[MLIR] Add initial convert-memref-to-emitc pass (#85389)

This converts `memref.alloca`, `memref.load` & `memref.store` to
`emitc.variable`, `emitc.subscript` and `emitc.assign`.

4 files changed, 188 insertions, 0 deletions

diff --git a/mlir/lib/Conversion/CMakeLists.txt b/mlir/lib/Conversion/CMakeLists.txt
index 8219cf9..41ab704 100644
--- a/mlir/lib/Conversion/CMakeLists.txt
+++ b/mlir/lib/Conversion/CMakeLists.txt
@@ -35,6 +35,7 @@ add_subdirectory(MathToFuncs)
 add_subdirectory(MathToLibm)
 add_subdirectory(MathToLLVM)
 add_subdirectory(MathToSPIRV)
+add_subdirectory(MemRefToEmitC)
 add_subdirectory(MemRefToLLVM)
 add_subdirectory(MemRefToSPIRV)
 add_subdirectory(NVGPUToNVVM)
diff --git a/mlir/lib/Conversion/MemRefToEmitC/CMakeLists.txt b/mlir/lib/Conversion/MemRefToEmitC/CMakeLists.txt
new file mode 100644
index 0000000..8a72e74
--- /dev/null
+++ b/mlir/lib/Conversion/MemRefToEmitC/CMakeLists.txt
@@ -0,0 +1,18 @@
+add_mlir_conversion_library(MLIRMemRefToEmitC
+  MemRefToEmitC.cpp
+  MemRefToEmitCPass.cpp
+
+  ADDITIONAL_HEADER_DIRS
+  ${MLIR_MAIN_INCLUDE_DIR}/mlir/Conversion/MemRefToEmitC
+
+  DEPENDS
+  MLIRConversionPassIncGen
+
+  LINK_COMPONENTS
+  Core
+
+  LINK_LIBS PUBLIC
+  MLIREmitCDialect
+  MLIRMemRefDialect
+  MLIRTransforms
+  )
diff --git a/mlir/lib/Conversion/MemRefToEmitC/MemRefToEmitC.cpp b/mlir/lib/Conversion/MemRefToEmitC/MemRefToEmitC.cpp
new file mode 100644
index 0000000..0e3b646
--- /dev/null
+++ b/mlir/lib/Conversion/MemRefToEmitC/MemRefToEmitC.cpp
@@ -0,0 +1,114 @@
+//===- MemRefToEmitC.cpp - MemRef to EmitC 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 patterns to convert memref ops into emitc ops.
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Conversion/MemRefToEmitC/MemRefToEmitC.h"
+
+#include "mlir/Dialect/EmitC/IR/EmitC.h"
+#include "mlir/Dialect/MemRef/IR/MemRef.h"
+#include "mlir/IR/Builders.h"
+#include "mlir/IR/PatternMatch.h"
+#include "mlir/Transforms/DialectConversion.h"
+
+using namespace mlir;
+
+namespace {
+struct ConvertAlloca final : public OpConversionPattern<memref::AllocaOp> {
+  using OpConversionPattern::OpConversionPattern;
+
+  LogicalResult
+  matchAndRewrite(memref::AllocaOp op, OpAdaptor operands,
+                  ConversionPatternRewriter &rewriter) const override {
+
+    if (!op.getType().hasStaticShape()) {
+      return rewriter.notifyMatchFailure(
+          op.getLoc(), "cannot transform alloca with dynamic shape");
+    }
+
+    if (op.getAlignment().value_or(1) > 1) {
+      // TODO: Allow alignment if it is not more than the natural alignment
+      // of the C array.
+      return rewriter.notifyMatchFailure(
+          op.getLoc(), "cannot transform alloca with alignment requirement");
+    }
+
+    auto resultTy = getTypeConverter()->convertType(op.getType());
+    if (!resultTy) {
+      return rewriter.notifyMatchFailure(op.getLoc(), "cannot convert type");
+    }
+    auto noInit = emitc::OpaqueAttr::get(getContext(), "");
+    rewriter.replaceOpWithNewOp<emitc::VariableOp>(op, resultTy, noInit);
+    return success();
+  }
+};
+
+struct ConvertLoad final : public OpConversionPattern<memref::LoadOp> {
+  using OpConversionPattern::OpConversionPattern;
+
+  LogicalResult
+  matchAndRewrite(memref::LoadOp op, OpAdaptor operands,
+                  ConversionPatternRewriter &rewriter) const override {
+
+    auto resultTy = getTypeConverter()->convertType(op.getType());
+    if (!resultTy) {
+      return rewriter.notifyMatchFailure(op.getLoc(), "cannot convert type");
+    }
+
+    auto subscript = rewriter.create<emitc::SubscriptOp>(
