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Diffstat (limited to 'llvm/lib/IR/BasicBlock.cpp')
| -rw-r--r-- | llvm/lib/IR/BasicBlock.cpp | 496 |
1 files changed, 496 insertions, 0 deletions
diff --git a/llvm/lib/IR/BasicBlock.cpp b/llvm/lib/IR/BasicBlock.cpp new file mode 100644 index 0000000000000..bdee6990f9324 --- /dev/null +++ b/llvm/lib/IR/BasicBlock.cpp @@ -0,0 +1,496 @@ +//===-- BasicBlock.cpp - Implement BasicBlock related methods -------------===// +// +// 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 +// +//===----------------------------------------------------------------------===// +// +// This file implements the BasicBlock class for the IR library. +// +//===----------------------------------------------------------------------===// + +#include "llvm/IR/BasicBlock.h" +#include "SymbolTableListTraitsImpl.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/IR/CFG.h" +#include "llvm/IR/Constants.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/IntrinsicInst.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/IR/Type.h" +#include <algorithm> + +using namespace llvm; + +ValueSymbolTable *BasicBlock::getValueSymbolTable() { + if (Function *F = getParent()) + return F->getValueSymbolTable(); + return nullptr; +} + +LLVMContext &BasicBlock::getContext() const { + return getType()->getContext(); +} + +// Explicit instantiation of SymbolTableListTraits since some of the methods +// are not in the public header file... +template class llvm::SymbolTableListTraits<Instruction>; + +BasicBlock::BasicBlock(LLVMContext &C, const Twine &Name, Function *NewParent, + BasicBlock *InsertBefore) + : Value(Type::getLabelTy(C), Value::BasicBlockVal), Parent(nullptr) { + + if (NewParent) + insertInto(NewParent, InsertBefore); + else + assert(!InsertBefore && + "Cannot insert block before another block with no function!"); + + setName(Name); +} + +void BasicBlock::insertInto(Function *NewParent, BasicBlock *InsertBefore) { + assert(NewParent && "Expected a parent"); + assert(!Parent && "Already has a parent"); + + if (InsertBefore) + NewParent->getBasicBlockList().insert(InsertBefore->getIterator(), this); + else + NewParent->getBasicBlockList().push_back(this); +} + +BasicBlock::~BasicBlock() { + // If the address of the block is taken and it is being deleted (e.g. because + // it is dead), this means that there is either a dangling constant expr + // hanging off the block, or an undefined use of the block (source code + // expecting the address of a label to keep the block alive even though there + // is no indirect branch). Handle these cases by zapping the BlockAddress + // nodes. There are no other possible uses at this point. + if (hasAddressTaken()) { + assert(!use_empty() && "There should be at least one blockaddress!"); + Constant *Replacement = + ConstantInt::get(llvm::Type::getInt32Ty(getContext()), 1); + while (!use_empty()) { + BlockAddress *BA = cast<BlockAddress>(user_back()); + BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement, + BA->getType())); + BA->destroyConstant(); + } + } + + assert(getParent() == nullptr && "BasicBlock still linked into the program!"); + dropAllReferences(); + InstList.clear(); +} + +void BasicBlock::setParent(Function *parent) { + // Set Parent=parent, updating instruction symtab entries as appropriate. + InstList.setSymTabObject(&Parent, parent); +} + +iterator_range<filter_iterator<BasicBlock::const_iterator, + std::function<bool(const Instruction &)>>> +BasicBlock::instructionsWithoutDebug() const { + std::function<bool(const Instruction &)> Fn = [](const Instruction &I) { + return !isa<DbgInfoIntrinsic>(I); + }; + return make_filter_range(*this, Fn); +} + +iterator_range<filter_iterator<BasicBlock::iterator, + std::function<bool(Instruction &)>>> +BasicBlock::instructionsWithoutDebug() { + std::function<bool(Instruction &)> Fn = [](Instruction &I) { + return !isa<DbgInfoIntrinsic>(I); + }; + return make_filter_range(*this, Fn); +} + +filter_iterator<BasicBlock::const_iterator, + std::function<bool(const Instruction &)>>::difference_type +BasicBlock::sizeWithoutDebug() const { + return std::distance(instructionsWithoutDebug().begin(), + instructionsWithoutDebug().end()); +} + +void