add test, remove fixme comment

Author: bob80905

clang/lib/Driver/ToolChains/HLSL.cpp

@@ -279,9 +279,6 @@ HLSLToolChain::TranslateArgs(const DerivedArgList &Args, StringRef BoundArch,
     DAL->AddJoinedArg(nullptr, Opts.getOption(options::OPT_O), "3");
   }
 
-  // FIXME: add validation for enable_16bit_types should be after HLSL 2018 and
-  // shader model 6.2.
-  // See: https://github.com/llvm/llvm-project/issues/57876
   if (DAL->hasArg(options::OPT_fnative_half_type)) {
 
     bool HVArgIsValid = true;

clang/test/Options/enable_16bit_types_validation.hlsl

@@ -7,6 +7,7 @@
 // both_invalid: error: enable_16bit_types option only valid when target shader model [-T] is >= 6.2 and HLSL Version [-HV] is >= 2021
 // HV_invalid: error: enable_16bit_types option only valid when target shader model [-T] is >= 6.2 and HLSL Version [-HV] is >= 2021
 // TP_invalid: error: enable_16bit_types option only valid when target shader model [-T] is >= 6.2 and HLSL Version [-HV] is >= 2021
+
 // valid: "dxil-unknown-shadermodel6.4-library"
 // valid-SAME: "-std=hlsl2021"
 // valid-SAME: "-fnative-half-type"