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Chris Lattner184b2982002-09-08 18:59:35 +00001//===-- BasicBlock.cpp - Implement BasicBlock related methods -------------===//
John Criswell482202a2003-10-20 19:43:21 +00002//
3// 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.
7//
8//===----------------------------------------------------------------------===//
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 Lattner2f7c9632001-06-06 20:29:01 +000015#include "llvm/iTerminators.h"
Chris Lattner2f7c9632001-06-06 20:29:01 +000016#include "llvm/Type.h"
Chris Lattner83d485b2002-02-12 22:39:50 +000017#include "llvm/Support/CFG.h"
Chris Lattner5cd012d2002-05-23 16:52:34 +000018#include "llvm/Constant.h"
Chris Lattnerfb5ae022001-12-03 18:02:31 +000019#include "llvm/iPHINode.h"
Chris Lattner113f4f42002-06-25 16:13:24 +000020#include "llvm/SymbolTable.h"
Chris Lattner184b2982002-09-08 18:59:35 +000021#include "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
Chris Lattnera2960002003-11-21 16:52:05 +000026namespace {
27 /// DummyInst - An instance of this class is used to mark the end of the
28 /// instruction list. This is not a real instruction.
29 struct DummyInst : public Instruction {
30 DummyInst() : Instruction(Type::VoidTy, OtherOpsEnd) {
31 // This should not be garbage monitored.
32 LeakDetector::removeGarbageObject(this);
33 }
Brian Gaeke960707c2003-11-11 22:41:34 +000034
Chris Lattnera2960002003-11-21 16:52:05 +000035 virtual Instruction *clone() const {
36 assert(0 && "Cannot clone EOL");abort();
37 return 0;
38 }
39 virtual const char *getOpcodeName() const { return "*end-of-list-inst*"; }
Chris Lattner113f4f42002-06-25 16:13:24 +000040
Chris Lattnera2960002003-11-21 16:52:05 +000041 // Methods for support type inquiry through isa, cast, and dyn_cast...
42 static inline bool classof(const DummyInst *) { return true; }
43 static inline bool classof(const Instruction *I) {
44 return I->getOpcode() == OtherOpsEnd;
45 }
46 static inline bool classof(const Value *V) {
47 return isa<Instruction>(V) && classof(cast<Instruction>(V));
48 }
49 };
50}
Chris Lattner113f4f42002-06-25 16:13:24 +000051
52Instruction *ilist_traits<Instruction>::createNode() {
53 return new DummyInst();
54}
55iplist<Instruction> &ilist_traits<Instruction>::getList(BasicBlock *BB) {
56 return BB->getInstList();
57}
58
59// Explicit instantiation of SymbolTableListTraits since some of the methods
60// are not in the public header file...
Chris Lattner41baa982003-11-05 05:15:42 +000061template class SymbolTableListTraits<Instruction, BasicBlock, Function>;
Chris Lattner113f4f42002-06-25 16:13:24 +000062
Chris Lattner2f7c9632001-06-06 20:29:01 +000063
Chris Lattner9ed7aef2002-09-06 21:33:15 +000064// BasicBlock ctor - If the function parameter is specified, the basic block is
65// automatically inserted at the end of the function.
66//
Chris Lattnerf739fa82002-04-08 22:03:57 +000067BasicBlock::BasicBlock(const std::string &name, Function *Parent)
Vikram S. Adve6e792fc2002-07-08 22:31:11 +000068 : Value(Type::LabelTy, Value::BasicBlockVal, name) {
Chris Lattner113f4f42002-06-25 16:13:24 +000069 // Initialize the instlist...
