Driver: parse -mcmodel earlier

This addresses an existing FIXME item in the driver.  The code model flag was
parsed in the actual tool rather than in the driver.  This was problematic since
the value may be invalid.  In that case, we would silently treat it as a default
value in non-assert builds, and abort in assert builds.  Add a check in the
driver to validate that the value being passed is valid, and if not provide a
proper error message.

llvm-svn: 208275
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 0b6b765..a6b1b45 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -27,6 +27,7 @@
 #include "llvm/Option/ArgList.h"
 #include "llvm/Option/OptTable.h"
 #include "llvm/Option/Option.h"
+#include "llvm/Support/CodeGen.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Host.h"
@@ -295,6 +296,17 @@
   Opts.ParseAllComments = Args.hasArg(OPT_fparse_all_comments);
 }
 
+static StringRef getCodeModel(ArgList &Args, DiagnosticsEngine &Diags) {
+  if (Arg *A = Args.getLastArg(OPT_mcode_model)) {
+    StringRef Value = A->getValue();
+    if (Value == "small" || Value == "kernel" || Value == "medium" ||
+        Value == "large")
+      return Value;
+    Diags.Report(diag::err_drv_invalid_value) << A->getAsString(Args) << Value;
+  }
+  return "default";
+}
+
 static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
                              DiagnosticsEngine &Diags,
                              const TargetOptions &TargetOpts) {
@@ -376,7 +388,7 @@
   Opts.CUDAIsDevice = Args.hasArg(OPT_fcuda_is_device);
   Opts.CXAAtExit = !Args.hasArg(OPT_fno_use_cxa_atexit);
   Opts.CXXCtorDtorAliases = Args.hasArg(OPT_mconstructor_aliases);
-  Opts.CodeModel = Args.getLastArgValue(OPT_mcode_model);
+  Opts.CodeModel = getCodeModel(Args, Diags);
   Opts.DebugPass = Args.getLastArgValue(OPT_mdebug_pass);
   Opts.DisableFPElim = Args.hasArg(OPT_mdisable_fp_elim);
   Opts.DisableFree = Args.hasArg(OPT_disable_free);