[clang] [X86][clang-cl] Add CL option /vlen (PR #166375)

[Phoebe Wang via cfe-commits]

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@@ -9218,6 +9218,10 @@ def : CLFlag<"Qscatter-">, Alias<mno_scatter>,
 
 def _SLASH_arch : CLCompileJoined<"arch:">,
   HelpText<"Set architecture for code generation">;
+def _SLASH_vlen : CLCompileJoined<"vlen">,
+  HelpText<"Set vector length for autovectorization and other optimizations">;
+def _SLASH_vlen_default : CLFlag<"vlen">,
+  HelpText<"Set default vector length for autovectorization and other optimizations">;
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phoebewang wrote:

Good idea! No, unfortunately: https://godbolt.org/z/hhvjP8W34

https://github.com/llvm/llvm-project/pull/166375