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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//
5// This file was developed by the LLVM research group and is distributed under
6// the University of Illinois Open Source 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
Chris Lattner113f4f42002-06-25 16:13:24 +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"
Chris Lattner2f7c9632001-06-06 20:29:01 +000017#include "llvm/Type.h"
Chris Lattner83d485b2002-02-12 22:39:50 +000018#include "llvm/Support/CFG.h"
Reid Spencer7c16caa2004-09-01 22:55:40 +000019#include "llvm/Support/LeakDetector.h"
Chris Lattner3d27be12006-08-27 12:54:02 +000020#include "llvm/Support/Compiler.h"
Chris Lattner113f4f42002-06-25 16:13:24 +000021#include "SymbolTableListTraitsImpl.h"
22#include <algorithm>
Chris Lattnera2960002003-11-21 16:52:05 +000023using namespace llvm;
Chris Lattner2f7c9632001-06-06 20:29:01 +000024
Chris Lattnera2960002003-11-21 16:52:05 +000025namespace {
26 /// DummyInst - An instance of this class is used to mark the end of the
27 /// instruction list. This is not a real instruction.
Chris Lattnerd6cba042006-06-28 22:57:00 +000028 struct VISIBILITY_HIDDEN DummyInst : public Instruction {
Chris Lattner5d1bc2c2005-01-29 00:35:33 +000029 DummyInst() : Instruction(Type::VoidTy, OtherOpsEnd, 0, 0) {
Chris Lattnera2960002003-11-21 16:52:05 +000030 // This should not be garbage monitored.
31 LeakDetector::removeGarbageObject(this);
32 }
Brian Gaeke960707c2003-11-11 22:41:34 +000033
Chris Lattnera2960002003-11-21 16:52:05 +000034 virtual Instruction *clone() const {
35 assert(0 && "Cannot clone EOL");abort();
36 return 0;
37 }
38 virtual const char *getOpcodeName() const { return "*end-of-list-inst*"; }
Chris Lattner113f4f42002-06-25 16:13:24 +000039
Chris Lattnera2960002003-11-21 16:52:05 +000040 // Methods for support type inquiry through isa, cast, and dyn_cast...
41 static inline bool classof(const DummyInst *) { return true; }
42 static inline bool classof(const Instruction *I) {
43 return I->getOpcode() == OtherOpsEnd;
44 }
45 static inline bool classof(const Value *V) {
46 return isa<Instruction>(V) && classof(cast<Instruction>(V));
47 }
48 };
49}
Chris Lattner113f4f42002-06-25 16:13:24 +000050
Chris Lattnerf6c93e32005-01-30 00:09:23 +000051Instruction *ilist_traits<Instruction>::createSentinel() {
Chris Lattner113f4f42002-06-25 16:13:24 +000052 return new DummyInst();
53}
54iplist<Instruction> &ilist_traits<Instruction>::getList(BasicBlock *BB) {
55 return BB->getInstList();
56}
57
58// Explicit instantiation of SymbolTableListTraits since some of the methods
59// are not in the public header file...
Chris Lattner41baa982003-11-05 05:15:42 +000060template class SymbolTableListTraits<Instruction, BasicBlock, Function>;
Chris Lattner113f4f42002-06-25 16:13:24 +000061
Chris Lattner2f7c9632001-06-06 20:29:01 +000062
Chris Lattnerbb5f0db2004-02-04 03:57:50 +000063BasicBlock::BasicBlock(const std::string &Name, Function *Parent,
64 BasicBlock *InsertBefore)
Chris Lattner32ab6432007-02-12 05:18:08 +000065 : Value(Type::LabelTy, Value::BasicBlockVal) {
Chris Lattner4dfede82002-09-26 05:03:22 +000066 // Initialize the instlist...
