[llvm] [VPlan] Add legal checks in VPWidenMemoryRecipe::computeCost(). NFC (PR #110445)

[Elvis Wang via llvm-commits]

https://github.com/ElvisWang123 created https://github.com/llvm/llvm-project/pull/110445

Add legal checks in the vplan-based cost model that align to the legacy cost model (setCostBasedWideningDecision()).

This is patch is not quite a NFC patch but currently we don't have a target that support `ActiveVectorLength && ScalableVector` but not support `gather/scatter` nor return a valid cost by `TTI.getGatherScatterOpCost`.

Fixing the gap can prevent potentail failure in the future.

>From 987ecd845a0d920c8a3465db672e856420aaa11c Mon Sep 17 00:00:00 2001
From: Elvis Wang <elvis.wang at sifive.com>
Date: Fri, 27 Sep 2024 00:04:27 -0700
Subject: [PATCH] [VPlan] Add legal checks in
 VPWidenMemoryRecipe::computeCost(). NFC

Add legal checks in the vplan-based cost model that align to the legacy
cost model (setCostBasedWideningDecision()).

This is patch is not quite a NFC patch but currently we don't have a
target that support `ActiveVectorLength && ScalableVector` but not support
`gather/scatter` nor return valid cost by `TTI.getGatherScatterOpCost`.

Fixing the gap can prevent potentail failure in the future.
---
 llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
index 2f0ba5510b8f34..c941479e7c6589 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
@@ -2148,6 +2148,11 @@ InstructionCost VPWidenMemoryRecipe::computeCost(ElementCount VF,
     const Value *Ptr = getLoadStorePointerOperand(&Ingredient);
     assert(!Reverse &&
            "Inconsecutive memory access should not have the order.");
+    if ((isa<LoadInst>(Ingredient) &&
+         !Ctx.TTI.isLegalMaskedGather(Ty, Alignment)) ||
+        (isa<StoreInst>(Ingredient) &&
+         !Ctx.TTI.isLegalMaskedScatter(Ty, Alignment)))
+      return InstructionCost::getInvalid();
     return Ctx.TTI.getAddressComputationCost(Ty) +
            Ctx.TTI.getGatherScatterOpCost(Ingredient.getOpcode(), Ty, Ptr,
                                           IsMasked, Alignment, CostKind,