Permalink
Fetching contributors…
Cannot retrieve contributors at this time
442 lines (375 sloc) 17.7 KB
//===- llvm/BasicBlock.h - Represent a basic block in the VM ----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the declaration of the BasicBlock class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_IR_BASICBLOCK_H
#define LLVM_IR_BASICBLOCK_H
#include "llvm-c/Types.h"
#include "llvm/ADT/Twine.h"
#include "llvm/ADT/ilist.h"
#include "llvm/ADT/ilist_node.h"
#include "llvm/ADT/iterator.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/SymbolTableListTraits.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/CBindingWrapping.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Compiler.h"
#include <cassert>
#include <cstddef>
#include <iterator>
namespace llvm {
class CallInst;
class Function;
class LandingPadInst;
class LLVMContext;
class Module;
class PHINode;
class ValueSymbolTable;
/// LLVM Basic Block Representation
///
/// This represents a single basic block in LLVM. A basic block is simply a
/// container of instructions that execute sequentially. Basic blocks are Values
/// because they are referenced by instructions such as branches and switch
/// tables. The type of a BasicBlock is "Type::LabelTy" because the basic block
/// represents a label to which a branch can jump.
///
/// A well formed basic block is formed of a list of non-terminating
/// instructions followed by a single terminator instruction. Terminator
/// instructions may not occur in the middle of basic blocks, and must terminate
/// the blocks. The BasicBlock class allows malformed basic blocks to occur
/// because it may be useful in the intermediate stage of constructing or
/// modifying a program. However, the verifier will ensure that basic blocks are
/// "well formed".
class BasicBlock final : public Value, // Basic blocks are data objects also
public ilist_node_with_parent<BasicBlock, Function> {
public:
using InstListType = SymbolTableList<Instruction>;
private:
friend class BlockAddress;
friend class SymbolTableListTraits<BasicBlock>;
InstListType InstList;
Function *Parent;
void setParent(Function *parent);
/// Constructor.
///
/// If the function parameter is specified, the basic block is automatically
/// inserted at either the end of the function (if InsertBefore is null), or
/// before the specified basic block.
explicit BasicBlock(LLVMContext &C, const Twine &Name = "",
Function *Parent = nullptr,
BasicBlock *InsertBefore = nullptr);
public:
BasicBlock(const BasicBlock &) = delete;
BasicBlock &operator=(const BasicBlock &) = delete;
~BasicBlock();
/// Get the context in which this basic block lives.
LLVMContext &getContext() const;
/// Instruction iterators...
using iterator = InstListType::iterator;
using const_iterator = InstListType::const_iterator;
using reverse_iterator = InstListType::reverse_iterator;
using const_reverse_iterator = InstListType::const_reverse_iterator;
/// Creates a new BasicBlock.
///
/// If the Parent parameter is specified, the basic block is automatically
/// inserted at either the end of the function (if InsertBefore is 0), or
/// before the specified basic block.
static BasicBlock *Create(LLVMContext &Context, const Twine &Name = "",
Function *Parent = nullptr,
BasicBlock *InsertBefore = nullptr) {
return new BasicBlock(Context, Name, Parent, InsertBefore);
}
/// Return the enclosing method, or null if none.
const Function *getParent() const { return Parent; }
Function *getParent() { return Parent; }
/// Return the module owning the function this basic block belongs to, or
/// nullptr if the function does not have a module.
