-//===-- BasicBlock.cpp - Implement BasicBlock related functions --*- C++ -*--=//
+//===-- BasicBlock.cpp - Implement BasicBlock related methods -------------===//
//
-// This file implements the Method class for the VMCore library.
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the BasicBlock class for the VMCore library.
//
//===----------------------------------------------------------------------===//
-#include "llvm/ValueHolderImpl.h"
#include "llvm/BasicBlock.h"
-#include "llvm/iTerminators.h"
-#include "llvm/Module.h"
-#include "llvm/Method.h"
-#include "llvm/SymbolTable.h"
+#include "llvm/Constants.h"
+#include "llvm/Instructions.h"
#include "llvm/Type.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/Support/LeakDetector.h"
+#include "llvm/Support/Compiler.h"
+#include "SymbolTableListTraitsImpl.h"
+#include <algorithm>
+using namespace llvm;
-// 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>;
+inline ValueSymbolTable *
+ilist_traits<Instruction>::getSymTab(BasicBlock *BB) {
+ if (BB)
+ if (Function *F = BB->getParent())
+ return &F->getValueSymbolTable();
+ return 0;
+}
+
+
+namespace {
+ /// DummyInst - An instance of this class is used to mark the end of the
+ /// instruction list. This is not a real instruction.
+ struct VISIBILITY_HIDDEN DummyInst : public Instruction {
+ DummyInst() : Instruction(Type::VoidTy, OtherOpsEnd, 0, 0) {
+ // This should not be garbage monitored.
+ LeakDetector::removeGarbageObject(this);
+ }
+
+ Instruction *clone() const {
+ assert(0 && "Cannot clone EOL");abort();
+ return 0;
+ }
+ const char *getOpcodeName() const { return "*end-of-list-inst*"; }
+
+ // Methods for support type inquiry through isa, cast, and dyn_cast...
+ static inline bool classof(const DummyInst *) { return true; }
+ static inline bool classof(const Instruction *I) {
+ return I->getOpcode() == OtherOpsEnd;
+ }
+ static inline bool classof(const Value *V) {
+ return isa<Instruction>(V) && classof(cast<Instruction>(V));
+ }
+ };
+}
-BasicBlock::BasicBlock(const string &name, Method *parent)
- : Value(Type::LabelTy, Value::BasicBlockVal, name), InstList(this, 0) {
+Instruction *ilist_traits<Instruction>::createSentinel() {
+ return new DummyInst();
+}
+iplist<Instruction> &ilist_traits<Instruction>::getList(BasicBlock *BB) {
+ return BB->getInstList();
+}
+
+// Explicit instantiation of SymbolTableListTraits since some of the methods
+// are not in the public header file...
+template class SymbolTableListTraits<Instruction, BasicBlock>;
+
+
+BasicBlock::BasicBlock(const std::string &Name, Function *NewParent,
+ BasicBlock *InsertBefore, BasicBlock *Dest)
+ : User(Type::LabelTy, Value::BasicBlockVal, &unwindDest, 0), Parent(0) {
+
+ // Make sure that we get added to a function
+ LeakDetector::addGarbageObject(this);
- if (parent)
- parent->getBasicBlocks().push_back(this);
+ if (InsertBefore) {
+ assert(NewParent &&
+ "Cannot insert block before another block with no function!");
+ NewParent->getBasicBlockList().insert(InsertBefore, this);
+ } else if (NewParent) {
+ NewParent->getBasicBlockList().push_back(this);
+ }
+
+ setName(Name);
+ unwindDest.init(NULL, this);
+ setUnwindDest(Dest);
}
+
BasicBlock::~BasicBlock() {
+ assert(getParent() == 0 && "BasicBlock still linked into the program!");
dropAllReferences();
- InstList.delete_all();
+ InstList.clear();
+}
+
+void BasicBlock::setParent(Function *parent) {
+ if (getParent())
+ LeakDetector::addGarbageObject(this);
+
+ // Set Parent=parent, updating instruction symtab entries as appropriate.
