[clang] [llvm] [AArch64][Driver] Fix behavior of +nofeat modifier on -mcpu (PR #203458)

[Tomas Matheson via cfe-commits]

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@@ -340,14 +340,22 @@ void AArch64::ExtensionSet::disable(ArchExtKind E) {
       disable(Dep.Later);
 }
 
+static void setEnableIfMandatory(AArch64::ExtensionSet &Exts,
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tommat01 wrote:

There aren't really any "mandatory" extensions as far as the compiler is concerned; you are free to avoid code generation for features even if they are required to be implemented in the CPU.

I'd probably inline this function and use the existing `ExtensionSet::addArchDefaults`.

https://github.com/llvm/llvm-project/pull/203458