70 InstList.setItemParent(this);
71
Chris Lattner184b2982002-09-08 18:59:35 +000072 // Make sure that we get added to a function
73 LeakDetector::addGarbageObject(this);
74
Chris Lattnerf2a738c2001-07-14 06:13:19 +000075 if (Parent)
Chris Lattner113f4f42002-06-25 16:13:24 +000076 Parent->getBasicBlockList().push_back(this);
Chris Lattner2f7c9632001-06-06 20:29:01 +000077}
78
Chris Lattner4dfede82002-09-26 05:03:22 +000079/// BasicBlock ctor - If the InsertBefore parameter is specified, the basic
80/// block is automatically inserted right before the specified block.
81///
82BasicBlock::BasicBlock(const std::string &Name, BasicBlock *InsertBefore)
83 : Value(Type::LabelTy, Value::BasicBlockVal, Name) {
84 // Initialize the instlist...
85 InstList.setItemParent(this);
86
87 // Make sure that we get added to a function
88 LeakDetector::addGarbageObject(this);
89
90 if (InsertBefore) {
91 assert(InsertBefore->getParent() &&
92 "Cannot insert block before another block that is not embedded into"
93 " a function yet!");
94 InsertBefore->getParent()->getBasicBlockList().insert(InsertBefore, this);
95 }
96}
97
98
Chris Lattner2f7c9632001-06-06 20:29:01 +000099BasicBlock::~BasicBlock() {
100 dropAllReferences();
Chris Lattner113f4f42002-06-25 16:13:24 +0000101 InstList.clear();
Chris Lattner2f7c9632001-06-06 20:29:01 +0000102}
103
Chris Lattner9ed7aef2002-09-06 21:33:15 +0000104void BasicBlock::setParent(Function *parent) {
Chris Lattner184b2982002-09-08 18:59:35 +0000105 if (getParent())
106 LeakDetector::addGarbageObject(this);
107
Chris Lattner9ed7aef2002-09-06 21:33:15 +0000108 InstList.setParent(parent);
Chris Lattner184b2982002-09-08 18:59:35 +0000109
110 if (getParent())
111 LeakDetector::removeGarbageObject(this);
Chris Lattner9ed7aef2002-09-06 21:33:15 +0000112}
113
Chris Lattner2f7c9632001-06-06 20:29:01 +0000114// Specialize setName to take care of symbol table majik
Chris Lattner7f74a562002-01-20 22:54:45 +0000115void BasicBlock::setName(const std::string &name, SymbolTable *ST) {
Chris Lattnerf739fa82002-04-08 22:03:57 +0000116 Function *P;
Chris Lattner98cf1f52002-11-20 18:36:02 +0000117 assert((ST == 0 || (!getParent() || ST == &getParent()->getSymbolTable())) &&
Chris Lattner2d189a52001-09-07 16:44:17 +0000118 "Invalid symtab argument!");
Chris Lattner98cf1f52002-11-20 18:36:02 +0000119 if ((P = getParent()) && hasName()) P->getSymbolTable().remove(this);
Chris Lattner2f7c9632001-06-06 20:29:01 +0000120 Value::setName(name);
Chris Lattner98cf1f52002-11-20 18:36:02 +0000121 if (P && hasName()) P->getSymbolTable().insert(this);
Chris Lattner2f7c9632001-06-06 20:29:01 +0000122}
123
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
134void BasicBlock::dropAllReferences() {
Chris Lattner113f4f42002-06-25 16:13:24 +0000135 for(iterator I = begin(), E = end(); I != E; ++I)
136 I->dropAllReferences();
Chris Lattner2f7c9632001-06-06 20:29:01 +0000137}
138
Chris Lattner3462ae32001-12-03 22:26:30 +0000139// hasConstantReferences() - This predicate is true if there is a
Chris Lattner2f7c9632001-06-06 20:29:01 +0000140// reference to this basic block in the constant pool for this method. For
141// example, if a block is reached through a switch table, that table resides
142// in the constant pool, and the basic block is reference from it.
