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

[Ramkumar Ramachandra via llvm-commits]

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

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.

>From a24d4e1c7c875a397b09b14c5ec5f758a5ca505d Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <ramkumar.ramachandra at codasip.com>
Date: Fri, 23 Aug 2024 14:52:53 +0100
Subject: [PATCH] LV: reuse getSmallBestKnownTC in RT-check TC estimation

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.
---
 llvm/lib/Transforms/Vectorize/LoopVectorize.cpp | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

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;