Imported Upstream version 5.18.0.246

Former-commit-id: 0c7ce5b1a7851e13f22acfd379b7f9fb304e4833

external/llvm/lib/Target/AMDGPU/SIAnnotateControlFlow.cpp

@@ -0,0 +1,432 @@
+//===- SIAnnotateControlFlow.cpp ------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// Annotates the control flow with hardware specific intrinsics.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPU.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Analysis/DivergenceAnalysis.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/CFG.h"
+#include "llvm/IR/Constant.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instruction.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Type.h"
+#include "llvm/IR/ValueHandle.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include <cassert>
+#include <utility>
+
+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 {
+  DivergenceAnalysis *DA;
+
+  Type *Boolean;
+  Type *Void;
+  Type *Int64;
+  Type *ReturnStruct;
+
+  ConstantInt *BoolTrue;
+  ConstantInt *BoolFalse;
+  UndefValue *BoolUndef;
+  Constant *Int64Zero;
+
+  Function *If;
+  Function *Else;
+  Function *Break;
+  Function *IfBreak;
+  Function *ElseBreak;
+  Function *Loop;
+  Function *EndCf;
+
+  DominatorTree *DT;
+  StackVector Stack;
+
+  LoopInfo *LI;
+
+  bool isUniform(BranchInst *T);
+
+  bool isTopOfStack(BasicBlock *BB);
+
+  Value *popSaved();
+
+  void push(BasicBlock *BB, Value *Saved);
+
+  bool isElse(PHINode *Phi);
+
+  void eraseIfUnused(PHINode *Phi);
+
+  void openIf(BranchInst *Term);
+
+  void insertElse(BranchInst *Term);
+
+  Value *
+  handleLoopCondition(Value *Cond, PHINode *Broken, llvm::Loop *L,
+                      BranchInst *Term,
+                      SmallVectorImpl<WeakTrackingVH> &LoopPhiConditions);
+
+  void handleLoop(BranchInst *Term);
+
+  void closeControlFlow(BasicBlock *BB);
+
+public:
+  static char ID;
+
+  SIAnnotateControlFlow() : FunctionPass(ID) {}
+
+  bool doInitialization(Module &M) override;
+
+  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<DivergenceAnalysis>();
+    AU.addPreserved<DominatorTreeWrapperPass>();
+    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(DivergenceAnalysis)
+INITIALIZE_PASS_END(SIAnnotateControlFlow, DEBUG_TYPE,
+                    "Annotate SI Control Flow", false, false)
+
+char SIAnnotateControlFlow::ID = 0;
+
+/// \brief Initialize all the types and constants used in the pass
+bool SIAnnotateControlFlow::doInitialization(Module &M) {
+  LLVMContext &Context = M.getContext();
+
+  Void = Type::getVoidTy(Context);
+  Boolean = Type::getInt1Ty(Context);
+  Int64 = Type::getInt64Ty(Context);
+  ReturnStruct = StructType::get(Boolean, Int64);
+
+  BoolTrue = ConstantInt::getTrue(Context);
+  BoolFalse = ConstantInt::getFalse(Context);
+  BoolUndef = UndefValue::get(Boolean);
+  Int64Zero = ConstantInt::get(Int64, 0);
+
+  If = Intrinsic::getDeclaration(&M, Intrinsic::amdgcn_if);
+  Else = Intrinsic::getDeclaration(&M, Intrinsic::amdgcn_else);
+  Break = Intrinsic::getDeclaration(&M, Intrinsic::amdgcn_break);
+  IfBreak = Intrinsic::getDeclaration(&M, Intrinsic::amdgcn_if_break);
+  ElseBreak = Intrinsic::getDeclaration(&M, Intrinsic::amdgcn_else_break);
+  Loop = Intrinsic::getDeclaration(&M, Intrinsic::amdgcn_loop);
+  EndCf = Intrinsic::getDeclaration(&M, Intrinsic::amdgcn_end_cf);
+  return false;
+}
+
+/// \brief Is the branch condition uniform or did the StructurizeCFG pass
+/// consider it as such?
+bool SIAnnotateControlFlow::isUniform(BranchInst *T) {
+  return DA->isUniform(T->getCondition()) ||
+         T->getMetadata("structurizecfg.uniform") != nullptr;
+}
+
+/// \brief Is BB the last block saved on the stack ?
+bool SIAnnotateControlFlow::isTopOfStack(BasicBlock *BB) {
+  return !Stack.empty() && Stack.back().first == BB;
+}
+
+/// \brief Pop the last saved value from the control flow stack
+Value *SIAnnotateControlFlow::popSaved() {
+  return Stack.pop_back_val().second;
+}
+
+/// \brief 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));
+}
+
+/// \brief 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;
+}
+
+// \brief Erase "Phi" if it is not used any more
+void SIAnnotateControlFlow::eraseIfUnused(PHINode *Phi) {
+  if (RecursivelyDeleteDeadPHINode(Phi)) {
+    DEBUG(dbgs() << "Erased unused condition phi\n");
+  }
+}
+
+/// \brief 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));
+}
+
+/// \brief 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));
+}
+
+/// \brief Recursively handle the condition leading to a loop
+Value *SIAnnotateControlFlow::handleLoopCondition(
+    Value *Cond, PHINode *Broken, llvm::Loop *L, BranchInst *Term,