///
/// Note: this is undefined behavior if the block does not have a parent.
const Module *getModule() const;
Module *getModule() {
return const_cast<Module *>(
static_cast<const BasicBlock *>(this)->getModule());
}
/// Returns the terminator instruction if the block is well formed or null
/// if the block is not well formed.
const Instruction *getTerminator() const LLVM_READONLY;
Instruction *getTerminator() {
return const_cast<Instruction *>(
static_cast<const BasicBlock *>(this)->getTerminator());
}
/// Returns the call instruction calling \@llvm.experimental.deoptimize
/// prior to the terminating return instruction of this basic block, if such
/// a call is present. Otherwise, returns null.
const CallInst *getTerminatingDeoptimizeCall() const;
CallInst *getTerminatingDeoptimizeCall() {
return const_cast<CallInst *>(
static_cast<const BasicBlock *>(this)->getTerminatingDeoptimizeCall());
}
/// Returns the call instruction marked 'musttail' prior to the terminating
/// return instruction of this basic block, if such a call is present.
/// Otherwise, returns null.
const CallInst *getTerminatingMustTailCall() const;
CallInst *getTerminatingMustTailCall() {
return const_cast<CallInst *>(
static_cast<const BasicBlock *>(this)->getTerminatingMustTailCall());
}
/// Returns a pointer to the first instruction in this block that is not a
/// PHINode instruction.
///
/// When adding instructions to the beginning of the basic block, they should
/// be added before the returned value, not before the first instruction,
/// which might be PHI. Returns 0 is there's no non-PHI instruction.
const Instruction* getFirstNonPHI() const;
Instruction* getFirstNonPHI() {
return const_cast<Instruction *>(
static_cast<const BasicBlock *>(this)->getFirstNonPHI());
}
/// Returns a pointer to the first instruction in this block that is not a
/// PHINode or a debug intrinsic.
const Instruction* getFirstNonPHIOrDbg() const;
Instruction* getFirstNonPHIOrDbg() {
return const_cast<Instruction *>(
static_cast<const BasicBlock *>(this)->getFirstNonPHIOrDbg());
}
/// Returns a pointer to the first instruction in this block that is not a
/// PHINode, a debug intrinsic, or a lifetime intrinsic.
const Instruction* getFirstNonPHIOrDbgOrLifetime() const;
Instruction* getFirstNonPHIOrDbgOrLifetime() {
return const_cast<Instruction *>(
static_cast<const BasicBlock *>(this)->getFirstNonPHIOrDbgOrLifetime());
}
/// Returns an iterator to the first instruction in this block that is
/// suitable for inserting a non-PHI instruction.
///
/// In particular, it skips all PHIs and LandingPad instructions.
const_iterator getFirstInsertionPt() const;
iterator getFirstInsertionPt() {
return static_cast<const BasicBlock *>(this)
->getFirstInsertionPt().getNonConst();
}
/// Return a const iterator range over the instructions in the block, skipping
/// any debug instructions.
iterator_range<filter_iterator<BasicBlock::const_iterator,
std::function<bool(const Instruction &)>>>
instructionsWithoutDebug() const;
/// Return an iterator range over the instructions in the block, skipping any
/// debug instructions.
iterator_range<filter_iterator<BasicBlock::iterator,
std::function<bool(Instruction &)>>>
instructionsWithoutDebug();
/// Unlink 'this' from the containing function, but do not delete it.
void removeFromParent();
/// Unlink 'this' from the containing function and delete it.
///
// \returns an iterator pointing to the element after the erased one.
SymbolTableList<BasicBlock>::iterator eraseFromParent();
/// Unlink this basic block from its current function and insert it into
/// the function that \p MovePos lives in, right before \p MovePos.
void moveBefore(BasicBlock *MovePos);
/// Unlink this basic block from its current function and insert it
/// right after \p MovePos in the function \p MovePos lives in.
void moveAfter(BasicBlock *MovePos);
/// Insert unlinked basic block into a function.
///
/// Inserts an unlinked basic block into \c Parent. If \c InsertBefore is
/// provided, inserts before that basic block, otherwise inserts at the end.
