llvm-project/mlir/lib/Dialect/Vector/Transforms/LowerVectorTranspose.cpp
Benjamin Maxwell 88610b7951
[mlir][vector] Disable transpose -> shuffle lowering for scalable vectors (#79979)
vector.shuffle is not supported for scalable vectors (outside of splats)
2024-01-31 09:21:44 +00:00

488 lines
20 KiB
C++

//===- LowerVectorTranspose.cpp - Lower 'vector.transpose' operation ------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements target-independent rewrites and utilities to lower the
// 'vector.transpose' operation.
//
//===----------------------------------------------------------------------===//
#include "mlir/Dialect/Affine/IR/AffineOps.h"
#include "mlir/Dialect/Arith/IR/Arith.h"
#include "mlir/Dialect/Arith/Utils/Utils.h"
#include "mlir/Dialect/Linalg/IR/Linalg.h"
#include "mlir/Dialect/MemRef/IR/MemRef.h"
#include "mlir/Dialect/SCF/IR/SCF.h"
#include "mlir/Dialect/Tensor/IR/Tensor.h"
#include "mlir/Dialect/Utils/IndexingUtils.h"
#include "mlir/Dialect/Utils/StructuredOpsUtils.h"
#include "mlir/Dialect/Vector/IR/VectorOps.h"
#include "mlir/Dialect/Vector/Transforms/LoweringPatterns.h"
#include "mlir/Dialect/Vector/Utils/VectorUtils.h"
#include "mlir/IR/BuiltinAttributeInterfaces.h"
#include "mlir/IR/BuiltinTypes.h"
#include "mlir/IR/ImplicitLocOpBuilder.h"
#include "mlir/IR/Location.h"
#include "mlir/IR/Matchers.h"
#include "mlir/IR/PatternMatch.h"
#include "mlir/IR/TypeUtilities.h"
#include "mlir/Interfaces/VectorInterfaces.h"
#include "mlir/Support/LogicalResult.h"
#define DEBUG_TYPE "lower-vector-transpose"
using namespace mlir;
using namespace mlir::vector;
/// Given a 'transpose' pattern, prune the rightmost dimensions that are not
/// transposed.
static void pruneNonTransposedDims(ArrayRef<int64_t> transpose,
SmallVectorImpl<int64_t> &result) {
size_t numTransposedDims = transpose.size();
for (size_t transpDim : llvm::reverse(transpose)) {
if (transpDim != numTransposedDims - 1)
break;
numTransposedDims--;
}
result.append(transpose.begin(), transpose.begin() + numTransposedDims);
}
/// Returns true if the lowering option is a vector shuffle based approach.
static bool isShuffleLike(VectorTransposeLowering lowering) {
return lowering == VectorTransposeLowering::Shuffle1D ||
lowering == VectorTransposeLowering::Shuffle16x16;
}
/// Returns a shuffle mask that builds on `vals`. `vals` is the offset base of
/// shuffle ops, i.e., the unpack pattern. The method iterates with `vals` to
/// create the mask for `numBits` bits vector. The `numBits` have to be a
/// multiple of 128. For example, if `vals` is {0, 1, 16, 17} and `numBits` is
/// 512, there should be 16 elements in the final result. It constructs the
/// below mask to get the unpack elements.
/// [0, 1, 16, 17,
/// 0+4, 1+4, 16+4, 17+4,
/// 0+8, 1+8, 16+8, 17+8,
/// 0+12, 1+12, 16+12, 17+12]
static SmallVector<int64_t>
getUnpackShufflePermFor128Lane(ArrayRef<int64_t> vals, int numBits) {
assert(numBits % 128 == 0 && "expected numBits is a multiple of 128");
int numElem = numBits / 32;
SmallVector<int64_t> res;
for (int i = 0; i < numElem; i += 4)
for (int64_t v : vals)
res.push_back(v + i);
return res;
}
/// Lower to vector.shuffle on v1 and v2 with UnpackLoPd shuffle mask. For
/// example, if it is targeting 512 bit vector, returns
/// vector.shuffle on v1, v2, [0, 1, 16, 17,
/// 0+4, 1+4, 16+4, 17+4,
/// 0+8, 1+8, 16+8, 17+8,
/// 0+12, 1+12, 16+12, 17+12].
