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Chris Lattner184b2982002-09-08 18:59:35 +00001//===-- BasicBlock.cpp - Implement BasicBlock related methods -------------===//
Misha Brukmanb1c93172005-04-21 23:48:37 +00002//
John Criswell482202a2003-10-20 19:43:21 +00003// The LLVM Compiler Infrastructure
4//
Chris Lattnerf3ebc3f2007-12-29 20:36:04 +00005// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
Misha Brukmanb1c93172005-04-21 23:48:37 +00007//
John Criswell482202a2003-10-20 19:43:21 +00008//===----------------------------------------------------------------------===//
Chris Lattner2f7c9632001-06-06 20:29:01 +00009//
Chris Lattnerf739fa82002-04-08 22:03:57 +000010// This file implements the BasicBlock class for the VMCore library.
Chris Lattner2f7c9632001-06-06 20:29:01 +000011//
12//===----------------------------------------------------------------------===//
13
Gabor Greifa3de9e42008-05-27 17:26:02 +000014#include "llvm/BasicBlock.h"
Chris Lattner9daef352005-04-12 18:52:14 +000015#include "llvm/Constants.h"
Misha Brukman2d3fa9e2004-07-29 16:53:53 +000016#include "llvm/Instructions.h"
Dale Johannesenc268ced2010-04-02 21:49:27 +000017#include "llvm/IntrinsicInst.h"
Owen Anderson155dccd82009-07-07 23:43:39 +000018#include "llvm/LLVMContext.h"
Chris Lattner2f7c9632001-06-06 20:29:01 +000019#include "llvm/Type.h"
Dan Gohman804c95d2008-07-28 21:51:04 +000020#include "llvm/ADT/STLExtras.h"
Chris Lattner83d485b2002-02-12 22:39:50 +000021#include "llvm/Support/CFG.h"
Reid Spencer7c16caa2004-09-01 22:55:40 +000022#include "llvm/Support/LeakDetector.h"
Chris Lattner113f4f42002-06-25 16:13:24 +000023#include "SymbolTableListTraitsImpl.h"
24#include <algorithm>
Chris Lattnera2960002003-11-21 16:52:05 +000025using namespace llvm;
Chris Lattner2f7c9632001-06-06 20:29:01 +000026
Gabor Greif51bbcf82009-03-07 12:33:24 +000027ValueSymbolTable *BasicBlock::getValueSymbolTable() {
28 if (Function *F = getParent())
29 return &F->getValueSymbolTable();
Chris Lattnerb47aa542007-04-17 03:26:42 +000030 return 0;
31}
32
Owen Anderson47db9412009-07-22 00:24:57 +000033LLVMContext &BasicBlock::getContext() const {
34 return getType()->getContext();
Owen Andersone70b6372009-07-05 22:41:43 +000035}
36
Chris Lattner113f4f42002-06-25 16:13:24 +000037// Explicit instantiation of SymbolTableListTraits since some of the methods
38// are not in the public header file...
