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

Previously, the clang compiler with the dxc driver would accept the
-enable-16bit-types flag without checking to see if the required
conditions are met for proper processing of the flag.
Specifically, -enable-16bit-types requires a shader model of at least
6.2 and an HLSL version of at least 2021.
This PR adds a validation check for these other options having the
required values, and emits an error if these constraints are not met.
Fixes #57876

---------

Co-authored-by: Damyan Pepper <damyanp@microsoft.com>
Co-authored-by: Chris B <cbieneman@microsoft.com>

2 files changed, 20 insertions, 3 deletions

diff --git a/clang/lib/Driver/ToolChains/HLSL.cpp b/clang/lib/Driver/ToolChains/HLSL.cpp
index 05aac9c..1169b5d 100644
--- a/clang/lib/Driver/ToolChains/HLSL.cpp
+++ b/clang/lib/Driver/ToolChains/HLSL.cpp
@@ -255,9 +255,7 @@ HLSLToolChain::TranslateArgs(const DerivedArgList &Args, StringRef BoundArch,
   if (!DAL->hasArg(options::OPT_O_Group)) {
     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
+
   return DAL;
 }
 
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 7bd91d4..f1bd3cd 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -4284,11 +4284,30 @@ bool CompilerInvocation::ParseLangArgs(LangOptions &Opts, ArgList &Args,
           Diags.Report(diag::err_drv_hlsl_bad_shader_unsupported)
               << ShaderModel << T.getOSName() << T.str();
         }
+        // Validate that if fnative-half-type is given, that
+        // the language standard is at least hlsl2018, and that
+        // the target shader model is at least 6.2.
+        if (Args.getLastArg(OPT_fnative_half_type)) {
+          const LangStandard &Std =
+              LangStandard::getLangStandardForKind(Opts.LangStd);
+          if (!(Opts.LangStd >= LangStandard::lang_hlsl2018 &&
+                T.getOSVersion() >= VersionTuple(6, 2)))
+            Diags.Report(diag::err_drv_hlsl_16bit_types_unsupported)
+                << "-enable-16bit-types" << true << Std.getName()
+                << T.getOSVersion().getAsString();
+        }
       } else if (T.isSPIRVLogical()) {
         if (!T.isVulkanOS() || T.getVulkanVersion() == VersionTuple(0)) {
           Diags.Report(diag::err_drv_hlsl_bad_shader_unsupported)
               << VulkanEnv << T.getOSName() << T.str();
         }
+        if (Args.getLastArg(OPT_fnative_half_type)) {
+          const LangStandard &Std =
+              LangStandard::getLangStandardForKind(Opts.LangStd);
+          if (!(Opts.LangStd >= LangStandard::lang_hlsl2018))
+            Diags.Report(diag::err_drv_hlsl_16bit_types_unsupported)
+                << "-fnative-half-type" << false << Std.getName();
+        }
       } else {
         llvm_unreachable("expected DXIL or SPIR-V target");
       }