67 InstList.setItemParent(this);
68
69 // Make sure that we get added to a function
70 LeakDetector::addGarbageObject(this);
71
72 if (InsertBefore) {
Chris Lattnerbb5f0db2004-02-04 03:57:50 +000073 assert(Parent &&
74 "Cannot insert block before another block with no function!");
75 Parent->getBasicBlockList().insert(InsertBefore, this);
76 } else if (Parent) {
77 Parent->getBasicBlockList().push_back(this);
Chris Lattner4dfede82002-09-26 05:03:22 +000078 }
Chris Lattner32ab6432007-02-12 05:18:08 +000079
80 setName(Name);
Chris Lattner4dfede82002-09-26 05:03:22 +000081}
82
83
Chris Lattner2f7c9632001-06-06 20:29:01 +000084BasicBlock::~BasicBlock() {
Misha Brukmanede10c92004-04-16 17:37:12 +000085 assert(getParent() == 0 && "BasicBlock still linked into the program!");
Chris Lattner2f7c9632001-06-06 20:29:01 +000086 dropAllReferences();
Chris Lattner113f4f42002-06-25 16:13:24 +000087 InstList.clear();
Chris Lattner2f7c9632001-06-06 20:29:01 +000088}
89
Chris Lattner9ed7aef2002-09-06 21:33:15 +000090void BasicBlock::setParent(Function *parent) {
Chris Lattner184b2982002-09-08 18:59:35 +000091 if (getParent())
92 LeakDetector::addGarbageObject(this);
93
Chris Lattner9ed7aef2002-09-06 21:33:15 +000094 InstList.setParent(parent);
Chris Lattner184b2982002-09-08 18:59:35 +000095
96 if (getParent())
97 LeakDetector::removeGarbageObject(this);
Chris Lattner9ed7aef2002-09-06 21:33:15 +000098}
99
Chris Lattner02a71e72004-10-11 22:21:39 +0000100void BasicBlock::removeFromParent() {
101 getParent()->getBasicBlockList().remove(this);
102}
103
104void BasicBlock::eraseFromParent() {
105 getParent()->getBasicBlockList().erase(this);
106}
107
Chris Lattner4091f462006-09-23 04:03:45 +0000108/// moveBefore - Unlink this basic block from its current function and
109/// insert it into the function that MovePos lives in, right before MovePos.
Chris Lattnere09bbc82005-08-12 22:14:06 +0000110void BasicBlock::moveBefore(BasicBlock *MovePos) {
111 MovePos->getParent()->getBasicBlockList().splice(MovePos,
112 getParent()->getBasicBlockList(), this);
113}
114
Chris Lattner4091f462006-09-23 04:03:45 +0000115/// moveAfter - Unlink this basic block from its current function and
116/// insert it into the function that MovePos lives in, right after MovePos.
117void BasicBlock::moveAfter(BasicBlock *MovePos) {
118 Function::iterator I = MovePos;
119 MovePos->getParent()->getBasicBlockList().splice(++I,
120 getParent()->getBasicBlockList(), this);
121}
122
Chris Lattner02a71e72004-10-11 22:21:39 +0000123
Chris Lattner2f7c9632001-06-06 20:29:01 +0000124TerminatorInst *BasicBlock::getTerminator() {
125 if (InstList.empty()) return 0;
Chris Lattner113f4f42002-06-25 16:13:24 +0000126 return dyn_cast<TerminatorInst>(&InstList.back());
Chris Lattner2f7c9632001-06-06 20:29:01 +0000127}
128
129const TerminatorInst *const BasicBlock::getTerminator() const {
130 if (InstList.empty()) return 0;
Chris Lattner113f4f42002-06-25 16:13:24 +0000131 return dyn_cast<TerminatorInst>(&InstList.back());
Chris Lattner2f7c9632001-06-06 20:29:01 +0000132}
133
Vladimir Prusb5b6dc42006-06-08 15:46:18 +0000134Instruction* BasicBlock::getFirstNonPHI()
135{
Vladimir Prus9bc40092006-06-08 16:03:13 +0000136 BasicBlock::iterator i = begin();
Vladimir Prusb5b6dc42006-06-08 15:46:18 +0000137 // All valid basic blocks should have a terminator,
138 // which is not a PHINode. If we have invalid basic
139 // block we'll get assert when dereferencing past-the-end
140 // iterator.
141 while (isa<PHINode>(i)) ++i;
142 return &*i;
143}
144
Chris Lattner2f7c9632001-06-06 20:29:01 +0000145void BasicBlock::dropAllReferences() {
Chris Lattner113f4f42002-06-25 16:13:24 +0000146 for(iterator I = begin(), E = end(); I != E; ++I)
147 I->dropAllReferences();
Chris Lattner2f7c9632001-06-06 20:29:01 +0000148}
149
Chris Lattnerce046ac2005-02-24 02:37:26 +0000150/// getSinglePredecessor - If this basic block has a single predecessor block,
151/// return the block, otherwise return a null pointer.
152BasicBlock *BasicBlock::getSinglePredecessor() {
153 pred_iterator PI = pred_begin(this), E = pred_end(this);
154 if (PI == E) return 0; // No preds.
155 BasicBlock *ThePred = *PI;
156 ++PI;
157 return (PI == E) ? ThePred : 0 /*multiple preds*/;
158}
159
Chris Lattner954c64d2005-04-21 16:06:03 +0000160/// removePredecessor - This method is used to notify a BasicBlock that the
161/// specified Predecessor of the block is no longer able to reach it. This is
Misha Brukmanb1c93172005-04-21 23:48:37 +0000162/// actually not used to update the Predecessor list, but is actually used to
Chris Lattner954c64d2005-04-21 16:06:03 +0000163/// update the PHI nodes that reside in the block. Note that this should be
164/// called while the predecessor still refers to this block.
