return nullptr;
}
-
-
-
/// TryToSinkInstruction - Try to move the specified instruction from its
/// current block into the beginning of DestBlock, which can only happen if it's
/// safe to move the instruction past all of the instructions between it and the
return true;
}
-
-/// AddReachableCodeToWorklist - Walk the function in depth-first order, adding
-/// all reachable code to the worklist.
-///
-/// This has a couple of tricks to make the code faster and more powerful. In
-/// particular, we constant fold and DCE instructions as we go, to avoid adding
-/// them to the worklist (this significantly speeds up instcombine on code where
-/// many instructions are dead or constant). Additionally, if we find a branch
-/// whose condition is a known constant, we only visit the reachable successors.
-///
-static bool AddReachableCodeToWorklist(BasicBlock *BB,
- SmallPtrSetImpl<BasicBlock*> &Visited,
- InstCombiner &IC,
- const DataLayout *DL,
- const TargetLibraryInfo *TLI) {
- bool MadeIRChange = false;
- SmallVector<BasicBlock*, 256> Worklist;
- Worklist.push_back(BB);
-
- SmallVector<Instruction*, 128> InstrsForInstCombineWorklist;
- DenseMap<ConstantExpr*, Constant*> FoldedConstants;
-
- do {
- BB = Worklist.pop_back_val();
-
- // We have now visited this block! If we've already been here, ignore it.
- if (!Visited.insert(BB).second)
- continue;
-
- for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) {
- Instruction *Inst = BBI++;
-
- // DCE instruction if trivially dead.
- if (isInstructionTriviallyDead(Inst, TLI)) {
- ++NumDeadInst;
- DEBUG(dbgs() << "IC: DCE: " << *Inst << '\n');
- Inst->eraseFromParent();
- continue;
- }
-
- // ConstantProp instruction if trivially constant.
- if (!Inst->use_empty() && isa<Constant>(Inst->getOperand(0)))
- if (Constant *C = ConstantFoldInstruction(Inst, DL, TLI)) {
- DEBUG(dbgs() << "IC: ConstFold to: " << *C << " from: "
- << *Inst << '\n');
- Inst->replaceAllUsesWith(C);
- ++NumConstProp;
- Inst->eraseFromParent();
- continue;
- }
-
- if (DL) {
- // See if we can constant fold its operands.
- for (User::op_iterator i = Inst->op_begin(), e = Inst->op_end();
- i != e; ++i) {
- ConstantExpr *CE = dyn_cast<ConstantExpr>(i);
- if (CE == nullptr) continue;
-
- Constant*& FoldRes = FoldedConstants[CE];
- if (!FoldRes)
- FoldRes = ConstantFoldConstantExpression(CE, DL, TLI);
- if (!FoldRes)
- FoldRes = CE;
-
- if (FoldRes != CE) {
- *i = FoldRes;
- MadeIRChange = true;
- }
- }
- }
-
- InstrsForInstCombineWorklist.push_back(Inst);
- }
-
- // Recursively visit successors. If this is a branch or switch on a
- // constant, only visit the reachable successor.
- TerminatorInst *TI = BB->getTerminator();
- if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
- if (BI->isConditional() && isa<ConstantInt>(BI->getCondition())) {
- bool CondVal = cast<ConstantInt>(BI->getCondition())->getZExtValue();
- BasicBlock *ReachableBB = BI->getSuccessor(!CondVal);
- Worklist.push_back(ReachableBB);
- continue;
- }
- } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
- if (ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition())) {
- // See if this is an explicit destination.
- for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
- i != e; ++i)
- if (i.getCaseValue() == Cond) {
- BasicBlock *ReachableBB = i.getCaseSuccessor();
- Worklist.push_back(ReachableBB);
- continue;
- }
-
- // Otherwise it is the default destination.
- Worklist.push_back(SI->getDefaultDest());
- continue;
- }
- }
-
- for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
- Worklist.push_back(TI->getSuccessor(i));
- } while (!Worklist.empty());
-
- // Once we've found all of the instructions to add to instcombine's worklist,
- // add them in reverse order. This way instcombine will visit from the top
- // of the function down. This jives well with the way that it adds all uses
- // of instructions to the worklist after doing a transformation, thus avoiding
- // some N^2 behavior in pathological cases.
