[llvm] [LV][VPlan] Remove any-of reduction from precomputeCost. NFC (PR #117109)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Elvis Wang (ElvisWang123)

<details>
<summary>Changes</summary>

The any-of reduction contains phi and select instructions. 

The select instruction might be optimized and removed in the vplan which may cause VF difference between legacy and VPlan-based model. But if the select instruction be removed, `planContainsAdditionalSimplifications()` will catch it and disable the assertion.

Therefore, we can just remove the ayn-of reduction calculation in the precomputeCost().

---
Full diff: https://github.com/llvm/llvm-project/pull/117109.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/LoopVectorize.cpp (+2-22) 


``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 1ebc62f9843905..e2b76948cb6b19 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7278,34 +7278,14 @@ LoopVectorizationPlanner::precomputeCosts(VPlan &Plan, ElementCount VF,
 
   // The legacy cost model has special logic to compute the cost of in-loop
   // reductions, which may be smaller than the sum of all instructions involved
-  // in the reduction. For AnyOf reductions, VPlan codegen may remove the select
-  // which the legacy cost model uses to assign cost. Pre-compute their costs
-  // for now.
+  // in the reduction.
   // TODO: Switch to costing based on VPlan once the logic has been ported.
   for (const auto &[RedPhi, RdxDesc] : Legal->getReductionVars()) {
     if (ForceTargetInstructionCost.getNumOccurrences())
       continue;
 
-    if (!CM.isInLoopReduction(RedPhi) &&
-        !RecurrenceDescriptor::isAnyOfRecurrenceKind(
-            RdxDesc.getRecurrenceKind()))
-      continue;
-
-    // AnyOf reduction codegen may remove the select. To match the legacy cost
-    // model, pre-compute the cost for AnyOf reductions here.
-    if (RecurrenceDescriptor::isAnyOfRecurrenceKind(
-            RdxDesc.getRecurrenceKind())) {
-      auto *Select = cast<SelectInst>(*find_if(
-          RedPhi->users(), [](User *U) { return isa<SelectInst>(U); }));
-      assert(!CostCtx.SkipCostComputation.contains(Select) &&
-             "reduction op visited multiple times");
-      CostCtx.SkipCostComputation.insert(Select);
-      auto ReductionCost = CostCtx.getLegacyCost(Select, VF);
-      LLVM_DEBUG(dbgs() << "Cost of " << ReductionCost << " for VF " << VF
-                        << ":\n any-of reduction " << *Select << "\n");
-      Cost += ReductionCost;
+    if (!CM.isInLoopReduction(RedPhi))
       continue;
-    }
 
     const auto &ChainOps = RdxDesc.getReductionOpChain(RedPhi, OrigLoop);
     SetVector<Instruction *> ChainOpsAndOperands(ChainOps.begin(),

``````````

</details>


https://github.com/llvm/llvm-project/pull/117109