Introduce a new technique for merging BasicBlock with Instruction sentinel by superposition.

This looks dangerous, but isn't because the sentinel is accessed in special way only,
namely the Next and Prev fields of it, and these are guaranteed to exist.

llvm-svn: 65626
This commit is contained in:
Gabor Greif 2009-02-27 08:41:37 +00:00
parent 918ae24edd
commit bf4da856e4
3 changed files with 12 additions and 37 deletions

View File

@ -20,6 +20,9 @@ namespace llvm {
template<typename NodeTy>
struct ilist_nextprev_traits;
template<typename NodeTy>
struct ilist_traits;
/// ilist_node - Base class that provides next/prev services for nodes
/// that use ilist_nextprev_traits or ilist_default_traits.
///
@ -36,6 +39,7 @@ private:
void setNext(NodeTy *N) { Next = N; }
protected:
ilist_node() : Prev(0), Next(0) {}
friend struct ilist_traits<NodeTy>;
};
} // End llvm namespace

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@ -26,11 +26,15 @@ class TerminatorInst;
template<> struct ilist_traits<Instruction>
: public SymbolTableListTraits<Instruction, BasicBlock> {
// createSentinel is used to create a node that marks the end of the list...
static Instruction *createSentinel();
static void destroySentinel(Instruction *I) { delete I; }
Instruction *createSentinel() const {
return const_cast<Instruction*>(static_cast<const Instruction*>(&Sentinel));
}
static void destroySentinel(Instruction *I) { }
static iplist<Instruction> &getList(BasicBlock *BB);
static ValueSymbolTable *getSymTab(BasicBlock *ItemParent);
static int getListOffset();
private:
ilist_node<Instruction> Sentinel;
};
/// This represents a single basic block in LLVM. A basic block is simply a
@ -49,9 +53,10 @@ template<> struct ilist_traits<Instruction>
/// @brief LLVM Basic Block Representation
class BasicBlock : public Value, // Basic blocks are data objects also
public ilist_node<BasicBlock> {
public:
typedef iplist<Instruction> InstListType;
private :
private:
InstListType InstList;
Function *Parent;

View File

@ -31,40 +31,6 @@ ilist_traits<Instruction>::getSymTab(BasicBlock *BB) {
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 {
// allocate space for exactly zero operands
void *operator new(size_t s) {
return User::operator new(s, 0);
}
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));
}
};
}
Instruction *ilist_traits<Instruction>::createSentinel() {
return new DummyInst();
}
iplist<Instruction> &ilist_traits<Instruction>::getList(BasicBlock *BB) {
return BB->getInstList();
}