[clang] [clang] Fix Variable Length Array `_Countof` Crash (PR #154627)

[Aaron Ballman via cfe-commits]

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@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -std=c2y -verify %s
+// RUN: %clang_cc1 -std=c2y -verify -fexperimental-new-constant-interpreter %s
+// expected-no-diagnostics
+
+void gh152826(char (*a)[*][5], int (*x)[_Countof (*a)]);
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AaronBallman wrote:

We should also add a codegen test to verify that we emit the correct LLVM IR to runtime evaluate the `_Countof`

https://github.com/llvm/llvm-project/pull/154627