[clang] [lld] [llvm] [WIP][IR][Constants] Change the semantic of `ConstantPointerNull` to represent an actual `nullptr` instead of a zero-value pointer (PR #166667)

[Alexander Richardson via llvm-commits]

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@@ -1330,7 +1330,7 @@ TEST(InstructionsTest, ShuffleMaskIsReplicationMask) {
       for (int OpVF : seq_inclusive(VF, 2 * VF + 1)) {
         LLVMContext Ctx;
         Type *OpVFTy = FixedVectorType::get(IntegerType::getInt1Ty(Ctx), OpVF);
-        Value *Op = ConstantVector::getNullValue(OpVFTy);
+        Value *Op = Constant::getNullValue(OpVFTy);
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arichardson wrote:

```suggestion
        Value *Op = Constant::getZeroValue(OpVFTy);
```

https://github.com/llvm/llvm-project/pull/166667