Add -fauto-profile option to Clang driver

[Hans Wennborg]

On Mon, Oct 7, 2013 at 11:09 AM, Diego Novillo <dnovillo at google.com> wrote:
> This adds a new option -fauto-profile=filename to Clang. It tells the
> driver to schedule the auto-profile pass and passes on the name of the
> profile file to use.
>
> This patch depends on the initial auto profile patch I posted a
> couple of weeks ago: http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20130923/188838.html

This looks good as far as I can tell, just minor comments:

> From bcfe88d501ad4ea299f0b64ce98b375c248a45c9 Mon Sep 17 00:00:00 2001
> From: Diego Novillo <dnovillo at google.com>
> Date: Wed, 2 Oct 2013 10:46:34 -0400
> Subject: [PATCH] Add -fauto-profile to Clang's driver.
>
> This adds a new option -fauto-profile=filename to Clang. It tells the
> driver to schedule the auto-profile pass and passes on the name of the
> profile file to use.

> +++ b/lib/CodeGen/BackendUtil.cpp
> @@ -154,6 +154,14 @@ static void addObjCARCOptPass(const PassManagerBuilder &Builder, PassManagerBase
>      PM.add(createObjCARCOptPass());
>  }
>
> +static void addAutoProfilePass(const PassManagerBuilder &Builder,
> +                               PassManagerBase &PM) {
> +  const PassManagerBuilderWrapper &BuilderWrapper =
> +      static_cast<const PassManagerBuilderWrapper&>(Builder);
> +  const CodeGenOptions &opts = BuilderWrapper.getCGOpts();

I'd have called the variable CGOpts, but whatever.

> +++ b/lib/Driver/Tools.cpp
> @@ -3020,6 +3020,10 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
>
>    // Forward -f options with positive and negative forms; we translate
>    // these by hand.
> +  if (Arg *A = Args.getLastArg(options::OPT_fauto_profile_EQ)) {
> +    StringRef fname = A->getValue();
> +    CmdArgs.push_back(Args.MakeArgString("-fauto-profile=" + fname));

I think you can just use A->render(Args, CmdArgs); here, saving you
the trouble of doing the MakeArgString dance.

Would this be a good point to check for the existence of the file, or
what's the plan there?