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[SLPVectorizer] Widen constant strided loads. #162324

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[SLPVectorizer] Widen constant strided loads. #162324

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130 changes: 104 additions & 26 deletions llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2248,7 +2248,6 @@ class BoUpSLP {
/// Return true if an array of scalar loads can be replaced with a strided
/// load (with constant stride).
///
/// TODO:
/// It is possible that the load gets "widened". Suppose that originally each
/// load loads `k` bytes and `PointerOps` can be arranged as follows (`%s` is
/// constant): %b + 0 * %s + 0 %b + 0 * %s + 1 %b + 0 * %s + 2
Expand Down Expand Up @@ -6921,36 +6920,105 @@ bool BoUpSLP::isStridedLoad(ArrayRef<Value *> PointerOps, Type *ScalarTy,
}

bool BoUpSLP::analyzeConstantStrideCandidate(
const ArrayRef<Value *> PointerOps, Type *ScalarTy, Align Alignment,
ArrayRef<Value *> PointerOps, Type *ElemTy, Align Alignment,
const SmallVectorImpl<unsigned> &SortedIndices, const int64_t Diff,
Value *Ptr0, Value *PtrN, StridedPtrInfo &SPtrInfo) const {
const size_t Sz = PointerOps.size();
if (!isStridedLoad(PointerOps, ScalarTy, Alignment, Diff, Sz))
return false;
const unsigned Sz = PointerOps.size();
SmallVector<int64_t> SortedOffsetsFromBase(Sz);
// Go through `PointerOps` in sorted order and record offsets from `Ptr0`.
for (unsigned I : seq<unsigned>(Sz)) {
Value *Ptr =
SortedIndices.empty() ? PointerOps[I] : PointerOps[SortedIndices[I]];
SortedOffsetsFromBase[I] =
*getPointersDiff(ElemTy, Ptr0, ElemTy, Ptr, *DL, *SE);
}
assert(SortedOffsetsFromBase.size() > 1 &&
"Trying to generate strided load for less than 2 loads");
// The code below checks that `SortedOffsetsFromBase` looks as follows:
// ```
// [
// (e_{0, 0}, e_{0, 1}, ..., e_{0, GroupSize - 1}), // first group
// (e_{1, 0}, e_{1, 1}, ..., e_{1, GroupSize - 1}), // secon group
// ...
// (e_{NumGroups - 1, 0}, e_{NumGroups - 1, 1}, ..., e_{NumGroups - 1,
// GroupSize - 1}), // last group
// ]
// ```
// The distance between consecutive elements within each group should all be
// the same `StrideWithinGroup`. The distance between the first elements of
// consecutive groups should all be the same `StrideBetweenGroups`.

int64_t StrideWithinGroup =
SortedOffsetsFromBase[1] - SortedOffsetsFromBase[0];
// Determine size of the first group. Later we will check that all other
// groups have the same size.
unsigned GroupSize = 1;
for (; GroupSize != SortedOffsetsFromBase.size(); ++GroupSize) {
if (SortedOffsetsFromBase[GroupSize] -
SortedOffsetsFromBase[GroupSize - 1] !=
StrideWithinGroup)
break;
}
unsigned VecSz = Sz;
Type *ScalarTy = ElemTy;
int64_t StrideIntVal = StrideWithinGroup;
FixedVectorType *StridedLoadTy = getWidenedType(ScalarTy, VecSz);

int64_t Stride = Diff / static_cast<int64_t>(Sz - 1);
// Quick detour: at this point we can say what the type of strided load would
// be if all the checks pass. Check if this type is legal for the target.
bool NeedsWidening = Sz != GroupSize;
if (NeedsWidening) {
if (Sz % GroupSize != 0)
return false;
VecSz = Sz / GroupSize;