BasicBlock::removeFromParent() { + getParent()->getBasicBlockList().remove(getIterator()); +} + +iplist<BasicBlock>::iterator BasicBlock::eraseFromParent() { + return getParent()->getBasicBlockList().erase(getIterator()); +} + +/// Unlink this basic block from its current function and +/// insert it into the function that MovePos lives in, right before MovePos. +void BasicBlock::moveBefore(BasicBlock *MovePos) { + MovePos->getParent()->getBasicBlockList().splice( + MovePos->getIterator(), getParent()->getBasicBlockList(), getIterator()); +} + +/// Unlink this basic block from its current function and +/// insert it into the function that MovePos lives in, right after MovePos. +void BasicBlock::moveAfter(BasicBlock *MovePos) { + MovePos->getParent()->getBasicBlockList().splice( + ++MovePos->getIterator(), getParent()->getBasicBlockList(), + getIterator()); +} + +const Module *BasicBlock::getModule() const { + return getParent()->getParent(); +} + +const Instruction *BasicBlock::getTerminator() const { + if (InstList.empty() || !InstList.back().isTerminator()) + return nullptr; + return &InstList.back(); +} + +const CallInst *BasicBlock::getTerminatingMustTailCall() const { + if (InstList.empty()) + return nullptr; + const ReturnInst *RI = dyn_cast<ReturnInst>(&InstList.back()); + if (!RI || RI == &InstList.front()) + return nullptr; + + const Instruction *Prev = RI->getPrevNode(); + if (!Prev) + return nullptr; + + if (Value *RV = RI->getReturnValue()) { + if (RV != Prev) + return nullptr; + + // Look through the optional bitcast. + if (auto *BI = dyn_cast<BitCastInst>(Prev)) { + RV = BI->getOperand(0); + Prev = BI->getPrevNode(); + if (!Prev || RV != Prev) + return nullptr; + } + } + + if (auto *CI = dyn_cast<CallInst>(Prev)) { + if (CI->isMustTailCall()) + return CI; + } + return nullptr; +} + +const CallInst *BasicBlock::getTerminatingDeoptimizeCall() const { + if (InstList.empty()) + return nullptr; + auto *RI = dyn_cast<ReturnInst>(&InstList.back()); + if (!RI || RI == &InstList.front()) + return nullptr; + + if (auto *CI = dyn_cast_or_null<CallInst>(RI->getPrevNode())) + if (Function *F = CI->getCalledFunction()) + if (F->getIntrinsicID() == Intrinsic::experimental_deoptimize) + return CI; + + return nullptr; +} + +const Instruction* BasicBlock::getFirstNonPHI() const { + for (const Instruction &I : *this) + if (!isa<PHINode>(I)) + return &I; + return nullptr; +} + +const Instruction* BasicBlock::getFirstNonPHIOrDbg() const { + for (const Instruction &I : *this) + if (!isa<PHINode>(I) && !isa<DbgInfoIntrinsic>(I)) + return &I; + return nullptr; +} + +const Instruction* BasicBlock::getFirstNonPHIOrDbgOrLifetime() const { + for (const Instruction &I : *this) { + if (isa<PHINode>(I) || isa<DbgInfoIntrinsic>(I)) + continue; + + if (I.isLifetimeStartOrEnd()) + continue; + + return &I; + } + return nullptr; +} + +BasicBlock::const_iterator BasicBlock::getFirstInsertionPt() const { + const Instruction *FirstNonPHI = getFirstNonPHI(); + if (!FirstNonPHI) + return end(); + + const_iterator InsertPt = FirstNonPHI->getIterator(); + if (InsertPt->isEHPad()) ++InsertPt; + return InsertPt; +} + +void BasicBlock::dropAllReferences() { + for (Instruction &I : *this) + I.dropAllReferences(); +} + +/// If this basic block has a single predecessor block, +/// return the block, otherwise return a null pointer. +const BasicBlock *BasicBlock::getSinglePredecessor() const { + const_pred_iterator PI = pred_begin(this), E = pred_end(this); + if (PI == E) return nullptr; // No preds. + const BasicBlock *ThePred = *PI; + ++PI; + return (PI == E) ? ThePred : nullptr /*multiple preds*/; +} + +/// If this basic block has a unique predecessor block, +/// return the block, otherwise return a null pointer. +/// Note that unique predecessor doesn't mean single edge, there can be +/// multiple edges from the unique predecessor to this block (for example +/// a switch statement with multiple cases having the same destination). +const BasicBlock *BasicBlock::getUniquePredecessor() const { + const_pred_iterator PI = pred_begin(this), E = pred_end(this); + if (PI == E) return nullptr; // No preds. + const BasicBlock *PredBB = *PI; + ++PI; + for (;PI != E; ++PI) { + if (*PI != PredBB) + return nullptr; + // The same predecessor appears multiple