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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"
Owen Anderson155dccd82009-07-07 23:43:39 +000017#include "llvm/LLVMContext.h"
Chris Lattner2f7c9632001-06-06 20:29:01 +000018#include "llvm/Type.h"
Dan Gohman804c95d2008-07-28 21:51:04 +000019#include "llvm/ADT/STLExtras.h"
Chris Lattner83d485b2002-02-12 22:39:50 +000020#include "llvm/Support/CFG.h"
Reid Spencer7c16caa2004-09-01 22:55:40 +000021#include "llvm/Support/LeakDetector.h"
Chris Lattner113f4f42002-06-25 16:13:24 +000022#include "SymbolTableListTraitsImpl.h"
23#include <algorithm>
Chris Lattnera2960002003-11-21 16:52:05 +000024using namespace llvm;
Chris Lattner2f7c9632001-06-06 20:29:01 +000025
Gabor Greif51bbcf82009-03-07 12:33:24 +000026ValueSymbolTable *BasicBlock::getValueSymbolTable() {
27 if (Function *F = getParent())
28 return &F->getValueSymbolTable();
Chris Lattnerb47aa542007-04-17 03:26:42 +000029 return 0;
30}
31
Owen Anderson47db9412009-07-22 00:24:57 +000032LLVMContext &BasicBlock::getContext() const {
33 return getType()->getContext();
Owen Andersone70b6372009-07-05 22:41:43 +000034}
35
Chris Lattner113f4f42002-06-25 16:13:24 +000036// Explicit instantiation of SymbolTableListTraits since some of the methods
37// are not in the public header file...
Chris Lattnerb47aa542007-04-17 03:26:42 +000038template class SymbolTableListTraits<Instruction, BasicBlock>;
Chris Lattner113f4f42002-06-25 16:13:24 +000039
Chris Lattner2f7c9632001-06-06 20:29:01 +000040
Owen Anderson55f1c092009-08-13 21:58:54 +000041BasicBlock::BasicBlock(LLVMContext &C, const Twine &Name, Function *NewParent,
Nick Lewycky4d43d3c2008-04-25 16:53:59 +000042 BasicBlock *InsertBefore)
Owen Anderson55f1c092009-08-13 21:58:54 +000043 : Value(Type::getLabelTy(C), Value::BasicBlockVal), Parent(0) {
Chris Lattner4dfede82002-09-26 05:03:22 +000044
45 // Make sure that we get added to a function
46 LeakDetector::addGarbageObject(this);
47
48 if (InsertBefore) {
Chris Lattnerb47aa542007-04-17 03:26:42 +000049 assert(NewParent &&
Chris Lattnerbb5f0db2004-02-04 03:57:50 +000050 "Cannot insert block before another block with no function!");
Chris Lattnerb47aa542007-04-17 03:26:42 +000051 NewParent->getBasicBlockList().insert(InsertBefore, this);
52 } else if (NewParent) {
53 NewParent->getBasicBlockList().push_back(this);
Chris Lattner4dfede82002-09-26 05:03:22 +000054 }
Chris Lattner32ab6432007-02-12 05:18:08 +000055
56 setName(Name);
Chris Lattner4dfede82002-09-26 05:03:22 +000057}
58
59
Gordon Henriksen14a55692007-12-10 02:14:30 +000060BasicBlock::~BasicBlock() {
61 assert(getParent() == 0 && "BasicBlock still linked into the program!");
62 dropAllReferences();
63 InstList.clear();
Chris Lattner2f7c9632001-06-06 20:29:01 +000064}
65
Chris Lattner9ed7aef2002-09-06 21:33:15 +000066void BasicBlock::setParent(Function *parent) {
Chris Lattner184b2982002-09-08 18:59:35 +000067 if (getParent())
68 LeakDetector::addGarbageObject(this);
69
Chris Lattnerb47aa542007-04-17 03:26:42 +000070 // Set Parent=parent, updating instruction symtab entries as appropriate.
