[MLIR] Add a utility pass to linearize memref

mlir/include/mlir/Dialect/MemRef/Transforms/Passes.td

@@ -245,5 +245,15 @@ def ExpandReallocPass : Pass<"expand-realloc"> {
   ];
 }
 
+def FlattenMemrefsPass : Pass<"flatten-memref"> {
+  let summary = "Flatten a multiple dimensional memref to 1-dimensional";
+  let description = [{
+
+  }];
+  let dependentDialects = [
+      "affine::AffineDialect", "memref::MemRefDialect", "vector::VectorDialect"
+  ];
+}
+
 #endif // MLIR_DIALECT_MEMREF_TRANSFORMS_PASSES
 

mlir/include/mlir/Dialect/MemRef/Transforms/Transforms.h

@@ -144,6 +144,8 @@ FailureOr<memref::AllocOp> multiBuffer(memref::AllocOp allocOp,
 /// ```
 void populateExtractAddressComputationsPatterns(RewritePatternSet &patterns);
 
+void populateFlattenMemrefsPatterns(RewritePatternSet &patterns);
+
 /// Build a new memref::AllocaOp whose dynamic sizes are independent of all
 /// given independencies. If the op is already independent of all
 /// independencies, the same AllocaOp result is returned.

mlir/lib/Dialect/MemRef/Transforms/CMakeLists.txt

@@ -8,6 +8,7 @@ add_mlir_dialect_library(MLIRMemRefTransforms
   EmulateWideInt.cpp
   EmulateNarrowType.cpp
   ExtractAddressComputations.cpp
+  FlattenMemRefs.cpp
   FoldMemRefAliasOps.cpp
   IndependenceTransforms.cpp
   MultiBuffer.cpp