times in the predecessor list. + // This is OK. + } + return PredBB; +} + +bool BasicBlock::hasNPredecessors(unsigned N) const { + return hasNItems(pred_begin(this), pred_end(this), N); +} + +bool BasicBlock::hasNPredecessorsOrMore(unsigned N) const { + return hasNItemsOrMore(pred_begin(this), pred_end(this), N); +} + +const BasicBlock *BasicBlock::getSingleSuccessor() const { + succ_const_iterator SI = succ_begin(this), E = succ_end(this); + if (SI == E) return nullptr; // no successors + const BasicBlock *TheSucc = *SI; + ++SI; + return (SI == E) ? TheSucc : nullptr /* multiple successors */; +} + +const BasicBlock *BasicBlock::getUniqueSuccessor() const { + succ_const_iterator SI = succ_begin(this), E = succ_end(this); + if (SI == E) return nullptr; // No successors + const BasicBlock *SuccBB = *SI; + ++SI; + for (;SI != E; ++SI) { + if (*SI != SuccBB) + return nullptr; + // The same successor appears multiple times in the successor list. + // This is OK. + } + return SuccBB; +} + +iterator_range<BasicBlock::phi_iterator> BasicBlock::phis() { + PHINode *P = empty() ? nullptr : dyn_cast<PHINode>(&*begin()); + return make_range<phi_iterator>(P, nullptr); +} + +/// This method is used to notify a BasicBlock that the +/// specified Predecessor of the block is no longer able to reach it. This is +/// actually not used to update the Predecessor list, but is actually used to +/// update the PHI nodes that reside in the block. Note that this should be +/// called while the predecessor still refers to this block. +/// +void BasicBlock::removePredecessor(BasicBlock *Pred, + bool KeepOneInputPHIs) { + assert((hasNUsesOrMore(16)||// Reduce cost of this assertion for complex CFGs. + find(pred_begin(this), pred_end(this), Pred) != pred_end(this)) && + "removePredecessor: BB is not a predecessor!"); + + if (InstList.empty()) return; + PHINode *APN = dyn_cast<PHINode>(&front()); + if (!APN) return; // Quick exit. + + // If there are exactly two predecessors, then we want to nuke the PHI nodes + // altogether. However, we cannot do this, if this in this case: + // + // Loop: + // %x = phi [X, Loop] + // %x2 = add %x, 1 ;; This would become %x2 = add %x2, 1 + // br Loop ;; %x2 does not dominate all uses + // + // This is because the PHI node input is actually taken from the predecessor + // basic block. The only case this can happen is with a self loop, so we + // check for this case explicitly now. + // + unsigned max_idx = APN->getNumIncomingValues(); + assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!"); + if (max_idx == 2) { + BasicBlock *Other = APN->getIncomingBlock(APN->getIncomingBlock(0) == Pred); + + // Disable PHI elimination! + if (this == Other) max_idx = 3; + } + + // <= Two predecessors BEFORE I remove one? + if (max_idx <= 2 && !KeepOneInputPHIs) { + // Yup, loop through and nuke the PHI nodes + while (PHINode *PN = dyn_cast<PHINode>(&front())) { + // Remove the predecessor first. + PN->removeIncomingValue(Pred, !KeepOneInputPHIs); + + // If the PHI _HAD_ two uses, replace PHI node with its now *single* value + if (max_idx == 2) { + if (PN->getIncomingValue(0) != PN) + PN->replaceAllUsesWith(PN->getIncomingValue(0)); + else + // We are left with an infinite loop with no entries: kill the PHI. + PN->replaceAllUsesWith(UndefValue::get(PN->getType())); + getInstList().pop_front(); // Remove the PHI node + } + + // If the PHI node already only had one entry, it got deleted by + // removeIncomingValue. + } + } else { + // Okay, now we know that we need to remove predecessor #pred_idx from all + // PHI nodes. Iterate over each PHI node fixing them up + PHINode *PN; + for (iterator II = begin(); (PN = dyn_cast<PHINode>(II)); ) { + ++II; + PN->removeIncomingValue(Pred, false); + // If all incoming values to the Phi are the same, we can replace the Phi + // with that value. + Value* PNV = nullptr; + if (!KeepOneInputPHIs && (PNV = PN->hasConstantValue())) + if (PNV != PN) { + PN->replaceAllUsesWith(PNV); + PN->eraseFromParent(); + } + } + } +} + +bool BasicBlock::canSplitPredecessors() const { + const Instruction *FirstNonPHI = getFirstNonPHI(); + if (isa<LandingPadInst>(FirstNonPHI)) + return true; + // This is perhaps a little conservative because constructs like + // CleanupBlockInst