[llvm] [SLPVectorizer][NFC] Small change to `calculateRtStride` (PR #156503)
Mikhail Gudim via llvm-commits
llvm-commits at lists.llvm.org
Tue Sep 2 10:31:12 PDT 2025
https://github.com/mgudim created https://github.com/llvm/llvm-project/pull/156503
Make `calculateRtStride` return the SCEV of rt stride value and let the caller expand it where needed.
>From 7fa96384ffb17383ac2d7af37254a60bc32bd2c1 Mon Sep 17 00:00:00 2001
From: Mikhail Gudim <mgudim at ventanamicro.com>
Date: Tue, 2 Sep 2025 09:21:34 -0700
Subject: [PATCH] [SLPVectorizer][NFC] Small change to `calculateRtStride`
Make `calculateRtStride` return the SCEV of rt stride value and let the
caller expand it where needed.
---
.../Transforms/Vectorize/SLPVectorizer.cpp | 56 +++++++++----------
1 file changed, 25 insertions(+), 31 deletions(-)
diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 040e2dafb56a6..c85d994cf09d6 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -6323,17 +6323,11 @@ static bool isReverseOrder(ArrayRef<unsigned> Order) {
}
/// Checks if the provided list of pointers \p Pointers represents the strided
-/// pointers for type ElemTy. If they are not, std::nullopt is returned.
-/// Otherwise, if \p Inst is not specified, just initialized optional value is
-/// returned to show that the pointers represent strided pointers. If \p Inst
-/// specified, the runtime stride is materialized before the given \p Inst.
-/// \returns std::nullopt if the pointers are not pointers with the runtime
-/// stride, nullptr or actual stride value, otherwise.
-static std::optional<Value *>
-calculateRtStride(ArrayRef<Value *> PointerOps, Type *ElemTy,
- const DataLayout &DL, ScalarEvolution &SE,
- SmallVectorImpl<unsigned> &SortedIndices,
- Instruction *Inst = nullptr) {
+/// pointers for type ElemTy. If they are not, nullptr is returned.
+/// Otherwise, SCEV* of the stride value is returned.
+static const SCEV *calculateRtStride(ArrayRef<Value *> PointerOps, Type *ElemTy,
+ const DataLayout &DL, ScalarEvolution &SE,
+ SmallVectorImpl<unsigned> &SortedIndices) {
SmallVector<const SCEV *> SCEVs;
const SCEV *PtrSCEVLowest = nullptr;
const SCEV *PtrSCEVHighest = nullptr;
@@ -6342,7 +6336,7 @@ calculateRtStride(ArrayRef<Value *> PointerOps, Type *ElemTy,
for (Value *Ptr : PointerOps) {
const SCEV *PtrSCEV = SE.getSCEV(Ptr);
if (!PtrSCEV)
- return std::nullopt;
+ return nullptr;
SCEVs.push_back(PtrSCEV);
if (!PtrSCEVLowest && !PtrSCEVHighest) {
PtrSCEVLowest = PtrSCEVHighest = PtrSCEV;
@@ -6350,14 +6344,14 @@ calculateRtStride(ArrayRef<Value *> PointerOps, Type *ElemTy,
}
const SCEV *Diff = SE.getMinusSCEV(PtrSCEV, PtrSCEVLowest);
if (isa<SCEVCouldNotCompute>(Diff))
- return std::nullopt;
+ return nullptr;
if (Diff->isNonConstantNegative()) {
PtrSCEVLowest = PtrSCEV;
continue;
}
const SCEV *Diff1 = SE.getMinusSCEV(PtrSCEVHighest, PtrSCEV);
if (isa<SCEVCouldNotCompute>(Diff1))
- return std::nullopt;
+ return nullptr;
if (Diff1->isNonConstantNegative()) {
PtrSCEVHighest = PtrSCEV;
continue;
@@ -6366,7 +6360,7 @@ calculateRtStride(ArrayRef<Value *> PointerOps, Type *ElemTy,
// Dist = PtrSCEVHighest - PtrSCEVLowest;
const SCEV *Dist = SE.getMinusSCEV(PtrSCEVHighest, PtrSCEVLowest);
if (isa<SCEVCouldNotCompute>(Dist))
- return std::nullopt;
+ return nullptr;
int Size = DL.getTypeStoreSize(ElemTy);
auto TryGetStride = [&](const SCEV *Dist,
const SCEV *Multiplier) -> const SCEV * {
@@ -6387,10 +6381,10 @@ calculateRtStride(ArrayRef<Value *> PointerOps, Type *ElemTy,
const SCEV *Sz = SE.getConstant(Dist->getType(), Size * (SCEVs.size() - 1));
Stride = TryGetStride(Dist, Sz);
if (!Stride)
- return std::nullopt;
+ return nullptr;
}
if (!Stride || isa<SCEVConstant>(Stride))
- return std::nullopt;
+ return nullptr;
// Iterate through all pointers and check if all distances are
// unique multiple of Stride.
