[PATCH] D157462: LoopRotate: Add code to update branch weights

[Matthias Braun via Phabricator via llvm-commits]

MatzeB added inline comments.


================
Comment at: llvm/lib/Transforms/Utils/LoopRotationUtils.cpp:291-306
+  uint32_t ExitCount0; // aka x0
+  if (!ConditionalPreHeader) {
+    // pre-header turned into an unconditional jump.
+    ExitCount0 = 0;
+  } else {
+    // Here we cannot know how many 0-trip count loops we have, so we guess:
+    if (Weights[1] > Weights[0]) {
----------------
MatzeB wrote:
> paulkirth wrote:
> > This could probably be a helper function. It would also allow for expressive names for the `Weight[0]`/`Weight[1]` values, which will probably make it easier to follow. 
> > 
> > Alternatively, you could group all of these counts into a struct. I'm not convinced that is worth it in this case, but it may make the code simpler to reason about and keep all the logic regarding the heuristic together.
> > 
> > This does come down to personal coding style, so don't consider these suggestions blocking.
> What's the point though? The only other thing here is the construction of two MDNodes. Feels needlessly complicated to introduce a struct and separate function just for that...
I did introduce two local variables now, that give a name to `Weights[0]` and `Weights[1]`, hope that is enough to resolve this.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D157462/new/

https://reviews.llvm.org/D157462