John McCall086bb4e2009-12-19 00:55:12 +000039template class llvm::SymbolTableListTraits<Instruction, BasicBlock>;
Chris Lattner113f4f42002-06-25 16:13:24 +000040
Bill Wendling35a9c3c2011-04-10 23:18:04 +000041
Owen Anderson55f1c092009-08-13 21:58:54 +000042BasicBlock::BasicBlock(LLVMContext &C, const Twine &Name, Function *NewParent,
Nick Lewycky4d43d3c2008-04-25 16:53:59 +000043 BasicBlock *InsertBefore)
Bill Wendling35a9c3c2011-04-10 23:18:04 +000044 : Value(Type::getLabelTy(C), Value::BasicBlockVal), Parent(0) {
Chris Lattner4dfede82002-09-26 05:03:22 +000045
46 // Make sure that we get added to a function
47 LeakDetector::addGarbageObject(this);
48
49 if (InsertBefore) {
Chris Lattnerb47aa542007-04-17 03:26:42 +000050 assert(NewParent &&
Chris Lattnerbb5f0db2004-02-04 03:57:50 +000051 "Cannot insert block before another block with no function!");
Chris Lattnerb47aa542007-04-17 03:26:42 +000052 NewParent->getBasicBlockList().insert(InsertBefore, this);
53 } else if (NewParent) {
54 NewParent->getBasicBlockList().push_back(this);
Chris Lattner4dfede82002-09-26 05:03:22 +000055 }
Chris Lattner32ab6432007-02-12 05:18:08 +000056
57 setName(Name);
Chris Lattner4dfede82002-09-26 05:03:22 +000058}
59
Bill Wendling35a9c3c2011-04-10 23:18:04 +000060
Gordon Henriksen14a55692007-12-10 02:14:30 +000061BasicBlock::~BasicBlock() {
Chris Lattnerdd5d0352009-10-30 22:39:36 +000062 // If the address of the block is taken and it is being deleted (e.g. because
63 // it is dead), this means that there is either a dangling constant expr
64 // hanging off the block, or an undefined use of the block (source code
65 // expecting the address of a label to keep the block alive even though there
66 // is no indirect branch). Handle these cases by zapping the BlockAddress
Chris Lattneraa99c942009-11-01 01:27:45 +000067 // nodes. There are no other possible uses at this point.
Chris Lattnerdd5d0352009-10-30 22:39:36 +000068 if (hasAddressTaken()) {
69 assert(!use_empty() && "There should be at least one blockaddress!");
Chris Lattneraa99c942009-11-01 01:27:45 +000070 Constant *Replacement =
71 ConstantInt::get(llvm::Type::getInt32Ty(getContext()), 1);
Chris Lattnerdd5d0352009-10-30 22:39:36 +000072 while (!use_empty()) {
73 BlockAddress *BA = cast<BlockAddress>(use_back());
Chris Lattneraa99c942009-11-01 01:27:45 +000074 BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement,
75 BA->getType()));
Chris Lattnerdd5d0352009-10-30 22:39:36 +000076 BA->destroyConstant();
77 }
78 }
79
Gordon Henriksen14a55692007-12-10 02:14:30 +000080 assert(getParent() == 0 && "BasicBlock still linked into the program!");
81 dropAllReferences();
82 InstList.clear();
Chris Lattner2f7c9632001-06-06 20:29:01 +000083}
84
Chris Lattner9ed7aef2002-09-06 21:33:15 +000085void BasicBlock::setParent(Function *parent) {
Chris Lattner184b2982002-09-08 18:59:35 +000086 if (getParent())
87 LeakDetector::addGarbageObject(this);
88
Chris Lattnerb47aa542007-04-17 03:26:42 +000089 // Set Parent=parent, updating instruction symtab entries as appropriate.
90 InstList.setSymTabObject(&Parent, parent);
Chris Lattner184b2982002-09-08 18:59:35 +000091
92 if (getParent())
93 LeakDetector::removeGarbageObject(this);
Chris Lattner9ed7aef2002-09-06 21:33:15 +000094}
95
Chris Lattner02a71e72004-10-11 22:21:39 +000096void BasicBlock::removeFromParent() {
97 getParent()->getBasicBlockList().remove(this);
98}
99
100void BasicBlock::eraseFromParent() {
101 getParent()->getBasicBlockList().erase(this);
102}
103
Chris Lattner4091f462006-09-23 04:03:45 +0000104/// moveBefore - Unlink this basic block from its current function and
105/// insert it into the function that MovePos lives in, right before MovePos.
Chris Lattnere09bbc82005-08-12 22:14:06 +0000106void BasicBlock::moveBefore(BasicBlock *MovePos) {
107 MovePos->getParent()->getBasicBlockList().splice(MovePos,
108 getParent()->getBasicBlockList(), this);
109}
110
Chris Lattner4091f462006-09-23 04:03:45 +0000111/// moveAfter - Unlink this basic block from its current function and
112/// insert it into the function that MovePos lives in, right after MovePos.
