[PATCH] D19488: [CodeGenPrepare] use branch weight metadata to decide if a select should be turned into a branch

[Hal Finkel via llvm-commits]

hfinkel added inline comments.

================
Comment at: include/llvm/Target/TargetLowering.h:268
@@ +267,3 @@
+  virtual BranchProbability getPredictableBranchThreshold() const {
+    return BranchProbability(99, 100);
+  }
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Agreed. A command-line option to override the default would be significantly more convenient.

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Comment at: lib/CodeGen/CodeGenPrepare.cpp:4558
@@ +4557,3 @@
+    auto Probability = BranchProbability::getBranchProbability(Max, Sum);
+    if (Probability > TLI->getPredictableBranchThreshold())
+      return true;
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davidxl wrote:
> Hal,  this is an example that profile meta data is directly looked at instead of via BPI (I don't have an issue with it -- but just a note this scenario exists).
I was thinking that :-) -- but this use did not seem to fit into BPI's interface. If/when we start preserving BPI, we'd need to update here, however.


http://reviews.llvm.org/D19488