[Mlir-commits] [mlir] [mlir][bufferization] Adding the optimize-allocation-liveness pass (PR #101827)

[Dennis Filimonov]

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+//===- OptimizeAllocationliveness.cpp - impl. for buffer dealloc. ---===//
+//
+// 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 an algorithem for optimization of allocation liveness,
+// The algorithm moves the dealloc op to right after the last user of the
+// allocation and on the same block as the allocation.
+//
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Dialect/Arith/IR/Arith.h"
+#include "mlir/Dialect/Bufferization/Transforms/BufferViewFlowAnalysis.h"
+#include "mlir/Dialect/Bufferization/Transforms/Passes.h"
+#include "mlir/Dialect/Func/IR/FuncOps.h"
+#include "mlir/Dialect/MemRef/IR/MemRef.h"
+#include "mlir/Dialect/SCF/IR/SCF.h"
+#include "mlir/Dialect/SCF/Transforms/Transforms.h"
+#include "mlir/IR/Operation.h"
+#include "mlir/IR/Value.h"
+#include "llvm/Support/Debug.h"
+
+#include <optional>
+#include <utility>
+
+#define DEBUG_TYPE "optimize-allocation-liveness"
+#define DBGS() (llvm::dbgs() << '[' << DEBUG_TYPE << "] ")
+#define LDBG(X) LLVM_DEBUG(DBGS() << X << "\n")
+
+namespace mlir {
+namespace bufferization {
+#define GEN_PASS_DEF_OPTIMIZEALLOCATIONLIVENESS
+#include "mlir/Dialect/Bufferization/Transforms/Passes.h.inc"
+} // namespace bufferization
+} // namespace mlir
+
+using namespace mlir;
+
+namespace {
+
+//===----------------------------------------------------------------------===//
+// Helper functions
+//===----------------------------------------------------------------------===//
+
+/// Return true if `a` happens before `b`, i.e., `a` or one of its ancestors
+/// properly dominates `b` and `b` is not inside `a`.
+/// TODO find proper location for this function, since its copied from the llvm project.
+static bool happensBefore(Operation *a, Operation *b) {
+  do {
+    if (a->isProperAncestor(b))
+      return false;
+    if (Operation *bAncestor = a->getBlock()->findAncestorOpInBlock(*b)) {
+      return a->isBeforeInBlock(bAncestor);
+    }
+  } while ((a = a->getParentOp()));
+  return false;
+}
+
+/// This method will find all the users of an op according to given templete
+/// user type.
+/// TODO find proper location for this helper function.
+template <typename T> FailureOr<T> getUserOfType(Value val) {
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DennisFily wrote:

Simplified this method. It will search for a user with free memory effect and check that only one such user exists.

https://github.com/llvm/llvm-project/pull/101827