[Mlir-commits] [mlir] [mlir][x86] Decouple Accumulator from ADD-Based Vector Contractions (over loops) (PR #204327)

[Julian Oppermann]

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@@ -0,0 +1,115 @@
+//===- MoveAccumulatorForContractLoop.cpp ---------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Dialect/SCF/IR/SCF.h"
+#include "mlir/Dialect/Vector/IR/VectorOps.h"
+#include "mlir/Dialect/Vector/Utils/VectorUtils.h"
+#include "mlir/Dialect/X86/Transforms.h"
+#include "mlir/Dialect/X86/Utils/X86Utils.h"
+#include "mlir/Dialect/X86/X86Dialect.h"
+
+#include "mlir/IR/BuiltinAttributes.h"
+#include "mlir/IR/Dominance.h"
+#include "mlir/IR/PatternMatch.h"
+#include "llvm/Support/Casting.h"
+
+#include "mlir/Pass/Pass.h"
+#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
+
+using namespace mlir;
+using namespace mlir::vector;
+using namespace mlir::x86;
+
+namespace {
+// Transforms vector.contract(A, B, Acc) into vector.contract(A, B, 0) + Acc
+// to decouple the contraction computation from the accumulator update.
+struct MoveAccumulatorForContractLoop
+    : public OpRewritePattern<vector::ContractionOp> {
+  using OpRewritePattern<vector::ContractionOp>::OpRewritePattern;
+
+  LogicalResult matchAndRewrite(vector::ContractionOp contractOp,
+                                PatternRewriter &rewriter) const override {
+
+    if (contractOp.getKind() != vector::CombiningKind::ADD)
+      return rewriter.notifyMatchFailure(contractOp,
+                                         "Expects add combining kind.");
+
+    Operation *accReadOp =
+        traceToVectorReadLikeParentOperation(contractOp.getAcc());
+
+    Value contractValue = contractionUsersAfterYield(contractOp.getResult());
+
+    if (!contractValue)
+      return rewriter.notifyMatchFailure(
+          contractOp, "Final acc write might have multiple users.");
+
+    Operation *resultWriteOp = *contractValue.getUsers().begin();
+
+    if (!accReadOp || !resultWriteOp)
+      return rewriter.notifyMatchFailure(
+          contractOp, "Read/write from/to acc matrix is not by "
+                      "transfer_read/load/transfer_write/store ops.");
----------------
jopperm wrote:

Potential misnomer: `contractionUsersAfterYield` doesn't guarantee that the user is a `transfer_write` or `store` op, and the pattern doesn't require it IIUC.

https://github.com/llvm/llvm-project/pull/204327