[llvm] [mlir] [mlir][transforms]-Extract dead code elimination util (PR #124606)
Amir Bishara via llvm-commits
llvm-commits at lists.llvm.org
Mon Jan 27 10:34:43 PST 2025
https://github.com/amirBish created https://github.com/llvm/llvm-project/pull/124606
Extract the dead code elimination into an exposed util file to have a simple usage of the cpp API.
>From d2a30d9e5c12e97087a941f7d558a03dc9d87a70 Mon Sep 17 00:00:00 2001
From: Amir Bishara <amir.bishara at mobileye.com>
Date: Mon, 27 Jan 2025 20:11:33 +0200
Subject: [PATCH] [mlir][transforms]-Extract dead code elimination util
Extract the dead code elimination into an exposed util
file to have a simple usage of the cpp API.
Change-Id: Ic013ba06b778f8d5221bea226131e5343b543f51
---
mlir/include/mlir/Transforms/DCEUtils.h | 26 ++++++++
.../lib/Dialect/Transform/IR/TransformOps.cpp | 44 +------------
mlir/lib/Transforms/Utils/CMakeLists.txt | 1 +
mlir/lib/Transforms/Utils/DCEUtils.cpp | 62 +++++++++++++++++++
.../llvm-project-overlay/mlir/BUILD.bazel | 1 +
5 files changed, 92 insertions(+), 42 deletions(-)
create mode 100644 mlir/include/mlir/Transforms/DCEUtils.h
create mode 100644 mlir/lib/Transforms/Utils/DCEUtils.cpp
diff --git a/mlir/include/mlir/Transforms/DCEUtils.h b/mlir/include/mlir/Transforms/DCEUtils.h
new file mode 100644
index 00000000000000..9432a136a811eb
--- /dev/null
+++ b/mlir/include/mlir/Transforms/DCEUtils.h
@@ -0,0 +1,26 @@
+//===- DCE.h - Dead Code Elimination -----------------*- C++ -*-===//
+//
+// 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 declares methods for eliminating dead code.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_TRANSFORMS_DCE_H_
+#define MLIR_TRANSFORMS_DCE_H_
+
+namespace mlir {
+
+class Operation;
+class RewriterBase;
+
+/// Eliminate dead code within the given `target`.
+void deadCodeElimination(RewriterBase &rewriter, Operation *target);
+
+} // namespace mlir
+
+#endif // MLIR_TRANSFORMS_DCE_H_
\ No newline at end of file
diff --git a/mlir/lib/Dialect/Transform/IR/TransformOps.cpp b/mlir/lib/Dialect/Transform/IR/TransformOps.cpp
index 798853a75441a1..79257cf16efed5 100644
--- a/mlir/lib/Dialect/Transform/IR/TransformOps.cpp
+++ b/mlir/lib/Dialect/Transform/IR/TransformOps.cpp
@@ -31,6 +31,7 @@
#include "mlir/Pass/PassManager.h"
#include "mlir/Pass/PassRegistry.h"
#include "mlir/Transforms/CSE.h"
+#include "mlir/Transforms/DCEUtils.h"
#include "mlir/Transforms/DialectConversion.h"
#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
#include "mlir/Transforms/LoopInvariantCodeMotionUtils.h"
@@ -314,48 +315,7 @@ DiagnosedSilenceableFailure transform::ApplyDeadCodeEliminationOp::applyToOne(
if (!payloadCheck.succeeded())
return payloadCheck;
- // Maintain a worklist of potentially dead ops.
- SetVector<Operation *> worklist;
-
- // Helper function that adds all defining ops of used values (operands and
- // operands of nested ops).
- auto addDefiningOpsToWorklist = [&](Operation *op) {
- op->walk([&](Operation *op) {
- for (Value v : op->getOperands())
- if (Operation *defOp = v.getDefiningOp())
- if (target->isProperAncestor(defOp))
- worklist.insert(defOp);
- });
- };
-
- // Helper function that erases an op.
- auto eraseOp = [&](Operation *op) {
- // Remove op and nested ops from the worklist.
- op->walk([&](Operation *op) {
- const auto *it = llvm::find(worklist, op);
- if (it != worklist.end())
- worklist.erase(it);
- });
- rewriter.eraseOp(op);
- };
-
- // Initial walk over the IR.
