[IR] Use LLVM_ENABLE_ABI_BREAKING_CHECKS to guard ABI changes.

Incorrect usage of NDEBUG to guard ABI changes can prevent clients
from enabling assertions for their C++ code while having assertions in
LLVM turned off. So we use LLVM_ENABLE_ABI_BREAKING_CHECKS instead, as
described in llvm/docs/ProgrammersManual.rst. Most types already use this
macro, however, there were a couple of stragglers in ValueHandle.h, which
are fixed by this revision.

Reviewed By: dblaikie, dexonsmith

Differential Revision: https://reviews.llvm.org/D93433

llvm/include/llvm/IR/ValueHandle.h

@@ -258,13 +258,13 @@ template <> struct simplify_type<const WeakTrackingVH> {
 /// class turns into a trivial wrapper around a pointer.
 template <typename ValueTy>
 class AssertingVH
-#ifndef NDEBUG
-  : public ValueHandleBase
+#if LLVM_ENABLE_ABI_BREAKING_CHECKS
+    : public ValueHandleBase
 #endif
-  {
+{
   friend struct DenseMapInfo<AssertingVH<ValueTy>>;
 
-#ifndef NDEBUG
+#if LLVM_ENABLE_ABI_BREAKING_CHECKS
   Value *getRawValPtr() const { return ValueHandleBase::getValPtr(); }
   void setRawValPtr(Value *P) { ValueHandleBase::operator=(P); }
 #else
@@ -280,7 +280,7 @@ class AssertingVH
   void setValPtr(ValueTy *P) { setRawValPtr(GetAsValue(P)); }
 
 public:
-#ifndef NDEBUG
+#if LLVM_ENABLE_ABI_BREAKING_CHECKS
   AssertingVH() : ValueHandleBase(Assert) {}
   AssertingVH(ValueTy *P) : ValueHandleBase(Assert, GetAsValue(P)) {}
   AssertingVH(const AssertingVH &RHS) : ValueHandleBase(Assert, RHS) {}
@@ -443,7 +443,7 @@ public:
 /// class turns into a trivial wrapper around a pointer.
 template <typename ValueTy>
 class PoisoningVH
-#ifndef NDEBUG
+#if LLVM_ENABLE_ABI_BREAKING_CHECKS
     final : public CallbackVH
 #endif
 {
@@ -453,7 +453,7 @@ class PoisoningVH
   static Value *GetAsValue(Value *V) { return V; }
   static Value *GetAsValue(const Value *V) { return const_cast<Value *>(V); }
 
-#ifndef NDEBUG
+#if LLVM_ENABLE_ABI_BREAKING_CHECKS
   /// A flag tracking whether this value has been poisoned.
   ///
   /// On delete and RAUW, we leave the value pointer alone so that as a raw
@@ -478,7 +478,7 @@ class PoisoningVH
     Poisoned = true;
     RemoveFromUseList();
   }
-#else // NDEBUG
+#else // LLVM_ENABLE_ABI_BREAKING_CHECKS
   Value *ThePtr = nullptr;
 
   Value *getRawValPtr() const { return ThePtr; }
@@ -493,7 +493,7 @@ class PoisoningVH
 
 public:
   PoisoningVH() = default;
-#ifndef NDEBUG
+#if LLVM_ENABLE_ABI_BREAKING_CHECKS
   PoisoningVH(ValueTy *P) : CallbackVH(GetAsValue(P)) {}
   PoisoningVH(const PoisoningVH &RHS)
       : CallbackVH(RHS), Poisoned(RHS.Poisoned) {}