Rename NumOperands to make it clear its managed by the User. NFC.

This is to try make it very clear that subclasses shouldn't be changing
the value directly.  Now that OperandList for normal instructions is computed
using the NumOperands, its critical that the NumOperands is accurate or we
could compute the wrong offset to the first operand.

I looked over all places which update NumOperands and they are all safe.
Hung off use User's don't use NumOperands to compute the OperandList so they
are safe to continue to manipulate it.  The only other User which changed it
was GlobalVariable which has an optional init list but always allocated space
for a single Use.  It was correctly setting NumOperands to 1 before setting an
initializer, and setting it to 0 after clearing the init list, so the order was safe.

Added some comments to that code to make sure that this isn't changed in future
without being aware of this constraint.

Reviewed by Duncan Exon Smith.

llvm-svn: 239621

1 files changed, 20 insertions, 19 deletions

diff --git a/llvm/lib/IR/Instructions.cpp b/llvm/lib/IR/Instructions.cpp
index dff31bee093..0e2fe391aa6 100644
--- a/llvm/lib/IR/Instructions.cpp
+++ b/llvm/lib/IR/Instructions.cpp
@@ -108,7 +108,7 @@ Value *PHINode::removeIncomingValue(unsigned Idx, bool DeletePHIIfEmpty) {
 
   // Nuke the last value.
   Op<-1>().set(nullptr);
-  --NumOperands;
+  setNumHungOffUseOperands(getNumOperands() - 1);
 
   // If the PHI node is dead, because it has zero entries, nuke it now.
   if (getNumOperands() == 0 && DeletePHIIfEmpty) {
@@ -199,7 +199,7 @@ LandingPadInst *LandingPadInst::Create(Type *RetTy, Value *PersonalityFn,
 void LandingPadInst::init(Value *PersFn, unsigned NumReservedValues,
                           const Twine &NameStr) {
   ReservedSpace = NumReservedValues;
-  NumOperands = 1;
+  setNumHungOffUseOperands(1);
   allocHungoffUses(ReservedSpace);
   Op<0>() = PersFn;
   setName(NameStr);
@@ -219,7 +219,7 @@ void LandingPadInst::addClause(Constant *Val) {
   unsigned OpNo = getNumOperands();
   growOperands(1);
   assert(OpNo < ReservedSpace && "Growing didn't work!");
-  ++NumOperands;
+  setNumHungOffUseOperands(getNumOperands() + 1);
   getOperandList()[OpNo] = Val;
 }
 
@@ -233,7 +233,7 @@ CallInst::~CallInst() {
 void CallInst::init(FunctionType *FTy, Value *Func, ArrayRef<Value *> Args,
                     const Twine &NameStr) {
   this->FTy = FTy;
-  assert(NumOperands == Args.size() + 1 && "NumOperands not set up?");
+  assert(getNumOperands() == Args.size() + 1 && "NumOperands not set up?");
   Op<-1>() = Func;
 
 #ifndef NDEBUG
@@ -254,7 +254,7 @@ void CallInst::init(FunctionType *FTy, Value *Func, ArrayRef<Value *> Args,
 void CallInst::init(Value *Func, const Twine &NameStr) {
   FTy =
       cast<FunctionType>(cast<PointerType>(Func->getType())->getElementType());
-  assert(NumOperands == 1 && "NumOperands not set up?");
+  assert(getNumOperands() == 1 && "NumOperands not set up?");
   Op<-1>() = Func;
 
   assert(FTy->getNumParams() == 0 && "Calling a function with bad signature");
@@ -509,7 +509,7 @@ void InvokeInst::init(FunctionType *FTy, Value *Fn, BasicBlock *IfNormal,
                       const Twine &NameStr) {
   this->FTy = FTy;
 
-  assert(NumOperands == 3 + Args.size() && "NumOperands not set up?");
+  assert(getNumOperands() == 3 + Args.size() && "NumOperands not set up?");
   Op<-3>() = Fn;
   Op<-2>() = IfNormal;
   Op<-1>() = IfException;
@@ -1205,7 +1205,8 @@ FenceInst::FenceInst(LLVMContext &C, AtomicOrdering Ordering,
 
 void GetElementPtrInst::init(Value *Ptr, ArrayRef<Value *> IdxList,
                              const Twine &Name) {
-  assert(NumOperands == 1 + IdxList.size() && "NumOperands not initialized?");
+  assert(getNumOperands() == 1 + IdxList.size() &&
+         "NumOperands not initialized?");
   Op<0>() = Ptr;
   std::copy(IdxList.begin(), IdxList.end(), op_begin() + 1);
   setName(Name);
@@ -1518,7 +1519,7 @@ void ShuffleVectorInst::getShuffleMask(Constant *Mask,
 
 void InsertValueInst::init(Value *Agg, Value *Val, ArrayRef<unsigned> Idxs, 
                            const Twine &Name) {
-  assert(NumOperands == 2 && "NumOperands not initialized?");
+  assert(getNumOperands() == 2 && "NumOperands not initialized?");
 
