[PATCH] D71883: [PowerPC] Use PredictableSelectIsExpensive to enable select to branch in CGP

[Nemanja Ivanovic via Phabricator via llvm-commits]

nemanjai added inline comments.


================
Comment at: llvm/lib/Target/PowerPC/PPC.td:288
+     FeatureISA3_0,
+     FeaturePredictableSelectIsExpensive
+     ];
----------------
This should certainly be set for Power8 as well.


================
Comment at: llvm/lib/Target/PowerPC/PPCISelLowering.cpp:1261
+  // Select is more expensive than a branch if the feature
+  // FeaturePredictableSelectIsExpensive has been set.
+  PredictableSelectIsExpensive = Subtarget.isPredictableSelectIsExpensive();
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I think that having the same name `PredictableSelectIsExpensive` as members of both the TLI and the Subtarget is a bit confusing. At the very least, the comment should be a bit more descriptive. Perhaps:
```
// Let the subtarget (CPU) decide if a predictable select is more
// expensive than the corresponding branch. This information is used
// in CGP to decide when to convert selects into branches.
```


================
Comment at: llvm/lib/Target/PowerPC/PPCSubtarget.h:142
   bool UsePPCPostRASchedStrategy;
+  bool PredictableSelectIsExpensive = false;
 
----------------
For the sake of convention, leave this uninitialized here and initialize it in `PPCSubtarget::initializeEnvironment()` just like all the rest of these.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D71883/new/

https://reviews.llvm.org/D71883