using DistOrdPair = std::pair<int64_t, int>;
@@ -6404,28 +6398,28 @@ calculateRtStride(ArrayRef<Value *> PointerOps, Type *ElemTy,
const SCEV *Diff = SE.getMinusSCEV(PtrSCEV, PtrSCEVLowest);
const SCEV *Coeff = TryGetStride(Diff, Stride);
if (!Coeff)
- return std::nullopt;
+ return nullptr;
const auto *SC = dyn_cast<SCEVConstant>(Coeff);
if (!SC || isa<SCEVCouldNotCompute>(SC))
- return std::nullopt;
+ return nullptr;
if (!SE.getMinusSCEV(PtrSCEV, SE.getAddExpr(PtrSCEVLowest,
SE.getMulExpr(Stride, SC)))
->isZero())
- return std::nullopt;
+ return nullptr;
Dist = SC->getAPInt().getZExtValue();
}
// If the strides are not the same or repeated, we can't vectorize.
if ((Dist / Size) * Size != Dist || (Dist / Size) >= SCEVs.size())
- return std::nullopt;
+ return nullptr;
auto Res = Offsets.emplace(Dist, Cnt);
if (!Res.second)
- return std::nullopt;
+ return nullptr;
// Consecutive order if the inserted element is the last one.
IsConsecutive = IsConsecutive && std::next(Res.first) == Offsets.end();
++Cnt;
}
if (Offsets.size() != SCEVs.size())
- return std::nullopt;
+ return nullptr;
SortedIndices.clear();
if (!IsConsecutive) {
// Fill SortedIndices array only if it is non-consecutive.
@@ -6436,10 +6430,7 @@ calculateRtStride(ArrayRef<Value *> PointerOps, Type *ElemTy,
++Cnt;
}
}
- if (!Inst)
- return nullptr;
- SCEVExpander Expander(SE, DL, "strided-load-vec");
- return Expander.expandCodeFor(Stride, Stride->getType(), Inst);
+ return Stride;
}
static std::pair<InstructionCost, InstructionCost>
@@ -19520,11 +19511,14 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
return cast<LoadInst>(V)->getPointerOperand();
});
OrdersType Order;
- std::optional<Value *> Stride =
- calculateRtStride(PointerOps, ScalarTy, *DL, *SE, Order,
- &*Builder.GetInsertPoint());
+ const SCEV *StrideSCEV =
+ calculateRtStride(PointerOps, ScalarTy, *DL, *SE, Order);
+ assert(StrideSCEV && "At this point stride should be known");
+ SCEVExpander Expander(*SE, *DL, "strided-load-vec");
+ Value *Stride = Expander.expandCodeFor(
+ StrideSCEV, StrideSCEV->getType(), &*Builder.GetInsertPoint());
Value *NewStride =
- Builder.CreateIntCast(*Stride, StrideTy, /*isSigned=*/true);
+ Builder.CreateIntCast(Stride, StrideTy, /*isSigned=*/true);
StrideVal = Builder.CreateMul(
NewStride,
ConstantInt::get(
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