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diff --git a/llvm/lib/IR/BasicBlock.cpp b/llvm/lib/IR/BasicBlock.cpp
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+//===-- 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;
+}
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