- IC.Worklist.AddInitialGroup(&InstrsForInstCombineWorklist[0],
- InstrsForInstCombineWorklist.size());
-
- return MadeIRChange;
-}
-
-bool InstCombiner::DoOneIteration(Function &F, unsigned Iteration) {
- MadeIRChange = false;
-
- DEBUG(dbgs() << "\n\nINSTCOMBINE ITERATION #" << Iteration << " on "
- << F.getName() << "\n");
-
- {
- // Do a depth-first traversal of the function, populate the worklist with
- // the reachable instructions. Ignore blocks that are not reachable. Keep
- // track of which blocks we visit.
- SmallPtrSet<BasicBlock*, 64> Visited;
- MadeIRChange |= AddReachableCodeToWorklist(F.begin(), Visited, *this, DL,
- TLI);
-
- // Do a quick scan over the function. If we find any blocks that are
- // unreachable, remove any instructions inside of them. This prevents
- // the instcombine code from having to deal with some bad special cases.
- for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
- if (Visited.count(BB)) continue;
-
- // Delete the instructions backwards, as it has a reduced likelihood of
- // having to update as many def-use and use-def chains.
- Instruction *EndInst = BB->getTerminator(); // Last not to be deleted.
- while (EndInst != BB->begin()) {
- // Delete the next to last instruction.
- BasicBlock::iterator I = EndInst;
- Instruction *Inst = --I;
- if (!Inst->use_empty())
- Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
- if (isa<LandingPadInst>(Inst)) {
- EndInst = Inst;
- continue;
- }
- if (!isa<DbgInfoIntrinsic>(Inst)) {
- ++NumDeadInst;
- MadeIRChange = true;
- }
- Inst->eraseFromParent();
- }
- }
- }
-
+bool InstCombiner::run() {
while (!Worklist.isEmpty()) {
Instruction *I = Worklist.RemoveOne();
if (I == nullptr) continue; // skip null values.
return MadeIRChange;
}
-// FIXME: Passing all of the analyses here in the run method is ugly. We should
-// separate out the worklist from the combiner so that we can construct
-// a combiner once per function while re-using the storage of an external
-// worklist.
-bool InstCombiner::run(Function &F, AssumptionCache *AC, const DataLayout *DL,
- TargetLibraryInfo *TLI, DominatorTree *DT,
- LoopInfo *LI) {
- // Set up our analysis pointers.
- this->AC = AC;
- this->DL = DL;
- this->TLI = TLI;
- this->DT = DT;
- this->LI = LI;
+/// AddReachableCodeToWorklist - Walk the function in depth-first order, adding
+/// all reachable code to the worklist.
+///
+/// This has a couple of tricks to make the code faster and more powerful. In
+/// particular, we constant fold and DCE instructions as we go, to avoid adding
+/// them to the worklist (this significantly speeds up instcombine on code where
+/// many instructions are dead or constant). Additionally, if we find a branch
+/// whose condition is a known constant, we only visit the reachable successors.
+///
+static bool AddReachableCodeToWorklist(BasicBlock *BB,
+ SmallPtrSetImpl<BasicBlock*> &Visited,
+ InstCombineWorklist &ICWorklist,
+ const DataLayout *DL,
+ const TargetLibraryInfo *TLI) {
+ bool MadeIRChange = false;
+ SmallVector<BasicBlock*, 256> Worklist;
+ Worklist.push_back(BB);
+
+ SmallVector<Instruction*, 128> InstrsForInstCombineWorklist;
+ DenseMap<ConstantExpr*, Constant*> FoldedConstants;
- // Minimizing size?
- MinimizeSize = F.getAttributes().hasAttribute(AttributeSet::FunctionIndex,
- Attribute::MinSize);
+ do {
+ BB = Worklist.pop_back_val();
- /// Builder - This is an IRBuilder that automatically inserts new
- /// instructions into the worklist when they are created.
