[PATCH] D19189: Expose the list of available features in MCSubtargetInfo

[Johan Engelen via llvm-commits]

johanengelen added a comment.

I want to know whether a certain feature (say, "avx") is enabled for the current target.

This works for us though:

  bool traitsTargetHasFeature(Dstring feature) {
     auto feat = llvm::StringRef(feature.ptr, feature.len);
   
     // Copy MCSubtargetInfo so we can modify it.
     llvm::MCSubtargetInfo mcinfo = *gTargetMachine->getMCSubtargetInfo();
     auto savedFeatbits = mcinfo.getFeatureBits();
   
     // Nothing will change if the feature string is not recognized or if the
     // feature is disabled.
     {
       auto newFeatbits = mcinfo.ApplyFeatureFlag(("-" + feat).str());
       if (savedFeatbits == newFeatbits) {
         return false;
       }
       mcinfo.setFeatureBits(savedFeatbits);
     }
     {
       // Now that unrecognized feature strings are excluded,
       // nothing will change iff the feature and its implied features are enabled.
       auto newFeatbits = mcinfo.ApplyFeatureFlag(("+" + feat).str());
       return savedFeatbits == newFeatbits;
     }
   }


http://reviews.llvm.org/D19189