static Value createUnpackLoPd(ImplicitLocOpBuilder &b, Value v1, Value v2,
int numBits) {
int numElem = numBits / 32;
return b.create<vector::ShuffleOp>(
v1, v2,
getUnpackShufflePermFor128Lane({0, 1, numElem, numElem + 1}, numBits));
}
/// Lower to vector.shuffle on v1 and v2 with UnpackHiPd shuffle mask. For
/// example, if it is targeting 512 bit vector, returns
/// vector.shuffle, v1, v2, [2, 3, 18, 19,
/// 2+4, 3+4, 18+4, 19+4,
/// 2+8, 3+8, 18+8, 19+8,
/// 2+12, 3+12, 18+12, 19+12].
static Value createUnpackHiPd(ImplicitLocOpBuilder &b, Value v1, Value v2,
int numBits) {
int numElem = numBits / 32;
return b.create<vector::ShuffleOp>(
v1, v2,
getUnpackShufflePermFor128Lane({2, 3, numElem + 2, numElem + 3},
numBits));
}
/// Lower to vector.shuffle on v1 and v2 with UnpackLoPs shuffle mask. For
/// example, if it is targeting 512 bit vector, returns
/// vector.shuffle, v1, v2, [0, 16, 1, 17,
/// 0+4, 16+4, 1+4, 17+4,
/// 0+8, 16+8, 1+8, 17+8,
/// 0+12, 16+12, 1+12, 17+12].
static Value createUnpackLoPs(ImplicitLocOpBuilder &b, Value v1, Value v2,
int numBits) {
int numElem = numBits / 32;
auto shuffle = b.create<vector::ShuffleOp>(
v1, v2,
getUnpackShufflePermFor128Lane({0, numElem, 1, numElem + 1}, numBits));
return shuffle;
}
/// Lower to vector.shuffle on v1 and v2 with UnpackHiPs shuffle mask. For
/// example, if it is targeting 512 bit vector, returns
/// vector.shuffle, v1, v2, [2, 18, 3, 19,
/// 2+4, 18+4, 3+4, 19+4,
/// 2+8, 18+8, 3+8, 19+8,
/// 2+12, 18+12, 3+12, 19+12].
static Value createUnpackHiPs(ImplicitLocOpBuilder &b, Value v1, Value v2,
int numBits) {
int numElem = numBits / 32;
return b.create<vector::ShuffleOp>(
v1, v2,
getUnpackShufflePermFor128Lane({2, numElem + 2, 3, numElem + 3},
numBits));
}
/// Returns a vector.shuffle that shuffles 128-bit lanes (composed of 4 32-bit
/// elements) selected by `mask` from `v1` and `v2`. I.e.,
///
/// DEFINE SELECT4(src, control) {
/// CASE(control[1:0]) OF
/// 0: tmp[127:0] := src[127:0]
/// 1: tmp[127:0] := src[255:128]
/// 2: tmp[127:0] := src[383:256]
/// 3: tmp[127:0] := src[511:384]
/// ESAC
/// RETURN tmp[127:0]
/// }
/// dst[127:0] := SELECT4(v1[511:0], mask[1:0])
/// dst[255:128] := SELECT4(v1[511:0], mask[3:2])
/// dst[383:256] := SELECT4(v2[511:0], mask[5:4])
/// dst[511:384] := SELECT4(v2[511:0], mask[7:6])
static Value create4x128BitSuffle(ImplicitLocOpBuilder &b, Value v1, Value v2,
uint8_t mask) {
assert(cast<VectorType>(v1.getType()).getShape()[0] == 16 &&
"expected a vector with length=16");
SmallVector<int64_t> shuffleMask;
auto appendToMask = [&](int64_t base, uint8_t control) {
switch (control) {
case 0:
