlock &BB : ExitSet) {
if (VisitedBB.count(&BB))
continue;
VisitedBB.insert(&BB);
auto PHIs = BB.phis();
for (auto It = PHIs.begin(), E = PHIs.end(); It != E;) {
PHINode *PHI = &*It;
It++;
if (Debug) {
errs() << "Solving PHI node:";
PHI->dump();
}
IRBuilder<> Builder(PHI);
PHINode *NewPHI = Builder.CreatePHI(PHI->getType(), 0);
CG.insert(NewPHI);
VMap[PHI] = NewPHI;
ReplacedPHIs[PHI] = NewPHI;
// Same block can be a predecessor multiple times and can have multiple incoming edges into BB
// To keep BB's predecessor information consistent with the phi incoming values,
// we need to keep track of the number of incoming edges from each predecessor block
//std::map<BasicBlock *, std::map<BasicBlock *, Value *>> NewEntries;
std::map<BasicBlock *, std::map<BasicBlock *, std::pair<Value *, int>>> NewEntries;
std::set<BasicBlock *> OldEntries;
for (unsigned i = 0; i < PHI->getNumIncomingValues(); i++) {
BasicBlock *InBB = PHI->getIncomingBlock(i);
if (KnownBBs.count(InBB)) {
Value *NewV = PHI->getIncomingValue(i);
auto Pair = CG.getNewEdge(InBB, &BB);
BasicBlock *NewBB = Pair.first;
if (Instruction *OpI =
dyn_cast<Instruction>(PHI->getIncomingValue(i))) {
NewV = VMap[OpI];
if (NewV == nullptr) {
errs() << "ERROR: Null mapped value!\n";
return false;
}
}
auto result_pair = NewEntries[NewBB].insert({InBB, {NewV, 1}});
if (!result_pair.second)
result_pair.first->second.second++;
//NewEntries[NewBB][InBB] = NewV;
OldEntries.insert(InBB);
} else {
//simply copy incoming values from outside the two regions being merged
NewPHI->addIncoming(PHI->getIncomingValue(i),PHI->getIncomingBlock(i));
}
}
if (Debug) {
errs() << "Num entries: " << NewEntries.size() << "\n";
for (auto &Pair : NewEntries) {
errs() << "Incoming Block: " << Pair.first->getName().str() << "\n";
for (auto &Pair2 : Pair.second) {
errs() << "Block: " << Pair2.first->getName().str() << " -> "; Pair2.second.first->dump();
}
}
}
if (Debug) {
errs() << "Creating New PHI\n";
PHI->dump();
}
for (auto &Pair : NewEntries) {
if (Debug) {
errs() << "Incoming Block: " << Pair.first->getName().str() << "\n";
}
if (Pair.second.size() == 1) {
auto &InnerPair = *(Pair.second.begin());
Value *V = InnerPair.second.first;
int repeats = InnerPair.second.second;
for (int i = 0; i < repeats; ++i)
NewPHI->addIncoming(V, Pair.first);
} else if (Pair.second.size() == 2) {
/*
Values that were originally coming from different basic blocks that
have been merged must be properly handled. In this case, we add a
selection in the merged incomming block to produce the correct value
for the phi node.
*/
if (Debug) {
errs() << "Found PHI incoming from two different blocks\n";
}
Value *LeftV = nullptr;
Value *RightV = nullptr;
int repeats = 0;
for (auto &InnerPair : Pair.second) {
if (LeftR.contains(InnerPair.first)) {
if (Debug) {
errs() << "Value coming from the Left block: "
<< GetValueName(InnerPair.first) << " : ";
InnerPair.second.first->dump();
}
LeftV = InnerPair.second.first;
}
if (RightR.contains(InnerPair.first)) {
if (Debug) {
errs() << "Value coming from the Right block: "
<< GetValueName(InnerPair.first) << " : ";
InnerPair.second.first->dump();
}
RightV = InnerPair.second.first;
}
repeats = repeats > InnerPair.second.second ? repeats : InnerPair.second.second;
}
if (LeftV && RightV) {
Value *MergedV = LeftV;
if (LeftV != RightV) {
IRBuilder<> Builder(Pair.first->getTerminator());
// TODO: handle if one of the values is the terminator itself!
