[llvm] LV: reuse getSmallBestKnownTC in RT-check TC estimation (PR #105834)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Ramkumar Ramachandra (artagnon)

<details>
<summary>Changes</summary>

GeneratedRTChecks::getCost duplicates getSmallBestKnownTC partially, when attempting to get the best trip-count estimate. Since the intent of this code is to get the best trip-count estimate, and getSmallBestKnownTC is written for exactly this purpose, replace the partial code-duplication with a call to this function.

---
Full diff: https://github.com/llvm/llvm-project/pull/105834.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/LoopVectorize.cpp (+3-8) 


``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 2145bb8c9ca872..c1135e81feb33d 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -1971,14 +1971,9 @@ class GeneratedRTChecks {
           // count. Assume that the outer loop executes at least twice.
           unsigned BestTripCount = 2;
 
-          // If exact trip count is known use that.
-          if (unsigned SmallTC = SE->getSmallConstantTripCount(OuterLoop))
-            BestTripCount = SmallTC;
-          else if (LoopVectorizeWithBlockFrequency) {
-            // Else use profile data if available.
-            if (auto EstimatedTC = getLoopEstimatedTripCount(OuterLoop))
-              BestTripCount = *EstimatedTC;
-          }
+          // Get the best known TC estimate.
+          if (auto EstimatedTC = getSmallBestKnownTC(*SE, OuterLoop))
+            BestTripCount = *EstimatedTC;
 
           BestTripCount = std::max(BestTripCount, 1U);
           InstructionCost NewMemCheckCost = MemCheckCost / BestTripCount;

``````````

</details>


https://github.com/llvm/llvm-project/pull/105834