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Chris Lattner184b2982002-09-08 18:59:35 +00001//===-- BasicBlock.cpp - Implement BasicBlock related methods -------------===//
Chris Lattner2f7c9632001-06-06 20:29:01 +00002//
Chris Lattnerf739fa82002-04-08 22:03:57 +00003// This file implements the BasicBlock class for the VMCore library.
Chris Lattner2f7c9632001-06-06 20:29:01 +00004//
5//===----------------------------------------------------------------------===//
6
Chris Lattner113f4f42002-06-25 16:13:24 +00007#include "llvm/BasicBlock.h"
Chris Lattner2f7c9632001-06-06 20:29:01 +00008#include "llvm/iTerminators.h"
Chris Lattner2f7c9632001-06-06 20:29:01 +00009#include "llvm/Type.h"
Chris Lattner83d485b2002-02-12 22:39:50 +000010#include "llvm/Support/CFG.h"
Chris Lattner5cd012d2002-05-23 16:52:34 +000011#include "llvm/Constant.h"
Chris Lattnerfb5ae022001-12-03 18:02:31 +000012#include "llvm/iPHINode.h"
Chris Lattner113f4f42002-06-25 16:13:24 +000013#include "llvm/SymbolTable.h"
Chris Lattner184b2982002-09-08 18:59:35 +000014#include "Support/LeakDetector.h"
Chris Lattner113f4f42002-06-25 16:13:24 +000015#include "SymbolTableListTraitsImpl.h"
16#include <algorithm>
Chris Lattner2f7c9632001-06-06 20:29:01 +000017
Chris Lattner113f4f42002-06-25 16:13:24 +000018// DummyInst - An instance of this class is used to mark the end of the
19// instruction list. This is not a real instruction.
Chris Lattner2f7c9632001-06-06 20:29:01 +000020//
Chris Lattner113f4f42002-06-25 16:13:24 +000021struct DummyInst : public Instruction {
Chris Lattner69ce8672002-10-13 19:39:16 +000022 DummyInst() : Instruction(Type::VoidTy, OtherOpsEnd) {
Chris Lattner184b2982002-09-08 18:59:35 +000023 // This should not be garbage monitored.
24 LeakDetector::removeGarbageObject(this);
25 }
Chris Lattner113f4f42002-06-25 16:13:24 +000026
Chris Lattnerc678c172002-07-25 15:39:05 +000027 virtual Instruction *clone() const {
28 assert(0 && "Cannot clone EOL");abort();
29 return 0;
30 }
Chris Lattner113f4f42002-06-25 16:13:24 +000031 virtual const char *getOpcodeName() const { return "*end-of-list-inst*"; }
32
33 // Methods for support type inquiry through isa, cast, and dyn_cast...
34 static inline bool classof(const DummyInst *) { return true; }
35 static inline bool classof(const Instruction *I) {
Chris Lattner69ce8672002-10-13 19:39:16 +000036 return I->getOpcode() == OtherOpsEnd;
Chris Lattner113f4f42002-06-25 16:13:24 +000037 }
38 static inline bool classof(const Value *V) {
39 return isa<Instruction>(V) && classof(cast<Instruction>(V));
40 }
41};
42
43Instruction *ilist_traits<Instruction>::createNode() {
44 return new DummyInst();
45}
46iplist<Instruction> &ilist_traits<Instruction>::getList(BasicBlock *BB) {
47 return BB->getInstList();
48}
49
50// Explicit instantiation of SymbolTableListTraits since some of the methods
51// are not in the public header file...
52template SymbolTableListTraits<Instruction, BasicBlock, Function>;
53
Chris Lattner2f7c9632001-06-06 20:29:01 +000054
Chris Lattner9ed7aef2002-09-06 21:33:15 +000055// BasicBlock ctor - If the function parameter is specified, the basic block is
56// automatically inserted at the end of the function.
57//
Chris Lattnerf739fa82002-04-08 22:03:57 +000058BasicBlock::BasicBlock(const std::string &name, Function *Parent)
Vikram S. Adve6e792fc2002-07-08 22:31:11 +000059 : Value(Type::LabelTy, Value::BasicBlockVal, name) {
Chris Lattner113f4f42002-06-25 16:13:24 +000060 // Initialize the instlist...
