//===-- 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();
}
template <> void llvm::invalidateParentIListOrdering(BasicBlock *BB) {
BB->invalidateOrders();
}
// 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() {
validateInstrOrdering();
// 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(bool SkipPseudoOp) const {
std::function<bool(const Instruction &)> Fn = [=](const Instruction &I) {
return !isa<DbgInfoIntrinsic>(I) &&
!(SkipPseudoOp && isa<PseudoProbeInst>(I));
};
return make_filter_range(*this, Fn);
}
iterator_range<
filter_iterator<BasicBlock::iterator, std::function<bool(Instruction &)>>>
BasicBlock::instructionsWithoutDebug(bool SkipPseudoOp) {
std::function<bool(Instruction &)> Fn = [=](Instruction &I) {
return !isa<DbgInfoIntrinsic>(I) &&
!(SkipPseudoOp && isa<PseudoProbeInst>(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());
}
void BasicBlock::moveBefore(BasicBlock *MovePos) {
MovePos->getParent()->getBasicBlockList().splice(
MovePos->getIterator(), getParent()->getBasicBlockList(), getIterator());
}
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 CallInst *BasicBlock::getPostdominatingDeoptimizeCall() const {
const BasicBlock* BB = this;
SmallPtrSet<const BasicBlock *, 8> Visited;
Visited.insert(BB);
while (auto *Succ = BB->getUniqueSuccessor()) {
if (!Visited.insert(Succ).second)
return nullptr;
BB = Succ;
}
return BB->getTerminatingDeoptimizeCall();
}
const Instruction* BasicBlock::getFirstNonPHI() const {
for (const Instruction &I : *this)
if (!isa<PHINode>(I))
return &I;
return nullptr;
}
const Instruction *BasicBlock::getFirstNonPHIOrDbg(bool SkipPseudoOp) const {
for (const Instruction &I : *this) {
if (isa<PHINode>(I) || isa<DbgInfoIntrinsic>(I))
continue;
if (SkipPseudoOp && isa<PseudoProbeInst>(I))
continue;
return &I;
}
return nullptr;
}
const Instruction *
BasicBlock::getFirstNonPHIOrDbgOrLifetime(bool SkipPseudoOp) const {
for (const Instruction &I : *this) {
if (isa<PHINode>(I) || isa<DbgInfoIntrinsic>(I))
continue;
if (I.isLifetimeStartOrEnd())
continue;
if (SkipPseudoOp && isa<PseudoProbeInst>(I))
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();
}
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*/;
}
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 {
const_succ_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 {
const_succ_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);
}
void BasicBlock::removePredecessor(BasicBlock *Pred,
bool KeepOneInputPHIs) {
// Use hasNUsesOrMore to bound the cost of this assertion for complex CFGs.
assert((hasNUsesOrMore(16) || llvm::is_contained(predecessors(this), Pred)) &&
"Pred is not a predecessor!");
// Return early if there are no PHI nodes to update.
if (empty() || !isa<PHINode>(begin()))
return;
unsigned NumPreds = cast<PHINode>(front()).getNumIncomingValues();
for (PHINode &Phi : make_early_inc_range(phis())) {
Phi.removeIncomingValue(Pred, !KeepOneInputPHIs);
if (KeepOneInputPHIs)
continue;
// If we have a single predecessor, removeIncomingValue may have erased the
// PHI node itself.
if (NumPreds == 1)
continue;
// Try to replace the PHI node with a constant value.
if (Value *PhiConstant = Phi.hasConstantValue()) {
Phi.replaceAllUsesWith(PhiConstant);
Phi.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();
}
BasicBlock *BasicBlock::splitBasicBlock(iterator I, const Twine &BBName,
bool Before) {
if (Before)
return splitBasicBlockBefore(I, 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;
}
BasicBlock *BasicBlock::splitBasicBlockBefore(iterator I, const Twine &BBName) {
assert(getTerminator() &&
"Can't use splitBasicBlockBefore on degenerate BB!");
assert(I != InstList.end() &&
"Trying to get me to create degenerate basic block!");
assert((!isa<PHINode>(*I) || getSinglePredecessor()) &&
"cannot split on multi incoming phis");
BasicBlock *New = BasicBlock::Create(getContext(), BBName, getParent(), this);
// 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(), begin(), I);
// Loop through all of the predecessors of the 'this' block (which will be the
// predecessors of the New block), replace the specified successor 'this'
// block to point at the New block and update any PHI nodes in 'this' block.
// If there were PHI nodes in 'this' block, the PHI nodes are updated
// to reflect that the incoming branches will be from the New block and not
// from predecessors of the 'this' block.
for (BasicBlock *Pred : predecessors(this)) {
Instruction *TI = Pred->getTerminator();
TI->replaceSuccessorWith(this, New);
this->replacePhiUsesWith(Pred, New);
}
// Add a branch instruction from "New" to "this" Block.
BranchInst *BI = BranchInst::Create(this, New);
BI->setDebugLoc(Loc);
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);
}
bool BasicBlock::isLandingPad() const {
return isa<LandingPadInst>(getFirstNonPHI());
}
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;
}
void BasicBlock::renumberInstructions() {
unsigned Order = 0;
for (Instruction &I : *this)
I.Order = Order++;
// Set the bit to indicate that the instruction order valid and cached.
BasicBlockBits Bits = getBasicBlockBits();
Bits.InstrOrderValid = true;
setBasicBlockBits(Bits);
}
#ifndef NDEBUG
/// In asserts builds, this checks the numbering. In non-asserts builds, it
/// is defined as a no-op inline function in BasicBlock.h.
void BasicBlock::validateInstrOrdering() const {
if (!isInstrOrderValid())
return;
const Instruction *Prev = nullptr;
for (const Instruction &I : *this) {
assert((!Prev || Prev->comesBefore(&I)) &&
"cached instruction ordering is incorrect");
Prev = &I;
}
}
#endif
