[Mlir-commits] [mlir] [SCFToAffine] Add a pass to raise scf to affine ops. (PR #152925)

[Oleksandr Alex Zinenko]

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@@ -0,0 +1,100 @@
+//===- SCFToAffine.cpp - SCF to Affine conversion -------------------------===//
+//
+// 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 a pass to raise scf.for, scf.if and loop.terminator
+// ops into affine ops.
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Conversion/SCFToAffine/SCFToAffine.h"
+#include "mlir/Dialect/Affine/IR/AffineOps.h"
+#include "mlir/Dialect/SCF/IR/SCF.h"
+#include "mlir/IR/Verifier.h"
+#include "mlir/Transforms/DialectConversion.h"
+#include "mlir/Transforms/Passes.h"
+
+namespace mlir {
+#define GEN_PASS_DEF_RAISESCFTOAFFINEPASS
+#include "mlir/Conversion/Passes.h.inc"
+} // namespace mlir
+
+using namespace mlir;
+
+namespace {
+
+struct SCFToAffinePass
+    : public impl::RaiseSCFToAffinePassBase<SCFToAffinePass> {
+  void runOnOperation() override;
+};
+
+struct ForOpRewrite : public OpRewritePattern<scf::ForOp> {
+  using OpRewritePattern<scf::ForOp>::OpRewritePattern;
+
+  LogicalResult matchAndRewrite(scf::ForOp op,
+                                PatternRewriter &rewriter) const override {
+    auto loc = op.getLoc();
+    auto lower = op.getLowerBound();
+    auto upper = op.getUpperBound();
+    auto step = op.getStep();
+
+    if (!affine::isValidDim(lower) || !affine::isValidDim(upper) ||
+        !affine::isValidSymbol(step))
+      return llvm::failure();
+
+    auto lowerDim = rewriter.getAffineDimExpr(0);
+    auto upperDim = rewriter.getAffineDimExpr(1);
+    auto stepSym = rewriter.getAffineSymbolExpr(0);
+    auto affineFor = affine::AffineForOp::create(
+        rewriter, loc, ValueRange(), rewriter.getConstantAffineMap(0),
+        ValueRange({lower, upper, step}),
+        AffineMap::get(2, 1,
+                       (upperDim - lowerDim + stepSym - 1).floorDiv(stepSym)),
+        1, op.getInits());
+    auto affineBody = affineFor.getBody();
+
+    if (affineBody->mightHaveTerminator())
+      rewriter.eraseOp(affineBody->getTerminator());
+
+    rewriter.setInsertionPointToStart(affineBody);
+    auto actualIndexMap =
+        AffineMap::get(2, 1, lowerDim + rewriter.getAffineDimExpr(1) * stepSym);
+    Value newIndVar =
+        affine::AffineApplyOp::create(
+            rewriter, op.getLoc(), actualIndexMap,
+            ValueRange({lower, affineFor.getInductionVar(), step}))
+            .getResult();
+
+    SmallVector<Value> argValues;
+    argValues.push_back(newIndVar);
+    llvm::append_range(argValues, affineFor.getRegionIterArgs());
+    rewriter.inlineBlockBefore(op.getBody(), affineBody, affineBody->end(),
+                               argValues);
+
+    auto scfYieldOp = cast<scf::YieldOp>(affineBody->getTerminator());
+    rewriter.setInsertionPointToEnd(affineBody);
+    rewriter.replaceOpWithNewOp<affine::AffineYieldOp>(
+        scfYieldOp, scfYieldOp->getOperands());
+
+    rewriter.replaceOp(op, affineFor);
+    return success();
+  }
+};
+
+} // namespace
+
+void mlir::populateSCFToAffineConversionPatterns(RewritePatternSet &patterns) {
+  patterns.add<ForOpRewrite>(patterns.getContext());
+}
+
+void SCFToAffinePass::runOnOperation() {
+  RewritePatternSet patterns(&getContext());
+  populateSCFToAffineConversionPatterns(patterns);
+
+  if (failed(applyPatternsGreedily(getOperation(), std::move(patterns))))
+    signalPassFailure();
----------------
ftynse wrote:

Do we actually need the greedy rewriter with its overhead here or would a simple walk calling a function suffice?

https://github.com/llvm/llvm-project/pull/152925