| //===- SIAnnotateControlFlow.cpp ------------------------------------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| /// \file |
| /// Annotates the control flow with hardware specific intrinsics. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "AMDGPU.h" |
| #include "GCNSubtarget.h" |
| #include "llvm/Analysis/LegacyDivergenceAnalysis.h" |
| #include "llvm/Analysis/LoopInfo.h" |
| #include "llvm/CodeGen/TargetPassConfig.h" |
| #include "llvm/IR/BasicBlock.h" |
| #include "llvm/IR/Constants.h" |
| #include "llvm/IR/Dominators.h" |
| #include "llvm/IR/IntrinsicsAMDGPU.h" |
| #include "llvm/InitializePasses.h" |
| #include "llvm/Target/TargetMachine.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "si-annotate-control-flow" |
| |
| namespace { |
| |
| // Complex types used in this pass |
| using StackEntry = std::pair<BasicBlock *, Value *>; |
| using StackVector = SmallVector<StackEntry, 16>; |
| |
| class SIAnnotateControlFlow : public FunctionPass { |
| LegacyDivergenceAnalysis *DA; |
| |
| Type *Boolean; |
| Type *Void; |
| Type *IntMask; |
| Type *ReturnStruct; |
| |
| ConstantInt *BoolTrue; |
| ConstantInt *BoolFalse; |
| UndefValue *BoolUndef; |
| Constant *IntMaskZero; |
| |
| Function *If; |
| Function *Else; |
| Function *IfBreak; |
| Function *Loop; |
| Function *EndCf; |
| |
| DominatorTree *DT; |
| StackVector Stack; |
| |
| LoopInfo *LI; |
| |
| void initialize(Module &M, const GCNSubtarget &ST); |
| |
| bool isUniform(BranchInst *T); |
| |
| bool isTopOfStack(BasicBlock *BB); |
| |
| Value *popSaved(); |
| |
| void push(BasicBlock *BB, Value *Saved); |
| |
| bool isElse(PHINode *Phi); |
| |
| bool hasKill(const BasicBlock *BB); |
| |
| void eraseIfUnused(PHINode *Phi); |
| |
| void openIf(BranchInst *Term); |
| |
| void insertElse(BranchInst *Term); |
| |
| Value * |
| handleLoopCondition(Value *Cond, PHINode *Broken, llvm::Loop *L, |
| BranchInst *Term); |
| |
| void handleLoop(BranchInst *Term); |
| |
| void closeControlFlow(BasicBlock *BB); |
| |
| public: |
| static char ID; |
| |
| SIAnnotateControlFlow() : FunctionPass(ID) {} |
| |
| bool runOnFunction(Function &F) override; |
| |
| StringRef getPassName() const override { return "SI annotate control flow"; } |
| |
| void getAnalysisUsage(AnalysisUsage &AU) const override { |
| AU.addRequired<LoopInfoWrapperPass>(); |
| AU.addRequired<DominatorTreeWrapperPass>(); |
| AU.addRequired<LegacyDivergenceAnalysis>(); |
| AU.addPreserved<LoopInfoWrapperPass>(); |
| AU.addPreserved<DominatorTreeWrapperPass>(); |
| AU.addRequired<TargetPassConfig>(); |
| FunctionPass::getAnalysisUsage(AU); |
| } |
| }; |
| |
| } // end anonymous namespace |
| |
| INITIALIZE_PASS_BEGIN(SIAnnotateControlFlow, DEBUG_TYPE, |
| "Annotate SI Control Flow", false, false) |
| INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) |
| INITIALIZE_PASS_DEPENDENCY(LegacyDivergenceAnalysis) |
| INITIALIZE_PASS_DEPENDENCY(TargetPassConfig) |
| INITIALIZE_PASS_END(SIAnnotateControlFlow, DEBUG_TYPE, |
| "Annotate SI Control Flow", false, false) |
| |
| char SIAnnotateControlFlow::ID = 0; |
| |
| /// Initialize all the types and constants used in the pass |
| void SIAnnotateControlFlow::initialize(Module &M, const GCNSubtarget &ST) { |
| LLVMContext &Context = M.getContext(); |
| |
| Void = Type::getVoidTy(Context); |
| Boolean = Type::getInt1Ty(Context); |
| IntMask = ST.isWave32() ? Type::getInt32Ty(Context) |
| : Type::getInt64Ty(Context); |
| ReturnStruct = StructType::get(Boolean, IntMask); |
| |
| BoolTrue = ConstantInt::getTrue(Context); |
| BoolFalse = ConstantInt::getFalse(Context); |
| BoolUndef = UndefValue::get(Boolean); |
| IntMaskZero = ConstantInt::get(IntMask, 0); |
| |
| If = Intrinsic::getDeclaration(&M, Intrinsic::amdgcn_if, { IntMask }); |
| Else = Intrinsic::getDeclaration(&M, Intrinsic::amdgcn_else, |
| { IntMask, IntMask }); |