143//
Chris Lattner3462ae32001-12-03 22:26:30 +0000144bool BasicBlock::hasConstantReferences() const {
Chris Lattner2f7c9632001-06-06 20:29:01 +0000145 for (use_const_iterator I = use_begin(), E = use_end(); I != E; ++I)
Brian Gaeke960707c2003-11-11 22:41:34 +0000146 if (isa<Constant>((Value*)*I))
Chris Lattner2f7c9632001-06-06 20:29:01 +0000147 return true;
148
149 return false;
150}
151
Chris Lattner615d3cf2001-06-29 05:25:23 +0000152// removePredecessor - This method is used to notify a BasicBlock that the
153// specified Predecessor of the block is no longer able to reach it. This is
154// actually not used to update the Predecessor list, but is actually used to
155// update the PHI nodes that reside in the block. Note that this should be
156// called while the predecessor still refers to this block.
157//
158void BasicBlock::removePredecessor(BasicBlock *Pred) {
Chris Lattner83d485b2002-02-12 22:39:50 +0000159 assert(find(pred_begin(this), pred_end(this), Pred) != pred_end(this) &&
Chris Lattner615d3cf2001-06-29 05:25:23 +0000160 "removePredecessor: BB is not a predecessor!");
Chris Lattnerda558102001-10-02 03:41:24 +0000161 if (!isa<PHINode>(front())) return; // Quick exit.
Chris Lattner615d3cf2001-06-29 05:25:23 +0000162
Chris Lattner83d485b2002-02-12 22:39:50 +0000163 pred_iterator PI(pred_begin(this)), EI(pred_end(this));
Chris Lattner615d3cf2001-06-29 05:25:23 +0000164 unsigned max_idx;
165
166 // Loop over the rest of the predecessors until we run out, or until we find
167 // out that there are more than 2 predecessors.
168 for (max_idx = 0; PI != EI && max_idx < 3; ++PI, ++max_idx) /*empty*/;
169
170 // If there are exactly two predecessors, then we want to nuke the PHI nodes
Chris Lattnerf7373e42002-05-21 19:52:49 +0000171 // altogether. We cannot do this, however if this in this case however:
172 //
173 // Loop:
174 // %x = phi [X, Loop]
175 // %x2 = add %x, 1 ;; This would become %x2 = add %x2, 1
176 // br Loop ;; %x2 does not dominate all uses
177 //
178 // This is because the PHI node input is actually taken from the predecessor
179 // basic block. The only case this can happen is with a self loop, so we
180 // check for this case explicitly now.
181 //
Chris Lattner615d3cf2001-06-29 05:25:23 +0000182 assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!");
Chris Lattnerf7373e42002-05-21 19:52:49 +0000183 if (max_idx == 2) {
184 PI = pred_begin(this);
185 BasicBlock *Other = *PI == Pred ? *++PI : *PI;
186
187 // Disable PHI elimination!
188 if (this == Other) max_idx = 3;
189 }
190
Chris Lattner615d3cf2001-06-29 05:25:23 +0000191 if (max_idx <= 2) { // <= Two predecessors BEFORE I remove one?
Chris Lattnerda558102001-10-02 03:41:24 +0000192 // Yup, loop through and nuke the PHI nodes
Chris Lattner113f4f42002-06-25 16:13:24 +0000193 while (PHINode *PN = dyn_cast<PHINode>(&front())) {
Chris Lattner615d3cf2001-06-29 05:25:23 +0000194 PN->removeIncomingValue(Pred); // Remove the predecessor first...
Chris Lattner615d3cf2001-06-29 05:25:23 +0000195
196 // If the PHI _HAD_ two uses, replace PHI node with its now *single* value
Chris Lattnercaf5b502002-10-08 21:36:34 +0000197 if (max_idx == 2) {
Chris Lattneref8c8332003-04-25 23:14:19 +0000198 if (PN->getOperand(0) != PN)
199 PN->replaceAllUsesWith(PN->getOperand(0));
200 else
201 // We are left with an infinite loop with no entries: kill the PHI.