71 InstList.setSymTabObject(&Parent, parent);
Chris Lattner184b2982002-09-08 18:59:35 +000072
73 if (getParent())
74 LeakDetector::removeGarbageObject(this);
Chris Lattner9ed7aef2002-09-06 21:33:15 +000075}
76
Chris Lattner02a71e72004-10-11 22:21:39 +000077void BasicBlock::removeFromParent() {
78 getParent()->getBasicBlockList().remove(this);
79}
80
81void BasicBlock::eraseFromParent() {
82 getParent()->getBasicBlockList().erase(this);
83}
84
Chris Lattner4091f462006-09-23 04:03:45 +000085/// moveBefore - Unlink this basic block from its current function and
86/// insert it into the function that MovePos lives in, right before MovePos.
Chris Lattnere09bbc82005-08-12 22:14:06 +000087void BasicBlock::moveBefore(BasicBlock *MovePos) {
88 MovePos->getParent()->getBasicBlockList().splice(MovePos,
89 getParent()->getBasicBlockList(), this);
90}
91
Chris Lattner4091f462006-09-23 04:03:45 +000092/// moveAfter - Unlink this basic block from its current function and
93/// insert it into the function that MovePos lives in, right after MovePos.
94void BasicBlock::moveAfter(BasicBlock *MovePos) {
95 Function::iterator I = MovePos;
96 MovePos->getParent()->getBasicBlockList().splice(++I,
97 getParent()->getBasicBlockList(), this);
98}
99
Chris Lattner02a71e72004-10-11 22:21:39 +0000100
Chris Lattner2f7c9632001-06-06 20:29:01 +0000101TerminatorInst *BasicBlock::getTerminator() {
102 if (InstList.empty()) return 0;
Chris Lattner113f4f42002-06-25 16:13:24 +0000103 return dyn_cast<TerminatorInst>(&InstList.back());
Chris Lattner2f7c9632001-06-06 20:29:01 +0000104}
105
Dan Gohmanaad83c82007-11-19 20:46:23 +0000106const TerminatorInst *BasicBlock::getTerminator() const {
Chris Lattner2f7c9632001-06-06 20:29:01 +0000107 if (InstList.empty()) return 0;
Chris Lattner113f4f42002-06-25 16:13:24 +0000108 return dyn_cast<TerminatorInst>(&InstList.back());
Chris Lattner2f7c9632001-06-06 20:29:01 +0000109}
110
Dan Gohmanf96e1372008-05-23 21:05:58 +0000111Instruction* BasicBlock::getFirstNonPHI() {
112 BasicBlock::iterator i = begin();
113 // All valid basic blocks should have a terminator,
114 // which is not a PHINode. If we have an invalid basic
115 // block we'll get an assertion failure when dereferencing
116 // a past-the-end iterator.
117 while (isa<PHINode>(i)) ++i;
118 return &*i;
Vladimir Prusb5b6dc42006-06-08 15:46:18 +0000119}
120
Chris Lattner2f7c9632001-06-06 20:29:01 +0000121void BasicBlock::dropAllReferences() {
Chris Lattner113f4f42002-06-25 16:13:24 +0000122 for(iterator I = begin(), E = end(); I != E; ++I)
123 I->dropAllReferences();
Chris Lattner2f7c9632001-06-06 20:29:01 +0000124}
125
Chris Lattnerce046ac2005-02-24 02:37:26 +0000126/// getSinglePredecessor - If this basic block has a single predecessor block,
127/// return the block, otherwise return a null pointer.
128BasicBlock *BasicBlock::getSinglePredecessor() {
129 pred_iterator PI = pred_begin(this), E = pred_end(this);
130 if (PI == E) return 0; // No preds.
131 BasicBlock *ThePred = *PI;
132 ++PI;
133 return (PI == E) ? ThePred : 0 /*multiple preds*/;
134}
135
Torok Edwinc8080122008-12-11 10:36:07 +0000136/// getUniquePredecessor - If this basic block has a unique predecessor block,
137/// return the block, otherwise return a null pointer.
