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

[Johan Engelen via llvm-commits]

johanengelen created this revision.
johanengelen added reviewers: grosbach, mkuper.
johanengelen added a subscriber: llvm-commits.

I have not found a way to obtain a list of features available for the target machine. MCSubtargetInfo provides the getFeatureBits() method, but I have not found a way to translate the FeatureBitset to feature names (e.g. "sse2", "avx") or their description. MCSubtargetInfo does contain a reference to that information but does not expose that to the user.
This patch exposes the private ProcFeatures list to user code, similar to exposing the FeatureBits.

I intend to use this in our front-end (LDC) to check whether a feature is enabled or not:
```
  auto *mcinfo = gTargetMachine->getMCSubtargetInfo();
  auto featbits = mcinfo->getFeatureBits();
  auto featTable = mcinfo->getProcFeatures();
  for (auto &feat : featTable) {
    if ((featbits & feat.Value) == feat.Value)
      //check if feat.Key is equal to the feature we seek
  }
```

Thanks for reviewing.

http://reviews.llvm.org/D19189

Files:
  include/llvm/MC/MCSubtargetInfo.h

Index: include/llvm/MC/MCSubtargetInfo.h
===================================================================
--- include/llvm/MC/MCSubtargetInfo.h
+++ include/llvm/MC/MCSubtargetInfo.h
@@ -78,6 +78,14 @@
     FeatureBits = FeatureBits_;
   }
 
+  /// getProcFeatures - Return the subtarget feature list.
+  ///
+  /// Use this list in conjunction with getFeatureBits() to get which features
+  /// are enabled for the current CPU.
+  ArrayRef<SubtargetFeatureKV> getProcFeatures() const {
+    return ProcFeatures;
+  }
+
 protected:
   /// Initialize the scheduling model and feature bits.
   ///


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