[llvm] 0e3c791 - Revert "[LV][VPlan] Remove any-of reduction from precomputeCost. NFC" (#117280)

[via llvm-commits]

Author: Elvis Wang
Date: 2024-11-22T11:32:52+08:00
New Revision: 0e3c791916a918cd2d7391ddb633fbe5faa00b86

URL: https://github.com/llvm/llvm-project/commit/0e3c791916a918cd2d7391ddb633fbe5faa00b86
DIFF: https://github.com/llvm/llvm-project/commit/0e3c791916a918cd2d7391ddb633fbe5faa00b86.diff

LOG: Revert "[LV][VPlan] Remove any-of reduction from precomputeCost. NFC" (#117280)

Reverts llvm/llvm-project#117109

Some test cases need to update.

Added: 
    

Modified: 
    llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

Removed: 
    


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diff  --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 5b556058cc762c..d13770a35c108f 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7303,14 +7303,34 @@ 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.
+  // 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.
   // 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))
+    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;
       continue;
+    }
 
     const auto &ChainOps = RdxDesc.getReductionOpChain(RedPhi, OrigLoop);
     SetVector<Instruction *> ChainOpsAndOperands(ChainOps.begin(),