[clang] [llvm] [RISCV] Implement the implications of C extension (PR #132259)

[Sam Elliott via llvm-commits]

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@@ -378,6 +370,14 @@ def FeatureStdExtZca
                      "part of the C extension, excluding compressed "
                      "floating point loads/stores">;
 
+def FeatureStdExtC
+    : RISCVExtension<2, 0, "Compressed Instructions", [FeatureStdExtZca]>,
+      RISCVExtensionBitmask<0, 2>;
+def HasStdExtC : Predicate<"Subtarget->hasStdExtC()">,
+                 AssemblerPredicate<(all_of FeatureStdExtC),
+                                    "'C' (Compressed Instructions)">;
+
+
 def HasStdExtCOrZca
     : Predicate<"Subtarget->hasStdExtCOrZca()">,
       AssemblerPredicate<(any_of FeatureStdExtC, FeatureStdExtZca),
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lenary wrote:

I think this can be refactored now, as any time you have C you have Zca, so maybe this should just be `HasStdExtZca`

https://github.com/llvm/llvm-project/pull/132259