+ InstList.setSymTabObject(&Parent, parent);
+
+ if (getParent())
+ LeakDetector::removeGarbageObject(this);
+}
+
+void BasicBlock::removeFromParent() {
+ getParent()->getBasicBlockList().remove(this);
+}
+
+void BasicBlock::eraseFromParent() {
+ getParent()->getBasicBlockList().erase(this);
}
-// Specialize setName to take care of symbol table majik
-void BasicBlock::setName(const string &name) {
- Method *P;
- if ((P = getParent()) && hasName()) P->getSymbolTable()->remove(this);
- Value::setName(name);
- if (P && hasName()) P->getSymbolTable()->insert(this);
+const BasicBlock *BasicBlock::getUnwindDest() const {
+ return cast_or_null<const BasicBlock>(unwindDest.get());
}
-void BasicBlock::setParent(Method *parent) {
- if (getParent() && hasName())
- getParent()->getSymbolTable()->remove(this);
+BasicBlock *BasicBlock::getUnwindDest() {
+ return cast_or_null<BasicBlock>(unwindDest.get());
+}
+
+void BasicBlock::setUnwindDest(BasicBlock *dest) {
+ NumOperands = unwindDest ? 1 : 0;
+ unwindDest.set(dest);
+}
- InstList.setParent(parent);
+/// moveBefore - Unlink this basic block from its current function and
+/// insert it into the function that MovePos lives in, right before MovePos.
+void BasicBlock::moveBefore(BasicBlock *MovePos) {
+ MovePos->getParent()->getBasicBlockList().splice(MovePos,
+ getParent()->getBasicBlockList(), this);
+}
- if (getParent() && hasName())
- getParent()->getSymbolTableSure()->insert(this);
+/// moveAfter - Unlink this basic block from its current function and
+/// insert it into the function that MovePos lives in, right after MovePos.
+void BasicBlock::moveAfter(BasicBlock *MovePos) {
+ Function::iterator I = MovePos;
+ MovePos->getParent()->getBasicBlockList().splice(++I,
+ getParent()->getBasicBlockList(), this);
}
+
TerminatorInst *BasicBlock::getTerminator() {
if (InstList.empty()) return 0;
- Instruction *T = InstList.back();
- if (T->isTerminator()) return (TerminatorInst*)T;
- return 0;
+ return dyn_cast<TerminatorInst>(&InstList.back());
}
-const TerminatorInst *const BasicBlock::getTerminator() const {
+const TerminatorInst *BasicBlock::getTerminator() const {
if (InstList.empty()) return 0;
- const Instruction *T = InstList.back();
- if (T->isTerminator()) return (TerminatorInst*)T;
- return 0;
+ return dyn_cast<TerminatorInst>(&InstList.back());
+}
+
+Instruction* BasicBlock::getFirstNonPHI()
+{
+ BasicBlock::iterator i = begin();
+ // All valid basic blocks should have a terminator,
+ // which is not a PHINode. If we have invalid basic
+ // block we'll get assert when dereferencing past-the-end
+ // iterator.
+ while (isa<PHINode>(i)) ++i;
+ return &*i;
}
void BasicBlock::dropAllReferences() {
- for_each(InstList.begin(), InstList.end(),
- std::mem_fun(&Instruction::dropAllReferences));
+ setUnwindDest(NULL);
+ for(iterator I = begin(), E = end(); I != E; ++I)
+ I->dropAllReferences();
}
-// hasConstantPoolReferences() - 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::hasConstantPoolReferences() const {
- for (use_const_iterator I = use_begin(), E = use_end(); I != E; ++I)
- if ((*I)->getValueType() == ConstantVal)
- return true;
+/// getSinglePredecessor - If this basic block has a single predecessor block,
+/// return the block, otherwise return a null pointer.
+BasicBlock *BasicBlock::getSinglePredecessor() {
+ pred_iterator PI = pred_begin(this), E = pred_end(this);
+ if (PI == E) return 0; // No preds.
+ BasicBlock *ThePred = *PI;
+ ++PI;
+ return (PI == E) ? ThePred : 0 /*multiple preds*/;
+}
+
+/// 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,
+ bool DontDeleteUselessPHIs) {
+ assert((hasNUsesOrMore(16)||// Reduce cost of this assertion for complex CFGs.
+ find(pred_begin(this), pred_end(this), Pred) != pred_end(this)) &&
+ "removePredecessor: BB is not a predecessor!");
+
+ if (Pred == getUnwindDest())
+ setUnwindDest(NULL);
+
+ if (InstList.empty()) return;
+ PHINode *APN = dyn_cast<PHINode>(&front());
+ if (!APN) return; // Quick exit.