are pretty easy to split. However, SplitBlockPredecessors + // cannot handle such things just yet. + if (FirstNonPHI->isEHPad()) + return false; + return true; +} + +bool BasicBlock::isLegalToHoistInto() const { + auto *Term = getTerminator(); + // No terminator means the block is under construction. + if (!Term) + return true; + + // If the block has no successors, there can be no instructions to hoist. + assert(Term->getNumSuccessors() > 0); + + // Instructions should not be hoisted across exception handling boundaries. + return !Term->isExceptionalTerminator(); +} + +/// This splits a basic block into two at the specified +/// instruction. Note that all instructions BEFORE the specified iterator stay +/// as part of the original basic block, an unconditional branch is added to +/// the new BB, and the rest of the instructions in the BB are moved to the new +/// BB, including the old terminator. This invalidates the iterator. +/// +/// Note that this only works on well formed basic blocks (must have a +/// terminator), and 'I' must not be the end of instruction list (which would +/// cause a degenerate basic block to be formed, having a terminator inside of +/// the basic block). +/// +BasicBlock *BasicBlock::splitBasicBlock(iterator I, const Twine &BBName) { + assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!"); + assert(I != InstList.end() && + "Trying to get me to create degenerate basic block!"); + + BasicBlock *New = BasicBlock::Create(getContext(), BBName, getParent(), + this->getNextNode()); + + // Save DebugLoc of split point before invalidating iterator. + DebugLoc Loc = I->getDebugLoc(); + // Move all of the specified instructions from the original basic block into + // the new basic block. + New->getInstList().splice(New->end(), this->getInstList(), I, end()); + + // Add a branch instruction to the newly formed basic block. + BranchInst *BI = BranchInst::Create(New, this); + BI->setDebugLoc(Loc); + + // Now we must loop through all of the successors of the New block (which + // _were_ the successors of the 'this' block), and update any PHI nodes in + // successors. If there were PHI nodes in the successors, then they need to + // know that incoming branches will be from New, not from Old (this). + // + New->replaceSuccessorsPhiUsesWith(this, New); + return New; +} + +void BasicBlock::replacePhiUsesWith(BasicBlock *Old, BasicBlock *New) { + // N.B. This might not be a complete BasicBlock, so don't assume + // that it ends with a non-phi instruction. + for (iterator II = begin(), IE = end(); II != IE; ++II) { + PHINode *PN = dyn_cast<PHINode>(II); + if (!PN) + break; + PN->replaceIncomingBlockWith(Old, New); + } +} + +void BasicBlock::replaceSuccessorsPhiUsesWith(BasicBlock *Old, + BasicBlock *New) { + Instruction *TI = getTerminator(); + if (!TI) + // Cope with being called on a BasicBlock that doesn't have a terminator + // yet. Clang's CodeGenFunction::EmitReturnBlock() likes to do this. + return; + llvm::for_each(successors(TI), [Old, New](BasicBlock *Succ) { + Succ->replacePhiUsesWith(Old, New); + }); +} + +void BasicBlock::replaceSuccessorsPhiUsesWith(BasicBlock *New) { + this->replaceSuccessorsPhiUsesWith(this, New); +} + +/// Return true if this basic block is a landing pad. I.e., it's +/// the destination of the 'unwind' edge of an invoke instruction. +bool BasicBlock::isLandingPad() const { + return isa<LandingPadInst>(getFirstNonPHI()); +} + +/// Return the landingpad instruction associated with the landing pad. +const LandingPadInst *BasicBlock::getLandingPadInst() const { + return dyn_cast<LandingPadInst>(getFirstNonPHI()); +} + +Optional<uint64_t> BasicBlock::getIrrLoopHeaderWeight() const { + const Instruction *TI = getTerminator(); + if (MDNode *MDIrrLoopHeader = + TI->getMetadata(LLVMContext::MD_irr_loop)) { + MDString *MDName = cast<MDString>(MDIrrLoopHeader->getOperand(0)); + if (MDName->getString().equals("loop_header_weight")) { + auto *CI = mdconst::extract<ConstantInt>(MDIrrLoopHeader->getOperand(1)); + return Optional<uint64_t>(CI->getValue().getZExtValue()); + } + } + return Optional<uint64_t>(); +} + +BasicBlock::iterator llvm::skipDebugIntrinsics(BasicBlock::iterator It) { + while (isa<DbgInfoIntrinsic>(It)) + ++It; + return It; +} |