- IRBuilder<true, TargetFolder, InstCombineIRInserter> TheBuilder(
- F.getContext(), TargetFolder(DL), InstCombineIRInserter(Worklist, AC));
- Builder = &TheBuilder;
+ // We have now visited this block! If we've already been here, ignore it.
+ if (!Visited.insert(BB).second)
+ continue;
- bool EverMadeChange = false;
+ for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) {
+ Instruction *Inst = BBI++;
- // Lower dbg.declare intrinsics otherwise their value may be clobbered
- // by instcombiner.
- EverMadeChange = LowerDbgDeclare(F);
+ // DCE instruction if trivially dead.
+ if (isInstructionTriviallyDead(Inst, TLI)) {
+ ++NumDeadInst;
+ DEBUG(dbgs() << "IC: DCE: " << *Inst << '\n');
+ Inst->eraseFromParent();
+ continue;
+ }
- // Iterate while there is work to do.
- unsigned Iteration = 0;
- while (DoOneIteration(F, Iteration++))
- EverMadeChange = true;
+ // ConstantProp instruction if trivially constant.
+ if (!Inst->use_empty() && isa<Constant>(Inst->getOperand(0)))
+ if (Constant *C = ConstantFoldInstruction(Inst, DL, TLI)) {
+ DEBUG(dbgs() << "IC: ConstFold to: " << *C << " from: "
+ << *Inst << '\n');
+ Inst->replaceAllUsesWith(C);
+ ++NumConstProp;
+ Inst->eraseFromParent();
+ continue;
+ }
+
+ if (DL) {
+ // See if we can constant fold its operands.
+ for (User::op_iterator i = Inst->op_begin(), e = Inst->op_end();
+ i != e; ++i) {
+ ConstantExpr *CE = dyn_cast<ConstantExpr>(i);
+ if (CE == nullptr) continue;
+
+ Constant*& FoldRes = FoldedConstants[CE];
+ if (!FoldRes)
+ FoldRes = ConstantFoldConstantExpression(CE, DL, TLI);
+ if (!FoldRes)
+ FoldRes = CE;
- Builder = nullptr;
- return EverMadeChange;
+ if (FoldRes != CE) {
+ *i = FoldRes;
+ MadeIRChange = true;
+ }
+ }
+ }
+
+ InstrsForInstCombineWorklist.push_back(Inst);
+ }
+
+ // Recursively visit successors. If this is a branch or switch on a
+ // constant, only visit the reachable successor.
+ TerminatorInst *TI = BB->getTerminator();
+ if (BranchInst *BI = dyn_cast<BranchInst>(TI)) {
+ if (BI->isConditional() && isa<ConstantInt>(BI->getCondition())) {
+ bool CondVal = cast<ConstantInt>(BI->getCondition())->getZExtValue();
+ BasicBlock *ReachableBB = BI->getSuccessor(!CondVal);
+ Worklist.push_back(ReachableBB);
+ continue;
+ }
+ } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
+ if (ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition())) {
+ // See if this is an explicit destination.
+ for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
+ i != e; ++i)
+ if (i.getCaseValue() == Cond) {
+ BasicBlock *ReachableBB = i.getCaseSuccessor();
+ Worklist.push_back(ReachableBB);
+ continue;
+ }
+
+ // Otherwise it is the default destination.
+ Worklist.push_back(SI->getDefaultDest());
+ continue;
+ }
+ }
+
+ for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
+ Worklist.push_back(TI->getSuccessor(i));
+ } while (!Worklist.empty());
+
+ // Once we've found all of the instructions to add to instcombine's worklist,
+ // add them in reverse order. This way instcombine will visit from the top
+ // of the function down. This jives well with the way that it adds all uses
+ // of instructions to the worklist after doing a transformation, thus avoiding
+ // some N^2 behavior in pathological cases.
+ ICWorklist.AddInitialGroup(&InstrsForInstCombineWorklist[0],
+ InstrsForInstCombineWorklist.size());
+
+ return MadeIRChange;
+}
+
+/// \brief Populate the IC worklist from a function, and prune any dead basic
+/// blocks discovered in the process.
+///
+/// This also does basic constant propagation and other forward fixing to make
+/// the combiner itself run much faster.
