llvm-project/llvm/lib/Target/R600/SIAnnotateControlFlow.cpp

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//===-- 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/Analysis/LoopInfo.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
using namespace llvm;
#define DEBUG_TYPE "si-annotate-control-flow"
namespace {
// Complex types used in this pass
typedef std::pair<BasicBlock *, Value *> StackEntry;
typedef SmallVector<StackEntry, 16> StackVector;
// Intrinsic names the control flow is annotated with
static const char *const IfIntrinsic = "llvm.SI.if";
static const char *const ElseIntrinsic = "llvm.SI.else";
static const char *const BreakIntrinsic = "llvm.SI.break";
static const char *const IfBreakIntrinsic = "llvm.SI.if.break";
static const char *const ElseBreakIntrinsic = "llvm.SI.else.break";
static const char *const LoopIntrinsic = "llvm.SI.loop";
static const char *const EndCfIntrinsic = "llvm.SI.end.cf";
class SIAnnotateControlFlow : public FunctionPass {
static char ID;
Type *Boolean;
Type *Void;
Type *Int64;
Type *ReturnStruct;
ConstantInt *BoolTrue;
ConstantInt *BoolFalse;
UndefValue *BoolUndef;
Constant *Int64Zero;
Constant *If;
Constant *Else;
Constant *Break;
Constant *IfBreak;
Constant *ElseBreak;
Constant *Loop;
Constant *EndCf;
DominatorTree *DT;
StackVector Stack;
LoopInfo *LI;
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);
void handleLoop(BranchInst *Term);
void closeControlFlow(BasicBlock *BB);
public:
SIAnnotateControlFlow():
FunctionPass(ID) { }
bool doInitialization(Module &M) override;
bool runOnFunction(Function &F) override;
const char *getPassName() const override {
return "SI annotate control flow";
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<LoopInfoWrapperPass>();
AU.addRequired<DominatorTreeWrapperPass>();
AU.addPreserved<DominatorTreeWrapperPass>();
FunctionPass::getAnalysisUsage(AU);
}
};
} // end anonymous namespace
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, (Type *)nullptr);
BoolTrue = ConstantInt::getTrue(Context);
BoolFalse = ConstantInt::getFalse(Context);
BoolUndef = UndefValue::get(Boolean);
Int64Zero = ConstantInt::get(Int64, 0);
If = M.getOrInsertFunction(
IfIntrinsic, ReturnStruct, Boolean, (Type *)nullptr);
Else = M.getOrInsertFunction(
ElseIntrinsic, ReturnStruct, Int64, (Type *)nullptr);
Break = M.getOrInsertFunction(
BreakIntrinsic, Int64, Int64, (Type *)nullptr);
IfBreak = M.getOrInsertFunction(
IfBreakIntrinsic, Int64, Boolean, Int64, (Type *)nullptr);
ElseBreak = M.getOrInsertFunction(
ElseBreakIntrinsic, Int64, Int64, Int64, (Type *)nullptr);
Loop = M.getOrInsertFunction(
LoopIntrinsic, Boolean, Int64, (Type *)nullptr);
EndCf = M.getOrInsertFunction(
EndCfIntrinsic, Void, Int64, (Type *)nullptr);
return false;
}
/// \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 (!Phi->hasNUsesOrMore(1))
Phi->eraseFromParent();
}
/// \brief Open a new "If" block
void SIAnnotateControlFlow::openIf(BranchInst *Term) {
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) {
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) {
if (PHINode *Phi = dyn_cast<PHINode>(Cond)) {
BasicBlock *Parent = Phi->getParent();
PHINode *NewPhi = PHINode::Create(Int64, 0, "", &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);
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) {
CallInst *OldEnd = dyn_cast<CallInst>(Parent->getFirstInsertionPt());
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);
}
eraseIfUnused(Phi);
return Ret;
} else if (Instruction *Inst = dyn_cast<Instruction>(Cond)) {
BasicBlock *Parent = Inst->getParent();
TerminatorInst *Insert = Parent->getTerminator();
Value *Args[] = { Cond, Broken };
return CallInst::Create(IfBreak, Args, "", Insert);
} else {
llvm_unreachable("Unhandled loop condition!");
}
return 0;
}
/// \brief Handle a back edge (loop)
void SIAnnotateControlFlow::handleLoop(BranchInst *Term) {
BasicBlock *Target = Term->getSuccessor(1);
PHINode *Broken = PHINode::Create(Int64, 0, "", &Target->front());
Value *Cond = Term->getCondition();
Term->setCondition(BoolTrue);
Value *Arg = handleLoopCondition(Cond, Broken);
BasicBlock *BB = Term->getParent();
for (pred_iterator PI = pred_begin(Target), PE = pred_end(Target);
PI != PE; ++PI) {
Broken->addIncoming(*PI == BB ? Arg : Int64Zero, *PI);
}
Term->setCondition(CallInst::Create(Loop, Arg, "", Term));
push(Term->getSuccessor(0), Arg);
}/// \brief Close the last opened control flow
void SIAnnotateControlFlow::closeControlFlow(BasicBlock *BB) {
llvm::Loop *L = LI->getLoopFor(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);
std::vector<BasicBlock*> Preds;
for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
if (std::find(Latches.begin(), Latches.end(), *PI) == Latches.end())
Preds.push_back(*PI);
}
BB = llvm::SplitBlockPredecessors(BB, Preds, "endcf.split", nullptr, DT,
LI, false);
}
CallInst::Create(EndCf, popSaved(), "", BB->getFirstInsertionPt());
}
/// \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();
for (df_iterator<BasicBlock *> I = df_begin(&F.getEntryBlock()),
E = df_end(&F.getEntryBlock()); I != E; ++I) {
BranchInst *Term = dyn_cast<BranchInst>((*I)->getTerminator());
if (!Term || Term->isUnconditional()) {
if (isTopOfStack(*I))
closeControlFlow(*I);
continue;
}
if (I.nodeVisited(Term->getSuccessor(1))) {
if (isTopOfStack(*I))
closeControlFlow(*I);
handleLoop(Term);
continue;
}
if (isTopOfStack(*I)) {
PHINode *Phi = dyn_cast<PHINode>(Term->getCondition());
if (Phi && Phi->getParent() == *I && isElse(Phi)) {
insertElse(Term);
eraseIfUnused(Phi);
continue;
}
closeControlFlow(*I);
}
openIf(Term);
}
assert(Stack.empty());
return true;
}
/// \brief Create the annotation pass
FunctionPass *llvm::createSIAnnotateControlFlowPass() {
return new SIAnnotateControlFlow();
}