///
/// \pre \a getParent() is \c nullptr.
void insertInto(Function *Parent, BasicBlock *InsertBefore = nullptr);
/// Return the predecessor of this block if it has a single predecessor
/// block. Otherwise return a null pointer.
const BasicBlock *getSinglePredecessor() const;
BasicBlock *getSinglePredecessor() {
return const_cast<BasicBlock *>(
static_cast<const BasicBlock *>(this)->getSinglePredecessor());
}
/// Return the predecessor of this block if it has a unique predecessor
/// 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 *getUniquePredecessor() const;
BasicBlock *getUniquePredecessor() {
return const_cast<BasicBlock *>(
static_cast<const BasicBlock *>(this)->getUniquePredecessor());
}
/// Return the successor of this block if it has a single successor.
/// Otherwise return a null pointer.
///
/// This method is analogous to getSinglePredecessor above.
const BasicBlock *getSingleSuccessor() const;
BasicBlock *getSingleSuccessor() {
return const_cast<BasicBlock *>(
static_cast<const BasicBlock *>(this)->getSingleSuccessor());
}
/// Return the successor of this block if it has a unique successor.
/// Otherwise return a null pointer.
///
/// This method is analogous to getUniquePredecessor above.
const BasicBlock *getUniqueSuccessor() const;
BasicBlock *getUniqueSuccessor() {
return const_cast<BasicBlock *>(
static_cast<const BasicBlock *>(this)->getUniqueSuccessor());
}
//===--------------------------------------------------------------------===//
/// Instruction iterator methods
///
inline iterator begin() { return InstList.begin(); }
inline const_iterator begin() const { return InstList.begin(); }
inline iterator end () { return InstList.end(); }
inline const_iterator end () const { return InstList.end(); }
inline reverse_iterator rbegin() { return InstList.rbegin(); }
inline const_reverse_iterator rbegin() const { return InstList.rbegin(); }
inline reverse_iterator rend () { return InstList.rend(); }
inline const_reverse_iterator rend () const { return InstList.rend(); }
inline size_t size() const { return InstList.size(); }
inline bool empty() const { return InstList.empty(); }
inline const Instruction &front() const { return InstList.front(); }
inline Instruction &front() { return InstList.front(); }
inline const Instruction &back() const { return InstList.back(); }
inline Instruction &back() { return InstList.back(); }
/// Iterator to walk just the phi nodes in the basic block.
template <typename PHINodeT = PHINode, typename BBIteratorT = iterator>
class phi_iterator_impl
: public iterator_facade_base<phi_iterator_impl<PHINodeT, BBIteratorT>,
std::forward_iterator_tag, PHINodeT> {
friend BasicBlock;
PHINodeT *PN;
phi_iterator_impl(PHINodeT *PN) : PN(PN) {}
public:
// Allow default construction to build variables, but this doesn't build
// a useful iterator.
phi_iterator_impl() = default;
// Allow conversion between instantiations where valid.
template <typename PHINodeU, typename BBIteratorU>
phi_iterator_impl(const phi_iterator_impl<PHINodeU, BBIteratorU> &Arg)
: PN(Arg.PN) {}
bool operator==(const phi_iterator_impl &Arg) const { return PN == Arg.PN; }
PHINodeT &operator*() const { return *PN; }
using phi_iterator_impl::iterator_facade_base::operator++;
phi_iterator_impl &operator++() {
assert(PN && "Cannot increment the end iterator!");
PN = dyn_cast<PHINodeT>(std::next(BBIteratorT(PN)));
return *this;
}
};
using phi_iterator = phi_iterator_impl<>;
using const_phi_iterator =
phi_iterator_impl<const PHINode, BasicBlock::const_iterator>;
/// Returns a range that iterates over the phis in the basic block.
///
/// Note that this cannot be used with basic blocks that have no terminator.
iterator_range<const_phi_iterator> phis() const {
return const_cast<BasicBlock *>(this)->phis();
}
iterator_range<phi_iterator> phis();
/// Return the underlying instruction list container.