+static bool prepareICWorklistFromFunction(Function &F, const DataLayout *DL,
+ TargetLibraryInfo *TLI,
+ InstCombineWorklist &ICWorklist) {
+ bool MadeIRChange = false;
+
+ // Do a depth-first traversal of the function, populate the worklist with
+ // the reachable instructions. Ignore blocks that are not reachable. Keep
+ // track of which blocks we visit.
+ SmallPtrSet<BasicBlock *, 64> Visited;
+ MadeIRChange |=
+ AddReachableCodeToWorklist(F.begin(), Visited, ICWorklist, DL, TLI);
+
+ // Do a quick scan over the function. If we find any blocks that are
+ // unreachable, remove any instructions inside of them. This prevents
+ // the instcombine code from having to deal with some bad special cases.
+ for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
+ if (Visited.count(BB))
+ continue;
+
+ // Delete the instructions backwards, as it has a reduced likelihood of
+ // having to update as many def-use and use-def chains.
+ Instruction *EndInst = BB->getTerminator(); // Last not to be deleted.
+ while (EndInst != BB->begin()) {
+ // Delete the next to last instruction.
+ BasicBlock::iterator I = EndInst;
+ Instruction *Inst = --I;
+ if (!Inst->use_empty())
+ Inst->replaceAllUsesWith(UndefValue::get(Inst->getType()));
+ if (isa<LandingPadInst>(Inst)) {
+ EndInst = Inst;
+ continue;
+ }
+ if (!isa<DbgInfoIntrinsic>(Inst)) {
+ ++NumDeadInst;
+ MadeIRChange = true;
+ }
+ Inst->eraseFromParent();
+ }
+ }
+
+ return MadeIRChange;
}
namespace {
/// This is a basic whole-function wrapper around the instcombine utility. It
/// will try to combine all instructions in the function.
class InstructionCombiningPass : public FunctionPass {
- InstCombiner IC;
+ InstCombineWorklist Worklist;
public:
static char ID; // Pass identification, replacement for typeid
if (skipOptnoneFunction(F))
return false;
+ // Lower dbg.declare intrinsics otherwise their value may be clobbered
+ // by instcombiner.
+ bool DbgDeclaresChanged = LowerDbgDeclare(F);
+
+ // Required analyses.
auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
- auto *DLP = getAnalysisIfAvailable<DataLayoutPass>();
- auto *DL = DLP ? &DLP->getDataLayout() : nullptr;
auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+
+ // Optional analyses.
+ auto *DLP = getAnalysisIfAvailable<DataLayoutPass>();
+ auto *DL = DLP ? &DLP->getDataLayout() : nullptr;
auto *LIWP = getAnalysisIfAvailable<LoopInfoWrapperPass>();
auto *LI = LIWP ? &LIWP->getLoopInfo() : nullptr;
- return IC.run(F, &AC, DL, &TLI, &DT, LI);
+ // Minimizing size?
+ bool MinimizeSize = F.getAttributes().hasAttribute(
+ AttributeSet::FunctionIndex, Attribute::MinSize);
+
+ /// Builder - This is an IRBuilder that automatically inserts new
+ /// instructions into the worklist when they are created.
+ IRBuilder<true, TargetFolder, InstCombineIRInserter> Builder(
+ F.getContext(), TargetFolder(DL), InstCombineIRInserter(Worklist, &AC));
+
+ // Iterate while there is work to do.
+ int Iteration = 0;
+ for (;;) {
+ ++Iteration;
+ DEBUG(dbgs() << "\n\nINSTCOMBINE ITERATION #" << Iteration << " on "
+ << F.getName() << "\n");
+
+ bool Changed = false;
+ if (prepareICWorklistFromFunction(F, DL, &TLI, Worklist))
+ Changed = true;
+
+ InstCombiner IC(Worklist, &Builder, MinimizeSize, &AC, &TLI, &DT, DL, LI);
+ if (IC.run())
+ Changed = true;
+
+ if (!Changed)
+ break;
+ }
+
+ return DbgDeclaresChanged || Iteration > 1;
}
char InstructionCombiningPass::ID = 0;
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