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332 lines
9.5 KiB
C++
332 lines
9.5 KiB
C++
//===-- SIAnnotateControlFlow.cpp - ------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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/// \file
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/// Annotates the control flow with hardware specific intrinsics.
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//
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//===----------------------------------------------------------------------===//
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#include "AMDGPU.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/SSAUpdater.h"
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using namespace llvm;
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namespace {
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// Complex types used in this pass
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typedef std::pair<BasicBlock *, Value *> StackEntry;
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typedef SmallVector<StackEntry, 16> StackVector;
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// Intrinsic names the control flow is annotated with
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static const char *const IfIntrinsic = "llvm.SI.if";
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static const char *const ElseIntrinsic = "llvm.SI.else";
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static const char *const BreakIntrinsic = "llvm.SI.break";
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static const char *const IfBreakIntrinsic = "llvm.SI.if.break";
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static const char *const ElseBreakIntrinsic = "llvm.SI.else.break";
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static const char *const LoopIntrinsic = "llvm.SI.loop";
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static const char *const EndCfIntrinsic = "llvm.SI.end.cf";
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class SIAnnotateControlFlow : public FunctionPass {
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static char ID;
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Type *Boolean;
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Type *Void;
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Type *Int64;
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Type *ReturnStruct;
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ConstantInt *BoolTrue;
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ConstantInt *BoolFalse;
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UndefValue *BoolUndef;
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Constant *Int64Zero;
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Constant *If;
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Constant *Else;
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Constant *Break;
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Constant *IfBreak;
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Constant *ElseBreak;
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Constant *Loop;
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Constant *EndCf;
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DominatorTree *DT;
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StackVector Stack;
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SSAUpdater PhiInserter;
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bool isTopOfStack(BasicBlock *BB);
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Value *popSaved();
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void push(BasicBlock *BB, Value *Saved);
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bool isElse(PHINode *Phi);
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void eraseIfUnused(PHINode *Phi);
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void openIf(BranchInst *Term);
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void insertElse(BranchInst *Term);
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void handleLoopCondition(Value *Cond);
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void handleLoop(BranchInst *Term);
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void closeControlFlow(BasicBlock *BB);
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public:
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SIAnnotateControlFlow():
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FunctionPass(ID) { }
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virtual bool doInitialization(Module &M);
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virtual bool runOnFunction(Function &F);
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virtual const char *getPassName() const {
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return "SI annotate control flow";
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}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<DominatorTree>();
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AU.addPreserved<DominatorTree>();
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FunctionPass::getAnalysisUsage(AU);
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}
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};
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} // end anonymous namespace
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char SIAnnotateControlFlow::ID = 0;
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/// \brief Initialize all the types and constants used in the pass
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bool SIAnnotateControlFlow::doInitialization(Module &M) {
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LLVMContext &Context = M.getContext();
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Void = Type::getVoidTy(Context);
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Boolean = Type::getInt1Ty(Context);
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Int64 = Type::getInt64Ty(Context);
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ReturnStruct = StructType::get(Boolean, Int64, (Type *)0);
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BoolTrue = ConstantInt::getTrue(Context);
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BoolFalse = ConstantInt::getFalse(Context);
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BoolUndef = UndefValue::get(Boolean);
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Int64Zero = ConstantInt::get(Int64, 0);
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If = M.getOrInsertFunction(
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IfIntrinsic, ReturnStruct, Boolean, (Type *)0);
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Else = M.getOrInsertFunction(
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ElseIntrinsic, ReturnStruct, Int64, (Type *)0);
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Break = M.getOrInsertFunction(
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BreakIntrinsic, Int64, Int64, (Type *)0);
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IfBreak = M.getOrInsertFunction(
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IfBreakIntrinsic, Int64, Boolean, Int64, (Type *)0);
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ElseBreak = M.getOrInsertFunction(
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ElseBreakIntrinsic, Int64, Int64, Int64, (Type *)0);
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Loop = M.getOrInsertFunction(
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LoopIntrinsic, Boolean, Int64, (Type *)0);
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EndCf = M.getOrInsertFunction(
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EndCfIntrinsic, Void, Int64, (Type *)0);
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return false;
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}
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/// \brief Is BB the last block saved on the stack ?
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bool SIAnnotateControlFlow::isTopOfStack(BasicBlock *BB) {
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return !Stack.empty() && Stack.back().first == BB;
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}
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/// \brief Pop the last saved value from the control flow stack
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Value *SIAnnotateControlFlow::popSaved() {
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return Stack.pop_back_val().second;
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}
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/// \brief Push a BB and saved value to the control flow stack
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void SIAnnotateControlFlow::push(BasicBlock *BB, Value *Saved) {
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Stack.push_back(std::make_pair(BB, Saved));
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}
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/// \brief Can the condition represented by this PHI node treated like
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/// an "Else" block?