61 InstList.setItemParent(this);
62
Chris Lattner184b2982002-09-08 18:59:35 +000063 // Make sure that we get added to a function
64 LeakDetector::addGarbageObject(this);
65
Chris Lattnerf2a738c2001-07-14 06:13:19 +000066 if (Parent)
Chris Lattner113f4f42002-06-25 16:13:24 +000067 Parent->getBasicBlockList().push_back(this);
Chris Lattner2f7c9632001-06-06 20:29:01 +000068}
69
Chris Lattner4dfede82002-09-26 05:03:22 +000070/// BasicBlock ctor - If the InsertBefore parameter is specified, the basic
71/// block is automatically inserted right before the specified block.
72///
73BasicBlock::BasicBlock(const std::string &Name, BasicBlock *InsertBefore)
74 : Value(Type::LabelTy, Value::BasicBlockVal, Name) {
75 // Initialize the instlist...
76 InstList.setItemParent(this);
77
78 // Make sure that we get added to a function
79 LeakDetector::addGarbageObject(this);
80
81 if (InsertBefore) {
82 assert(InsertBefore->getParent() &&
83 "Cannot insert block before another block that is not embedded into"
84 " a function yet!");
85 InsertBefore->getParent()->getBasicBlockList().insert(InsertBefore, this);
86 }
87}
88
89
Chris Lattner2f7c9632001-06-06 20:29:01 +000090BasicBlock::~BasicBlock() {
91 dropAllReferences();
Chris Lattner113f4f42002-06-25 16:13:24 +000092 InstList.clear();
Chris Lattner2f7c9632001-06-06 20:29:01 +000093}
94
Chris Lattner9ed7aef2002-09-06 21:33:15 +000095void BasicBlock::setParent(Function *parent) {
Chris Lattner184b2982002-09-08 18:59:35 +000096 if (getParent())
97 LeakDetector::addGarbageObject(this);
98
Chris Lattner9ed7aef2002-09-06 21:33:15 +000099 InstList.setParent(parent);
Chris Lattner184b2982002-09-08 18:59:35 +0000100
101 if (getParent())
102 LeakDetector::removeGarbageObject(this);
Chris Lattner9ed7aef2002-09-06 21:33:15 +0000103}
104
Chris Lattner2f7c9632001-06-06 20:29:01 +0000105// Specialize setName to take care of symbol table majik
Chris Lattner7f74a562002-01-20 22:54:45 +0000106void BasicBlock::setName(const std::string &name, SymbolTable *ST) {
Chris Lattnerf739fa82002-04-08 22:03:57 +0000107 Function *P;
Chris Lattner98cf1f52002-11-20 18:36:02 +0000108 assert((ST == 0 || (!getParent() || ST == &getParent()->getSymbolTable())) &&
Chris Lattner2d189a52001-09-07 16:44:17 +0000109 "Invalid symtab argument!");
Chris Lattner98cf1f52002-11-20 18:36:02 +0000110 if ((P = getParent()) && hasName()) P->getSymbolTable().remove(this);
Chris Lattner2f7c9632001-06-06 20:29:01 +0000111 Value::setName(name);
Chris Lattner98cf1f52002-11-20 18:36:02 +0000112 if (P && hasName()) P->getSymbolTable().insert(this);
Chris Lattner2f7c9632001-06-06 20:29:01 +0000113}
114
Chris Lattner2f7c9632001-06-06 20:29:01 +0000115TerminatorInst *BasicBlock::getTerminator() {
116 if (InstList.empty()) return 0;
Chris Lattner113f4f42002-06-25 16:13:24 +0000117 return dyn_cast<TerminatorInst>(&InstList.back());
Chris Lattner2f7c9632001-06-06 20:29:01 +0000118}
119
120const TerminatorInst *const BasicBlock::getTerminator() const {
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
125void BasicBlock::dropAllReferences() {
Chris Lattner113f4f42002-06-25 16:13:24 +0000126 for(iterator I = begin(), E = end(); I != E; ++I)
127 I->dropAllReferences();
Chris Lattner2f7c9632001-06-06 20:29:01 +0000128}
129
Chris Lattner3462ae32001-12-03 22:26:30 +0000130// hasConstantReferences() - This predicate is true if there is a
Chris Lattner2f7c9632001-06-06 20:29:01 +0000131// reference to this basic block in the constant pool for this method. For
132// example, if a block is reached through a switch table, that table resides
133// in the constant pool, and the basic block is reference from it.
