1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
| //===- llvm/BasicBlock.h - Represent a basic block in the VM ----*- C++ -*-===//
//
// 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 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();
/// Return the size of the basic block ignoring debug instructions
filter_iterator<BasicBlock::const_iterator,
std::function<bool(const Instruction &)>>::difference_type
sizeWithoutDebug() const;
/// 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 true if this block has exactly N predecessors.
bool hasNPredecessors(unsigned N) const;
/// Return true if this block has N predecessors or more.
bool hasNPredecessorsOrMore(unsigned N) const;
/// 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 KeepOneInputPHIs = 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 to refer to basic block \p New
/// instead of basic block \p Old.
void replacePhiUsesWith(BasicBlock *Old, BasicBlock *New);
/// Update all phi nodes in this basic block's successors to refer to basic
/// block \p New instead of basic block \p Old.
void replaceSuccessorsPhiUsesWith(BasicBlock *Old, BasicBlock *New);
/// 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
|