+
+ // If there are exactly two predecessors, then we want to nuke the PHI nodes
+ // altogether. However, we cannot do this, if this in this case:
+ //
+ // Loop:
+ // %x = phi [X, Loop]
+ // %x2 = add %x, 1 ;; This would become %x2 = add %x2, 1
+ // br Loop ;; %x2 does not dominate all uses
+ //
+ // This is because the PHI node input is actually taken from the predecessor
+ // basic block. The only case this can happen is with a self loop, so we
+ // check for this case explicitly now.
+ //
+ unsigned max_idx = APN->getNumIncomingValues();
+ assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!");
+ if (max_idx == 2) {
+ BasicBlock *Other = APN->getIncomingBlock(APN->getIncomingBlock(0) == Pred);
- return false;
+ // Disable PHI elimination!
+ if (this == Other) max_idx = 3;
+ }
+
+ // <= Two predecessors BEFORE I remove one?
+ if (max_idx <= 2 && !DontDeleteUselessPHIs) {
+ // Yup, loop through and nuke the PHI nodes
+ while (PHINode *PN = dyn_cast<PHINode>(&front())) {
+ // Remove the predecessor first.
+ PN->removeIncomingValue(Pred, !DontDeleteUselessPHIs);
+
+ // If the PHI _HAD_ two uses, replace PHI node with its now *single* value
+ if (max_idx == 2) {
+ if (PN->getOperand(0) != PN)
+ PN->replaceAllUsesWith(PN->getOperand(0));
+ else
+ // We are left with an infinite loop with no entries: kill the PHI.
+ PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
+ getInstList().pop_front(); // Remove the PHI node
+ }
+
+ // If the PHI node already only had one entry, it got deleted by
+ // removeIncomingValue.
+ }
+ } 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
+ PHINode *PN;
+ for (iterator II = begin(); (PN = dyn_cast<PHINode>(II)); ) {
+ ++II;
+ PN->removeIncomingValue(Pred, false);
+ // If all incoming values to the Phi are the same, we can replace the Phi
+ // with that value.
+ Value* PNV = 0;
+ if (!DontDeleteUselessPHIs && (PNV = PN->hasConstantValue())) {
+ PN->replaceAllUsesWith(PNV);
+ PN->eraseFromParent();
+ }
+ }
+ }
}
-// 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(InstListType::iterator I) {
+/// 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, const std::string &BBName) {
assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!");
- assert(I != InstList.end() &&
- "Trying to get me to create degenerate basic block!");
+ assert(I != InstList.end() &&
+ "Trying to get me to create degenerate basic block!");
- BasicBlock *New = new BasicBlock("", getParent());
+ BasicBlock *New = new BasicBlock(BBName, getParent(), getNext());
- // Go from the end of the basic block through to the iterator pointer, moving
- // to the new basic block...
- Instruction *Inst = 0;
- do {
- InstListType::iterator EndIt = InstList.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.
+ // Move all of the specified instructions from the original basic block into
+ // the new basic block.
+ New->getInstList().splice(New->end(), this->getInstList(), I, end());
// Add a branch instruction to the newly formed basic block.
- InstList.push_back(new BranchInst(New));
+ new BranchInst(New, this);
+
+ // Now we must loop through all of the successors of the New block (which
+ // _were_ the successors of the 'this' block), and update any PHI nodes in
+ // successors. If there were PHI nodes in the successors, then they need to
+ // know that incoming branches will be from New, not from Old.
+ //
+ for (succ_iterator I = succ_begin(New), E = succ_end(New); I != E; ++I) {
+ // Loop over any phi nodes in the basic block, updating the BB field of
+ // incoming values...
+ BasicBlock *Successor = *I;
+ PHINode *PN;
+ for (BasicBlock::iterator II = Successor->begin();
+ (PN = dyn_cast<PHINode>(II)); ++II) {
+ int IDX = PN->getBasicBlockIndex(this);
+ while (IDX != -1) {
+ PN->setIncomingBlock((unsigned)IDX, New);
+ IDX = PN->getBasicBlockIndex(this);
+ }
+ }
+ }
return New;
}