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/Method.h"
11 #include "llvm/SymbolTable.h"
12 #include "llvm/Type.h"
14 #include "llvm/iOther.h"
15 #include "llvm/CodeGen/MachineInstr.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),
24 machineInstrVec(new MachineCodeForBasicBlock) {
26 Parent->getBasicBlocks().push_back(this);
29 BasicBlock::~BasicBlock() {
31 InstList.delete_all();
32 delete machineInstrVec;
35 // Specialize setName to take care of symbol table majik
36 void BasicBlock::setName(const string &name, SymbolTable *ST) {
38 assert((ST == 0 || (!getParent() || ST == getParent()->getSymbolTable())) &&
39 "Invalid symtab argument!");
40 if ((P = getParent()) && hasName()) P->getSymbolTable()->remove(this);
42 if (P && hasName()) P->getSymbolTable()->insert(this);
45 void BasicBlock::setParent(Method *parent) {
46 if (getParent() && hasName())
47 getParent()->getSymbolTable()->remove(this);
49 InstList.setParent(parent);
51 if (getParent() && hasName())
52 getParent()->getSymbolTableSure()->insert(this);
55 TerminatorInst *BasicBlock::getTerminator() {
56 if (InstList.empty()) return 0;
57 Instruction *T = InstList.back();
58 if (T->isTerminator()) return (TerminatorInst*)T;
62 const TerminatorInst *const BasicBlock::getTerminator() const {
63 if (InstList.empty()) return 0;
64 const Instruction *T = InstList.back();
65 if (T->isTerminator()) return (TerminatorInst*)T;
69 void BasicBlock::dropAllReferences() {
70 for_each(InstList.begin(), InstList.end(),
71 std::mem_fun(&Instruction::dropAllReferences));
74 // hasConstantPoolReferences() - This predicate is true if there is a
75 // reference to this basic block in the constant pool for this method. For
76 // example, if a block is reached through a switch table, that table resides
77 // in the constant pool, and the basic block is reference from it.
79 bool BasicBlock::hasConstantPoolReferences() const {
80 for (use_const_iterator I = use_begin(), E = use_end(); I != E; ++I)
81 if ((*I)->isConstant())
87 // removePredecessor - This method is used to notify a BasicBlock that the
88 // specified Predecessor of the block is no longer able to reach it. This is
89 // actually not used to update the Predecessor list, but is actually used to
90 // update the PHI nodes that reside in the block. Note that this should be
91 // called while the predecessor still refers to this block.
93 void BasicBlock::removePredecessor(BasicBlock *Pred) {
94 using cfg::pred_begin; using cfg::pred_end; using cfg::pred_iterator;
95 assert(find(pred_begin(this), pred_end(this), Pred) != pred_end(this) &&
96 "removePredecessor: BB is not a predecessor!");
97 if (!front()->isPHINode()) return; // Quick exit.
99 pred_iterator PI(pred_begin(this)), EI(pred_end(this));
102 // Loop over the rest of the predecessors until we run out, or until we find
103 // out that there are more than 2 predecessors.
104 for (max_idx = 0; PI != EI && max_idx < 3; ++PI, ++max_idx) /*empty*/;
106 // If there are exactly two predecessors, then we want to nuke the PHI nodes
108 assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!");
109 if (max_idx <= 2) { // <= Two predecessors BEFORE I remove one?
110 while (front()->isPHINode()) { // Yup, loop through and nuke the PHI nodes
111 PHINode *PN = (PHINode*)front();
112 PN->removeIncomingValue(Pred); // Remove the predecessor first...
114 assert(PN->getNumIncomingValues() == max_idx-1 &&
115 "PHI node shouldn't have this many values!!!");
117 // If the PHI _HAD_ two uses, replace PHI node with its now *single* value
119 PN->replaceAllUsesWith(PN->getOperand(0));
120 delete getInstList().remove(begin()); // Remove the PHI node
123 // Okay, now we know that we need to remove predecessor #pred_idx from all
124 // PHI nodes. Iterate over each PHI node fixing them up
125 iterator II(begin());
126 for (; (*II)->isPHINode(); ++II) {
127 PHINode *PN = (PHINode*)*II;
128 PN->removeIncomingValue(Pred);
134 // splitBasicBlock - This splits a basic block into two at the specified
135 // instruction. Note that all instructions BEFORE the specified iterator stay
136 // as part of the original basic block, an unconditional branch is added to
137 // the new BB, and the rest of the instructions in the BB are moved to the new
138 // BB, including the old terminator. This invalidates the iterator.
140 // Note that this only works on well formed basic blocks (must have a
141 // terminator), and 'I' must not be the end of instruction list (which would
142 // cause a degenerate basic block to be formed, having a terminator inside of
145 BasicBlock *BasicBlock::splitBasicBlock(iterator I) {
146 assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!");
147 assert(I != InstList.end() &&
148 "Trying to get me to create degenerate basic block!");
150 BasicBlock *New = new BasicBlock("", getParent());
152 // Go from the end of the basic block through to the iterator pointer, moving
153 // to the new basic block...
154 Instruction *Inst = 0;
156 iterator EndIt = end();
157 Inst = InstList.remove(--EndIt); // Remove from end
158 New->InstList.push_front(Inst); // Add to front
159 } while (Inst != *I); // Loop until we move the specified instruction.
161 // Add a branch instruction to the newly formed basic block.
162 InstList.push_back(new BranchInst(New));