   // There's no fundamental reason why we require at least one index
   // (other than weirdness with &*IdxBegin being invalid; see
@@ -1549,7 +1550,7 @@ InsertValueInst::InsertValueInst(const InsertValueInst &IVI)
 //===----------------------------------------------------------------------===//
 
 void ExtractValueInst::init(ArrayRef<unsigned> Idxs, const Twine &Name) {
-  assert(NumOperands == 1 && "NumOperands not initialized?");
+  assert(getNumOperands() == 1 && "NumOperands not initialized?");
 
   // There's no fundamental reason why we require at least one index.
   // But there's no present need to support it.
@@ -3263,7 +3264,7 @@ bool CmpInst::isFalseWhenEqual(unsigned short predicate) {
 void SwitchInst::init(Value *Value, BasicBlock *Default, unsigned NumReserved) {
   assert(Value && Default && NumReserved);
   ReservedSpace = NumReserved;
-  NumOperands = 2;
+  setNumHungOffUseOperands(2);
   allocHungoffUses(ReservedSpace);
 
   Op<0>() = Value;
@@ -3295,7 +3296,7 @@ SwitchInst::SwitchInst(Value *Value, BasicBlock *Default, unsigned NumCases,
 SwitchInst::SwitchInst(const SwitchInst &SI)
   : TerminatorInst(SI.getType(), Instruction::Switch, nullptr, 0) {
   init(SI.getCondition(), SI.getDefaultDest(), SI.getNumOperands());
-  NumOperands = SI.getNumOperands();
+  setNumHungOffUseOperands(SI.getNumOperands());
   Use *OL = getOperandList();
   const Use *InOL = SI.getOperandList();
   for (unsigned i = 2, E = SI.getNumOperands(); i != E; i += 2) {
@@ -3309,13 +3310,13 @@ SwitchInst::SwitchInst(const SwitchInst &SI)
 /// addCase - Add an entry to the switch instruction...
 ///
 void SwitchInst::addCase(ConstantInt *OnVal, BasicBlock *Dest) {
-  unsigned NewCaseIdx = getNumCases(); 
-  unsigned OpNo = NumOperands;
+  unsigned NewCaseIdx = getNumCases();
+  unsigned OpNo = getNumOperands();
   if (OpNo+2 > ReservedSpace)
     growOperands();  // Get more space!
   // Initialize some new operands.
   assert(OpNo+1 < ReservedSpace && "Growing didn't work!");
-  NumOperands = OpNo+2;
+  setNumHungOffUseOperands(OpNo+2);
   CaseIt Case(this, NewCaseIdx);
   Case.setValue(OnVal);
   Case.setSuccessor(Dest);
@@ -3340,7 +3341,7 @@ void SwitchInst::removeCase(CaseIt i) {
   // Nuke the last value.
   OL[NumOps-2].set(nullptr);
   OL[NumOps-2+1].set(nullptr);
-  NumOperands = NumOps-2;
+  setNumHungOffUseOperands(NumOps-2);
 }
 
 /// growOperands - grow operands - This grows the operand list in response
@@ -3373,7 +3374,7 @@ void IndirectBrInst::init(Value *Address, unsigned NumDests) {
   assert(Address && Address->getType()->isPointerTy() &&
          "Address of indirectbr must be a pointer");
   ReservedSpace = 1+NumDests;
-  NumOperands = 1;
+  setNumHungOffUseOperands(1);
   allocHungoffUses(ReservedSpace);
 
   Op<0>() = Address;
@@ -3419,12 +3420,12 @@ IndirectBrInst::IndirectBrInst(const IndirectBrInst &IBI)
 /// addDestination - Add a destination.
 ///
 void IndirectBrInst::addDestination(BasicBlock *DestBB) {
-  unsigned OpNo = NumOperands;
+  unsigned OpNo = getNumOperands();
   if (OpNo+1 > ReservedSpace)
     growOperands();  // Get more space!
   // Initialize some new operands.
   assert(OpNo < ReservedSpace && "Growing didn't work!");
-  NumOperands = OpNo+1;
+  setNumHungOffUseOperands(OpNo+1);
   getOperandList()[OpNo] = DestBB;
 }
 
@@ -3441,7 +3442,7 @@ void IndirectBrInst::removeDestination(unsigned idx) {
   
   // Nuke the last value.
   OL[NumOps-1].set(nullptr);
-  NumOperands = NumOps-1;
+  setNumHungOffUseOperands(NumOps-1);
 }
 
 BasicBlock *IndirectBrInst::getSuccessorV(unsigned idx) const {