113void BasicBlock::moveAfter(BasicBlock *MovePos) {
114 Function::iterator I = MovePos;
115 MovePos->getParent()->getBasicBlockList().splice(++I,
116 getParent()->getBasicBlockList(), this);
117}
118
Chris Lattner02a71e72004-10-11 22:21:39 +0000119
Chris Lattner2f7c9632001-06-06 20:29:01 +0000120TerminatorInst *BasicBlock::getTerminator() {
121 if (InstList.empty()) return 0;
Chris Lattner113f4f42002-06-25 16:13:24 +0000122 return dyn_cast<TerminatorInst>(&InstList.back());
Chris Lattner2f7c9632001-06-06 20:29:01 +0000123}
124
Dan Gohmanaad83c82007-11-19 20:46:23 +0000125const TerminatorInst *BasicBlock::getTerminator() const {
Chris Lattner2f7c9632001-06-06 20:29:01 +0000126 if (InstList.empty()) return 0;
Chris Lattner113f4f42002-06-25 16:13:24 +0000127 return dyn_cast<TerminatorInst>(&InstList.back());
Chris Lattner2f7c9632001-06-06 20:29:01 +0000128}
129
Dan Gohmanf96e1372008-05-23 21:05:58 +0000130Instruction* BasicBlock::getFirstNonPHI() {
131 BasicBlock::iterator i = begin();
132 // All valid basic blocks should have a terminator,
133 // which is not a PHINode. If we have an invalid basic
134 // block we'll get an assertion failure when dereferencing
135 // a past-the-end iterator.
136 while (isa<PHINode>(i)) ++i;
137 return &*i;
Vladimir Prusb5b6dc42006-06-08 15:46:18 +0000138}
139
Dale Johannesenc268ced2010-04-02 21:49:27 +0000140Instruction* BasicBlock::getFirstNonPHIOrDbg() {
141 BasicBlock::iterator i = begin();
142 // All valid basic blocks should have a terminator,
143 // which is not a PHINode. If we have an invalid basic
144 // block we'll get an assertion failure when dereferencing
145 // a past-the-end iterator.
146 while (isa<PHINode>(i) || isa<DbgInfoIntrinsic>(i)) ++i;
147 return &*i;
148}
149
Chris Lattner2f7c9632001-06-06 20:29:01 +0000150void BasicBlock::dropAllReferences() {
Chris Lattner113f4f42002-06-25 16:13:24 +0000151 for(iterator I = begin(), E = end(); I != E; ++I)
152 I->dropAllReferences();
Chris Lattner2f7c9632001-06-06 20:29:01 +0000153}
154
Chris Lattnerce046ac2005-02-24 02:37:26 +0000155/// getSinglePredecessor - If this basic block has a single predecessor block,
156/// return the block, otherwise return a null pointer.
157BasicBlock *BasicBlock::getSinglePredecessor() {
158 pred_iterator PI = pred_begin(this), E = pred_end(this);
159 if (PI == E) return 0; // No preds.
160 BasicBlock *ThePred = *PI;
161 ++PI;
162 return (PI == E) ? ThePred : 0 /*multiple preds*/;
163}
164
Torok Edwinc8080122008-12-11 10:36:07 +0000165/// getUniquePredecessor - If this basic block has a unique predecessor block,
166/// return the block, otherwise return a null pointer.
167/// Note that unique predecessor doesn't mean single edge, there can be
Torok Edwin32bfb5d2008-12-11 11:44:49 +0000168/// multiple edges from the unique predecessor to this block (for example
169/// a switch statement with multiple cases having the same destination).
Torok Edwinc8080122008-12-11 10:36:07 +0000170BasicBlock *BasicBlock::getUniquePredecessor() {
171 pred_iterator PI = pred_begin(this), E = pred_end(this);
172 if (PI == E) return 0; // No preds.