///
/// Currently you need to access the underlying instruction list container
/// directly if you want to modify it.
const InstListType &getInstList() const { return InstList; }
InstListType &getInstList() { return InstList; }
/// Returns a pointer to a member of the instruction list.
static InstListType BasicBlock::*getSublistAccess(Instruction*) {
return &BasicBlock::InstList;
}
/// Returns a pointer to the symbol table if one exists.
ValueSymbolTable *getValueSymbolTable();
/// Methods for support type inquiry through isa, cast, and dyn_cast.
static bool classof(const Value *V) {
return V->getValueID() == Value::BasicBlockVal;
}
/// Cause all subinstructions to "let go" of all the references that said
/// subinstructions are maintaining.
///
/// This allows one to 'delete' a whole class at a time, even though there may
/// be circular references... first all references are dropped, and all use
/// counts go to zero. Then everything is delete'd for real. Note that no
/// operations are valid on an object that has "dropped all references",
/// except operator delete.
void dropAllReferences();
/// Notify the BasicBlock that the predecessor \p Pred 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 removePredecessor(BasicBlock *Pred, bool DontDeleteUselessPHIs = false);
bool canSplitPredecessors() const;
/// Split the basic block into two basic blocks 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 original
/// BB, and the rest of the instructions in the BB are moved to the new BB,
/// including the old terminator. The newly formed BasicBlock is returned.
/// This function invalidates the specified 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).
///
/// Also note that this doesn't preserve any passes. To split blocks while
/// keeping loop information consistent, use the SplitBlock utility function.
BasicBlock *splitBasicBlock(iterator I, const Twine &BBName = "");
BasicBlock *splitBasicBlock(Instruction *I, const Twine &BBName = "") {
return splitBasicBlock(I->getIterator(), BBName);
}
/// Returns true if there are any uses of this basic block other than
/// direct branches, switches, etc. to it.
bool hasAddressTaken() const { return getSubclassDataFromValue() != 0; }
/// Update all phi nodes in this basic block's successors to refer to basic
/// block \p New instead of to it.
void replaceSuccessorsPhiUsesWith(BasicBlock *New);
/// Return true if this basic block is an exception handling block.
bool isEHPad() const { return getFirstNonPHI()->isEHPad(); }
/// Return true if this basic block is a landing pad.
///
/// Being a ``landing pad'' means that the basic block is the destination of
/// the 'unwind' edge of an invoke instruction.
bool isLandingPad() const;
/// Return the landingpad instruction associated with the landing pad.
const LandingPadInst *getLandingPadInst() const;
LandingPadInst *getLandingPadInst() {
return const_cast<LandingPadInst *>(
static_cast<const BasicBlock *>(this)->getLandingPadInst());
}
/// Return true if it is legal to hoist instructions into this block.
bool isLegalToHoistInto() const;
Optional<uint64_t> getIrrLoopHeaderWeight() const;
private:
/// Increment the internal refcount of the number of BlockAddresses
/// referencing this BasicBlock by \p Amt.
///
/// This is almost always 0, sometimes one possibly, but almost never 2, and
/// inconceivably 3 or more.
void AdjustBlockAddressRefCount(int Amt) {
setValueSubclassData(getSubclassDataFromValue()+Amt);
assert((int)(signed char)getSubclassDataFromValue() >= 0 &&
"Refcount wrap-around");
}
/// Shadow Value::setValueSubclassData with a private forwarding method so
/// that any future subclasses cannot accidentally use it.
void setValueSubclassData(unsigned short D) {
Value::setValueSubclassData(D);
}
};
// Create wrappers for C Binding types (see CBindingWrapping.h).
DEFINE_SIMPLE_CONVERSION_FUNCTIONS(BasicBlock, LLVMBasicBlockRef)
/// Advance \p It while it points to a debug instruction and return the result.
/// This assumes that \p It is not at the end of a block.
BasicBlock::iterator skipDebugIntrinsics(BasicBlock::iterator It);
} // end namespace llvm
#endif // LLVM_IR_BASICBLOCK_H