138/// Note that unique predecessor doesn't mean single edge, there can be
Torok Edwin32bfb5d2008-12-11 11:44:49 +0000139/// multiple edges from the unique predecessor to this block (for example
140/// a switch statement with multiple cases having the same destination).
Torok Edwinc8080122008-12-11 10:36:07 +0000141BasicBlock *BasicBlock::getUniquePredecessor() {
142 pred_iterator PI = pred_begin(this), E = pred_end(this);
143 if (PI == E) return 0; // No preds.
144 BasicBlock *PredBB = *PI;
145 ++PI;
146 for (;PI != E; ++PI) {
147 if (*PI != PredBB)
148 return 0;
Torok Edwin32bfb5d2008-12-11 11:44:49 +0000149 // The same predecessor appears multiple times in the predecessor list.
150 // This is OK.
Torok Edwinc8080122008-12-11 10:36:07 +0000151 }
152 return PredBB;
153}
154
Chris Lattner954c64d2005-04-21 16:06:03 +0000155/// removePredecessor - This method is used to notify a BasicBlock that the
156/// specified Predecessor of the block is no longer able to reach it. This is
Misha Brukmanb1c93172005-04-21 23:48:37 +0000157/// actually not used to update the Predecessor list, but is actually used to
Chris Lattner954c64d2005-04-21 16:06:03 +0000158/// update the PHI nodes that reside in the block. Note that this should be
159/// called while the predecessor still refers to this block.
160///
Chris Lattner9daef352005-04-12 18:52:14 +0000161void BasicBlock::removePredecessor(BasicBlock *Pred,
Nick Lewycky4d43d3c2008-04-25 16:53:59 +0000162 bool DontDeleteUselessPHIs) {
Chris Lattner25169ca2005-02-23 16:53:04 +0000163 assert((hasNUsesOrMore(16)||// Reduce cost of this assertion for complex CFGs.
Chris Lattnercf08c212005-02-23 07:09:08 +0000164 find(pred_begin(this), pred_end(this), Pred) != pred_end(this)) &&
Jeff Cohen82639852005-04-23 21:38:35 +0000165 "removePredecessor: BB is not a predecessor!");
Chris Lattnercf08c212005-02-23 07:09:08 +0000166
Chris Lattner8d0b1b22004-12-11 22:10:29 +0000167 if (InstList.empty()) return;
Chris Lattnerbea72472004-07-06 17:44:17 +0000168 PHINode *APN = dyn_cast<PHINode>(&front());
169 if (!APN) return; // Quick exit.
Chris Lattner615d3cf2001-06-29 05:25:23 +0000170
171 // If there are exactly two predecessors, then we want to nuke the PHI nodes
Chris Lattnerbea72472004-07-06 17:44:17 +0000172 // altogether. However, we cannot do this, if this in this case:
Chris Lattnerf7373e42002-05-21 19:52:49 +0000173 //
174 // Loop:
175 // %x = phi [X, Loop]
176 // %x2 = add %x, 1 ;; This would become %x2 = add %x2, 1
177 // br Loop ;; %x2 does not dominate all uses
178 //
179 // This is because the PHI node input is actually taken from the predecessor
Misha Brukmanb1c93172005-04-21 23:48:37 +0000180 // basic block. The only case this can happen is with a self loop, so we
Chris Lattnerf7373e42002-05-21 19:52:49 +0000181 // check for this case explicitly now.
