[llvm] [SLP][NFC]Extract a check for strided loads into separate function, NFC (PR #134876)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Alexey Bataev (alexey-bataev)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/134876.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp (+69-46) 


``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 0e6f7e8435e3a..06c1840529eb0 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -5597,6 +5597,71 @@ static bool isMaskedLoadCompress(
   return TotalVecCost < GatherCost;
 }
 
+/// Checks if strided loads can be generated out of \p VL loads with pointers \p
+/// PointerOps:
+/// 1. Target with strided load support is detected.
+/// 2. The number of loads is greater than MinProfitableStridedLoads, or the
+/// potential stride <= MaxProfitableLoadStride and the potential stride is
+/// power-of-2 (to avoid perf regressions for the very small number of loads)
+/// and max distance > number of loads, or potential stride is -1.
+/// 3. The loads are ordered, or number of unordered loads <=
+/// MaxProfitableUnorderedLoads, or loads are in reversed order. (this check is
+/// to avoid extra costs for very expensive shuffles).
+/// 4. Any pointer operand is an instruction with the users outside of the
+/// current graph (for masked gathers extra extractelement instructions
+/// might be required).
+static bool isStridedLoad(ArrayRef<Value *> VL, ArrayRef<Value *> PointerOps,
+                          ArrayRef<unsigned> Order,
+                          const TargetTransformInfo &TTI, const DataLayout &DL,
+                          ScalarEvolution &SE,
+                          const bool IsAnyPointerUsedOutGraph, const int Diff) {
+  const unsigned Sz = VL.size();
+  const unsigned AbsoluteDiff = std::abs(Diff);
+  Type *ScalarTy = VL.front()->getType();
+  auto *VecTy = getWidenedType(ScalarTy, Sz);
+  if (IsAnyPointerUsedOutGraph ||
+      (AbsoluteDiff > Sz &&
+       (Sz > MinProfitableStridedLoads ||
+        (AbsoluteDiff <= MaxProfitableLoadStride * Sz &&
+         AbsoluteDiff % Sz == 0 && has_single_bit(AbsoluteDiff / Sz)))) ||
+      Diff == -(static_cast<int>(Sz) - 1)) {
+    int Stride = Diff / static_cast<int>(Sz - 1);
+    if (Diff != Stride * static_cast<int>(Sz - 1))
+      return false;
+    Align Alignment =
+        cast<LoadInst>(Order.empty() ? VL.front() : VL[Order.front()])
+            ->getAlign();
+    if (!TTI.isLegalStridedLoadStore(VecTy, Alignment))
+      return false;
+    Value *Ptr0;
+    Value *PtrN;
+    if (Order.empty()) {
+      Ptr0 = PointerOps.front();
+      PtrN = PointerOps.back();
+    } else {
+      Ptr0 = PointerOps[Order.front()];
+      PtrN = PointerOps[Order.back()];
+    }
+    // Iterate through all pointers and check if all distances are
+    // unique multiple of Dist.
+    SmallSet<int, 4> Dists;
+    for (Value *Ptr : PointerOps) {
+      int Dist = 0;
+      if (Ptr == PtrN)
+        Dist = Diff;
+      else if (Ptr != Ptr0)
+        Dist = *getPointersDiff(ScalarTy, Ptr0, ScalarTy, Ptr, DL, SE);
+      // If the strides are not the same or repeated, we can't
+      // vectorize.
+      if (((Dist / Stride) * Stride) != Dist || !Dists.insert(Dist).second)
+        break;
+    }
+    if (Dists.size() == Sz)
+      return true;
+  }
+  return false;
+}
+
 BoUpSLP::LoadsState
 BoUpSLP::canVectorizeLoads(ArrayRef<Value *> VL, const Value *VL0,
                            SmallVectorImpl<unsigned> &Order,
@@ -5670,59 +5735,17 @@ BoUpSLP::canVectorizeLoads(ArrayRef<Value *> VL, const Value *VL0,
       return LoadsState::Vectorize;
     // Simple check if not a strided access - clear order.
     bool IsPossibleStrided = *Diff % (Sz - 1) == 0;
-    // Try to generate strided load node if:
-    // 1. Target with strided load support is detected.
-    // 2. The number of loads is greater than MinProfitableStridedLoads,
-    // or the potential stride <= MaxProfitableLoadStride and the
-    // potential stride is power-of-2 (to avoid perf regressions for the very
-    // small number of loads) and max distance > number of loads, or potential
-    // stride is -1.
-    // 3. The loads are ordered, or number of unordered loads <=
-    // MaxProfitableUnorderedLoads, or loads are in reversed order.
-    // (this check is to avoid extra costs for very expensive shuffles).
-    // 4. Any pointer operand is an instruction with the users outside of the
-    // current graph (for masked gathers extra extractelement instructions
-    // might be required).
+    // Try to generate strided load node.
     auto IsAnyPointerUsedOutGraph =
         IsPossibleStrided && any_of(PointerOps, [&](Value *V) {
           return isa<Instruction>(V) && any_of(V->users(), [&](User *U) {
                    return !isVectorized(U) && !MustGather.contains(U);
                  });
         });
-    const unsigned AbsoluteDiff = std::abs(*Diff);
     if (IsPossibleStrided &&
-        (IsAnyPointerUsedOutGraph ||
-         (AbsoluteDiff > Sz &&
-          (Sz > MinProfitableStridedLoads ||
-           (AbsoluteDiff <= MaxProfitableLoadStride * Sz &&
-            AbsoluteDiff % Sz == 0 && has_single_bit(AbsoluteDiff / Sz)))) ||
-         *Diff == -(static_cast<int>(Sz) - 1))) {
-      int Stride = *Diff / static_cast<int>(Sz - 1);
-      if (*Diff == Stride * static_cast<int>(Sz - 1)) {
-        Align Alignment =
-            cast<LoadInst>(Order.empty() ? VL.front() : VL[Order.front()])
-                ->getAlign();
-        if (TTI->isLegalStridedLoadStore(VecTy, Alignment)) {
-          // Iterate through all pointers and check if all distances are
-          // unique multiple of Dist.
-          SmallSet<int, 4> Dists;
-          for (Value *Ptr : PointerOps) {
-            int Dist = 0;
-            if (Ptr == PtrN)
-              Dist = *Diff;
-            else if (Ptr != Ptr0)
-              Dist = *getPointersDiff(ScalarTy, Ptr0, ScalarTy, Ptr, *DL, *SE);
-            // If the strides are not the same or repeated, we can't
-            // vectorize.
-            if (((Dist / Stride) * Stride) != Dist ||
-                !Dists.insert(Dist).second)
-              break;
-          }
-          if (Dists.size() == Sz)
-            return LoadsState::StridedVectorize;
-        }
-      }
-    }
+        isStridedLoad(VL, PointerOps, Order, *TTI, *DL, *SE,
+                      IsAnyPointerUsedOutGraph, *Diff))
+      return LoadsState::StridedVectorize;
     bool IsMasked;
     unsigned InterleaveFactor;
     SmallVector<int> CompressMask;

``````````

</details>


https://github.com/llvm/llvm-project/pull/134876