[clang] [SPARC][clang] Add -m(no-)v8plus flags handling (PR #98713)

[Sergei Barannikov via cfe-commits]

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@@ -6077,6 +6077,10 @@ def mvis3 : Flag<["-"], "mvis3">, Group<m_sparc_Features_Group>;
 def mno_vis3 : Flag<["-"], "mno-vis3">, Group<m_sparc_Features_Group>;
 def mhard_quad_float : Flag<["-"], "mhard-quad-float">, Group<m_sparc_Features_Group>;
 def msoft_quad_float : Flag<["-"], "msoft-quad-float">, Group<m_sparc_Features_Group>;
+def mv8plus : Flag<["-"], "mv8plus">, Group<m_sparc_Features_Group>,
+  HelpText<"Enable V8+ mode, allowing use of 64-bit V9 instructions in 32-bit code">;
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s-barannikov wrote:

Maybe something like this would be more accurate?
```suggestion
  HelpText<"Enable V8+ mode, which allows using a limited set of V9 features in 32-bit code">;
```


https://github.com/llvm/llvm-project/pull/98713