+        op.getLoc(), operands.getMemref(), operands.getIndices());
+
+    auto noInit = emitc::OpaqueAttr::get(getContext(), "");
+    auto var =
+        rewriter.create<emitc::VariableOp>(op.getLoc(), resultTy, noInit);
+
+    rewriter.create<emitc::AssignOp>(op.getLoc(), var, subscript);
+    rewriter.replaceOp(op, var);
+    return success();
+  }
+};
+
+struct ConvertStore final : public OpConversionPattern<memref::StoreOp> {
+  using OpConversionPattern::OpConversionPattern;
+
+  LogicalResult
+  matchAndRewrite(memref::StoreOp op, OpAdaptor operands,
+                  ConversionPatternRewriter &rewriter) const override {
+
+    auto subscript = rewriter.create<emitc::SubscriptOp>(
+        op.getLoc(), operands.getMemref(), operands.getIndices());
+    rewriter.replaceOpWithNewOp<emitc::AssignOp>(op, subscript,
+                                                 operands.getValue());
+    return success();
+  }
+};
+} // namespace
+
+void mlir::populateMemRefToEmitCTypeConversion(TypeConverter &typeConverter) {
+  typeConverter.addConversion(
+      [&](MemRefType memRefType) -> std::optional<Type> {
+        if (!memRefType.hasStaticShape() ||
+            !memRefType.getLayout().isIdentity() || memRefType.getRank() == 0) {
+          return {};
+        }
+        Type convertedElementType =
+            typeConverter.convertType(memRefType.getElementType());
+        if (!convertedElementType)
+          return {};
+        return emitc::ArrayType::get(memRefType.getShape(),
+                                     convertedElementType);
+      });
+}
+
+void mlir::populateMemRefToEmitCConversionPatterns(RewritePatternSet &patterns,
+                                                   TypeConverter &converter) {
+  patterns.add<ConvertAlloca, ConvertLoad, ConvertStore>(converter,
+                                                         patterns.getContext());
+}
diff --git a/mlir/lib/Conversion/MemRefToEmitC/MemRefToEmitCPass.cpp b/mlir/lib/Conversion/MemRefToEmitC/MemRefToEmitCPass.cpp
new file mode 100644
index 0000000..4e5d191
--- /dev/null
+++ b/mlir/lib/Conversion/MemRefToEmitC/MemRefToEmitCPass.cpp
@@ -0,0 +1,55 @@
+//===- MemRefToEmitC.cpp - MemRef to EmitC 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 convert memref ops into emitc ops.
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Conversion/MemRefToEmitC/MemRefToEmitCPass.h"
+
+#include "mlir/Conversion/MemRefToEmitC/MemRefToEmitC.h"
+#include "mlir/Dialect/EmitC/IR/EmitC.h"
+#include "mlir/Dialect/MemRef/IR/MemRef.h"
+#include "mlir/Pass/Pass.h"
+#include "mlir/Transforms/DialectConversion.h"
+
+namespace mlir {
+#define GEN_PASS_DEF_CONVERTMEMREFTOEMITC
+#include "mlir/Conversion/Passes.h.inc"
+} // namespace mlir
+
+using namespace mlir;
+
+namespace {
+struct ConvertMemRefToEmitCPass
+    : public impl::ConvertMemRefToEmitCBase<ConvertMemRefToEmitCPass> {
+  void runOnOperation() override {
+    TypeConverter converter;
+
+    // Fallback for other types.
+    converter.addConversion([](Type type) -> std::optional<Type> {
+      if (isa<MemRefType>(type))
+        return {};
+      return type;
+    });
+
+    populateMemRefToEmitCTypeConversion(converter);
+
+    RewritePatternSet patterns(&getContext());
+    populateMemRefToEmitCConversionPatterns(patterns, converter);
+
+    ConversionTarget target(getContext());
+    target.addIllegalDialect<memref::MemRefDialect>();
+    target.addLegalDialect<emitc::EmitCDialect>();
+
+    if (failed(applyPartialConversion(getOperation(), target,
+                                      std::move(patterns))))
+      return signalPassFailure();
+  }
+};
+} // namespace