| IfBreak = Intrinsic::getDeclaration(&M, Intrinsic::amdgcn_if_break, |
| { IntMask }); |
| Loop = Intrinsic::getDeclaration(&M, Intrinsic::amdgcn_loop, { IntMask }); |
| EndCf = Intrinsic::getDeclaration(&M, Intrinsic::amdgcn_end_cf, { IntMask }); |
| } |
| |
| /// Is the branch condition uniform or did the StructurizeCFG pass |
| /// consider it as such? |
| bool SIAnnotateControlFlow::isUniform(BranchInst *T) { |
| return DA->isUniform(T) || |
| T->getMetadata("structurizecfg.uniform") != nullptr; |
| } |
| |
| /// Is BB the last block saved on the stack ? |
| bool SIAnnotateControlFlow::isTopOfStack(BasicBlock *BB) { |
| return !Stack.empty() && Stack.back().first == BB; |
| } |
| |
| /// Pop the last saved value from the control flow stack |
| Value *SIAnnotateControlFlow::popSaved() { |
| return Stack.pop_back_val().second; |
| } |
| |
| /// Push a BB and saved value to the control flow stack |
| void SIAnnotateControlFlow::push(BasicBlock *BB, Value *Saved) { |
| Stack.push_back(std::make_pair(BB, Saved)); |
| } |
| |
| /// Can the condition represented by this PHI node treated like |
| /// an "Else" block? |
| bool SIAnnotateControlFlow::isElse(PHINode *Phi) { |
| BasicBlock *IDom = DT->getNode(Phi->getParent())->getIDom()->getBlock(); |
| for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) { |
| if (Phi->getIncomingBlock(i) == IDom) { |
| |
| if (Phi->getIncomingValue(i) != BoolTrue) |
| return false; |
| |
| } else { |
| if (Phi->getIncomingValue(i) != BoolFalse) |
| return false; |
| |
| } |
| } |
| return true; |
| } |
| |
| bool SIAnnotateControlFlow::hasKill(const BasicBlock *BB) { |
| for (const Instruction &I : *BB) { |
| if (const CallInst *CI = dyn_cast<CallInst>(&I)) |
| if (CI->getIntrinsicID() == Intrinsic::amdgcn_kill) |
| return true; |
| } |
| return false; |
| } |
| |
| // Erase "Phi" if it is not used any more |
| void SIAnnotateControlFlow::eraseIfUnused(PHINode *Phi) { |
| if (RecursivelyDeleteDeadPHINode(Phi)) { |
| LLVM_DEBUG(dbgs() << "Erased unused condition phi\n"); |
| } |
| } |
| |
| /// Open a new "If" block |
| void SIAnnotateControlFlow::openIf(BranchInst *Term) { |
| if (isUniform(Term)) |
| return; |
| |
| Value *Ret = CallInst::Create(If, Term->getCondition(), "", Term); |
| Term->setCondition(ExtractValueInst::Create(Ret, 0, "", Term)); |
| push(Term->getSuccessor(1), ExtractValueInst::Create(Ret, 1, "", Term)); |
| } |
| |
| /// Close the last "If" block and open a new "Else" block |
| void SIAnnotateControlFlow::insertElse(BranchInst *Term) { |
| if (isUniform(Term)) { |
| return; |
| } |
| Value *Ret = CallInst::Create(Else, popSaved(), "", Term); |
| Term->setCondition(ExtractValueInst::Create(Ret, 0, "", Term)); |
| push(Term->getSuccessor(1), ExtractValueInst::Create(Ret, 1, "", Term)); |
| } |
| |
| /// Recursively handle the condition leading to a loop |
| Value *SIAnnotateControlFlow::handleLoopCondition( |
| Value *Cond, PHINode *Broken, llvm::Loop *L, BranchInst *Term) { |
| if (Instruction *Inst = dyn_cast<Instruction>(Cond)) { |
| BasicBlock *Parent = Inst->getParent(); |
| Instruction *Insert; |
| if (L->contains(Inst)) { |
| Insert = Parent->getTerminator(); |
| } else { |
| Insert = L->getHeader()->getFirstNonPHIOrDbgOrLifetime(); |
| } |
| |
| Value *Args[] = { Cond, Broken }; |
| return CallInst::Create(IfBreak, Args, "", Insert); |
| } |
| |
| // Insert IfBreak in the loop header TERM for constant COND other than true. |
| if (isa<Constant>(Cond)) { |
| Instruction *Insert = Cond == BoolTrue ? |
| Term : L->getHeader()->getTerminator(); |
| |
| Value *Args[] = { Cond, Broken }; |
| return CallInst::Create(IfBreak, Args, "", Insert); |
| } |
| |
| llvm_unreachable("Unhandled loop condition!"); |
| } |
| |
| /// Handle a back edge (loop) |
| void SIAnnotateControlFlow::handleLoop(BranchInst *Term) { |
| if (isUniform(Term)) |
| return; |
| |
| BasicBlock *BB = Term->getParent(); |
