[clang] [clang][Interp] Integral pointers (PR #84159)

[Aaron Ballman via cfe-commits]

================
@@ -172,72 +217,107 @@ class Pointer {
         Adjust = sizeof(InitMapPtr);
       else
         Adjust = sizeof(InlineDescriptor);
-      return Pointer(Pointee, Base, Base + getSize() + Adjust);
+      return Pointer(asBlockPointer().Pointee, asBlockPointer().Base,
+                     asBlockPointer().Base + getSize() + Adjust);
     }
 
     // Do not step out of array elements.
-    if (Base != Offset)
+    if (asBlockPointer().Base != Offset)
       return *this;
 
     // If at base, point to an array of base types.
-    if (Base == 0 || Base == sizeof(InlineDescriptor))
-      return Pointer(Pointee, RootPtrMark, 0);
+    if (asBlockPointer().Base == 0 ||
+        asBlockPointer().Base == sizeof(InlineDescriptor))
+      return Pointer(asBlockPointer().Pointee, RootPtrMark, 0);
 
     // Step into the containing array, if inside one.
-    unsigned Next = Base - getInlineDesc()->Offset;
+    unsigned Next = asBlockPointer().Base - getInlineDesc()->Offset;
     const Descriptor *Desc =
         Next == 0 ? getDeclDesc() : getDescriptor(Next)->Desc;
     if (!Desc->IsArray)
       return *this;
-    return Pointer(Pointee, Next, Offset);
+    return Pointer(asBlockPointer().Pointee, Next, Offset);
   }
 
   /// Checks if the pointer is null.
-  bool isZero() const { return Pointee == nullptr; }
+  bool isZero() const {
+    if (Offset != 0)
+      return false;
+
+    if (isBlockPointer())
+      return asBlockPointer().Pointee == nullptr;
+    else if (isIntegralPointer())
+      return asIntPointer().Value == 0;
+    llvm_unreachable("zomg");
----------------
AaronBallman wrote:

```suggestion
    assert(isIntegralPointer() && "expected an integral pointer");
    return asIntPointer().Value == 0;
```

https://github.com/llvm/llvm-project/pull/84159