[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 cfe-commits]

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@@ -5,8 +5,8 @@
 
 ; CHECK-NOT: bitcast
 ; CHECK-NOT: trunc
-; CHECK: addrspacecast
-; CHECK: addrspacecast
+; CHECK: ptr addrspace(1) null
+; CHECK: ptr null
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arichardson wrote:

Unrelated to this PR but these checks are not great, can we regen this test with UTC and --check-globals and pre-commit that?

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