// Iterate through all pointers and check if all distances are
// unique multiple of Dist.
SmallSet<int64_t, 4> Dists;
for (Value *Ptr : PointerOps) {
int64_t 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 (StrideWithinGroup != 1)
return false;
unsigned VecSz = Sz / GroupSize;
ScalarTy = Type::getIntNTy(SE->getContext(),
DL->getTypeSizeInBits(ElemTy).getFixedValue() *
GroupSize);
StridedLoadTy = getWidenedType(ScalarTy, VecSz);
}
if (Dists.size() == Sz) {
Type *StrideTy = DL->getIndexType(Ptr0->getType());
SPtrInfo.StrideVal = ConstantInt::get(StrideTy, Stride);
SPtrInfo.Ty = getWidenedType(ScalarTy, Sz);
return true;

if (!isStridedLoad(PointerOps, ScalarTy, Alignment, Diff, VecSz))
return false;

if (NeedsWidening) {
// Continue with checking the "shape" of `SortedOffsetsFromBase`.
// Check that the strides between groups are all the same.
unsigned CurrentGroupStartIdx = GroupSize;
int64_t StrideBetweenGroups =
SortedOffsetsFromBase[GroupSize] - SortedOffsetsFromBase[0];
StrideIntVal = StrideBetweenGroups;
for (; CurrentGroupStartIdx < Sz; CurrentGroupStartIdx += GroupSize) {
if (SortedOffsetsFromBase[CurrentGroupStartIdx] -
SortedOffsetsFromBase[CurrentGroupStartIdx - GroupSize] !=
StrideBetweenGroups)
return false;
}

auto CheckGroup = [&](const unsigned StartIdx, const unsigned GroupSize0,
const int64_t StrideWithinGroup) -> bool {
unsigned GroupEndIdx = StartIdx + 1;
for (; GroupEndIdx != Sz; ++GroupEndIdx) {
if (SortedOffsetsFromBase[GroupEndIdx] -
SortedOffsetsFromBase[GroupEndIdx - 1] !=
StrideWithinGroup)
break;
}
return GroupEndIdx - StartIdx == GroupSize0;
};
for (unsigned I = 0; I < Sz; I += GroupSize) {
if (!CheckGroup(I, GroupSize, StrideWithinGroup))
return false;
}
}
return false;

Type *StrideTy = DL->getIndexType(Ptr0->getType());
SPtrInfo.StrideVal = ConstantInt::get(StrideTy, StrideIntVal);
SPtrInfo.Ty = StridedLoadTy;
return true;
}

bool BoUpSLP::analyzeRtStrideCandidate(ArrayRef<Value *> PointerOps,
Expand Down Expand Up @@ -14972,11 +15040,19 @@ BoUpSLP::getEntryCost(const TreeEntry *E, ArrayRef<Value *> VectorizedVals,
}
break;
case TreeEntry::StridedVectorize: {
const StridedPtrInfo &SPtrInfo = TreeEntryToStridedPtrInfoMap.at(E);
FixedVectorType *StridedLoadTy = SPtrInfo.Ty;
assert(StridedLoadTy && "Missing StridedPoinerInfo for tree entry.");
Align CommonAlignment =
computeCommonAlignment<LoadInst>(UniqueValues.getArrayRef());
VecLdCost = TTI->getStridedMemoryOpCost(
Instruction::Load, VecTy, LI0->getPointerOperand(),
Instruction::Load, StridedLoadTy, LI0->getPointerOperand(),
/*VariableMask=*/false, CommonAlignment, CostKind);
if (StridedLoadTy != VecTy)
VecLdCost +=
TTI->getCastInstrCost(Instruction::BitCast, VecTy, StridedLoadTy,
getCastContextHint(*E), CostKind);

break;
}
case TreeEntry::CompressVectorize: {
Expand Down Expand Up @@ -19743,6 +19819,8 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E) {
? NewLI
: ::propagateMetadata(NewLI, E->Scalars);

if (StridedLoadTy != VecTy)
V = Builder.CreateBitOrPointerCast(V, VecTy);
V = FinalShuffle(V, E);
E->VectorizedValue = V;
++NumVectorInstructions;
Expand Down
18 changes: 3 additions & 15 deletions llvm/test/Transforms/SLPVectorizer/RISCV/basic-strided-loads.ll
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5

