[Mlir-commits] [mlir] [mlir][x86vector] Sink Vector.transfer_reads and vector.load before the consumer (PR #169333)

[Arun Thangamani]

================
@@ -0,0 +1,148 @@
+//===- SinkVectorProducerOps.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/Vector/IR/VectorOps.h"
+#include "mlir/Dialect/Vector/Utils/VectorUtils.h"
+#include "mlir/Dialect/X86Vector/Transforms.h"
+#include "mlir/Dialect/X86Vector/X86VectorDialect.h"
+
+#include "mlir/IR/BuiltinAttributes.h"
+#include "mlir/IR/Dominance.h"
+#include "mlir/IR/PatternMatch.h"
+
+#include "mlir/Pass/Pass.h"
+#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
+
+using namespace mlir;
+using namespace mlir::vector;
+using namespace mlir::x86vector;
+
+static FailureOr<llvm::SmallVector<Operation *>> getAllUsers(Operation *op) {
+  llvm::SmallVector<Operation *> opUsers;
+  for (OpResult result : op->getResults()) {
+    for (Operation *user : result.getUsers()) {
+      // Check prod and users belongs to same block.
+      if (op->getBlock() != user->getBlock())
+        return failure();
+      opUsers.push_back(user);
+    }
+  }
+
+  return opUsers;
+}
+
+// Prevent pathological looping:
+// If two/three producers are used by same consumer, will end in looping of
+// moving the producers.
+// For example:
+// %1 = prod1
+// %2 = prod2
+// %3 = prod3
+// %4 = op %1, %2, %3
+static bool checkLooping(Operation *op) {
+  llvm::SmallVector<Operation *> operations;
+  operations.push_back(op);
+
+  // Retrive the next immediate two/three operation until it is a vector.load or
+  // a vector.transfer_read
+  Operation *nextOp = op->getNextNode();
+  while (operations.size() < 3 && nextOp) {
+    if (isa<vector::LoadOp>(nextOp) || isa<vector::TransferReadOp>(nextOp)) {
+      operations.push_back(op);
+    } else {
+      break;
+    }
+    nextOp = nextOp->getNextNode();
+  }
+
+  // If all the loads or transfer_reads have same immediate nextOp as its
+  // user, then it loops.
+  for (Operation *op : operations) {
+    FailureOr<llvm::SmallVector<Operation *>> users = getAllUsers(op);
+    if (failed(users))
+      return false;
+
+    if (!llvm::is_contained(*users, nextOp))
+      return false;
+  }
+
+  return true;
+}
+
+/// Sink vector producers forward to reduce live ranges.
+/// This pattern applies to ops such as vector.load and vector.transfer_read.
+template <typename producerOp>
+struct SinkVectorProducerOps final : public OpRewritePattern<producerOp> {
+  using OpRewritePattern<producerOp>::OpRewritePattern;
+
+  LogicalResult matchAndRewrite(producerOp op,
+                                PatternRewriter &rewriter) const override {
+
+    auto users = getAllUsers(op);
+    if (failed(users))
+      return failure();
+
+    if (checkLooping(op))
+      return failure();
+
+    llvm::DenseMap<Operation *, llvm::SmallVector<Operation *>> prodsAllUsers;
+    llvm::DenseMap<Operation *, Operation *> prodsFirstUser;
+
+    llvm::SmallVector<Operation *> opUsers = *users;
+    prodsAllUsers.try_emplace(op, opUsers);
+
+    // Iterate until the last instruction to find the first users of all
+    // producers within the block.
+    Operation *nextOp = op->getNextNode();
+
+    while (nextOp) {
+
+      if (isa<vector::LoadOp>(nextOp) || isa<vector::TransferReadOp>(nextOp)) {
+        auto nextUsers = getAllUsers(nextOp);
+
+        if (failed(nextUsers))
+          continue;
----------------
arun-thmn wrote:

Thanks. This a `loop-hole`.
Corrected the `while` loop, should be fine now.

https://github.com/llvm/llvm-project/pull/169333