Define a DataFlowSolver helper that loads sensible default analyses (#143415)

Cf. https://discourse.llvm.org/t/mlir-dead-code-analysis/67568/10

Custom analysis passes will not work properly unless both
DeadCodeAnalysis and SparseConstantPropagation are loaded to the
DataFlowSolver. This is intended behavior, but surprising to many users
as shown in the thread. In lieu of a longer-term fix (which I am not
knowledgeable enough to implement myself, yet), this commit adds a
helper function that loads these two analyses, as well as providing
breadcrumbs for an explanation of the problem. The existing places in
the codebase where these two analyses are loaded for the purpose of
running other unrelated analyses are replaced by the use of the helper.

---------

Co-authored-by: Jeremy Kun <[email protected]>
Co-authored-by: Oleksandr "Alex" Zinenko <[email protected]>

Author: j2kun

mlir/include/mlir/Analysis/DataFlow/Utils.h

@@ -0,0 +1,37 @@
+//===-Utils.h - DataFlow utility functions ----------------------*- 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 defines utility functions for dataflow analyses.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_ANALYSIS_DATAFLOW_UTILS_H
+#define MLIR_ANALYSIS_DATAFLOW_UTILS_H
+
+#include "mlir/Analysis/DataFlow/ConstantPropagationAnalysis.h"
+#include "mlir/Analysis/DataFlow/DeadCodeAnalysis.h"
+#include "mlir/Analysis/DataFlowFramework.h"
+
+namespace mlir {
+namespace dataflow {
+
+/// Populates a DataFlowSolver with analyses that are required to ensure
+/// user-defined analyses are run properly.
+///
+/// This helper is intended to be an interim fix until a more robust solution
+/// can be implemented in the DataFlow framework directly. Cf.
+/// https://discourse.llvm.org/t/mlir-dead-code-analysis/67568
+inline void loadBaselineAnalyses(DataFlowSolver &solver) {
+  solver.load<dataflow::DeadCodeAnalysis>();
+  solver.load<dataflow::SparseConstantPropagation>();
+}
+
+} // end namespace dataflow
+} // end namespace mlir
+
+#endif // MLIR_ANALYSIS_DATAFLOW_INTEGERANGEANALYSIS_H

mlir/lib/Analysis/DataFlow/LivenessAnalysis.cpp

@@ -10,9 +10,8 @@
 #include <cassert>
 #include <mlir/Analysis/DataFlow/LivenessAnalysis.h>
 
-#include <mlir/Analysis/DataFlow/ConstantPropagationAnalysis.h>
-#include <mlir/Analysis/DataFlow/DeadCodeAnalysis.h>
 #include <mlir/Analysis/DataFlow/SparseAnalysis.h>
+#include <mlir/Analysis/DataFlow/Utils.h>
 #include <mlir/Analysis/DataFlowFramework.h>
 #include <mlir/IR/Operation.h>
 #include <mlir/IR/Value.h>
@@ -249,8 +248,7 @@ void LivenessAnalysis::setToExitState(Liveness *lattice) {
 RunLivenessAnalysis::RunLivenessAnalysis(Operation *op) {
   SymbolTableCollection symbolTable;
 
-  solver.load<DeadCodeAnalysis>();
-  solver.load<SparseConstantPropagation>();
+  loadBaselineAnalyses(solver);
   solver.load<LivenessAnalysis>(symbolTable);
   (void)solver.initializeAndRun(op);
 }

mlir/lib/Dialect/XeGPU/Transforms/XeGPUSubgroupDistribute.cpp

@@ -5,9 +5,8 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
-#include "mlir/Analysis/DataFlow/ConstantPropagationAnalysis.h"
-#include "mlir/Analysis/DataFlow/DeadCodeAnalysis.h"
 #include "mlir/Analysis/DataFlow/SparseAnalysis.h"
+#include "mlir/Analysis/DataFlow/Utils.h"
 #include "mlir/Analysis/DataFlowFramework.h"
 #include "mlir/Dialect/GPU/IR/GPUDialect.h"
 #include "mlir/Dialect/GPU/Utils/DistributionUtils.h"
@@ -620,8 +619,7 @@ class RunLayoutInfoPropagation {
 
