-//===-- 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/iTerminators.h"
-#include "llvm/SymbolTable.h"
+#include "llvm/BasicBlock.h"
+#include "llvm/Constants.h"
+#include "llvm/Instructions.h"
+#include "llvm/LLVMContext.h"
#include "llvm/Type.h"
+#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/CFG.h"
-#include "llvm/iPHINode.h"
-#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/Support/LeakDetector.h"
+#include "SymbolTableListTraitsImpl.h"
+#include <algorithm>
+using namespace llvm;
+
+ValueSymbolTable *BasicBlock::getValueSymbolTable() {
+ if (Function *F = getParent())
+ return &F->getValueSymbolTable();
+ return 0;
+}
+
+LLVMContext &BasicBlock::getContext() const {
+ return getType()->getContext();
+}
+
+// Explicit instantiation of SymbolTableListTraits since some of the methods
+// are not in the public header file...
+template class llvm::SymbolTableListTraits<Instruction, BasicBlock>;
-// 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 std::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(LLVMContext &C, const Twine &Name, Function *NewParent,
+ BasicBlock *InsertBefore)
+ : Value(Type::getLabelTy(C), Value::BasicBlockVal), Parent(0) {
+
+ // Make sure that we get added to a function
+ LeakDetector::addGarbageObject(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);
}
+
BasicBlock::~BasicBlock() {
+ // If the address of the block is taken and it is being deleted (e.g. because
+ // it is dead), this means that there is either a dangling constant expr
+ // hanging off the block, or an undefined use of the block (source code
+ // expecting the address of a label to keep the block alive even though there
+ // is no indirect branch). Handle these cases by zapping the BlockAddress
+ // nodes. There are no other possible uses at this point.
+ if (hasAddressTaken()) {
+ assert(!use_empty() && "There should be at least one blockaddress!");
+ Constant *Replacement =
+ ConstantInt::get(llvm::Type::getInt32Ty(getContext()), 1);
+ while (!use_empty()) {
+ BlockAddress *BA = cast<BlockAddress>(use_back());
+ BA->replaceAllUsesWith(ConstantExpr::getIntToPtr(Replacement,
+ BA->getType()));
+ BA->destroyConstant();
+ }
+ }
+
+ assert(getParent() == 0 && "BasicBlock still linked into the program!");
dropAllReferences();
- InstList.delete_all();
- delete machineInstrVec;
+ InstList.clear();
}
-// Specialize setName to take care of symbol table majik
-void BasicBlock::setName(const std::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(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::setParent(Method *parent) {
- if (getParent() && hasName())
- getParent()->getSymbolTable()->remove(this);
+void BasicBlock::removeFromParent() {
+ getParent()->getBasicBlockList().remove(this);
+}
+
+void BasicBlock::eraseFromParent() {
+ getParent()->getBasicBlockList().erase(this);
+}
- 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 (isa<TerminatorInst>(T)) return cast<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;
- if (const TerminatorInst *TI = dyn_cast<TerminatorInst>(InstList.back()))
- return TI;
- return 0;
+ return dyn_cast<TerminatorInst>(&InstList.back());
}
-void BasicBlock::dropAllReferences() {
- for_each(InstList.begin(), InstList.end(),
- std::mem_fun(&Instruction::dropAllReferences));
+Instruction* BasicBlock::getFirstNonPHI() {
+ BasicBlock::iterator i = begin();
+ // All valid basic blocks should have a terminator,
+ // which is not a PHINode. If we have an invalid basic
+ // block we'll get an assertion failure when dereferencing
+ // a past-the-end iterator.
+ while (isa<PHINode>(i)) ++i;
+ return &*i;
}
-// 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;
+void BasicBlock::dropAllReferences() {
+ for(iterator I = begin(), E = end(); I != E; ++I)
+ I->dropAllReferences();
+}
- return false;
+/// 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) {
- assert(find(pred_begin(this), pred_end(this), Pred) != pred_end(this) &&
- "removePredecessor: BB is not a predecessor!");
- if (!isa<PHINode>(front())) return; // Quick exit.
+/// getUniquePredecessor - If this basic block has a unique predecessor block,
+/// return the block, otherwise return a null pointer.
+/// Note that unique predecessor doesn't mean single edge, there can be
+/// multiple edges from the unique predecessor to this block (for example
+/// a switch statement with multiple cases having the same destination).
+BasicBlock *BasicBlock::getUniquePredecessor() {
+ pred_iterator PI = pred_begin(this), E = pred_end(this);
+ if (PI == E) return 0; // No preds.
+ BasicBlock *PredBB = *PI;
+ ++PI;
+ for (;PI != E; ++PI) {
+ if (*PI != PredBB)
+ return 0;
+ // The same predecessor appears multiple times in the predecessor list.
+ // This is OK.
+ }
+ return PredBB;
+}
- pred_iterator PI(pred_begin(this)), EI(pred_end(this));
- unsigned max_idx;
+/// 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!");
- // 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 (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.
+ // 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) { // <= Two predecessors BEFORE I remove one?
+ if (max_idx == 2) {
+ BasicBlock *Other = APN->getIncomingBlock(APN->getIncomingBlock(0) == Pred);
+
+ // 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())) {
- PN->removeIncomingValue(Pred); // Remove the predecessor first...
-
- assert(PN->getNumIncomingValues() == max_idx-1 &&
- "PHI node shouldn't have this many values!!!");
+ 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)
- PN->replaceAllUsesWith(PN->getOperand(0));
- delete getInstList().remove(begin()); // Remove the PHI node
+ 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
- iterator II(begin());
- for (; isa<PHINode>(*II); ++II)
- cast<PHINode>(*II)->removeIncomingValue(Pred);
+ 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(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 Twine &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 *InsertBefore = llvm::next(Function::iterator(this))
+ .getNodePtrUnchecked();
+ BasicBlock *New = BasicBlock::Create(getContext(), BBName,
+ getParent(), InsertBefore);
- // 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.
+ // 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));
+ BranchInst::Create(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;
}
+
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