[clang] [HLSL] Add validation for the -enable-16bit-types option (PR #85340)

[Damyan Pepper via cfe-commits]

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@@ -4258,6 +4258,18 @@ bool CompilerInvocation::ParseLangArgs(LangOptions &Opts, ArgList &Args,
       } else {
         llvm_unreachable("expected DXIL or SPIR-V target");
       }
+      // validate that if fnative-half-type is given, that
+      // the language standard is at least hlsl2021, and that
+      // the target shader model is at least 6.2
+      if (Args.getLastArg(OPT_fnative_half_type)) {
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damyanp wrote:

Impression I got from the code is that SPIR-V and DXIL use the value returned by `T.getOSVersion()` for different things.

https://github.com/llvm/llvm-project/pull/85340