165///
Chris Lattner9daef352005-04-12 18:52:14 +0000166void BasicBlock::removePredecessor(BasicBlock *Pred,
167 bool DontDeleteUselessPHIs) {
Chris Lattner25169ca2005-02-23 16:53:04 +0000168 assert((hasNUsesOrMore(16)||// Reduce cost of this assertion for complex CFGs.
Chris Lattnercf08c212005-02-23 07:09:08 +0000169 find(pred_begin(this), pred_end(this), Pred) != pred_end(this)) &&
Jeff Cohen82639852005-04-23 21:38:35 +0000170 "removePredecessor: BB is not a predecessor!");
Chris Lattnercf08c212005-02-23 07:09:08 +0000171
Chris Lattner8d0b1b22004-12-11 22:10:29 +0000172 if (InstList.empty()) return;
Chris Lattnerbea72472004-07-06 17:44:17 +0000173 PHINode *APN = dyn_cast<PHINode>(&front());
174 if (!APN) return; // Quick exit.
Chris Lattner615d3cf2001-06-29 05:25:23 +0000175
176 // If there are exactly two predecessors, then we want to nuke the PHI nodes
Chris Lattnerbea72472004-07-06 17:44:17 +0000177 // altogether. However, we cannot do this, if this in this case:
Chris Lattnerf7373e42002-05-21 19:52:49 +0000178 //
179 // Loop:
180 // %x = phi [X, Loop]
181 // %x2 = add %x, 1 ;; This would become %x2 = add %x2, 1
182 // br Loop ;; %x2 does not dominate all uses
183 //
184 // This is because the PHI node input is actually taken from the predecessor
Misha Brukmanb1c93172005-04-21 23:48:37 +0000185 // basic block. The only case this can happen is with a self loop, so we
Chris Lattnerf7373e42002-05-21 19:52:49 +0000186 // check for this case explicitly now.
Misha Brukmanb1c93172005-04-21 23:48:37 +0000187 //
Chris Lattnerbea72472004-07-06 17:44:17 +0000188 unsigned max_idx = APN->getNumIncomingValues();
Chris Lattner615d3cf2001-06-29 05:25:23 +0000189 assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!");
Chris Lattnerf7373e42002-05-21 19:52:49 +0000190 if (max_idx == 2) {
Chris Lattnerbea72472004-07-06 17:44:17 +0000191 BasicBlock *Other = APN->getIncomingBlock(APN->getIncomingBlock(0) == Pred);
Chris Lattnerf7373e42002-05-21 19:52:49 +0000192
193 // Disable PHI elimination!
194 if (this == Other) max_idx = 3;
195 }
196
Chris Lattner9daef352005-04-12 18:52:14 +0000197 // <= Two predecessors BEFORE I remove one?
198 if (max_idx <= 2 && !DontDeleteUselessPHIs) {
Chris Lattnerda558102001-10-02 03:41:24 +0000199 // Yup, loop through and nuke the PHI nodes
Chris Lattner113f4f42002-06-25 16:13:24 +0000200 while (PHINode *PN = dyn_cast<PHINode>(&front())) {
Chris Lattner9daef352005-04-12 18:52:14 +0000201 // Remove the predecessor first.
202 PN->removeIncomingValue(Pred, !DontDeleteUselessPHIs);
Chris Lattner615d3cf2001-06-29 05:25:23 +0000203
204 // If the PHI _HAD_ two uses, replace PHI node with its now *single* value
Chris Lattnercaf5b502002-10-08 21:36:34 +0000205 if (max_idx == 2) {
Chris Lattneref8c8332003-04-25 23:14:19 +0000206 if (PN->getOperand(0) != PN)
207 PN->replaceAllUsesWith(PN->getOperand(0));
208 else
209 // We are left with an infinite loop with no entries: kill the PHI.
Chris Lattner9daef352005-04-12 18:52:14 +0000210 PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
Chris Lattnercaf5b502002-10-08 21:36:34 +0000211 getInstList().pop_front(); // Remove the PHI node
212 }
213
214 // If the PHI node already only had one entry, it got deleted by
215 // removeIncomingValue.
Chris Lattner615d3cf2001-06-29 05:25:23 +0000216 }
217 } else {
218 // Okay, now we know that we need to remove predecessor #pred_idx from all
219 // PHI nodes. Iterate over each PHI node fixing them up
Chris Lattner708ee9d2004-06-05 00:11:27 +0000220 PHINode *PN;
Chris Lattner1749aaa2005-08-05 15:34:10 +0000221 for (iterator II = begin(); (PN = dyn_cast<PHINode>(II)); ) {
222 ++II;
Chris Lattner9daef352005-04-12 18:52:14 +0000223 PN->removeIncomingValue(Pred, false);
Nate Begemanb3923212005-08-04 23:24:19 +0000224 // If all incoming values to the Phi are the same, we can replace the Phi
225 // with that value.