; RUN: opt -mtriple=riscv64 -mattr=+m,+v -passes=slp-vectorizer -S < %s | FileCheck %s
; RUN: opt -mtriple=riscv64 -mattr=+m,+v,+unaligned-vector-mem -passes=slp-vectorizer -S < %s | FileCheck %s

define void @const_stride_1_no_reordering(ptr %pl, ptr %ps) {
; CHECK-LABEL: define void @const_stride_1_no_reordering(
Expand Down Expand Up @@ -621,21 +621,9 @@ define void @constant_stride_widen_no_reordering(ptr %pl, i64 %stride, ptr %ps)
; CHECK-LABEL: define void @constant_stride_widen_no_reordering(
; CHECK-SAME: ptr [[PL:%.*]], i64 [[STRIDE:%.*]], ptr [[PS:%.*]]) #[[ATTR0]] {
; CHECK-NEXT: [[GEP_L0:%.*]] = getelementptr inbounds i8, ptr [[PL]], i64 0
; CHECK-NEXT: [[GEP_L4:%.*]] = getelementptr inbounds i8, ptr [[PL]], i64 100
; CHECK-NEXT: [[GEP_L8:%.*]] = getelementptr inbounds i8, ptr [[PL]], i64 200
; CHECK-NEXT: [[GEP_L12:%.*]] = getelementptr inbounds i8, ptr [[PL]], i64 300
; CHECK-NEXT: [[GEP_S0:%.*]] = getelementptr inbounds i8, ptr [[PS]], i64 0
; CHECK-NEXT: [[TMP1:%.*]] = load <4 x i8>, ptr [[GEP_L0]], align 1
; CHECK-NEXT: [[TMP2:%.*]] = load <4 x i8>, ptr [[GEP_L4]], align 1
; CHECK-NEXT: [[TMP3:%.*]] = load <4 x i8>, ptr [[GEP_L8]], align 1
; CHECK-NEXT: [[TMP4:%.*]] = load <4 x i8>, ptr [[GEP_L12]], align 1
; CHECK-NEXT: [[TMP5:%.*]] = shufflevector <4 x i8> [[TMP1]], <4 x i8> poison, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison>
; CHECK-NEXT: [[TMP6:%.*]] = shufflevector <4 x i8> [[TMP2]], <4 x i8> poison, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison>
; CHECK-NEXT: [[TMP7:%.*]] = shufflevector <4 x i8> [[TMP1]], <4 x i8> [[TMP2]], <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison>
; CHECK-NEXT: [[TMP11:%.*]] = shufflevector <4 x i8> [[TMP3]], <4 x i8> poison, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison>
; CHECK-NEXT: [[TMP9:%.*]] = shufflevector <16 x i8> [[TMP7]], <16 x i8> [[TMP11]], <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 16, i32 17, i32 18, i32 19, i32 poison, i32 poison, i32 poison, i32 poison>
; CHECK-NEXT: [[TMP10:%.*]] = shufflevector <4 x i8> [[TMP4]], <4 x i8> poison, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison, i32 poison>
; CHECK-NEXT: [[TMP8:%.*]] = shufflevector <16 x i8> [[TMP9]], <16 x i8> [[TMP10]], <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 16, i32 17, i32 18, i32 19>
; CHECK-NEXT: [[TMP1:%.*]] = call <4 x i32> @llvm.experimental.vp.strided.load.v4i32.p0.i64(ptr align 1 [[GEP_L0]], i64 100, <4 x i1> splat (i1 true), i32 4)
; CHECK-NEXT: [[TMP8:%.*]] = bitcast <4 x i32> [[TMP1]] to <16 x i8>
; CHECK-NEXT: store <16 x i8> [[TMP8]], ptr [[GEP_S0]], align 1
; CHECK-NEXT: ret void
;
Expand Down
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