aboutsummaryrefslogtreecommitdiff
path: root/lib/IR/BasicBlock.cpp
diff options
context:
space:
mode:
Diffstat (limited to 'lib/IR/BasicBlock.cpp')
-rw-r--r--lib/IR/BasicBlock.cpp371
1 files changed, 371 insertions, 0 deletions
diff --git a/lib/IR/BasicBlock.cpp b/lib/IR/BasicBlock.cpp
new file mode 100644
index 000000000000..41e58ec5da2d
--- /dev/null
+++ b/lib/IR/BasicBlock.cpp
@@ -0,0 +1,371 @@
+//===-- BasicBlock.cpp - Implement BasicBlock related methods -------------===//
+//
+// 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 IR library.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/IR/BasicBlock.h"
+#include "SymbolTableListTraitsImpl.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Type.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/Support/LeakDetector.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>;
+
+
+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.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);
+}
+
+/// 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);
+}
+
+/// 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;
+ return dyn_cast<TerminatorInst>(&InstList.back());
+}
+
+const TerminatorInst *BasicBlock::getTerminator() const {
+ if (InstList.empty()) 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 an invalid basic
+ // block we'll get an assertion failure when dereferencing
+ // a past-the-end iterator.
+ while (isa<PHINode>(i)) ++i;
+ return &*i;
+}
+
+Instruction* BasicBlock::getFirstNonPHIOrDbg() {
+ 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) || isa<DbgInfoIntrinsic>(i)) ++i;
+ return &*i;
+}
+
+Instruction* BasicBlock::getFirstNonPHIOrDbgOrLifetime() {
+ // 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.
+ BasicBlock::iterator i = begin();
+ for (;; ++i) {
+ if (isa<PHINode>(i) || isa<DbgInfoIntrinsic>(i))
+ continue;
+
+ const IntrinsicInst *II = dyn_cast<IntrinsicInst>(i);
+ if (!II)
+ break;
+ if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
+ II->getIntrinsicID() != Intrinsic::lifetime_end)
+ break;
+ }
+ return &*i;
+}
+
+BasicBlock::iterator BasicBlock::getFirstInsertionPt() {
+ iterator InsertPt = getFirstNonPHI();
+ if (isa<LandingPadInst>(InsertPt)) ++InsertPt;
+ return InsertPt;
+}
+
+void BasicBlock::dropAllReferences() {
+ for(iterator I = begin(), E = end(); I != E; ++I)
+ I->dropAllReferences();
+}
+
+/// 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*/;
+}
+
+/// 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;
+}
+
+/// 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 (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);
+
+ // 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->getIncomingValue(0) != PN)
+ PN->replaceAllUsesWith(PN->getIncomingValue(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()))
+ if (PNV != PN) {
+ 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, 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!");
+
+ BasicBlock *InsertBefore = llvm::next(Function::iterator(this))
+ .getNodePtrUnchecked();
+ BasicBlock *New = BasicBlock::Create(getContext(), BBName,
+ getParent(), InsertBefore);
+
+ // 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.
+ 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;
+}
+
+void BasicBlock::replaceSuccessorsPhiUsesWith(BasicBlock *New) {
+ TerminatorInst *TI = getTerminator();
+ if (!TI)
+ // Cope with being called on a BasicBlock that doesn't have a terminator
+ // yet. Clang's CodeGenFunction::EmitReturnBlock() likes to do this.
+ return;
+ for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) {
+ BasicBlock *Succ = TI->getSuccessor(i);
+ // N.B. Succ might not be a complete BasicBlock, so don't assume
+ // that it ends with a non-phi instruction.
+ for (iterator II = Succ->begin(), IE = Succ->end(); II != IE; ++II) {
+ PHINode *PN = dyn_cast<PHINode>(II);
+ if (!PN)
+ break;
+ int i;
+ while ((i = PN->getBasicBlockIndex(this)) >= 0)
+ PN->setIncomingBlock(i, New);
+ }
+ }
+}
+
+/// isLandingPad - Return true if this basic block is a landing pad. I.e., it's
+/// the destination of the 'unwind' edge of an invoke instruction.
+bool BasicBlock::isLandingPad() const {
+ return isa<LandingPadInst>(getFirstNonPHI());
+}
+
+/// getLandingPadInst() - Return the landingpad instruction associated with
+/// the landing pad.
+LandingPadInst *BasicBlock::getLandingPadInst() {
+ return dyn_cast<LandingPadInst>(getFirstNonPHI());
+}
+const LandingPadInst *BasicBlock::getLandingPadInst() const {
+ return dyn_cast<LandingPadInst>(getFirstNonPHI());
+}
generated by cgit v1.2.3 (git 2.25.1) at 2025-02-23 09:39:28 +0000