[llvm-dev] LLVM issuse:AArch64 TargetParser

[Jojo Ma via llvm-dev]

Hi renato,

With the TargetParser, the idea is to avoid that specific knowledge on
> the tools themselves, and moving all string parsing (startswith,
> StringSwitch) to the parser.
>
> But that creates the conundrum that we've seen, that we can't parse it
> uniquely without more context.
>

 This is just as a filter,it should not affect the context,I think.
 But in order to filter out the invalid arch, I have no idea how to avoid
doing the string parsing in the tool for now.

 It also seems that we need the Triple
> to be able to infer anything about march. That is the logic that needs
> to be in Clang, not the string parsing.


Feature parsing is done after the triple identified. As we can see below：

static void getTargetFeatures(const ToolChain &TC, const llvm::Triple
&Triple,
                              const ArgList &Args, ArgStringList &CmdArgs,
                              bool ForAS) {
  ... ...
  case llvm::Triple::arm:
  case llvm::Triple::armeb:
  case llvm::Triple::thumb:
  case llvm::Triple::thumbeb:
    getARMTargetFeatures(TC, Triple, Args, Features, ForAS);
    break;
  ... ...
  case llvm::Triple::aarch64:
  case llvm::Triple::aarch64_be:
    getAArch64TargetFeatures(D, Args, Features);
    break;
  ... ...
}

Another alternative would be to create two checkValid functions, one
> explicitly for ARM and one for AArch64, and call them from different
> places in Clang.
>

Yes, it will be more clear.

Thank you very much! Renato.

Regards,
Jojo

>
On 9 May 2016 at 16:39, Renato Golin <renato.golin at linaro.org> wrote:

> On 9 May 2016 at 09:19, Jojo Ma <jojo.ma at linaro.org> wrote:
> > +//Only if -march startwith "armv" or "v" or "iwmmxt" or "xscale",it can
> be
> > seen valid and sended to TargetParser
> > +//for further parsing
> > +static bool checkArchValid(StringRef Arch)
> > +{
> > +  if ((Arch.startswith("armv")) || Arch[0] == 'v' ||
> > +         (Arch.startswith("iwmmxt")) || (Arch.startswith("xscale")))
> > +    return true;
> > +  return false;
> > +}
>
> Hi Jojo,
>
> With the TargetParser, the idea is to avoid that specific knowledge on
> the tools themselves, and moving all string parsing (startswith,
> StringSwitch) to the parser.
>
> But that creates the conundrum that we've seen, that we can't parse it
> uniquely without more context. It also seems that we need the Triple
> to be able to infer anything about march. That is the logic that needs
> to be in Clang, not the string parsing.
>
> Another alternative would be to create two checkValid functions, one
> explicitly for ARM and one for AArch64, and call them from different
> places in Clang.
>
> Hope that helps.
>
> cheers,
> --renato
>
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