[Mlir-commits] [mlir] [mlir][tosa] Introduce arith.constant -> tosa.const normalization pass (PR #167873)

[Luke Hutton]

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+//===- TosaArithConstantToConst.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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a pass that converts tensor-valued arith.constant ops
+// into tosa.const so that TOSA pipelines operate on a uniform constant form.
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Dialect/Tosa/Transforms/Passes.h"
+
+#include "mlir/Dialect/Arith/IR/Arith.h"
+#include "mlir/Dialect/Func/IR/FuncOps.h"
+#include "mlir/Dialect/Quant/IR/QuantTypes.h"
+#include "mlir/Dialect/Tosa/IR/TosaOps.h"
+#include "mlir/IR/BuiltinAttributes.h"
+#include "mlir/IR/BuiltinTypes.h"
+#include "mlir/IR/PatternMatch.h"
+#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
+
+namespace mlir {
+namespace tosa {
+#define GEN_PASS_DEF_TOSAARITHCONSTANTTOTOSACONSTPASS
+#include "mlir/Dialect/Tosa/Transforms/Passes.h.inc"
+} // namespace tosa
+} // namespace mlir
+
+using namespace mlir;
+using namespace mlir::tosa;
+
+namespace {
+
+/// Returns true when `elementType` is natively representable by tosa.const.
+static bool isSupportedElementType(Type elementType) {
+  if (isa<FloatType>(elementType))
+    return true;
+
+  if (auto intType = dyn_cast<IntegerType>(elementType))
+    return intType.isSignless() || intType.isUnsigned();
+
+  if (isa<quant::QuantizedType>(elementType))
+    return true;
+
+  return false;
+}
+
+class ArithConstantToTosaConst : public OpRewritePattern<arith::ConstantOp> {
+public:
+  using OpRewritePattern::OpRewritePattern;
+
+  LogicalResult matchAndRewrite(arith::ConstantOp constOp,
+                                PatternRewriter &rewriter) const override {
+    // TOSA constant verification requires a ranked, statically shaped tensor.
+    auto resultType = dyn_cast<RankedTensorType>(constOp.getResult().getType());
+    if (!resultType || !resultType.hasStaticShape())
+      return failure();
+
+    if (!isSupportedElementType(resultType.getElementType()))
+      return failure();
+
+    Attribute attr = constOp.getValueAttr();
+    auto elementsAttr = dyn_cast<ElementsAttr>(attr);
+    if (!elementsAttr)
+      return failure();
+
+    auto attrType = dyn_cast<RankedTensorType>(elementsAttr.getType());
+    if (!attrType || !attrType.hasStaticShape())
+      return failure();
+
+    if (attrType != resultType) {
+      // Allow reshape when the payload can be reinterpreted without altering
+      // the number of elements or element type. Dense resource attributes
+      // cannot be reshaped losslessly, so bail out in that case.
+      if (!isa<DenseElementsAttr>(elementsAttr))
+        return failure();
+
+      if (attrType.getElementType() != resultType.getElementType())
+        return failure();
+
+      auto denseAttr = cast<DenseElementsAttr>(elementsAttr);
+      if (denseAttr.getNumElements() != resultType.getNumElements())
+        return failure();
+
+      elementsAttr = denseAttr.reshape(resultType);
+    }
+
+    auto newConst = tosa::ConstOp::create(rewriter, constOp.getLoc(),
+                                          resultType, elementsAttr);
+    rewriter.replaceOp(constOp, newConst.getResult());
+    return success();
+  }
+};
+
+struct TosaArithConstantToTosaConstPass
+    : public tosa::impl::TosaArithConstantToTosaConstPassBase<
+          TosaArithConstantToTosaConstPass> {
+  using Base::Base;
+
+  void getDependentDialects(DialectRegistry &registry) const override {
+    registry.insert<tosa::TosaDialect>();
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lhutton1 wrote:

Should arith also be added here?

https://github.com/llvm/llvm-project/pull/167873