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

[via cfe-commits]

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@@ -179,6 +179,13 @@ void sparc::getSparcTargetFeatures(const Driver &D, const ArgList &Args,
       Features.push_back("-hard-quad-float");
   }
 
+  if (Arg *A = Args.getLastArg(options::OPT_mv8plus, options::OPT_mno_v8plus)) {
+    if (A->getOption().matches(options::OPT_mv8plus))
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koachan wrote:

It is true that those flags primarily control the target environment, however, on GCC, `-m[no-]v8plus` also implies that V9 instructions are available (or not, in case of `-mno-v8plus`) (e.g when multiplying 64-bit numbers: https://godbolt.org/z/5zdWez6qz).
Also, unlike `-mx32`, `-m[no-]v8plus` is intended for use with 32-bit target (`-m32`); again, with GCC, `-mv8plus` raises an error with `-m64`, and `-mno-v8plus` is ignored (i.e it still generates 64-bit instructions) (https://godbolt.org/z/PcfMcT8cf).

It would be possible to define the flags such that `-m[no-]v8plus` do not touch the V9 feature bit, but I feel like that would defeat the purpose of V8+ environment (that is, to let 32-bit code use some 64-bit V9 instructions).

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