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//===-- BasicBlock.cpp - Implement BasicBlock related functions --*- C++ -*--=//
//
// This file implements the Method class for the VMCore library.
//
//===----------------------------------------------------------------------===//
#include "llvm/ValueHolderImpl.h"
#include "llvm/BasicBlock.h"
#include "llvm/iTerminators.h"
#include "llvm/Method.h"
#include "llvm/SymbolTable.h"
#include "llvm/Type.h"
#include "llvm/iPHINode.h"
#include "llvm/CodeGen/MachineInstr.h"
// Instantiate Templates - This ugliness is the price we have to pay
// for having a ValueHolderImpl.h file seperate from ValueHolder.h! :(
//
template class ValueHolder<Instruction, BasicBlock, Method>;
BasicBlock::BasicBlock(const string &name, Method *Parent)
: Value(Type::LabelTy, Value::BasicBlockVal, name), InstList(this, 0),
machineInstrVec(new MachineCodeForBasicBlock) {
if (Parent)
Parent->getBasicBlocks().push_back(this);
}
BasicBlock::~BasicBlock() {
dropAllReferences();
InstList.delete_all();
delete machineInstrVec;
}
// Specialize setName to take care of symbol table majik
void BasicBlock::setName(const string &name, SymbolTable *ST) {
Method *P;
assert((ST == 0 || (!getParent() || ST == getParent()->getSymbolTable())) &&
"Invalid symtab argument!");
if ((P = getParent()) && hasName()) P->getSymbolTable()->remove(this);
Value::setName(name);
if (P && hasName()) P->getSymbolTable()->insert(this);
}
void BasicBlock::setParent(Method *parent) {
if (getParent() && hasName())
getParent()->getSymbolTable()->remove(this);
InstList.setParent(parent);
if (getParent() && hasName())
getParent()->getSymbolTableSure()->insert(this);
}
TerminatorInst *BasicBlock::getTerminator() {
if (InstList.empty()) return 0;
Instruction *T = InstList.back();
if (isa<TerminatorInst>(T)) return cast<TerminatorInst>(T);
return 0;
}
const TerminatorInst *const BasicBlock::getTerminator() const {
if (InstList.empty()) return 0;
if (const TerminatorInst *TI = dyn_cast<TerminatorInst>(InstList.back()))
return TI;
return 0;
}
void BasicBlock::dropAllReferences() {
for_each(InstList.begin(), InstList.end(),
std::mem_fun(&Instruction::dropAllReferences));
}
// hasConstantReferences() - This predicate is true if there is a
// reference to this basic block in the constant pool for this method. For
// example, if a block is reached through a switch table, that table resides
// in the constant pool, and the basic block is reference from it.
//
bool BasicBlock::hasConstantReferences() const {
for (use_const_iterator I = use_begin(), E = use_end(); I != E; ++I)
if (::isa<Constant>(*I))
return true;
return false;
}
// removePredecessor - This method is used to notify a BasicBlock that the
// specified Predecessor of the block is no longer able to reach it. This is
// actually not used to update the Predecessor list, but is actually used to
// update the PHI nodes that reside in the block. Note that this should be
// called while the predecessor still refers to this block.
//
void BasicBlock::removePredecessor(BasicBlock *Pred) {
assert(find(pred_begin(), pred_end(), Pred) != pred_end() &&
"removePredecessor: BB is not a predecessor!");
if (!isa<PHINode>(front())) return; // Quick exit.
pred_iterator PI(pred_begin()), EI(pred_end());
unsigned max_idx;
// Loop over the rest of the predecessors until we run out, or until we find
// out that there are more than 2 predecessors.
for (max_idx = 0; PI != EI && max_idx < 3; ++PI, ++max_idx) /*empty*/;
// If there are exactly two predecessors, then we want to nuke the PHI nodes
// altogether.
assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!");
if (max_idx <= 2) { // <= Two predecessors BEFORE I remove one?
// Yup, loop through and nuke the PHI nodes
while (PHINode *PN = dyn_cast<PHINode>(front())) {
PN->removeIncomingValue(Pred); // Remove the predecessor first...
assert(PN->getNumIncomingValues() == max_idx-1 &&
"PHI node shouldn't have this many values!!!");
// If the PHI _HAD_ two uses, replace PHI node with its now *single* value
if (max_idx == 2)
PN->replaceAllUsesWith(PN->getOperand(0));
delete getInstList().remove(begin()); // Remove the PHI node
}
} else {
// Okay, now we know that we need to remove predecessor #pred_idx from all
// PHI nodes. Iterate over each PHI node fixing them up
iterator II(begin());
for (; isa<PHINode>(*II); ++II)
cast<PHINode>(*II)->removeIncomingValue(Pred);
}
}
// splitBasicBlock - This splits a basic block into two at the specified
// instruction. Note that all instructions BEFORE the specified iterator stay
// as part of the original basic block, an unconditional branch is added to
// the new BB, and the rest of the instructions in the BB are moved to the new
// BB, including the old terminator. This invalidates the iterator.
//
// Note that this only works on well formed basic blocks (must have a
// terminator), and 'I' must not be the end of instruction list (which would
// cause a degenerate basic block to be formed, having a terminator inside of
// the basic block).
//
BasicBlock *BasicBlock::splitBasicBlock(iterator I) {
assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!");
assert(I != InstList.end() &&
"Trying to get me to create degenerate basic block!");
BasicBlock *New = new BasicBlock("", getParent());
// Go from the end of the basic block through to the iterator pointer, moving
// to the new basic block...
Instruction *Inst = 0;
do {
iterator EndIt = end();
Inst = InstList.remove(--EndIt); // Remove from end
New->InstList.push_front(Inst); // Add to front
} while (Inst != *I); // Loop until we move the specified instruction.
// Add a branch instruction to the newly formed basic block.
InstList.push_back(new BranchInst(New));
return New;
}
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