+    SmallVectorImpl<WeakTrackingVH> &LoopPhiConditions) {
+  // Only search through PHI nodes which are inside the loop.  If we try this
+  // with PHI nodes that are outside of the loop, we end up inserting new PHI
+  // nodes outside of the loop which depend on values defined inside the loop.
+  // This will break the module with
+  // 'Instruction does not dominate all users!' errors.
+  PHINode *Phi = nullptr;
+  if ((Phi = dyn_cast<PHINode>(Cond)) && L->contains(Phi)) {
+    BasicBlock *Parent = Phi->getParent();
+    PHINode *NewPhi = PHINode::Create(Int64, 0, "loop.phi", &Parent->front());
+    Value *Ret = NewPhi;
+
+    // Handle all non-constant incoming values first
+    for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
+      Value *Incoming = Phi->getIncomingValue(i);
+      BasicBlock *From = Phi->getIncomingBlock(i);
+      if (isa<ConstantInt>(Incoming)) {
+        NewPhi->addIncoming(Broken, From);
+        continue;
+      }
+
+      Phi->setIncomingValue(i, BoolFalse);
+      Value *PhiArg = handleLoopCondition(Incoming, Broken, L,
+                                          Term, LoopPhiConditions);
+      NewPhi->addIncoming(PhiArg, From);
+    }
+
+    BasicBlock *IDom = DT->getNode(Parent)->getIDom()->getBlock();
+
+    for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
+      Value *Incoming = Phi->getIncomingValue(i);
+      if (Incoming != BoolTrue)
+        continue;
+
+      BasicBlock *From = Phi->getIncomingBlock(i);
+      if (From == IDom) {
+        // We're in the following situation:
+        //   IDom/From
+        //      |   \
+        //      |   If-block
+        //      |   /
+        //     Parent
+        // where we want to break out of the loop if the If-block is not taken.
+        // Due to the depth-first traversal, there should be an end.cf
+        // intrinsic in Parent, and we insert an else.break before it.
+        //
+        // Note that the end.cf need not be the first non-phi instruction
+        // of parent, particularly when we're dealing with a multi-level
+        // break, but it should occur within a group of intrinsic calls
+        // at the beginning of the block.
+        CallInst *OldEnd = dyn_cast<CallInst>(Parent->getFirstInsertionPt());
+        while (OldEnd && OldEnd->getCalledFunction() != EndCf)
+          OldEnd = dyn_cast<CallInst>(OldEnd->getNextNode());
+        if (OldEnd && OldEnd->getCalledFunction() == EndCf) {
+          Value *Args[] = { OldEnd->getArgOperand(0), NewPhi };
+          Ret = CallInst::Create(ElseBreak, Args, "", OldEnd);
+          continue;
+        }
+      }
+
+      TerminatorInst *Insert = From->getTerminator();
+      Value *PhiArg = CallInst::Create(Break, Broken, "", Insert);
+      NewPhi->setIncomingValue(i, PhiArg);
+    }
+
+    LoopPhiConditions.push_back(WeakTrackingVH(Phi));
+    return Ret;
+  }
+
+  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!");
+}
+
+/// \brief 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(Int64, 0, "phi.broken", &Target->front());
+
+  SmallVector<WeakTrackingVH, 8> LoopPhiConditions;
+  Value *Cond = Term->getCondition();
+  Term->setCondition(BoolTrue);
+  Value *Arg = handleLoopCondition(Cond, Broken, L, Term, LoopPhiConditions);
+
+  for (BasicBlock *Pred : predecessors(Target))
+    Broken->addIncoming(Pred == BB ? Arg : Int64Zero, Pred);
+
+  Term->setCondition(CallInst::Create(Loop, Arg, "", Term));
+
+  for (WeakTrackingVH Val : llvm::reverse(LoopPhiConditions)) {
+    if (PHINode *Cond = cast_or_null<PHINode>(Val))
+      eraseIfUnused(Cond);
+  }
+
+  push(Term->getSuccessor(0), Arg);
+}
+
+/// \brief 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, false);
+  }
+
+  Value *Exec = popSaved();
+  Instruction *FirstInsertionPt = &*BB->getFirstInsertionPt();
+  if (!isa<UndefValue>(Exec) && !isa<UnreachableInst>(FirstInsertionPt))
+    CallInst::Create(EndCf, Exec, "", FirstInsertionPt);
+}
+
+/// \brief 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<DivergenceAnalysis>();
+
+  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);
+
+      handleLoop(Term);
+      continue;
+    }
+
+    if (isTopOfStack(BB)) {
+      PHINode *Phi = dyn_cast<PHINode>(Term->getCondition());
+      if (Phi && Phi->getParent() == BB && isElse(Phi)) {
+        insertElse(Term);
+        eraseIfUnused(Phi);
+        continue;
+      }
+
+      closeControlFlow(BB);
+    }
+
+    openIf(Term);
+  }
+
+  assert(Stack.empty());
+  return true;
+}
+
+/// \brief Create the annotation pass
+FunctionPass *llvm::createSIAnnotateControlFlowPass() {
+  return new SIAnnotateControlFlow();
+}