[llvm-dev] Enable / Disable a processor feature

[Eric Christopher via llvm-dev]

The easiest way here is to take a look at an existing target, say x86, and
do what it does :)

For specific guidance within x86, take a look at how -msse3 works.

-eric

On Fri, Mar 4, 2016 at 5:25 PM Rail Shafigulin via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> I'm trying to enable/disable a target feature through clang.
>
> Here is how my target looks like
>
> // Esencia subtarget features
>
> //===----------------------------------------------------------------------===//
> def FeatureMul   : SubtargetFeature<"mul", "HasMul", "true",
>                                    "Enable hardware multiplier">;
> def FeatureDiv   : SubtargetFeature<"div", "HasDiv", "true",
>                                    "Enable hardware divider">;
> def FeatureCmov  : SubtargetFeature<"cmov", "HasCmov", "true",
>                                     "Enable conditional move instruction">;
> def FeatureAddc  : SubtargetFeature<"addc", "HasAddc", "true",
>                                     "Enable add with carry instruction">;
>
>
> //===----------------------------------------------------------------------===//
> // Esencia processors supported.
>
> //===----------------------------------------------------------------------===//
> class Proc<string Name, SchedMachineModel Model,
>            list<SubtargetFeature> Features>
>  : ProcessorModel<Name, Model, Features>;
>
> def : Proc<"esencia", EsenciaModel, [FeatureMul,
>                                      FeatureDiv,
>                                      FeatureCmov,
>                                      FeatureAddc
>                                     ]>;
>
> This is what I have in EsenciaTargetInfo::setFeatureEnabled(...) in
> clang/lib/Basic/Targets.cpp
>
>   virtual void setFeatureEnabled(llvm::StringMap<bool> &Features,
>                                  StringRef Name,
>                                  bool Enabled) const {
>     if (Name == "mul" ||
>         Name == "div" ||
>         Name == "cmov" ||
>         Name == "addc") {
>       Features[Name] = Enabled;
>     }
>   }
>
> Is there a way to enable/disable a given feature through clang? Any flags
> I need to pass?
>
> Any help is appreciated.
>
> --
> Rail Shafigulin
> Software Engineer
> Esencia Technologies
> _______________________________________________
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> llvm-dev at lists.llvm.org
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>
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