1 //===-- BasicBlock.cpp - Implement BasicBlock related functions --*- C++ -*--=//
3 // This file implements the Method class for the VMCore library.
5 //===----------------------------------------------------------------------===//
7 #include "llvm/ValueHolderImpl.h"
8 #include "llvm/BasicBlock.h"
9 #include "llvm/iTerminators.h"
10 #include "llvm/Module.h"
11 #include "llvm/Method.h"
12 #include "llvm/SymbolTable.h"
13 #include "llvm/Type.h"
15 #include "llvm/iOther.h"
17 // Instantiate Templates - This ugliness is the price we have to pay
18 // for having a ValueHolderImpl.h file seperate from ValueHolder.h! :(
20 template class ValueHolder<Instruction, BasicBlock, Method>;
22 BasicBlock::BasicBlock(const string &name, Method *Parent)
23 : Value(Type::LabelTy, Value::BasicBlockVal, name), InstList(this, 0) {
25 Parent->getBasicBlocks().push_back(this);
28 BasicBlock::~BasicBlock() {
30 InstList.delete_all();
33 // Specialize setName to take care of symbol table majik
34 void BasicBlock::setName(const string &name) {
36 if ((P = getParent()) && hasName()) P->getSymbolTable()->remove(this);
38 if (P && hasName()) P->getSymbolTable()->insert(this);
41 void BasicBlock::setParent(Method *parent) {
42 if (getParent() && hasName())
43 getParent()->getSymbolTable()->remove(this);
45 InstList.setParent(parent);
47 if (getParent() && hasName())
48 getParent()->getSymbolTableSure()->insert(this);
51 TerminatorInst *BasicBlock::getTerminator() {
52 if (InstList.empty()) return 0;
53 Instruction *T = InstList.back();
54 if (T->isTerminator()) return (TerminatorInst*)T;
58 const TerminatorInst *const BasicBlock::getTerminator() const {
59 if (InstList.empty()) return 0;
60 const Instruction *T = InstList.back();
61 if (T->isTerminator()) return (TerminatorInst*)T;
65 void BasicBlock::dropAllReferences() {
66 for_each(InstList.begin(), InstList.end(),
67 std::mem_fun(&Instruction::dropAllReferences));
70 // hasConstantPoolReferences() - This predicate is true if there is a
71 // reference to this basic block in the constant pool for this method. For
72 // example, if a block is reached through a switch table, that table resides
73 // in the constant pool, and the basic block is reference from it.
75 bool BasicBlock::hasConstantPoolReferences() const {
76 for (use_const_iterator I = use_begin(), E = use_end(); I != E; ++I)
77 if ((*I)->isConstant())
83 // removePredecessor - This method is used to notify a BasicBlock that the
84 // specified Predecessor of the block is no longer able to reach it. This is
85 // actually not used to update the Predecessor list, but is actually used to
86 // update the PHI nodes that reside in the block. Note that this should be
87 // called while the predecessor still refers to this block.
89 void BasicBlock::removePredecessor(BasicBlock *Pred) {
90 using cfg::pred_begin; using cfg::pred_end; using cfg::pred_iterator;
91 assert(find(pred_begin(this), pred_end(this), Pred) != pred_end(this) &&
92 "removePredecessor: BB is not a predecessor!");
93 if (!front()->isPHINode()) return; // Quick exit.
95 pred_iterator PI(pred_begin(this)), EI(pred_end(this));
98 // Loop over the rest of the predecessors until we run out, or until we find
99 // out that there are more than 2 predecessors.
100 for (max_idx = 0; PI != EI && max_idx < 3; ++PI, ++max_idx) /*empty*/;
102 // If there are exactly two predecessors, then we want to nuke the PHI nodes
104 assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!");
105 if (max_idx <= 2) { // <= Two predecessors BEFORE I remove one?
106 while (front()->isPHINode()) { // Yup, loop through and nuke the PHI nodes
107 PHINode *PN = (PHINode*)front();
108 PN->removeIncomingValue(Pred); // Remove the predecessor first...
110 assert(PN->getNumIncomingValues() == max_idx-1 &&
111 "PHI node shouldn't have this many values!!!");
113 // If the PHI _HAD_ two uses, replace PHI node with its now *single* value
115 PN->replaceAllUsesWith(PN->getOperand(0));
116 delete getInstList().remove(begin()); // Remove the PHI node
119 // Okay, now we know that we need to remove predecessor #pred_idx from all
120 // PHI nodes. Iterate over each PHI node fixing them up
121 iterator II(begin());
122 for (; (*II)->isPHINode(); ++II) {
123 PHINode *PN = (PHINode*)*II;
124 PN->removeIncomingValue(Pred);
130 // splitBasicBlock - This splits a basic block into two at the specified
131 // instruction. Note that all instructions BEFORE the specified iterator stay
132 // as part of the original basic block, an unconditional branch is added to
133 // the new BB, and the rest of the instructions in the BB are moved to the new
134 // BB, including the old terminator. This invalidates the iterator.
136 // Note that this only works on well formed basic blocks (must have a
137 // terminator), and 'I' must not be the end of instruction list (which would
138 // cause a degenerate basic block to be formed, having a terminator inside of
141 BasicBlock *BasicBlock::splitBasicBlock(iterator I) {
142 assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!");
143 assert(I != InstList.end() &&
144 "Trying to get me to create degenerate basic block!");
146 BasicBlock *New = new BasicBlock("", getParent());
148 // Go from the end of the basic block through to the iterator pointer, moving
149 // to the new basic block...
150 Instruction *Inst = 0;
152 iterator EndIt = end();
153 Inst = InstList.remove(--EndIt); // Remove from end
154 New->InstList.push_front(Inst); // Add to front
155 } while (Inst != *I); // Loop until we move the specified instruction.
157 // Add a branch instruction to the newly formed basic block.
158 InstList.push_back(new BranchInst(New));