Owen Anderson4e744af2006-06-14 04:43:14 +0000226 Value* PNV = 0;
227 if (!DontDeleteUselessPHIs && (PNV = PN->hasConstantValue())) {
Chris Lattner6f583502005-08-05 01:02:04 +0000228 PN->replaceAllUsesWith(PNV);
229 PN->eraseFromParent();
230 }
Nate Begemanb3923212005-08-04 23:24:19 +0000231 }
Chris Lattner615d3cf2001-06-29 05:25:23 +0000232 }
233}
234
Chris Lattner2f7c9632001-06-06 20:29:01 +0000235
Chris Lattner7ceb0812005-04-21 16:04:49 +0000236/// splitBasicBlock - This splits a basic block into two at the specified
237/// instruction. Note that all instructions BEFORE the specified iterator stay
Misha Brukmanb1c93172005-04-21 23:48:37 +0000238/// as part of the original basic block, an unconditional branch is added to
Chris Lattner7ceb0812005-04-21 16:04:49 +0000239/// the new BB, and the rest of the instructions in the BB are moved to the new
240/// BB, including the old terminator. This invalidates the iterator.
241///
Misha Brukmanb1c93172005-04-21 23:48:37 +0000242/// Note that this only works on well formed basic blocks (must have a
Chris Lattner7ceb0812005-04-21 16:04:49 +0000243/// terminator), and 'I' must not be the end of instruction list (which would
244/// cause a degenerate basic block to be formed, having a terminator inside of
Misha Brukmanb1c93172005-04-21 23:48:37 +0000245/// the basic block).
Chris Lattner7ceb0812005-04-21 16:04:49 +0000246///
Chris Lattner6d569352003-08-24 03:41:39 +0000247BasicBlock *BasicBlock::splitBasicBlock(iterator I, const std::string &BBName) {
Chris Lattner2f7c9632001-06-06 20:29:01 +0000248 assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!");
Misha Brukmanb1c93172005-04-21 23:48:37 +0000249 assert(I != InstList.end() &&
Jeff Cohen82639852005-04-23 21:38:35 +0000250 "Trying to get me to create degenerate basic block!");
Chris Lattner2f7c9632001-06-06 20:29:01 +0000251
Chris Lattnerbb5f0db2004-02-04 03:57:50 +0000252 BasicBlock *New = new BasicBlock(BBName, getParent(), getNext());
Chris Lattner2f7c9632001-06-06 20:29:01 +0000253
Chris Lattnerc4c7ea52004-02-03 23:11:21 +0000254 // Move all of the specified instructions from the original basic block into
255 // the new basic block.
256 New->getInstList().splice(New->end(), this->getInstList(), I, end());
Chris Lattner2f7c9632001-06-06 20:29:01 +0000257
258 // Add a branch instruction to the newly formed basic block.
Chris Lattnera2960002003-11-21 16:52:05 +0000259 new BranchInst(New, this);
Chris Lattner4eed0b82002-02-25 00:35:07 +0000260
261 // Now we must loop through all of the successors of the New block (which
262 // _were_ the successors of the 'this' block), and update any PHI nodes in
263 // successors. If there were PHI nodes in the successors, then they need to
264 // know that incoming branches will be from New, not from Old.
265 //
Chris Lattner64d88bc2003-09-24 22:03:22 +0000266 for (succ_iterator I = succ_begin(New), E = succ_end(New); I != E; ++I) {
Chris Lattner4eed0b82002-02-25 00:35:07 +0000267 // Loop over any phi nodes in the basic block, updating the BB field of
268 // incoming values...
269 BasicBlock *Successor = *I;
Chris Lattner708ee9d2004-06-05 00:11:27 +0000270 PHINode *PN;
Chris Lattner4eed0b82002-02-25 00:35:07 +0000271 for (BasicBlock::iterator II = Successor->begin();
Chris Lattner08d1b9d2004-06-05 17:43:52 +0000272 (PN = dyn_cast<PHINode>(II)); ++II) {
Chris Lattner4eed0b82002-02-25 00:35:07 +0000273 int IDX = PN->getBasicBlockIndex(this);
274 while (IDX != -1) {
275 PN->setIncomingBlock((unsigned)IDX, New);
276 IDX = PN->getBasicBlockIndex(this);
277 }
278 }
279 }
Chris Lattner2f7c9632001-06-06 20:29:01 +0000280 return New;
281}