mlir/lib/Dialect/MemRef/Transforms/FlattenMemRefs.cpp

@@ -0,0 +1,286 @@
+//===----- FlattenMemRefs.cpp - MemRef ops flattener pass  ----------------===//
+//
+// 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 contains patterns for flattening an multi-rank memref-related
+// ops into 1-d memref ops.
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Dialect/Affine/IR/AffineOps.h"
+#include "mlir/Dialect/Arith/IR/Arith.h"
+#include "mlir/Dialect/MemRef/IR/MemRef.h"
+#include "mlir/Dialect/MemRef/Transforms/Passes.h"
+#include "mlir/Dialect/MemRef/Transforms/Transforms.h"
+#include "mlir/Dialect/MemRef/Utils/MemRefUtils.h"
+#include "mlir/Dialect/Utils/IndexingUtils.h"
+#include "mlir/Dialect/Utils/StaticValueUtils.h"
+#include "mlir/Dialect/Vector/IR/VectorOps.h"
+#include "mlir/IR/AffineExpr.h"
+#include "mlir/IR/Attributes.h"
+#include "mlir/IR/Builders.h"
+#include "mlir/IR/BuiltinTypes.h"
+#include "mlir/IR/OpDefinition.h"
+#include "mlir/IR/PatternMatch.h"
+#include "mlir/Pass/Pass.h"
+#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/TypeSwitch.h"
+
+#include <numeric>
+
+namespace mlir {
+namespace memref {
+#define GEN_PASS_DEF_FLATTENMEMREFSPASS
+#include "mlir/Dialect/MemRef/Transforms/Passes.h.inc"
+} // namespace memref
+} // namespace mlir
+
+using namespace mlir;
+
+static Value getValueFromOpFoldResult(OpBuilder &rewriter, Location loc,
+                                      OpFoldResult in) {
+  if (Attribute offsetAttr = dyn_cast<Attribute>(in)) {
+    return rewriter.create<arith::ConstantIndexOp>(
+        loc, cast<IntegerAttr>(offsetAttr).getInt());
+  }
+  return cast<Value>(in);
+}
+
+/// Returns a collapsed memref and the linearized index to access the element
+/// at the specified indices.
+static std::pair<Value, Value> getFlattenMemrefAndOffset(OpBuilder &rewriter,
+                                                         Location loc,
+                                                         Value source,
+                                                         ValueRange indices) {
+  int64_t sourceOffset;
+  SmallVector<int64_t, 4> sourceStrides;
+  auto sourceType = cast<MemRefType>(source.getType());
+  if (failed(sourceType.getStridesAndOffset(sourceStrides, sourceOffset))) {
+    assert(false);
+  }
+
+  memref::ExtractStridedMetadataOp stridedMetadata =
+      rewriter.create<memref::ExtractStridedMetadataOp>(loc, source);
+
+  auto typeBit = sourceType.getElementType().getIntOrFloatBitWidth();
+  OpFoldResult linearizedIndices;
+  memref::LinearizedMemRefInfo linearizedInfo;
+  std::tie(linearizedInfo, linearizedIndices) =
+      memref::getLinearizedMemRefOffsetAndSize(
+          rewriter, loc, typeBit, typeBit,
+          stridedMetadata.getConstifiedMixedOffset(),
+          stridedMetadata.getConstifiedMixedSizes(),
+          stridedMetadata.getConstifiedMixedStrides(),
+          getAsOpFoldResult(indices));
+
+  return std::make_pair(
+      rewriter.create<memref::ReinterpretCastOp>(
+          loc, source,
+          /* offset = */ linearizedInfo.linearizedOffset,
+          /* shapes = */
+          ArrayRef<OpFoldResult>{linearizedInfo.linearizedSize},
+          /* strides = */
+          ArrayRef<OpFoldResult>{rewriter.getIndexAttr(1)}),
+      getValueFromOpFoldResult(rewriter, loc, linearizedIndices));
+}
+
+static bool needFlattening(Value val) {
+  auto type = cast<MemRefType>(val.getType());
+  return type.getRank() > 1;
+}
+
+static bool checkLayout(Value val) {
+  auto type = cast<MemRefType>(val.getType());
+  return type.getLayout().isIdentity() ||
+         isa<StridedLayoutAttr>(type.getLayout());
+}
+
+namespace {
+static Value getTargetMemref(Operation *op) {
+  return llvm::TypeSwitch<Operation *, Value>(op)
+      .template Case<memref::LoadOp, memref::StoreOp, memref::AllocaOp,
+                     memref::AllocOp>([](auto op) { return op.getMemref(); })
+      .template Case<vector::LoadOp, vector::StoreOp, vector::MaskedLoadOp,
+                     vector::MaskedStoreOp, vector::TransferReadOp,
+                     vector::TransferWriteOp>(
+          [](auto op) { return op.getBase(); })
+      .Default([](auto) { return Value{}; });
+}
+
+template <typename T>
+static void castAllocResult(T oper, T newOper, Location loc,
+                            PatternRewriter &rewriter) {
+  memref::ExtractStridedMetadataOp stridedMetadata =
+      rewriter.create<memref::ExtractStridedMetadataOp>(loc, oper);
+  rewriter.replaceOpWithNewOp<memref::ReinterpretCastOp>(
+      oper, cast<MemRefType>(oper.getType()), newOper,
+      /*offset=*/rewriter.getIndexAttr(0),
+      stridedMetadata.getConstifiedMixedSizes(),
+      stridedMetadata.getConstifiedMixedStrides());
+}
+
+template <typename T>
+static void replaceOp(T op, PatternRewriter &rewriter, Value flatMemref,
+                      Value offset) {
+  Location loc = op->getLoc();
+  llvm::TypeSwitch<Operation *>(op.getOperation())
+      .template Case<memref::AllocOp>([&](auto oper) {
+        auto newAlloc = rewriter.create<memref::AllocOp>(
+            loc, cast<MemRefType>(flatMemref.getType()),
+            oper.getAlignmentAttr());
+        castAllocResult(oper, newAlloc, loc, rewriter);
+      })
+      .template Case<memref::AllocaOp>([&](auto oper) {
+        auto newAlloca = rewriter.create<memref::AllocaOp>(
+            loc, cast<MemRefType>(flatMemref.getType()),
+            oper.getAlignmentAttr());
+        castAllocResult(oper, newAlloca, loc, rewriter);
+      })
+      .template Case<memref::LoadOp>([&](auto op) {
+        auto newLoad = rewriter.create<memref::LoadOp>(
+            loc, op->getResultTypes(), flatMemref, ValueRange{offset});
+        newLoad->setAttrs(op->getAttrs());
+        rewriter.replaceOp(op, newLoad.getResult());
