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

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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 c72e0a278d
commit 9b51fe4ab1
3 changed files with 12 additions and 37 deletions
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4
include/llvm/ADT/ilist_node.h
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

11
include/llvm/BasicBlock.h
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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;

34
lib/VMCore/BasicBlock.cpp
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();
}