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"
16 #include "llvm/CodeGen/MachineInstr.h"
18 // Instantiate Templates - This ugliness is the price we have to pay
19 // for having a ValueHolderImpl.h file seperate from ValueHolder.h! :(
21 template class ValueHolder<Instruction, BasicBlock, Method>;
23 BasicBlock::BasicBlock(const string &name, Method *Parent)
24 : Value(Type::LabelTy, Value::BasicBlockVal, name),
26 machineInstrVec(new MachineCodeForBasicBlock)
29 Parent->getBasicBlocks().push_back(this);
32 BasicBlock::~BasicBlock() {
34 InstList.delete_all();
35 delete machineInstrVec;
38 // Specialize setName to take care of symbol table majik
39 void BasicBlock::setName(const string &name) {
41 if ((P = getParent()) && hasName()) P->getSymbolTable()->remove(this);
43 if (P && hasName()) P->getSymbolTable()->insert(this);
46 void BasicBlock::setParent(Method *parent) {
47 if (getParent() && hasName())
48 getParent()->getSymbolTable()->remove(this);
50 InstList.setParent(parent);
52 if (getParent() && hasName())
53 getParent()->getSymbolTableSure()->insert(this);
56 TerminatorInst *BasicBlock::getTerminator() {
57 if (InstList.empty()) return 0;
58 Instruction *T = InstList.back();
59 if (T->isTerminator()) return (TerminatorInst*)T;
63 const TerminatorInst *const BasicBlock::getTerminator() const {
64 if (InstList.empty()) return 0;
65 const Instruction *T = InstList.back();
66 if (T->isTerminator()) return (TerminatorInst*)T;
70 void BasicBlock::dropAllReferences() {
71 for_each(InstList.begin(), InstList.end(),
72 std::mem_fun(&Instruction::dropAllReferences));
75 // hasConstantPoolReferences() - This predicate is true if there is a
76 // reference to this basic block in the constant pool for this method. For
77 // example, if a block is reached through a switch table, that table resides
78 // in the constant pool, and the basic block is reference from it.
80 bool BasicBlock::hasConstantPoolReferences() const {
81 for (use_const_iterator I = use_begin(), E = use_end(); I != E; ++I)
82 if ((*I)->isConstant())
88 // removePredecessor - This method is used to notify a BasicBlock that the
89 // specified Predecessor of the block is no longer able to reach it. This is
90 // actually not used to update the Predecessor list, but is actually used to
91 // update the PHI nodes that reside in the block. Note that this should be
92 // called while the predecessor still refers to this block.
94 void BasicBlock::removePredecessor(BasicBlock *Pred) {
95 using cfg::pred_begin; using cfg::pred_end; using cfg::pred_iterator;
96 assert(find(pred_begin(this), pred_end(this), Pred) != pred_end(this) &&
97 "removePredecessor: BB is not a predecessor!");
98 if (!front()->isPHINode()) return; // Quick exit.
100 pred_iterator PI(pred_begin(this)), EI(pred_end(this));
103 // Loop over the rest of the predecessors until we run out, or until we find
104 // out that there are more than 2 predecessors.
105 for (max_idx = 0; PI != EI && max_idx < 3; ++PI, ++max_idx) /*empty*/;
107 // If there are exactly two predecessors, then we want to nuke the PHI nodes
109 assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!");
110 if (max_idx <= 2) { // <= Two predecessors BEFORE I remove one?
111 while (front()->isPHINode()) { // Yup, loop through and nuke the PHI nodes
112 PHINode *PN = (PHINode*)front();
113 PN->removeIncomingValue(Pred); // Remove the predecessor first...
115 assert(PN->getNumIncomingValues() == max_idx-1 &&
116 "PHI node shouldn't have this many values!!!");
118 // If the PHI _HAD_ two uses, replace PHI node with its now *single* value
120 PN->replaceAllUsesWith(PN->getOperand(0));
121 delete getInstList().remove(begin()); // Remove the PHI node
124 // Okay, now we know that we need to remove predecessor #pred_idx from all
125 // PHI nodes. Iterate over each PHI node fixing them up
126 iterator II(begin());
127 for (; (*II)->isPHINode(); ++II) {
128 PHINode *PN = (PHINode*)*II;
129 PN->removeIncomingValue(Pred);
135 // splitBasicBlock - This splits a basic block into two at the specified
136 // instruction. Note that all instructions BEFORE the specified iterator stay
137 // as part of the original basic block, an unconditional branch is added to
138 // the new BB, and the rest of the instructions in the BB are moved to the new
139 // BB, including the old terminator. This invalidates the iterator.
141 // Note that this only works on well formed basic blocks (must have a
142 // terminator), and 'I' must not be the end of instruction list (which would
143 // cause a degenerate basic block to be formed, having a terminator inside of
146 BasicBlock *BasicBlock::splitBasicBlock(iterator I) {
147 assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!");
148 assert(I != InstList.end() &&
149 "Trying to get me to create degenerate basic block!");
151 BasicBlock *New = new BasicBlock("", getParent());
153 // Go from the end of the basic block through to the iterator pointer, moving
154 // to the new basic block...
155 Instruction *Inst = 0;
157 iterator EndIt = end();
158 Inst = InstList.remove(--EndIt); // Remove from end
159 New->InstList.push_front(Inst); // Add to front
160 } while (Inst != *I); // Loop until we move the specified instruction.
162 // Add a branch instruction to the newly formed basic block.
163 InstList.push_back(new BranchInst(New));