[clang] [lld] [llvm] [RISCV] Make A implies Zaamo and Zalrsc (PR #116907)

[Sam Elliott via cfe-commits]

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@@ -203,9 +203,28 @@ def HasStdExtM : Predicate<"Subtarget->hasStdExtM()">,
 
 // Atomic Extensions
 
+def FeatureStdExtZaamo
+    : RISCVExtension<"zaamo", 1, 0,
+                     "'Zaamo' (Atomic Memory Operations)">;
+def HasStdExtAOrZaamo
+    : Predicate<"Subtarget->hasStdExtZaamo()">,
+      AssemblerPredicate<(any_of FeatureStdExtZaamo),
+                         "'A' (Atomic Instructions) or "
+                         "'Zaamo' (Atomic Memory Operations)">;
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lenary wrote:

```suggestion
def HasStdExtZaamo
    : Predicate<"Subtarget->hasStdExtZaamo()">,
      AssemblerPredicate<(any_of FeatureStdExtZaamo),
                         "'Zaamo' (Atomic Memory Operations)">;
```

Can we (eventually) do this cleanup (and similar for `HasStdExtAOrZalrsc`). Probably not in this PR, but it's nicer when the names and descriptions of the predicates line up closer with the extensions.

https://github.com/llvm/llvm-project/pull/116907