[PATCH] D36864: [Profile] backward propagate profile data in jump-threading

[Chandler Carruth via Phabricator via llvm-commits]

chandlerc accepted this revision.
chandlerc added a comment.

Cool! With the changes below, LGTM.

Any further testing you think this needs before relanding it? (I don't really have good ideas other than to patch it in internally and build some large things with PGO and ThinLTO)



================
Comment at: lib/Transforms/Scalar/JumpThreading.cpp:184-188
+      if(auto *SinglePredBB = PredBB->getSinglePredecessor()) {
+        SuccBB = PredBB;
+        PredBB = SinglePredBB;
+      } else
+        return {nullptr, nullptr};
----------------
I think this will be easier to read inverted:

  auto *SinglePredBB = PredBB->getSinglePredecessor();
  if (!SinglePredBB)
    return {nullptr, nullptr};

  SuccBB = PredBB;
  PredBB = SinglePredBB;


================
Comment at: lib/Transforms/Scalar/JumpThreading.cpp:189
+        return {nullptr, nullptr};
+    } while(true);
+
----------------
nit: When infinitely looping, I find ` for (;;) {` a shorter and still easy to read idiom.


================
Comment at: lib/Transforms/Scalar/JumpThreading.cpp:190-191
+    } while(true);
+
+    return {nullptr, nullptr};
+  };
----------------
No need for this once the loop above returns directly when exiting.


https://reviews.llvm.org/D36864