llvm::append_range(shuffleMask, ArrayRef<int64_t>{base + 0, base + 1,
base + 2, base + 3});
break;
case 1:
llvm::append_range(shuffleMask, ArrayRef<int64_t>{base + 4, base + 5,
base + 6, base + 7});
break;
case 2:
llvm::append_range(shuffleMask, ArrayRef<int64_t>{base + 8, base + 9,
base + 10, base + 11});
break;
case 3:
llvm::append_range(shuffleMask, ArrayRef<int64_t>{base + 12, base + 13,
base + 14, base + 15});
break;
default:
llvm_unreachable("control > 3 : overflow");
}
};
uint8_t b01 = mask & 0x3;
uint8_t b23 = (mask >> 2) & 0x3;
uint8_t b45 = (mask >> 4) & 0x3;
uint8_t b67 = (mask >> 6) & 0x3;
appendToMask(0, b01);
appendToMask(0, b23);
appendToMask(16, b45);
appendToMask(16, b67);
return b.create<vector::ShuffleOp>(v1, v2, shuffleMask);
}
/// Lowers the value to a vector.shuffle op. The `source` is expected to be a
/// 1-D vector and have `m`x`n` elements.
static Value transposeToShuffle1D(OpBuilder &b, Value source, int m, int n) {
SmallVector<int64_t> mask;
mask.reserve(m * n);
for (int64_t j = 0; j < n; ++j)
for (int64_t i = 0; i < m; ++i)
mask.push_back(i * n + j);
return b.create<vector::ShuffleOp>(source.getLoc(), source, source, mask);
}
/// Lowers the value to a sequence of vector.shuffle ops. The `source` is
/// expected to be a 16x16 vector.
static Value transposeToShuffle16x16(OpBuilder &builder, Value source, int m,
int n) {
ImplicitLocOpBuilder b(source.getLoc(), builder);
SmallVector<Value> vs;
for (int64_t i = 0; i < m; ++i)
vs.push_back(b.create<vector::ExtractOp>(source, i));
// Interleave 32-bit lanes using
// 8x _mm512_unpacklo_epi32
// 8x _mm512_unpackhi_epi32
Value t0 = createUnpackLoPs(b, vs[0x0], vs[0x1], 512);
Value t1 = createUnpackHiPs(b, vs[0x0], vs[0x1], 512);
Value t2 = createUnpackLoPs(b, vs[0x2], vs[0x3], 512);
Value t3 = createUnpackHiPs(b, vs[0x2], vs[0x3], 512);
Value t4 = createUnpackLoPs(b, vs[0x4], vs[0x5], 512);
Value t5 = createUnpackHiPs(b, vs[0x4], vs[0x5], 512);
Value t6 = createUnpackLoPs(b, vs[0x6], vs[0x7], 512);
Value t7 = createUnpackHiPs(b, vs[0x6], vs[0x7], 512);
Value t8 = createUnpackLoPs(b, vs[0x8], vs[0x9], 512);
Value t9 = createUnpackHiPs(b, vs[0x8], vs[0x9], 512);
Value ta = createUnpackLoPs(b, vs[0xa], vs[0xb], 512);
Value tb = createUnpackHiPs(b, vs[0xa], vs[0xb], 512);
Value tc = createUnpackLoPs(b, vs[0xc], vs[0xd], 512);
Value td = createUnpackHiPs(b, vs[0xc], vs[0xd], 512);
Value te = createUnpackLoPs(b, vs[0xe], vs[0xf], 512);
Value tf = createUnpackHiPs(b, vs[0xe], vs[0xf], 512);
// Interleave 64-bit lanes using
// 8x _mm512_unpacklo_epi64
// 8x _mm512_unpackhi_epi64
Value r0 = createUnpackLoPd(b, t0, t2, 512);
