[Driver] Reject -mcmodel=tiny on X86

clang/lib/Frontend/CompilerInvocation.cpp

@@ -1897,6 +1897,16 @@ bool CompilerInvocation::ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args,
     Opts.setInlining(CodeGenOptions::NormalInlining);
   }
 
+  // -mcmodel option.
+  if (const llvm::opt::Arg *A =
+          Args.getLastArg(clang::driver::options::OPT_mcmodel_EQ)) {
+    llvm::StringRef modelName = A->getValue();
+    if (modelName == "tiny" && !(T.isARM() || T.isAArch64())) {
+      Diags.Report(diag::err_drv_unsupported_option_argument_for_target)
+          << A->getSpelling() << modelName << T.getTriple();
+    }
+  }
+
   // PIC defaults to -fno-direct-access-external-data while non-PIC defaults to
   // -fdirect-access-external-data.
   Opts.DirectAccessExternalData =

clang/test/Driver/diag-mcmodel-tiny-x86.c

@@ -0,0 +1,2 @@
+// RUN: not %clang --target=x86_64 -c -mcmodel=tiny %s 2>&1 | FileCheck %s
+// CHECK: error: unsupported argument 'tiny' to option '-mcmodel=' for target '{{.*}}'

llvm/docs/ReleaseNotes.md

@@ -153,6 +153,9 @@ Changes to Sanitizers
 Other Changes
 -------------
 
+* The -mcmodel=tiny option for the x86 architecture now triggers a frontend diagnostic.
+
+
 External Open Source Projects Using LLVM {{env.config.release}}
 ===============================================================