[clang] [CIR] Match OGCG noalias and memory effects on operator new (PR #221818)

[Andy Kaylor via cfe-commits]

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@@ -1931,19 +1890,22 @@ def CIR_SideEffect : CIR_I32Enum<
       `__attribute__((pure))`.
     - const: The function or callee may not read or write data from memory. This
       has the same effect as the GNU C/C++ attribute `__attribute__((const))`.
+    - inaccessible_or_errno: The function or callee may only access inaccessible
+      memory and errno. This matches LLVM
+      `memory(inaccessiblemem: readwrite, errnomem: write)` used for sane
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andykaylor wrote:

Should we just jump to modeling memory effects the same way the LLVM dialect does? Or maybe even just use `LLVM::MemoryEffectsAttr` directly?

https://github.com/llvm/llvm-project/pull/221818