| llvm::Loop *L = LI->getLoopFor(BB); |
| if (!L) |
| return; |
| |
| BasicBlock *Target = Term->getSuccessor(1); |
| PHINode *Broken = PHINode::Create(IntMask, 0, "phi.broken", &Target->front()); |
| |
| Value *Cond = Term->getCondition(); |
| Term->setCondition(BoolTrue); |
| Value *Arg = handleLoopCondition(Cond, Broken, L, Term); |
| |
| for (BasicBlock *Pred : predecessors(Target)) { |
| Value *PHIValue = IntMaskZero; |
| if (Pred == BB) // Remember the value of the previous iteration. |
| PHIValue = Arg; |
| // If the backedge from Pred to Target could be executed before the exit |
| // of the loop at BB, it should not reset or change "Broken", which keeps |
| // track of the number of threads exited the loop at BB. |
| else if (L->contains(Pred) && DT->dominates(Pred, BB)) |
| PHIValue = Broken; |
| Broken->addIncoming(PHIValue, Pred); |
| } |
| |
| Term->setCondition(CallInst::Create(Loop, Arg, "", Term)); |
| |
| push(Term->getSuccessor(0), Arg); |
| } |
| |
| /// Close the last opened control flow |
| void SIAnnotateControlFlow::closeControlFlow(BasicBlock *BB) { |
| llvm::Loop *L = LI->getLoopFor(BB); |
| |
| assert(Stack.back().first == BB); |
| |
| if (L && L->getHeader() == BB) { |
| // We can't insert an EndCF call into a loop header, because it will |
| // get executed on every iteration of the loop, when it should be |
| // executed only once before the loop. |
| SmallVector <BasicBlock *, 8> Latches; |
| L->getLoopLatches(Latches); |
| |
| SmallVector<BasicBlock *, 2> Preds; |
| for (BasicBlock *Pred : predecessors(BB)) { |
| if (!is_contained(Latches, Pred)) |
| Preds.push_back(Pred); |
| } |
| |
| BB = SplitBlockPredecessors(BB, Preds, "endcf.split", DT, LI, nullptr, |
| false); |
| } |
| |
| Value *Exec = popSaved(); |
| Instruction *FirstInsertionPt = &*BB->getFirstInsertionPt(); |
| if (!isa<UndefValue>(Exec) && !isa<UnreachableInst>(FirstInsertionPt)) { |
| Instruction *ExecDef = cast<Instruction>(Exec); |
| BasicBlock *DefBB = ExecDef->getParent(); |
| if (!DT->dominates(DefBB, BB)) { |
| // Split edge to make Def dominate Use |
| FirstInsertionPt = &*SplitEdge(DefBB, BB, DT, LI)->getFirstInsertionPt(); |
| } |
| CallInst::Create(EndCf, Exec, "", FirstInsertionPt); |
| } |
| } |
| |
| /// Annotate the control flow with intrinsics so the backend can |
| /// recognize if/then/else and loops. |
| bool SIAnnotateControlFlow::runOnFunction(Function &F) { |
| DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree(); |
| LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); |
| DA = &getAnalysis<LegacyDivergenceAnalysis>(); |
| TargetPassConfig &TPC = getAnalysis<TargetPassConfig>(); |
| const TargetMachine &TM = TPC.getTM<TargetMachine>(); |
| |
| initialize(*F.getParent(), TM.getSubtarget<GCNSubtarget>(F)); |
| for (df_iterator<BasicBlock *> I = df_begin(&F.getEntryBlock()), |
| E = df_end(&F.getEntryBlock()); I != E; ++I) { |
| BasicBlock *BB = *I; |
| BranchInst *Term = dyn_cast<BranchInst>(BB->getTerminator()); |
| |
| if (!Term || Term->isUnconditional()) { |
| if (isTopOfStack(BB)) |
| closeControlFlow(BB); |
| |
| continue; |
| } |
| |
| if (I.nodeVisited(Term->getSuccessor(1))) { |
| if (isTopOfStack(BB)) |
| closeControlFlow(BB); |
| |
| if (DT->dominates(Term->getSuccessor(1), BB)) |
| handleLoop(Term); |
| continue; |
| } |
| |
| if (isTopOfStack(BB)) { |
| PHINode *Phi = dyn_cast<PHINode>(Term->getCondition()); |
| if (Phi && Phi->getParent() == BB && isElse(Phi) && !hasKill(BB)) { |
| insertElse(Term); |
| eraseIfUnused(Phi); |
| continue; |
| } |
| |
| closeControlFlow(BB); |
| } |
| |
| openIf(Term); |
| } |
| |
| if (!Stack.empty()) { |
| // CFG was probably not structured. |
| report_fatal_error("failed to annotate CFG"); |
| } |
| |
| return true; |
| } |
| |
| /// Create the annotation pass |
| FunctionPass *llvm::createSIAnnotateControlFlowPass() { |
| return new SIAnnotateControlFlow(); |
| } |