134//
Chris Lattner3462ae32001-12-03 22:26:30 +0000135bool BasicBlock::hasConstantReferences() const {
Chris Lattner2f7c9632001-06-06 20:29:01 +0000136 for (use_const_iterator I = use_begin(), E = use_end(); I != E; ++I)
Chris Lattnerca142372002-04-28 19:55:58 +0000137 if (::isa<Constant>((Value*)*I))
Chris Lattner2f7c9632001-06-06 20:29:01 +0000138 return true;
139
140 return false;
141}
142
Chris Lattner615d3cf2001-06-29 05:25:23 +0000143// removePredecessor - This method is used to notify a BasicBlock that the
144// specified Predecessor of the block is no longer able to reach it. This is
145// actually not used to update the Predecessor list, but is actually used to
146// update the PHI nodes that reside in the block. Note that this should be
147// called while the predecessor still refers to this block.
148//
149void BasicBlock::removePredecessor(BasicBlock *Pred) {
Chris Lattner83d485b2002-02-12 22:39:50 +0000150 assert(find(pred_begin(this), pred_end(this), Pred) != pred_end(this) &&
Chris Lattner615d3cf2001-06-29 05:25:23 +0000151 "removePredecessor: BB is not a predecessor!");
Chris Lattnerda558102001-10-02 03:41:24 +0000152 if (!isa<PHINode>(front())) return; // Quick exit.
Chris Lattner615d3cf2001-06-29 05:25:23 +0000153
Chris Lattner83d485b2002-02-12 22:39:50 +0000154 pred_iterator PI(pred_begin(this)), EI(pred_end(this));
Chris Lattner615d3cf2001-06-29 05:25:23 +0000155 unsigned max_idx;
156
157 // Loop over the rest of the predecessors until we run out, or until we find
158 // out that there are more than 2 predecessors.
159 for (max_idx = 0; PI != EI && max_idx < 3; ++PI, ++max_idx) /*empty*/;
160
161 // If there are exactly two predecessors, then we want to nuke the PHI nodes
Chris Lattnerf7373e42002-05-21 19:52:49 +0000162 // altogether. We cannot do this, however if this in this case however:
163 //
164 // Loop:
165 // %x = phi [X, Loop]
166 // %x2 = add %x, 1 ;; This would become %x2 = add %x2, 1
167 // br Loop ;; %x2 does not dominate all uses
168 //
169 // This is because the PHI node input is actually taken from the predecessor
170 // basic block. The only case this can happen is with a self loop, so we
171 // check for this case explicitly now.
172 //
Chris Lattner615d3cf2001-06-29 05:25:23 +0000173 assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!");
Chris Lattnerf7373e42002-05-21 19:52:49 +0000174 if (max_idx == 2) {
175 PI = pred_begin(this);
176 BasicBlock *Other = *PI == Pred ? *++PI : *PI;
177
178 // Disable PHI elimination!
179 if (this == Other) max_idx = 3;
180 }
181
Chris Lattner615d3cf2001-06-29 05:25:23 +0000182 if (max_idx <= 2) { // <= Two predecessors BEFORE I remove one?
Chris Lattnerda558102001-10-02 03:41:24 +0000183 // Yup, loop through and nuke the PHI nodes
Chris Lattner113f4f42002-06-25 16:13:24 +0000184 while (PHINode *PN = dyn_cast<PHINode>(&front())) {
Chris Lattner615d3cf2001-06-29 05:25:23 +0000185 PN->removeIncomingValue(Pred); // Remove the predecessor first...
