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"
13 #include "llvm/iPHINode.h"
14 #include "llvm/CodeGen/MachineInstr.h"
16 // Instantiate Templates - This ugliness is the price we have to pay
17 // for having a ValueHolderImpl.h file seperate from ValueHolder.h! :(
19 template class ValueHolder<Instruction, BasicBlock, Method>;
21 BasicBlock::BasicBlock(const string &name, Method *Parent)
22 : Value(Type::LabelTy, Value::BasicBlockVal, name), InstList(this, 0),
23 machineInstrVec(new MachineCodeForBasicBlock) {
25 Parent->getBasicBlocks().push_back(this);
28 BasicBlock::~BasicBlock() {
30 InstList.delete_all();
31 delete machineInstrVec;
34 // Specialize setName to take care of symbol table majik
35 void BasicBlock::setName(const string &name, SymbolTable *ST) {
37 assert((ST == 0 || (!getParent() || ST == getParent()->getSymbolTable())) &&
38 "Invalid symtab argument!");
39 if ((P = getParent()) && hasName()) P->getSymbolTable()->remove(this);
41 if (P && hasName()) P->getSymbolTable()->insert(this);
44 void BasicBlock::setParent(Method *parent) {
45 if (getParent() && hasName())
46 getParent()->getSymbolTable()->remove(this);
48 InstList.setParent(parent);
50 if (getParent() && hasName())
51 getParent()->getSymbolTableSure()->insert(this);
54 TerminatorInst *BasicBlock::getTerminator() {
55 if (InstList.empty()) return 0;
56 Instruction *T = InstList.back();
57 if (isa<TerminatorInst>(T)) return cast<TerminatorInst>(T);
61 const TerminatorInst *const BasicBlock::getTerminator() const {
62 if (InstList.empty()) return 0;
63 if (const TerminatorInst *TI = dyn_cast<TerminatorInst>(InstList.back()))
68 void BasicBlock::dropAllReferences() {
69 for_each(InstList.begin(), InstList.end(),
70 std::mem_fun(&Instruction::dropAllReferences));
73 // hasConstantReferences() - This predicate is true if there is a
74 // reference to this basic block in the constant pool for this method. For
75 // example, if a block is reached through a switch table, that table resides
76 // in the constant pool, and the basic block is reference from it.
78 bool BasicBlock::hasConstantReferences() const {
79 for (use_const_iterator I = use_begin(), E = use_end(); I != E; ++I)
80 if (::isa<Constant>(*I))
86 // removePredecessor - This method is used to notify a BasicBlock that the
87 // specified Predecessor of the block is no longer able to reach it. This is
88 // actually not used to update the Predecessor list, but is actually used to
89 // update the PHI nodes that reside in the block. Note that this should be
90 // called while the predecessor still refers to this block.
92 void BasicBlock::removePredecessor(BasicBlock *Pred) {
93 assert(find(pred_begin(), pred_end(), Pred) != pred_end() &&
94 "removePredecessor: BB is not a predecessor!");
95 if (!isa<PHINode>(front())) return; // Quick exit.
97 pred_iterator PI(pred_begin()), EI(pred_end());
100 // Loop over the rest of the predecessors until we run out, or until we find
101 // out that there are more than 2 predecessors.
102 for (max_idx = 0; PI != EI && max_idx < 3; ++PI, ++max_idx) /*empty*/;
104 // If there are exactly two predecessors, then we want to nuke the PHI nodes
106 assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!");
107 if (max_idx <= 2) { // <= Two predecessors BEFORE I remove one?
108 // Yup, loop through and nuke the PHI nodes
109 while (PHINode *PN = dyn_cast<PHINode>(front())) {
110 PN->removeIncomingValue(Pred); // Remove the predecessor first...
112 assert(PN->getNumIncomingValues() == max_idx-1 &&
113 "PHI node shouldn't have this many values!!!");
115 // If the PHI _HAD_ two uses, replace PHI node with its now *single* value
117 PN->replaceAllUsesWith(PN->getOperand(0));
118 delete getInstList().remove(begin()); // Remove the PHI node
121 // Okay, now we know that we need to remove predecessor #pred_idx from all
122 // PHI nodes. Iterate over each PHI node fixing them up
123 iterator II(begin());
124 for (; isa<PHINode>(*II); ++II)
125 cast<PHINode>(*II)->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));