MergedV = Builder.CreateSelect(BrCond, LeftV, RightV);
if (SelectInst *SelI = dyn_cast<SelectInst>(MergedV))
CG.insert(SelI);
}
for (int i = 0; i < repeats; ++i)
NewPHI->addIncoming(MergedV, Pair.first);
} else {
errs() << "ERROR: THIS IS WEIRD! MAYBE IT SHOULD NOT BE HERE!\n";
return false;
}
} else {
errs() << "ERROR: THIS IS WEIRD! MAYBE IT SHOULD NOT BE HERE!\n";
return false;
/*
IRBuilder<> Builder(&*F.getEntryBlock().getFirstInsertionPt());
AllocaInst *Addr = Builder.CreateAlloca(PHI->getType());
CG.insert(Addr);
for (Value *V : Pair.second) {
if (Instruction *OpI = dyn_cast<Instruction>(V)) {
CG.StoreInstIntoAddr(OpI, Addr);
} else {
errs() << "ERROR: must also handle non-instruction values "
"via a select\n";
}
}
Builder.SetInsertPoint(Pair.first->getTerminator());
Value *LI = Builder.CreateLoad(PHI->getType(), Addr);
PHI->addIncoming(LI, Pair.first);
*/
}
}
/*
unsigned CountPreds = 0;
for (auto It = pred_begin(&BB), E = pred_end(&BB); It != E; It++) {
BasicBlock *PredBB = *It;
if (!LeftR.contains(PredBB) && !RightR.contains(PredBB)) {
CountPreds++;
errs() << "+PredBB: " << PredBB->getName().str() << "\n";
} else {
errs() << "-PredBB: " << PredBB->getName().str() << "\n";
}
}
if (CountPreds!=NewPHI->getNumIncomingValues()) {
errs() << "ERROR: unexpected number of predecessor\n";
}
*/
if (Debug) {
errs() << "Resulting PHI node:";
NewPHI->dump();
}
}
}
return true;
};
bool Error = false;
std::set<BasicBlock *> VisitedBB;
Error = Error || !ProcessPHIs(LeftR.exits(), VisitedBB);
Error = Error || !ProcessPHIs(RightR.exits(), VisitedBB);
/*
VisitedBB.clear();
auto ProcessLPs = [&](auto ExitSet,
std::set<BasicBlock *> &VisitedBB) -> bool {
for (BasicBlock &BB : ExitSet) {
if (VisitedBB.count(&BB))
continue;
VisitedBB.insert(&BB);
if (BB.isLandingPad()) {
errs() << "Candidate for fix up\n";
BB.dump();
for (auto It = pred_begin(&BB), E = pred_end(&BB); It != E; It++) {
BasicBlock *PredBB = *It;
errs() << "predecessor: " << PredBB->getName().str() << "\n";
PredBB->dump();
if (!isa<InvokeInst>(PredBB->getTerminator()) && PredBB->isLandingPad()) {
//BB.getLandingPadInst()->replaceAllUsesWith(PredBB->getLandingPadInst());
//BB.getLandingPadInst()->eraseFromParent();
errs() << "add phi node edge\n";
}
}
}
}
return false;
};
Error = Error || !ProcessLPs(LeftR.exits(), VisitedBB);
Error = Error || !ProcessLPs(RightR.exits(), VisitedBB);
*/
if (Debug) {
errs() << "Modified function\n";
F.dump();
}
int MergedSize = 0;
if (Debug) {
errs() << "Computing size...\n";
}
for (Instruction *I : CG) {
auto cost = TTI.getInstructionCost(
I, TargetTransformInfo::TargetCostKind::TCK_CodeSize);
MergedSize += cost.getValue().getValue();
}
if (Debug) {
errs() << "SizeLeft: " << SizeLeft << "\n";
errs() << "SizeRight: " << SizeRight << "\n";
errs() << "Original Size: " << (SizeLeft + SizeRight) << "\n";
errs() << "New Size: " << MergedSize << "\n";
}
errs() << "SizeDiff: " << (SizeLeft + SizeRight) << " X " << MergedSize
<< " : " << ((int)(SizeLeft + SizeRight) - ((int)MergedSize)) << " : ";
// bool Profitable = MergedSize < SizeLeft + SizeRight + 2;
bool Profitable = MergedSize < SizeLeft + SizeRight;