173 BasicBlock *PredBB = *PI;
174 ++PI;
175 for (;PI != E; ++PI) {
176 if (*PI != PredBB)
177 return 0;
Torok Edwin32bfb5d2008-12-11 11:44:49 +0000178 // The same predecessor appears multiple times in the predecessor list.
179 // This is OK.
Torok Edwinc8080122008-12-11 10:36:07 +0000180 }
181 return PredBB;
182}
183
Chris Lattner954c64d2005-04-21 16:06:03 +0000184/// removePredecessor - This method is used to notify a BasicBlock that the
185/// specified Predecessor of the block is no longer able to reach it. This is
Misha Brukmanb1c93172005-04-21 23:48:37 +0000186/// actually not used to update the Predecessor list, but is actually used to
Chris Lattner954c64d2005-04-21 16:06:03 +0000187/// update the PHI nodes that reside in the block. Note that this should be
188/// called while the predecessor still refers to this block.
189///
Chris Lattner9daef352005-04-12 18:52:14 +0000190void BasicBlock::removePredecessor(BasicBlock *Pred,
Nick Lewycky4d43d3c2008-04-25 16:53:59 +0000191 bool DontDeleteUselessPHIs) {
Chris Lattner25169ca2005-02-23 16:53:04 +0000192 assert((hasNUsesOrMore(16)||// Reduce cost of this assertion for complex CFGs.
Chris Lattnercf08c212005-02-23 07:09:08 +0000193 find(pred_begin(this), pred_end(this), Pred) != pred_end(this)) &&
Jeff Cohen82639852005-04-23 21:38:35 +0000194 "removePredecessor: BB is not a predecessor!");
Chris Lattnercf08c212005-02-23 07:09:08 +0000195
Chris Lattner8d0b1b22004-12-11 22:10:29 +0000196 if (InstList.empty()) return;
Chris Lattnerbea72472004-07-06 17:44:17 +0000197 PHINode *APN = dyn_cast<PHINode>(&front());
198 if (!APN) return; // Quick exit.
Chris Lattner615d3cf2001-06-29 05:25:23 +0000199
200 // If there are exactly two predecessors, then we want to nuke the PHI nodes
Chris Lattnerbea72472004-07-06 17:44:17 +0000201 // altogether. However, we cannot do this, if this in this case:
Chris Lattnerf7373e42002-05-21 19:52:49 +0000202 //
203 // Loop:
204 // %x = phi [X, Loop]
205 // %x2 = add %x, 1 ;; This would become %x2 = add %x2, 1
206 // br Loop ;; %x2 does not dominate all uses
207 //
208 // This is because the PHI node input is actually taken from the predecessor
Misha Brukmanb1c93172005-04-21 23:48:37 +0000209 // basic block. The only case this can happen is with a self loop, so we
Chris Lattnerf7373e42002-05-21 19:52:49 +0000210 // check for this case explicitly now.
Misha Brukmanb1c93172005-04-21 23:48:37 +0000211 //
Chris Lattnerbea72472004-07-06 17:44:17 +0000212 unsigned max_idx = APN->getNumIncomingValues();
Chris Lattner615d3cf2001-06-29 05:25:23 +0000213 assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!");
Chris Lattnerf7373e42002-05-21 19:52:49 +0000214 if (max_idx == 2) {
Chris Lattnerbea72472004-07-06 17:44:17 +0000215 BasicBlock *Other = APN->getIncomingBlock(APN->getIncomingBlock(0) == Pred);
Chris Lattnerf7373e42002-05-21 19:52:49 +0000216
217 // Disable PHI elimination!
218 if (this == Other) max_idx = 3;
219 }
220
Chris Lattner9daef352005-04-12 18:52:14 +0000221 // <= Two predecessors BEFORE I remove one?