Chris Lattner615d3cf2001-06-29 05:25:23 +0000186
187 // If the PHI _HAD_ two uses, replace PHI node with its now *single* value
Chris Lattnercaf5b502002-10-08 21:36:34 +0000188 if (max_idx == 2) {
Chris Lattneref8c8332003-04-25 23:14:19 +0000189 if (PN->getOperand(0) != PN)
190 PN->replaceAllUsesWith(PN->getOperand(0));
191 else
192 // We are left with an infinite loop with no entries: kill the PHI.
193 PN->replaceAllUsesWith(Constant::getNullValue(PN->getType()));
Chris Lattnercaf5b502002-10-08 21:36:34 +0000194 getInstList().pop_front(); // Remove the PHI node
195 }
196
197 // If the PHI node already only had one entry, it got deleted by
198 // removeIncomingValue.
Chris Lattner615d3cf2001-06-29 05:25:23 +0000199 }
200 } else {
201 // Okay, now we know that we need to remove predecessor #pred_idx from all
202 // PHI nodes. Iterate over each PHI node fixing them up
Chris Lattner889f6202003-04-23 16:37:45 +0000203 for (iterator II = begin(); PHINode *PN = dyn_cast<PHINode>(II); ++II)
Chris Lattnerf7373e42002-05-21 19:52:49 +0000204 PN->removeIncomingValue(Pred);
Chris Lattner615d3cf2001-06-29 05:25:23 +0000205 }
206}
207
Chris Lattner2f7c9632001-06-06 20:29:01 +0000208
209// splitBasicBlock - This splits a basic block into two at the specified
210// instruction. Note that all instructions BEFORE the specified iterator stay
211// as part of the original basic block, an unconditional branch is added to
212// the new BB, and the rest of the instructions in the BB are moved to the new
213// BB, including the old terminator. This invalidates the iterator.
214//
215// Note that this only works on well formed basic blocks (must have a
216// terminator), and 'I' must not be the end of instruction list (which would
217// cause a degenerate basic block to be formed, having a terminator inside of
218// the basic block).
219//
Chris Lattner4cee8d82001-06-27 23:41:11 +0000220BasicBlock *BasicBlock::splitBasicBlock(iterator I) {
Chris Lattner2f7c9632001-06-06 20:29:01 +0000221 assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!");
222 assert(I != InstList.end() &&
223 "Trying to get me to create degenerate basic block!");
224
225 BasicBlock *New = new BasicBlock("", getParent());
226
227 // Go from the end of the basic block through to the iterator pointer, moving
228 // to the new basic block...
229 Instruction *Inst = 0;
230 do {
Chris Lattner4cee8d82001-06-27 23:41:11 +0000231 iterator EndIt = end();
Chris Lattner2f7c9632001-06-06 20:29:01 +0000232 Inst = InstList.remove(--EndIt); // Remove from end
233 New->InstList.push_front(Inst); // Add to front
Chris Lattner113f4f42002-06-25 16:13:24 +0000234 } while (Inst != &*I); // Loop until we move the specified instruction.
Chris Lattner2f7c9632001-06-06 20:29:01 +0000235
236 // Add a branch instruction to the newly formed basic block.
237 InstList.push_back(new BranchInst(New));
Chris Lattner4eed0b82002-02-25 00:35:07 +0000238
239 // Now we must loop through all of the successors of the New block (which
240 // _were_ the successors of the 'this' block), and update any PHI nodes in
241 // successors. If there were PHI nodes in the successors, then they need to
242 // know that incoming branches will be from New, not from Old.
243 //
244 for (BasicBlock::succ_iterator I = succ_begin(New), E = succ_end(New);
245 I != E; ++I) {
246 // Loop over any phi nodes in the basic block, updating the BB field of
247 // incoming values...
248 BasicBlock *Successor = *I;
249 for (BasicBlock::iterator II = Successor->begin();
Chris Lattner889f6202003-04-23 16:37:45 +0000250 PHINode *PN = dyn_cast<PHINode>(II); ++II) {
Chris Lattner4eed0b82002-02-25 00:35:07 +0000251 int IDX = PN->getBasicBlockIndex(this);
252 while (IDX != -1) {
253 PN->setIncomingBlock((unsigned)IDX, New);
254 IDX = PN->getBasicBlockIndex(this);
255 }
256 }
257 }
Chris Lattner2f7c9632001-06-06 20:29:01 +0000258 return New;
259}