Value r1 = createUnpackHiPd(b, t0, t2, 512);
Value r2 = createUnpackLoPd(b, t1, t3, 512);
Value r3 = createUnpackHiPd(b, t1, t3, 512);
Value r4 = createUnpackLoPd(b, t4, t6, 512);
Value r5 = createUnpackHiPd(b, t4, t6, 512);
Value r6 = createUnpackLoPd(b, t5, t7, 512);
Value r7 = createUnpackHiPd(b, t5, t7, 512);
Value r8 = createUnpackLoPd(b, t8, ta, 512);
Value r9 = createUnpackHiPd(b, t8, ta, 512);
Value ra = createUnpackLoPd(b, t9, tb, 512);
Value rb = createUnpackHiPd(b, t9, tb, 512);
Value rc = createUnpackLoPd(b, tc, te, 512);
Value rd = createUnpackHiPd(b, tc, te, 512);
Value re = createUnpackLoPd(b, td, tf, 512);
Value rf = createUnpackHiPd(b, td, tf, 512);
// Permute 128-bit lanes using
// 16x _mm512_shuffle_i32x4
t0 = create4x128BitSuffle(b, r0, r4, 0x88);
t1 = create4x128BitSuffle(b, r1, r5, 0x88);
t2 = create4x128BitSuffle(b, r2, r6, 0x88);
t3 = create4x128BitSuffle(b, r3, r7, 0x88);
t4 = create4x128BitSuffle(b, r0, r4, 0xdd);
t5 = create4x128BitSuffle(b, r1, r5, 0xdd);
t6 = create4x128BitSuffle(b, r2, r6, 0xdd);
t7 = create4x128BitSuffle(b, r3, r7, 0xdd);
t8 = create4x128BitSuffle(b, r8, rc, 0x88);
t9 = create4x128BitSuffle(b, r9, rd, 0x88);
ta = create4x128BitSuffle(b, ra, re, 0x88);
tb = create4x128BitSuffle(b, rb, rf, 0x88);
tc = create4x128BitSuffle(b, r8, rc, 0xdd);
td = create4x128BitSuffle(b, r9, rd, 0xdd);
te = create4x128BitSuffle(b, ra, re, 0xdd);
tf = create4x128BitSuffle(b, rb, rf, 0xdd);
// Permute 256-bit lanes using again
// 16x _mm512_shuffle_i32x4
vs[0x0] = create4x128BitSuffle(b, t0, t8, 0x88);
vs[0x1] = create4x128BitSuffle(b, t1, t9, 0x88);
vs[0x2] = create4x128BitSuffle(b, t2, ta, 0x88);
vs[0x3] = create4x128BitSuffle(b, t3, tb, 0x88);
vs[0x4] = create4x128BitSuffle(b, t4, tc, 0x88);
vs[0x5] = create4x128BitSuffle(b, t5, td, 0x88);
vs[0x6] = create4x128BitSuffle(b, t6, te, 0x88);
vs[0x7] = create4x128BitSuffle(b, t7, tf, 0x88);
vs[0x8] = create4x128BitSuffle(b, t0, t8, 0xdd);
vs[0x9] = create4x128BitSuffle(b, t1, t9, 0xdd);
vs[0xa] = create4x128BitSuffle(b, t2, ta, 0xdd);
vs[0xb] = create4x128BitSuffle(b, t3, tb, 0xdd);
vs[0xc] = create4x128BitSuffle(b, t4, tc, 0xdd);
vs[0xd] = create4x128BitSuffle(b, t5, td, 0xdd);
vs[0xe] = create4x128BitSuffle(b, t6, te, 0xdd);
vs[0xf] = create4x128BitSuffle(b, t7, tf, 0xdd);
auto reshInputType = VectorType::get(
{m, n}, cast<VectorType>(source.getType()).getElementType());
Value res =
b.create<arith::ConstantOp>(reshInputType, b.getZeroAttr(reshInputType));
for (int64_t i = 0; i < m; ++i)
res = b.create<vector::InsertOp>(vs[i], res, i);
return res;
}
namespace {
/// Progressive lowering of TransposeOp.