222 if (max_idx <= 2 && !DontDeleteUselessPHIs) {
Chris Lattnerda558102001-10-02 03:41:24 +0000223 // Yup, loop through and nuke the PHI nodes
Chris Lattner113f4f42002-06-25 16:13:24 +0000224 while (PHINode *PN = dyn_cast<PHINode>(&front())) {
Chris Lattner9daef352005-04-12 18:52:14 +0000225 // Remove the predecessor first.
Nick Lewycky4d43d3c2008-04-25 16:53:59 +0000226 PN->removeIncomingValue(Pred, !DontDeleteUselessPHIs);
Chris Lattner615d3cf2001-06-29 05:25:23 +0000227
228 // If the PHI _HAD_ two uses, replace PHI node with its now *single* value
Chris Lattnercaf5b502002-10-08 21:36:34 +0000229 if (max_idx == 2) {
Jay Foad372ad642011-06-20 14:18:48 +0000230 if (PN->getIncomingValue(0) != PN)
231 PN->replaceAllUsesWith(PN->getIncomingValue(0));
Chris Lattneref8c8332003-04-25 23:14:19 +0000232 else
233 // We are left with an infinite loop with no entries: kill the PHI.
Owen Andersonb292b8c2009-07-30 23:03:37 +0000234 PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
Chris Lattnercaf5b502002-10-08 21:36:34 +0000235 getInstList().pop_front(); // Remove the PHI node
236 }
237
238 // If the PHI node already only had one entry, it got deleted by
239 // removeIncomingValue.
Chris Lattner615d3cf2001-06-29 05:25:23 +0000240 }
241 } else {
242 // Okay, now we know that we need to remove predecessor #pred_idx from all
243 // PHI nodes. Iterate over each PHI node fixing them up
Chris Lattner708ee9d2004-06-05 00:11:27 +0000244 PHINode *PN;
Chris Lattner1749aaa2005-08-05 15:34:10 +0000245 for (iterator II = begin(); (PN = dyn_cast<PHINode>(II)); ) {
246 ++II;
Nick Lewycky4d43d3c2008-04-25 16:53:59 +0000247 PN->removeIncomingValue(Pred, false);
Nate Begemanb3923212005-08-04 23:24:19 +0000248 // If all incoming values to the Phi are the same, we can replace the Phi
249 // with that value.
Owen Anderson4e744af2006-06-14 04:43:14 +0000250 Value* PNV = 0;
Duncan Sandsec7a6ec2010-11-17 10:23:23 +0000251 if (!DontDeleteUselessPHIs && (PNV = PN->hasConstantValue()))
252 if (PNV != PN) {
253 PN->replaceAllUsesWith(PNV);
254 PN->eraseFromParent();
255 }
Nate Begemanb3923212005-08-04 23:24:19 +0000256 }
Chris Lattner615d3cf2001-06-29 05:25:23 +0000257 }
258}
259
Chris Lattner2f7c9632001-06-06 20:29:01 +0000260
Chris Lattner7ceb0812005-04-21 16:04:49 +0000261/// splitBasicBlock - This splits a basic block into two at the specified
262/// instruction. Note that all instructions BEFORE the specified iterator stay
Misha Brukmanb1c93172005-04-21 23:48:37 +0000263/// as part of the original basic block, an unconditional branch is added to
Chris Lattner7ceb0812005-04-21 16:04:49 +0000264/// the new BB, and the rest of the instructions in the BB are moved to the new
265/// BB, including the old terminator. This invalidates the iterator.
266///
Misha Brukmanb1c93172005-04-21 23:48:37 +0000267/// Note that this only works on well formed basic blocks (must have a
Chris Lattner7ceb0812005-04-21 16:04:49 +0000268/// terminator), and 'I' must not be the end of instruction list (which would
269/// cause a degenerate basic block to be formed, having a terminator inside of
Misha Brukmanb1c93172005-04-21 23:48:37 +0000270/// the basic block).