Misha Brukmanb1c93172005-04-21 23:48:37 +0000182 //
Chris Lattnerbea72472004-07-06 17:44:17 +0000183 unsigned max_idx = APN->getNumIncomingValues();
Chris Lattner615d3cf2001-06-29 05:25:23 +0000184 assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!");
Chris Lattnerf7373e42002-05-21 19:52:49 +0000185 if (max_idx == 2) {
Chris Lattnerbea72472004-07-06 17:44:17 +0000186 BasicBlock *Other = APN->getIncomingBlock(APN->getIncomingBlock(0) == Pred);
Chris Lattnerf7373e42002-05-21 19:52:49 +0000187
188 // Disable PHI elimination!
189 if (this == Other) max_idx = 3;
190 }
191
Chris Lattner9daef352005-04-12 18:52:14 +0000192 // <= Two predecessors BEFORE I remove one?
193 if (max_idx <= 2 && !DontDeleteUselessPHIs) {
Chris Lattnerda558102001-10-02 03:41:24 +0000194 // Yup, loop through and nuke the PHI nodes
Chris Lattner113f4f42002-06-25 16:13:24 +0000195 while (PHINode *PN = dyn_cast<PHINode>(&front())) {
Chris Lattner9daef352005-04-12 18:52:14 +0000196 // Remove the predecessor first.
Nick Lewycky4d43d3c2008-04-25 16:53:59 +0000197 PN->removeIncomingValue(Pred, !DontDeleteUselessPHIs);
Chris Lattner615d3cf2001-06-29 05:25:23 +0000198
199 // If the PHI _HAD_ two uses, replace PHI node with its now *single* value
Chris Lattnercaf5b502002-10-08 21:36:34 +0000200 if (max_idx == 2) {
Chris Lattneref8c8332003-04-25 23:14:19 +0000201 if (PN->getOperand(0) != PN)
202 PN->replaceAllUsesWith(PN->getOperand(0));
203 else
204 // We are left with an infinite loop with no entries: kill the PHI.
Owen Andersonb292b8c2009-07-30 23:03:37 +0000205 PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
Chris Lattnercaf5b502002-10-08 21:36:34 +0000206 getInstList().pop_front(); // Remove the PHI node
207 }
208
209 // If the PHI node already only had one entry, it got deleted by
210 // removeIncomingValue.
Chris Lattner615d3cf2001-06-29 05:25:23 +0000211 }
212 } else {
213 // Okay, now we know that we need to remove predecessor #pred_idx from all
214 // PHI nodes. Iterate over each PHI node fixing them up
Chris Lattner708ee9d2004-06-05 00:11:27 +0000215 PHINode *PN;
Chris Lattner1749aaa2005-08-05 15:34:10 +0000216 for (iterator II = begin(); (PN = dyn_cast<PHINode>(II)); ) {
217 ++II;
Nick Lewycky4d43d3c2008-04-25 16:53:59 +0000218 PN->removeIncomingValue(Pred, false);
Nate Begemanb3923212005-08-04 23:24:19 +0000219 // If all incoming values to the Phi are the same, we can replace the Phi
220 // with that value.
Owen Anderson4e744af2006-06-14 04:43:14 +0000221 Value* PNV = 0;
222 if (!DontDeleteUselessPHIs && (PNV = PN->hasConstantValue())) {
Chris Lattner6f583502005-08-05 01:02:04 +0000223 PN->replaceAllUsesWith(PNV);
224 PN->eraseFromParent();
225 }
Nate Begemanb3923212005-08-04 23:24:19 +0000226 }
Chris Lattner615d3cf2001-06-29 05:25:23 +0000227 }
228}
229
Chris Lattner2f7c9632001-06-06 20:29:01 +0000230
Chris Lattner7ceb0812005-04-21 16:04:49 +0000231/// splitBasicBlock - This splits a basic block into two at the specified
232/// instruction. Note that all instructions BEFORE the specified iterator stay
Misha Brukmanb1c93172005-04-21 23:48:37 +0000233/// as part of the original basic block, an unconditional branch is added to
Chris Lattner7ceb0812005-04-21 16:04:49 +0000234/// the new BB, and the rest of the instructions in the BB are moved to the new
235/// BB, including the old terminator. This invalidates the iterator.