/// One:
/// %x = vector.transpose %y, [1, 0]
/// is replaced by:
/// %z = arith.constant dense<0.000000e+00>
/// %0 = vector.extract %y[0, 0]
/// %1 = vector.insert %0, %z [0, 0]
/// ..
/// %x = vector.insert .., .. [.., ..]
class TransposeOpLowering : public OpRewritePattern<vector::TransposeOp> {
public:
using OpRewritePattern::OpRewritePattern;
TransposeOpLowering(vector::VectorTransformsOptions vectorTransformOptions,
MLIRContext *context, PatternBenefit benefit = 1)
: OpRewritePattern<vector::TransposeOp>(context, benefit),
vectorTransformOptions(vectorTransformOptions) {}
LogicalResult matchAndRewrite(vector::TransposeOp op,
PatternRewriter &rewriter) const override {
auto loc = op.getLoc();
Value input = op.getVector();
VectorType inputType = op.getSourceVectorType();
VectorType resType = op.getResultVectorType();
// Set up convenience transposition table.
ArrayRef<int64_t> transp = op.getPermutation();
if (isShuffleLike(vectorTransformOptions.vectorTransposeLowering) &&
succeeded(isTranspose2DSlice(op)))
return rewriter.notifyMatchFailure(
op, "Options specifies lowering to shuffle");
// Replace:
// vector.transpose %0, [1, 0] : vector<nx1x<eltty>> to
// vector<1xnxelty>
// with:
// vector.shape_cast %0 : vector<nx1x<eltty>> to vector<1xnxelty>
//
// Source with leading unit dim (inverse) is also replaced. Unit dim must
// be fixed. Non-unit can be scalable.
if (resType.getRank() == 2 &&
((resType.getShape().front() == 1 &&
!resType.getScalableDims().front()) ||
(resType.getShape().back() == 1 &&
!resType.getScalableDims().back())) &&
transp == ArrayRef<int64_t>({1, 0})) {
rewriter.replaceOpWithNewOp<vector::ShapeCastOp>(op, resType, input);
return success();
}
if (inputType.isScalable())
return failure();
// Handle a true 2-D matrix transpose differently when requested.
if (vectorTransformOptions.vectorTransposeLowering ==
vector::VectorTransposeLowering::Flat &&
resType.getRank() == 2 && transp[0] == 1 && transp[1] == 0) {
Type flattenedType =
VectorType::get(resType.getNumElements(), resType.getElementType());
auto matrix =
rewriter.create<vector::ShapeCastOp>(loc, flattenedType, input);
auto rows = rewriter.getI32IntegerAttr(resType.getShape()[0]);
auto columns = rewriter.getI32IntegerAttr(resType.getShape()[1]);
Value trans = rewriter.create<vector::FlatTransposeOp>(
loc, flattenedType, matrix, rows, columns);
rewriter.replaceOpWithNewOp<vector::ShapeCastOp>(op, resType, trans);
return success();
}
// Generate unrolled extract/insert ops. We do not unroll the rightmost
// (i.e., highest-order) dimensions that are not transposed and leave them
// in vector form to improve performance. Therefore, we prune those
// dimensions from the shape/transpose data structures used to generate the
// extract/insert ops.
SmallVector<int64_t> prunedTransp;
pruneNonTransposedDims(transp, prunedTransp);
size_t numPrunedDims = transp.size() - prunedTransp.size();
auto prunedInShape = inputType.getShape().drop_back(numPrunedDims);
auto prunedInStrides = computeStrides(prunedInShape);
// Generates the extract/insert operations for every scalar/vector element
// of the leftmost transposed dimensions. We traverse every transpose
// element using a linearized index that we delinearize to generate the
// appropriate indices for the extract/insert operations.