Chris Lattner7ceb0812005-04-21 16:04:49 +0000271///
Daniel Dunbar4975db62009-07-25 04:41:11 +0000272BasicBlock *BasicBlock::splitBasicBlock(iterator I, const Twine &BBName) {
Chris Lattner2f7c9632001-06-06 20:29:01 +0000273 assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!");
Misha Brukmanb1c93172005-04-21 23:48:37 +0000274 assert(I != InstList.end() &&
Jeff Cohen82639852005-04-23 21:38:35 +0000275 "Trying to get me to create degenerate basic block!");
Chris Lattner2f7c9632001-06-06 20:29:01 +0000276
Chris Lattnera48f44d2009-12-03 00:50:42 +0000277 BasicBlock *InsertBefore = llvm::next(Function::iterator(this))
Dan Gohman804c95d2008-07-28 21:51:04 +0000278 .getNodePtrUnchecked();
Owen Anderson55f1c092009-08-13 21:58:54 +0000279 BasicBlock *New = BasicBlock::Create(getContext(), BBName,
280 getParent(), InsertBefore);
Chris Lattner2f7c9632001-06-06 20:29:01 +0000281
Chris Lattnerc4c7ea52004-02-03 23:11:21 +0000282 // Move all of the specified instructions from the original basic block into
283 // the new basic block.
284 New->getInstList().splice(New->end(), this->getInstList(), I, end());
Chris Lattner2f7c9632001-06-06 20:29:01 +0000285
286 // Add a branch instruction to the newly formed basic block.
Gabor Greife9ecc682008-04-06 20:25:17 +0000287 BranchInst::Create(New, this);
Chris Lattner4eed0b82002-02-25 00:35:07 +0000288
289 // Now we must loop through all of the successors of the New block (which
290 // _were_ the successors of the 'this' block), and update any PHI nodes in
291 // successors. If there were PHI nodes in the successors, then they need to
292 // know that incoming branches will be from New, not from Old.
293 //
Chris Lattner64d88bc2003-09-24 22:03:22 +0000294 for (succ_iterator I = succ_begin(New), E = succ_end(New); I != E; ++I) {
Chris Lattner4eed0b82002-02-25 00:35:07 +0000295 // Loop over any phi nodes in the basic block, updating the BB field of
296 // incoming values...
297 BasicBlock *Successor = *I;
Chris Lattner708ee9d2004-06-05 00:11:27 +0000298 PHINode *PN;
Chris Lattner4eed0b82002-02-25 00:35:07 +0000299 for (BasicBlock::iterator II = Successor->begin();
Chris Lattner08d1b9d2004-06-05 17:43:52 +0000300 (PN = dyn_cast<PHINode>(II)); ++II) {
Chris Lattner4eed0b82002-02-25 00:35:07 +0000301 int IDX = PN->getBasicBlockIndex(this);
302 while (IDX != -1) {
303 PN->setIncomingBlock((unsigned)IDX, New);
304 IDX = PN->getBasicBlockIndex(this);
305 }
306 }
307 }
Chris Lattner2f7c9632001-06-06 20:29:01 +0000308 return New;
309}
Dan Gohman39033202009-10-29 00:09:08 +0000310
Jay Foad61ea0e42011-06-23 09:09:15 +0000311void BasicBlock::replaceSuccessorsPhiUsesWith(BasicBlock *New) {
312 TerminatorInst *TI = getTerminator();
313 if (!TI)
314 // Cope with being called on a BasicBlock that doesn't have a terminator
315 // yet. Clang's CodeGenFunction::EmitReturnBlock() likes to do this.
316 return;
317 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
318 BasicBlock *Succ = TI->getSuccessor(i);
319 for (iterator II = Succ->begin(); PHINode *PN = dyn_cast<PHINode>(II);
320 ++II) {
321 int i;
322 while ((i = PN->getBasicBlockIndex(this)) >= 0)
323 PN->setIncomingBlock(i, New);
324 }
325 }
326}