- target->walk<WalkOrder::PostOrder>([&](Operation *op) {
- if (op != target && isOpTriviallyDead(op)) {
- addDefiningOpsToWorklist(op);
- eraseOp(op);
- }
- });
-
- // Erase all ops that have become dead.
- while (!worklist.empty()) {
- Operation *op = worklist.pop_back_val();
- if (!isOpTriviallyDead(op))
- continue;
- addDefiningOpsToWorklist(op);
- eraseOp(op);
- }
-
+ deadCodeElimination(rewriter, target);
return DiagnosedSilenceableFailure::success();
}
diff --git a/mlir/lib/Transforms/Utils/CMakeLists.txt b/mlir/lib/Transforms/Utils/CMakeLists.txt
index 72eb34f36cf5f6..4b8c3b185f320b 100644
--- a/mlir/lib/Transforms/Utils/CMakeLists.txt
+++ b/mlir/lib/Transforms/Utils/CMakeLists.txt
@@ -2,6 +2,7 @@ add_mlir_library(MLIRTransformUtils
CFGToSCF.cpp
CommutativityUtils.cpp
ControlFlowSinkUtils.cpp
+ DCEUtils.cpp
DialectConversion.cpp
FoldUtils.cpp
GreedyPatternRewriteDriver.cpp
diff --git a/mlir/lib/Transforms/Utils/DCEUtils.cpp b/mlir/lib/Transforms/Utils/DCEUtils.cpp
new file mode 100644
index 00000000000000..102c04b4f6c734
--- /dev/null
+++ b/mlir/lib/Transforms/Utils/DCEUtils.cpp
@@ -0,0 +1,62 @@
+//===- DCEUtils.cpp - Dead Code Elimination ------------------------===//
+//
+// 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 transformation implements method for eliminating dead code.
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Transforms/DCEUtils.h"
+#include "mlir/IR/PatternMatch.h"
+#include "mlir/Interfaces/SideEffectInterfaces.h"
+#include "llvm/ADT/SetVector.h"
+
+using namespace mlir;
+
+void mlir::deadCodeElimination(RewriterBase &rewriter, Operation *target) {
+ // Maintain a worklist of potentially dead ops.
+ mlir::SetVector<Operation *> worklist;
+
+ // Helper function that adds all defining ops of used values (operands and
+ // operands of nested ops).
+ auto addDefiningOpsToWorklist = [&](Operation *op) {
+ op->walk([&](Operation *op) {
+ for (Value v : op->getOperands())
+ if (Operation *defOp = v.getDefiningOp())
+ if (target->isProperAncestor(defOp))
+ worklist.insert(defOp);
+ });
+ };
+
+ // Helper function that erases an op.
+ auto eraseOp = [&](Operation *op) {
+ // Remove op and nested ops from the worklist.
+ op->walk([&](Operation *op) {
+ const auto *it = llvm::find(worklist, op);
+ if (it != worklist.end())
+ worklist.erase(it);
+ });
+ rewriter.eraseOp(op);
+ };
+
+ // Initial walk over the IR.
+ target->walk<WalkOrder::PostOrder>([&](Operation *op) {
+ if (op != target && isOpTriviallyDead(op)) {
+ addDefiningOpsToWorklist(op);
+ eraseOp(op);
+ }
+ });
+
+ // Erase all ops that have become dead.
+ while (!worklist.empty()) {
+ Operation *op = worklist.pop_back_val();
+ if (!isOpTriviallyDead(op))
+ continue;
+ addDefiningOpsToWorklist(op);
+ eraseOp(op);
+ }
+}
diff --git a/utils/bazel/llvm-project-overlay/mlir/BUILD.bazel b/utils/bazel/llvm-project-overlay/mlir/BUILD.bazel
index 4d44396be98eec..10323cd54c522c 100644
--- a/utils/bazel/llvm-project-overlay/mlir/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/mlir/BUILD.bazel
@@ -8022,6 +8022,7 @@ cc_library(
"include/mlir/Transforms/CFGToSCF.h",
"include/mlir/Transforms/CommutativityUtils.h",
"include/mlir/Transforms/ControlFlowSinkUtils.h",
+ "include/mlir/Transforms/DCEUtils.h",
"include/mlir/Transforms/DialectConversion.h",
"include/mlir/Transforms/FoldUtils.h",
"include/mlir/Transforms/GreedyPatternRewriteDriver.h",
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