Value result = rewriter.create<arith::ConstantOp>(
loc, resType, rewriter.getZeroAttr(resType));
int64_t numTransposedElements = ShapedType::getNumElements(prunedInShape);
for (int64_t linearIdx = 0; linearIdx < numTransposedElements;
++linearIdx) {
auto extractIdxs = delinearize(linearIdx, prunedInStrides);
SmallVector<int64_t> insertIdxs(extractIdxs);
applyPermutationToVector(insertIdxs, prunedTransp);
Value extractOp =
rewriter.create<vector::ExtractOp>(loc, input, extractIdxs);
result =
rewriter.create<vector::InsertOp>(loc, extractOp, result, insertIdxs);
}
rewriter.replaceOp(op, result);
return success();
}
private:
/// Options to control the vector patterns.
vector::VectorTransformsOptions vectorTransformOptions;
};
/// Rewrite a 2-D vector.transpose as a sequence of shuffle ops.
/// If the strategy is Shuffle1D, it will be lowered to:
/// vector.shape_cast 2D -> 1D
/// vector.shuffle
/// vector.shape_cast 1D -> 2D
/// If the strategy is Shuffle16x16, it will be lowered to a sequence of shuffle
/// ops on 16xf32 vectors.
class TransposeOp2DToShuffleLowering
: public OpRewritePattern<vector::TransposeOp> {
public:
using OpRewritePattern::OpRewritePattern;
TransposeOp2DToShuffleLowering(
vector::VectorTransformsOptions vectorTransformOptions,
MLIRContext *context, PatternBenefit benefit = 1)
: OpRewritePattern<vector::TransposeOp>(context, benefit),
vectorTransformOptions(vectorTransformOptions) {}
LogicalResult matchAndRewrite(vector::TransposeOp op,
PatternRewriter &rewriter) const override {
if (!isShuffleLike(vectorTransformOptions.vectorTransposeLowering))
return rewriter.notifyMatchFailure(
op, "not using vector shuffle based lowering");
if (op.getSourceVectorType().isScalable())
return rewriter.notifyMatchFailure(
op, "vector shuffle lowering not supported for scalable vectors");
auto srcGtOneDims = isTranspose2DSlice(op);
if (failed(srcGtOneDims))
return rewriter.notifyMatchFailure(
op, "expected transposition on a 2D slice");
VectorType srcType = op.getSourceVectorType();
int64_t m = srcType.getDimSize(std::get<0>(srcGtOneDims.value()));
int64_t n = srcType.getDimSize(std::get<1>(srcGtOneDims.value()));
// Reshape the n-D input vector with only two dimensions greater than one
// to a 2-D vector.
Location loc = op.getLoc();
auto flattenedType = VectorType::get({n * m}, srcType.getElementType());
auto reshInputType = VectorType::get({m, n}, srcType.getElementType());
auto reshInput = rewriter.create<vector::ShapeCastOp>(loc, flattenedType,
op.getVector());
Value res;
if (vectorTransformOptions.vectorTransposeLowering ==
VectorTransposeLowering::Shuffle16x16 &&
m == 16 && n == 16) {
reshInput =
rewriter.create<vector::ShapeCastOp>(loc, reshInputType, reshInput);
res = transposeToShuffle16x16(rewriter, reshInput, m, n);
} else {
// Fallback to shuffle on 1D approach.
res = transposeToShuffle1D(rewriter, reshInput, m, n);
}
rewriter.replaceOpWithNewOp<vector::ShapeCastOp>(
op, op.getResultVectorType(), res);
return success();
}
private:
/// Options to control the vector patterns.
vector::VectorTransformsOptions vectorTransformOptions;
};
} // namespace
void mlir::vector::populateVectorTransposeLoweringPatterns(
RewritePatternSet &patterns, VectorTransformsOptions options,
PatternBenefit benefit) {
patterns.add<TransposeOpLowering, TransposeOp2DToShuffleLowering>(
options, patterns.getContext(), benefit);
}