236///
Misha Brukmanb1c93172005-04-21 23:48:37 +0000237/// Note that this only works on well formed basic blocks (must have a
Chris Lattner7ceb0812005-04-21 16:04:49 +0000238/// terminator), and 'I' must not be the end of instruction list (which would
239/// cause a degenerate basic block to be formed, having a terminator inside of
Misha Brukmanb1c93172005-04-21 23:48:37 +0000240/// the basic block).
Chris Lattner7ceb0812005-04-21 16:04:49 +0000241///
Daniel Dunbar4975db62009-07-25 04:41:11 +0000242BasicBlock *BasicBlock::splitBasicBlock(iterator I, const Twine &BBName) {
Chris Lattner2f7c9632001-06-06 20:29:01 +0000243 assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!");
Misha Brukmanb1c93172005-04-21 23:48:37 +0000244 assert(I != InstList.end() &&
Jeff Cohen82639852005-04-23 21:38:35 +0000245 "Trying to get me to create degenerate basic block!");
Chris Lattner2f7c9632001-06-06 20:29:01 +0000246
Dan Gohman804c95d2008-07-28 21:51:04 +0000247 BasicBlock *InsertBefore = next(Function::iterator(this))
248 .getNodePtrUnchecked();
Owen Anderson55f1c092009-08-13 21:58:54 +0000249 BasicBlock *New = BasicBlock::Create(getContext(), BBName,
250 getParent(), InsertBefore);
Chris Lattner2f7c9632001-06-06 20:29:01 +0000251
Chris Lattnerc4c7ea52004-02-03 23:11:21 +0000252 // Move all of the specified instructions from the original basic block into
253 // the new basic block.
254 New->getInstList().splice(New->end(), this->getInstList(), I, end());
Chris Lattner2f7c9632001-06-06 20:29:01 +0000255
256 // Add a branch instruction to the newly formed basic block.
Gabor Greife9ecc682008-04-06 20:25:17 +0000257 BranchInst::Create(New, this);
Chris Lattner4eed0b82002-02-25 00:35:07 +0000258
259 // Now we must loop through all of the successors of the New block (which
260 // _were_ the successors of the 'this' block), and update any PHI nodes in
261 // successors. If there were PHI nodes in the successors, then they need to
262 // know that incoming branches will be from New, not from Old.
263 //
Chris Lattner64d88bc2003-09-24 22:03:22 +0000264 for (succ_iterator I = succ_begin(New), E = succ_end(New); I != E; ++I) {
Chris Lattner4eed0b82002-02-25 00:35:07 +0000265 // Loop over any phi nodes in the basic block, updating the BB field of
266 // incoming values...
267 BasicBlock *Successor = *I;
Chris Lattner708ee9d2004-06-05 00:11:27 +0000268 PHINode *PN;
Chris Lattner4eed0b82002-02-25 00:35:07 +0000269 for (BasicBlock::iterator II = Successor->begin();
Chris Lattner08d1b9d2004-06-05 17:43:52 +0000270 (PN = dyn_cast<PHINode>(II)); ++II) {
Chris Lattner4eed0b82002-02-25 00:35:07 +0000271 int IDX = PN->getBasicBlockIndex(this);
272 while (IDX != -1) {
273 PN->setIncomingBlock((unsigned)IDX, New);
274 IDX = PN->getBasicBlockIndex(this);
275 }
276 }
277 }
Chris Lattner2f7c9632001-06-06 20:29:01 +0000278 return New;
279}
Dan Gohman39033202009-10-29 00:09:08 +0000280
281/// hasAddressTaken - returns true if there are any uses of this basic block
282/// other than direct branches, switches, etc. to it.
283bool BasicBlock::hasAddressTaken() const {
284 for (Value::use_const_iterator I = use_begin(), E = use_end(); I != E; ++I)
285 if (isa<BlockAddress>(*I))
286 return true;
287 return false;
288}