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

[Hans Wennborg via cfe-commits]

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@@ -8266,6 +8266,31 @@ void Clang::AddClangCLArgs(const ArgList &Args, types::ID InputType,
                                                      << "/kernel";
  }
 
+  if (const Arg *A = Args.getLastArg(options::OPT__SLASH_vlen,
+                                     options::OPT__SLASH_vlen_EQ_256,
+                                     options::OPT__SLASH_vlen_EQ_512)) {
+    llvm::SmallSet<std::string, 4> Arch512 = {"AVX512F", "AVX512"};
+    llvm::SmallSet<std::string, 4> Arch256 = {"AVX", "AVX2"};
+
+    StringRef Arch = Args.getLastArgValue(options::OPT__SLASH_arch);
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zmodem wrote:

What if the user didn't pass `/arch`?
What if they passed `-mavx512`?

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