+      })
+      .template Case<memref::StoreOp>([&](auto op) {
+        auto newStore = rewriter.create<memref::StoreOp>(
+            loc, op->getOperands().front(), flatMemref, ValueRange{offset});
+        newStore->setAttrs(op->getAttrs());
+        rewriter.replaceOp(op, newStore);
+      })
+      .template Case<vector::LoadOp>([&](auto op) {
+        auto newLoad = rewriter.create<vector::LoadOp>(
+            loc, op->getResultTypes(), flatMemref, ValueRange{offset});
+        newLoad->setAttrs(op->getAttrs());
+        rewriter.replaceOp(op, newLoad.getResult());
+      })
+      .template Case<vector::StoreOp>([&](auto op) {
+        auto newStore = rewriter.create<vector::StoreOp>(
+            loc, op->getOperands().front(), flatMemref, ValueRange{offset});
+        newStore->setAttrs(op->getAttrs());
+        rewriter.replaceOp(op, newStore);
+      })
+      .template Case<vector::MaskedLoadOp>([&](auto op) {
+        auto newMaskedLoad = rewriter.create<vector::MaskedLoadOp>(
+            loc, op.getType(), flatMemref, ValueRange{offset}, op.getMask(),
+            op.getPassThru());
+        newMaskedLoad->setAttrs(op->getAttrs());
+        rewriter.replaceOp(op, newMaskedLoad.getResult());
+      })
+      .template Case<vector::MaskedStoreOp>([&](auto op) {
+        auto newMaskedStore = rewriter.create<vector::MaskedStoreOp>(
+            loc, flatMemref, ValueRange{offset}, op.getMask(),
+            op.getValueToStore());
+        newMaskedStore->setAttrs(op->getAttrs());
+        rewriter.replaceOp(op, newMaskedStore);
+      })
+      .template Case<vector::TransferReadOp>([&](auto op) {
+        auto newTransferRead = rewriter.create<vector::TransferReadOp>(
+            loc, op.getType(), flatMemref, ValueRange{offset}, op.getPadding());
+        rewriter.replaceOp(op, newTransferRead.getResult());
+      })
+      .template Case<vector::TransferWriteOp>([&](auto op) {
+        auto newTransferWrite = rewriter.create<vector::TransferWriteOp>(
+            loc, op.getVector(), flatMemref, ValueRange{offset});
+        rewriter.replaceOp(op, newTransferWrite);
+      })
+      .Default([&](auto op) {
+        op->emitOpError("unimplemented: do not know how to replace op.");
+      });
+}
+
+template <typename T>
+static ValueRange getIndices(T op) {
+  if constexpr (std::is_same_v<T, memref::AllocaOp> ||
+                std::is_same_v<T, memref::AllocOp>) {
+    return ValueRange{};
+  } else {
+    return op.getIndices();
+  }
+}
+
+template <typename T>
+static LogicalResult canBeFlattened(T op, PatternRewriter &rewriter) {
+  return llvm::TypeSwitch<Operation *, LogicalResult>(op.getOperation())
+      .template Case<vector::TransferReadOp, vector::TransferWriteOp>(
+          [&](auto oper) {
+            // For vector.transfer_read/write, must make sure:
+            // 1. all accesses are inbound, and
+            // 2. has an identity or minor identity permutation map.
+            auto permutationMap = oper.getPermutationMap();
+            if (!permutationMap.isIdentity() &&
+                !permutationMap.isMinorIdentity()) {
+              return rewriter.notifyMatchFailure(
+                  oper, "only identity permutation map is supported");
+            }
+            mlir::ArrayAttr inbounds = oper.getInBounds();
+            if (llvm::any_of(inbounds, [](Attribute attr) {
+                  return !cast<BoolAttr>(attr).getValue();
+                })) {
+              return rewriter.notifyMatchFailure(oper,
+                                                 "only inbounds are supported");
+            }
+            return success();
+          })
+      .Default([&](auto op) { return success(); });
+}
+
+template <typename T>
+struct MemRefRewritePattern : public OpRewritePattern<T> {
+  using OpRewritePattern<T>::OpRewritePattern;
+  LogicalResult matchAndRewrite(T op,
+                                PatternRewriter &rewriter) const override {
+    LogicalResult canFlatten = canBeFlattened(op, rewriter);
+    if (failed(canFlatten)) {
+      return canFlatten;
+    }
+
+    Value memref = getTargetMemref(op);
+    if (!needFlattening(memref) || !checkLayout(memref))
+      return failure();
+    auto &&[flatMemref, offset] = getFlattenMemrefAndOffset(
+        rewriter, op->getLoc(), memref, getIndices<T>(op));
+    replaceOp<T>(op, rewriter, flatMemref, offset);
+    return success();
+  }
+};
+
+struct FlattenMemrefsPass
+    : public mlir::memref::impl::FlattenMemrefsPassBase<FlattenMemrefsPass> {
+  using Base::Base;
+
+  void getDependentDialects(DialectRegistry &registry) const override {
+    registry.insert<affine::AffineDialect, arith::ArithDialect,
+                    memref::MemRefDialect, vector::VectorDialect>();
+  }
+
+  void runOnOperation() override {
+    RewritePatternSet patterns(&getContext());
+
+    memref::populateFlattenMemrefsPatterns(patterns);
+
+    if (failed(applyPatternsGreedily(getOperation(), std::move(patterns))))
+      return signalPassFailure();
+  }
+};
+
+} // namespace
+
+void memref::populateFlattenMemrefsPatterns(RewritePatternSet &patterns) {
+  patterns.insert<MemRefRewritePattern<memref::LoadOp>,
+                  MemRefRewritePattern<memref::StoreOp>,
+                  MemRefRewritePattern<memref::AllocOp>,
+                  MemRefRewritePattern<memref::AllocaOp>,
+                  MemRefRewritePattern<vector::LoadOp>,
+                  MemRefRewritePattern<vector::StoreOp>,
+                  MemRefRewritePattern<vector::TransferReadOp>,
+                  MemRefRewritePattern<vector::TransferWriteOp>,
+                  MemRefRewritePattern<vector::MaskedLoadOp>,
+                  MemRefRewritePattern<vector::MaskedStoreOp>>(
+      patterns.getContext());
+}