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bool SIAnnotateControlFlow::isElse(PHINode *Phi) {
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BasicBlock *IDom = DT->getNode(Phi->getParent())->getIDom()->getBlock();
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for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
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if (Phi->getIncomingBlock(i) == IDom) {
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if (Phi->getIncomingValue(i) != BoolTrue)
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return false;
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} else {
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if (Phi->getIncomingValue(i) != BoolFalse)
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return false;
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}
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}
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return true;
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}
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// \brief Erase "Phi" if it is not used any more
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void SIAnnotateControlFlow::eraseIfUnused(PHINode *Phi) {
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if (!Phi->hasNUsesOrMore(1))
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Phi->eraseFromParent();
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}
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/// \brief Open a new "If" block
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void SIAnnotateControlFlow::openIf(BranchInst *Term) {
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Value *Ret = CallInst::Create(If, Term->getCondition(), "", Term);
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Term->setCondition(ExtractValueInst::Create(Ret, 0, "", Term));
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push(Term->getSuccessor(1), ExtractValueInst::Create(Ret, 1, "", Term));
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}
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/// \brief Close the last "If" block and open a new "Else" block
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void SIAnnotateControlFlow::insertElse(BranchInst *Term) {
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Value *Ret = CallInst::Create(Else, popSaved(), "", Term);
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Term->setCondition(ExtractValueInst::Create(Ret, 0, "", Term));
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push(Term->getSuccessor(1), ExtractValueInst::Create(Ret, 1, "", Term));
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}
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/// \brief Recursively handle the condition leading to a loop
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void SIAnnotateControlFlow::handleLoopCondition(Value *Cond) {
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if (PHINode *Phi = dyn_cast<PHINode>(Cond)) {
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// Handle all non constant incoming values first
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for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
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Value *Incoming = Phi->getIncomingValue(i);
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if (isa<ConstantInt>(Incoming))
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continue;
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Phi->setIncomingValue(i, BoolFalse);
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handleLoopCondition(Incoming);
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}
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BasicBlock *Parent = Phi->getParent();
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BasicBlock *IDom = DT->getNode(Parent)->getIDom()->getBlock();
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for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
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Value *Incoming = Phi->getIncomingValue(i);
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if (Incoming != BoolTrue)
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continue;
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BasicBlock *From = Phi->getIncomingBlock(i);
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if (From == IDom) {
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CallInst *OldEnd = dyn_cast<CallInst>(Parent->getFirstInsertionPt());
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if (OldEnd && OldEnd->getCalledFunction() == EndCf) {
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Value *Args[] = {
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OldEnd->getArgOperand(0),
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PhiInserter.GetValueAtEndOfBlock(Parent)
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};
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Value *Ret = CallInst::Create(ElseBreak, Args, "", OldEnd);
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PhiInserter.AddAvailableValue(Parent, Ret);
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continue;
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}
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}
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TerminatorInst *Insert = From->getTerminator();
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Value *Arg = PhiInserter.GetValueAtEndOfBlock(From);
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Value *Ret = CallInst::Create(Break, Arg, "", Insert);
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PhiInserter.AddAvailableValue(From, Ret);
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}
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eraseIfUnused(Phi);
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} else if (Instruction *Inst = dyn_cast<Instruction>(Cond)) {
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BasicBlock *Parent = Inst->getParent();
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TerminatorInst *Insert = Parent->getTerminator();
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Value *Args[] = { Cond, PhiInserter.GetValueAtEndOfBlock(Parent) };
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Value *Ret = CallInst::Create(IfBreak, Args, "", Insert);
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PhiInserter.AddAvailableValue(Parent, Ret);
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} else {
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assert(0 && "Unhandled loop condition!");
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}
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}
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/// \brief Handle a back edge (loop)
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void SIAnnotateControlFlow::handleLoop(BranchInst *Term) {
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BasicBlock *Target = Term->getSuccessor(1);
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PHINode *Broken = PHINode::Create(Int64, 0, "", &Target->front());
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PhiInserter.Initialize(Int64, "");
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PhiInserter.AddAvailableValue(Target, Broken);
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Value *Cond = Term->getCondition();
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Term->setCondition(BoolTrue);
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handleLoopCondition(Cond);
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BasicBlock *BB = Term->getParent();
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Value *Arg = PhiInserter.GetValueAtEndOfBlock(BB);
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for (pred_iterator PI = pred_begin(Target), PE = pred_end(Target);
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PI != PE; ++PI) {
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Broken->addIncoming(*PI == BB ? Arg : Int64Zero, *PI);
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}
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Term->setCondition(CallInst::Create(Loop, Arg, "", Term));
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push(Term->getSuccessor(0), Arg);
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}
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/// \brief Close the last opened control flow
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void SIAnnotateControlFlow::closeControlFlow(BasicBlock *BB) {
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CallInst::Create(EndCf, popSaved(), "", BB->getFirstInsertionPt());
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}
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/// \brief Annotate the control flow with intrinsics so the backend can
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/// recognize if/then/else and loops.
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bool SIAnnotateControlFlow::runOnFunction(Function &F) {
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DT = &getAnalysis<DominatorTree>();
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for (df_iterator<BasicBlock *> I = df_begin(&F.getEntryBlock()),
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E = df_end(&F.getEntryBlock()); I != E; ++I) {
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BranchInst *Term = dyn_cast<BranchInst>((*I)->getTerminator());
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if (!Term || Term->isUnconditional()) {
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if (isTopOfStack(*I))
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closeControlFlow(*I);
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continue;
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}
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if (I.nodeVisited(Term->getSuccessor(1))) {
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if (isTopOfStack(*I))
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closeControlFlow(*I);
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handleLoop(Term);
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continue;
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}
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if (isTopOfStack(*I)) {
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PHINode *Phi = dyn_cast<PHINode>(Term->getCondition());
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if (Phi && Phi->getParent() == *I && isElse(Phi)) {
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insertElse(Term);
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eraseIfUnused(Phi);
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continue;
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}
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closeControlFlow(*I);
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}
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openIf(Term);
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}
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assert(Stack.empty());
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return true;
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}
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/// \brief Create the annotation pass
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FunctionPass *llvm::createSIAnnotateControlFlowPass() {
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return new SIAnnotateControlFlow();
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}
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