   RunLayoutInfoPropagation(Operation *op) : target(op) {
     SymbolTableCollection symbolTable;
-    solver.load<DeadCodeAnalysis>();
-    solver.load<SparseConstantPropagation>();
+    loadBaselineAnalyses(solver);
     solver.load<LayoutInfoPropagation>(symbolTable);
     (void)solver.initializeAndRun(op);
   }

mlir/test/lib/Analysis/DataFlow/TestDenseBackwardDataFlowAnalysis.cpp

@@ -13,9 +13,8 @@
 #include "TestDenseDataFlowAnalysis.h"
 #include "TestDialect.h"
 #include "TestOps.h"
-#include "mlir/Analysis/DataFlow/ConstantPropagationAnalysis.h"
-#include "mlir/Analysis/DataFlow/DeadCodeAnalysis.h"
 #include "mlir/Analysis/DataFlow/DenseAnalysis.h"
+#include "mlir/Analysis/DataFlow/Utils.h"
 #include "mlir/Analysis/DataFlowFramework.h"
 #include "mlir/IR/Builders.h"
 #include "mlir/IR/SymbolTable.h"
@@ -283,9 +282,8 @@ struct TestNextAccessPass
 
     auto config = DataFlowConfig().setInterprocedural(interprocedural);
     DataFlowSolver solver(config);
-    solver.load<DeadCodeAnalysis>();
+    loadBaselineAnalyses(solver);
     solver.load<NextAccessAnalysis>(symbolTable, assumeFuncReads);
-    solver.load<SparseConstantPropagation>();
     solver.load<UnderlyingValueAnalysis>();
     if (failed(solver.initializeAndRun(op))) {
       emitError(op->getLoc(), "dataflow solver failed");

mlir/test/lib/Analysis/DataFlow/TestDenseForwardDataFlowAnalysis.cpp

@@ -13,9 +13,8 @@
 #include "TestDenseDataFlowAnalysis.h"
 #include "TestDialect.h"
 #include "TestOps.h"
-#include "mlir/Analysis/DataFlow/ConstantPropagationAnalysis.h"
-#include "mlir/Analysis/DataFlow/DeadCodeAnalysis.h"
 #include "mlir/Analysis/DataFlow/DenseAnalysis.h"
+#include "mlir/Analysis/DataFlow/Utils.h"
 #include "mlir/Interfaces/SideEffectInterfaces.h"
 #include "mlir/Pass/Pass.h"
 #include "mlir/Support/LLVM.h"
@@ -240,8 +239,7 @@ struct TestLastModifiedPass
     Operation *op = getOperation();
 
     DataFlowSolver solver(DataFlowConfig().setInterprocedural(interprocedural));
-    solver.load<DeadCodeAnalysis>();
-    solver.load<SparseConstantPropagation>();
+    loadBaselineAnalyses(solver);
     solver.load<LastModifiedAnalysis>(assumeFuncWrites);
     solver.load<UnderlyingValueAnalysis>();
     if (failed(solver.initializeAndRun(op)))

mlir/test/lib/Analysis/DataFlow/TestSparseBackwardDataFlowAnalysis.cpp

@@ -6,9 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "mlir/Analysis/DataFlow/ConstantPropagationAnalysis.h"
-#include "mlir/Analysis/DataFlow/DeadCodeAnalysis.h"
 #include "mlir/Analysis/DataFlow/SparseAnalysis.h"
+#include "mlir/Analysis/DataFlow/Utils.h"
 #include "mlir/Dialect/MemRef/IR/MemRef.h"
 #include "mlir/Interfaces/SideEffectInterfaces.h"
 #include "mlir/Pass/Pass.h"
@@ -182,8 +181,7 @@ struct TestWrittenToPass
     SymbolTableCollection symbolTable;
 
     DataFlowSolver solver(DataFlowConfig().setInterprocedural(interprocedural));
-    solver.load<DeadCodeAnalysis>();
-    solver.load<SparseConstantPropagation>();
+    loadBaselineAnalyses(solver);
     solver.load<WrittenToAnalysis>(symbolTable, assumeFuncWrites);
     if (failed(solver.initializeAndRun(op)))
       return signalPassFailure();