[clang] [clang] Adjust -mlarge-data-threshold handling (PR #77958)

[Fangrui Song via cfe-commits]

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@@ -5752,20 +5752,29 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     }
   }
 
-  if (Arg *A = Args.getLastArg(options::OPT_mlarge_data_threshold_EQ)) {
-    if (!Triple.isX86()) {
-      D.Diag(diag::err_drv_unsupported_opt_for_target)
-          << A->getOption().getName() << TripleStr;
-    } else {
-      bool IsMediumCM = false;
-      if (Arg *A = Args.getLastArg(options::OPT_mcmodel_EQ))
-        IsMediumCM = StringRef(A->getValue()) == "medium";
-      if (!IsMediumCM) {
+  if (Triple.getArch() == llvm::Triple::x86_64) {
+    bool IsMediumCM = false;
+    bool IsLargeCM = false;
+    if (Arg *A = Args.getLastArg(options::OPT_mcmodel_EQ)) {
+      IsMediumCM = StringRef(A->getValue()) == "medium";
+      IsLargeCM = StringRef(A->getValue()) == "large";
+    }
+    if (Arg *A = Args.getLastArg(options::OPT_mlarge_data_threshold_EQ)) {
+      if (!IsMediumCM && !IsLargeCM) {
         D.Diag(diag::warn_drv_large_data_threshold_invalid_code_model)
             << A->getOption().getRenderName();
       } else {
         A->render(Args, CmdArgs);
       }
+    } else if (IsMediumCM) {
+      CmdArgs.push_back("-mlarge-data-threshold=65536");
+    } else if (IsLargeCM) {
+      CmdArgs.push_back("-mlarge-data-threshold=0");
+    }
+  } else {
+    if (Arg *A = Args.getLastArg(options::OPT_mlarge_data_threshold_EQ)) {
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MaskRay wrote:

You can remove `err_drv_unsupported_opt_for_target` here in favor of `TargetSpecific` at `def mlarge_data_threshold_EQ`

https://github.com/llvm/llvm-project/pull/77958