202 PN->replaceAllUsesWith(Constant::getNullValue(PN->getType()));
Chris Lattnercaf5b502002-10-08 21:36:34 +0000203 getInstList().pop_front(); // Remove the PHI node
204 }
205
206 // If the PHI node already only had one entry, it got deleted by
207 // removeIncomingValue.
Chris Lattner615d3cf2001-06-29 05:25:23 +0000208 }
209 } else {
210 // Okay, now we know that we need to remove predecessor #pred_idx from all
211 // PHI nodes. Iterate over each PHI node fixing them up
Chris Lattner889f6202003-04-23 16:37:45 +0000212 for (iterator II = begin(); PHINode *PN = dyn_cast<PHINode>(II); ++II)
Chris Lattnerf7373e42002-05-21 19:52:49 +0000213 PN->removeIncomingValue(Pred);
Chris Lattner615d3cf2001-06-29 05:25:23 +0000214 }
215}
216
Chris Lattner2f7c9632001-06-06 20:29:01 +0000217
218// splitBasicBlock - This splits a basic block into two at the specified
219// instruction. Note that all instructions BEFORE the specified iterator stay
220// as part of the original basic block, an unconditional branch is added to
221// the new BB, and the rest of the instructions in the BB are moved to the new
222// BB, including the old terminator. This invalidates the iterator.
223//
224// Note that this only works on well formed basic blocks (must have a
225// terminator), and 'I' must not be the end of instruction list (which would
226// cause a degenerate basic block to be formed, having a terminator inside of
227// the basic block).
228//
Chris Lattner6d569352003-08-24 03:41:39 +0000229BasicBlock *BasicBlock::splitBasicBlock(iterator I, const std::string &BBName) {
Chris Lattner2f7c9632001-06-06 20:29:01 +0000230 assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!");
231 assert(I != InstList.end() &&
232 "Trying to get me to create degenerate basic block!");
233
Chris Lattner6d569352003-08-24 03:41:39 +0000234 BasicBlock *New = new BasicBlock(BBName, getParent());
Chris Lattner2f7c9632001-06-06 20:29:01 +0000235
Chris Lattnerc4c7ea52004-02-03 23:11:21 +0000236 // Move all of the specified instructions from the original basic block into
237 // the new basic block.
238 New->getInstList().splice(New->end(), this->getInstList(), I, end());
Chris Lattner2f7c9632001-06-06 20:29:01 +0000239
240 // Add a branch instruction to the newly formed basic block.
Chris Lattnera2960002003-11-21 16:52:05 +0000241 new BranchInst(New, this);
Chris Lattner4eed0b82002-02-25 00:35:07 +0000242
243 // Now we must loop through all of the successors of the New block (which
244 // _were_ the successors of the 'this' block), and update any PHI nodes in
245 // successors. If there were PHI nodes in the successors, then they need to
246 // know that incoming branches will be from New, not from Old.
247 //
Chris Lattner64d88bc2003-09-24 22:03:22 +0000248 for (succ_iterator I = succ_begin(New), E = succ_end(New); I != E; ++I) {
Chris Lattner4eed0b82002-02-25 00:35:07 +0000249 // Loop over any phi nodes in the basic block, updating the BB field of
250 // incoming values...
251 BasicBlock *Successor = *I;
252 for (BasicBlock::iterator II = Successor->begin();
Chris Lattner889f6202003-04-23 16:37:45 +0000253 PHINode *PN = dyn_cast<PHINode>(II); ++II) {
Chris Lattner4eed0b82002-02-25 00:35:07 +0000254 int IDX = PN->getBasicBlockIndex(this);
255 while (IDX != -1) {
256 PN->setIncomingBlock((unsigned)IDX, New);
257 IDX = PN->getBasicBlockIndex(this);
258 }
259 }
260 }
Chris Lattner2f7c9632001-06-06 20:29:01 +0000261 return New;
262}