BasicBlock.cpp revision a3d3c2b64545c00f70453642e5d84b028dfce671
1//===-- BasicBlock.cpp - Implement BasicBlock related functions --*- C++ -*--=// 2// 3// This file implements the Method class for the VMCore library. 4// 5//===----------------------------------------------------------------------===// 6 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" 14#include "llvm/CFG.h" 15#include "llvm/iOther.h" 16 17// Instantiate Templates - This ugliness is the price we have to pay 18// for having a ValueHolderImpl.h file seperate from ValueHolder.h! :( 19// 20template class ValueHolder<Instruction, BasicBlock, Method>; 21 22BasicBlock::BasicBlock(const string &name, Method *Parent) 23 : Value(Type::LabelTy, Value::BasicBlockVal, name), InstList(this, 0) { 24 if (Parent) 25 Parent->getBasicBlocks().push_back(this); 26} 27 28BasicBlock::~BasicBlock() { 29 dropAllReferences(); 30 InstList.delete_all(); 31} 32 33// Specialize setName to take care of symbol table majik 34void BasicBlock::setName(const string &name) { 35 Method *P; 36 if ((P = getParent()) && hasName()) P->getSymbolTable()->remove(this); 37 Value::setName(name); 38 if (P && hasName()) P->getSymbolTable()->insert(this); 39} 40 41void BasicBlock::setParent(Method *parent) { 42 if (getParent() && hasName()) 43 getParent()->getSymbolTable()->remove(this); 44 45 InstList.setParent(parent); 46 47 if (getParent() && hasName()) 48 getParent()->getSymbolTableSure()->insert(this); 49} 50 51TerminatorInst *BasicBlock::getTerminator() { 52 if (InstList.empty()) return 0; 53 Instruction *T = InstList.back(); 54 if (T->isTerminator()) return (TerminatorInst*)T; 55 return 0; 56} 57 58const TerminatorInst *const BasicBlock::getTerminator() const { 59 if (InstList.empty()) return 0; 60 const Instruction *T = InstList.back(); 61 if (T->isTerminator()) return (TerminatorInst*)T; 62 return 0; 63} 64 65void BasicBlock::dropAllReferences() { 66 for_each(InstList.begin(), InstList.end(), 67 std::mem_fun(&Instruction::dropAllReferences)); 68} 69 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. 74// 75bool BasicBlock::hasConstantPoolReferences() const { 76 for (use_const_iterator I = use_begin(), E = use_end(); I != E; ++I) 77 if ((*I)->isConstant()) 78 return true; 79 80 return false; 81} 82 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. 88// 89void 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. 94 95 pred_iterator PI(pred_begin(this)), EI(pred_end(this)); 96 unsigned max_idx; 97 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*/; 101 102 // If there are exactly two predecessors, then we want to nuke the PHI nodes 103 // altogether. 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... 109 110 assert(PN->getNumIncomingValues() == max_idx-1 && 111 "PHI node shouldn't have this many values!!!"); 112 113 // If the PHI _HAD_ two uses, replace PHI node with its now *single* value 114 if (max_idx == 2) 115 PN->replaceAllUsesWith(PN->getOperand(0)); 116 delete getInstList().remove(begin()); // Remove the PHI node 117 } 118 } else { 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); 125 } 126 } 127} 128 129 130// 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. 135// 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 139// the basic block). 140// 141BasicBlock *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!"); 145 146 BasicBlock *New = new BasicBlock("", getParent()); 147 148 // Go from the end of the basic block through to the iterator pointer, moving 149 // to the new basic block... 150 Instruction *Inst = 0; 151 do { 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. 156 157 // Add a branch instruction to the newly formed basic block. 158 InstList.push_back(new BranchInst(New)); 159 return New; 160} 161