[mlir][emitc] Add func to emitc conversion

This adds patterns and a pass to convert the Func dialect to EmitC.
A `func.func` op that is `private` is converted to `emitc.func` with a
`"static"` specifier.

Author: marbre

mlir/include/mlir/Conversion/FuncToEmitC/FuncToEmitC.h

@@ -0,0 +1,18 @@
+//===- FuncToEmitC.h - Func to EmitC Patterns -------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_CONVERSION_FUNCTOEMITC_FUNCTOEMITC_H
+#define MLIR_CONVERSION_FUNCTOEMITC_FUNCTOEMITC_H
+
+namespace mlir {
+class RewritePatternSet;
+
+void populateFuncToEmitCPatterns(RewritePatternSet &patterns);
+} // namespace mlir
+
+#endif // MLIR_CONVERSION_FUNCTOEMITC_FUNCTOEMITC_H

mlir/include/mlir/Conversion/FuncToEmitC/FuncToEmitCPass.h

@@ -0,0 +1,24 @@
+//===- FuncToEmitCPass.h - Func to EmitC Pass -------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef MLIR_CONVERSION_FUNCTOEMITC_FUNCTOEMITCPASS_H
+#define MLIR_CONVERSION_FUNCTOEMITC_FUNCTOEMITCPASS_H
+
+#include <memory>
+
+namespace mlir {
+class Pass;
+
+#define GEN_PASS_DECL_FUNCTOEMITC
+#include "mlir/Conversion/Passes.h.inc"
+
+std::unique_ptr<Pass> createConvertFuncToEmitC();
+
+} // namespace mlir
+
+#endif // MLIR_CONVERSION_FUNCTOEMITC_FUNCTOEMITCPASS_H

mlir/include/mlir/Conversion/Passes.h

@@ -28,6 +28,7 @@
 #include "mlir/Conversion/ControlFlowToSPIRV/ControlFlowToSPIRV.h"
 #include "mlir/Conversion/ControlFlowToSPIRV/ControlFlowToSPIRVPass.h"
 #include "mlir/Conversion/ConvertToLLVM/ToLLVMPass.h"
+#include "mlir/Conversion/FuncToEmitC/FuncToEmitCPass.h"
 #include "mlir/Conversion/FuncToLLVM/ConvertFuncToLLVMPass.h"
 #include "mlir/Conversion/FuncToSPIRV/FuncToSPIRVPass.h"
 #include "mlir/Conversion/GPUCommon/GPUCommonPass.h"

mlir/include/mlir/Conversion/Passes.td

@@ -344,6 +344,15 @@ def ConvertControlFlowToSPIRV : Pass<"convert-cf-to-spirv"> {
   ];
 }
 
+//===----------------------------------------------------------------------===//
+// FuncToEmitC
+//===----------------------------------------------------------------------===//
+
+def ConvertFuncToEmitC : Pass<"convert-func-to-emitc", "ModuleOp"> {
+  let summary = "Convert Func dialect to EmitC dialect";
+  let dependentDialects = ["emitc::EmitCDialect"];
+}
+
 //===----------------------------------------------------------------------===//
 // FuncToLLVM
 //===----------------------------------------------------------------------===//

mlir/lib/Conversion/CMakeLists.txt

@@ -17,6 +17,7 @@ add_subdirectory(ControlFlowToLLVM)
 add_subdirectory(ControlFlowToSCF)
 add_subdirectory(ControlFlowToSPIRV)
 add_subdirectory(ConvertToLLVM)
+add_subdirectory(FuncToEmitC)
 add_subdirectory(FuncToLLVM)
 add_subdirectory(FuncToSPIRV)
 add_subdirectory(GPUCommon)

mlir/lib/Conversion/FuncToEmitC/CMakeLists.txt

@@ -0,0 +1,16 @@
+add_mlir_conversion_library(MLIRFuncToEmitC
+  FuncToEmitC.cpp
+  FuncToEmitCPass.cpp
+
+  ADDITIONAL_HEADER_DIRS
+  ${MLIR_MAIN_INCLUDE_DIR}/mlir/Conversion/FuncToEmitC
+
+  DEPENDS
+  MLIRConversionPassIncGen
+
+  LINK_LIBS PUBLIC
+  MLIREmitCDialect
+  MLIRFuncDialect
+  MLIRPass
+  MLIRTransformUtils
+  )

mlir/lib/Conversion/FuncToEmitC/FuncToEmitC.cpp

@@ -0,0 +1,119 @@
+//===- FuncToEmitC.cpp - Func to EmitC Patterns -----------------*- 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 implements patterns to convert the Func dialect to the EmitC
+// dialect.
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Conversion/FuncToEmitC/FuncToEmitC.h"
+
+#include "mlir/Dialect/EmitC/IR/EmitC.h"
+#include "mlir/Dialect/Func/IR/FuncOps.h"
+#include "mlir/Transforms/DialectConversion.h"
+
+using namespace mlir;
+
+//===----------------------------------------------------------------------===//
+// Conversion Patterns
+//===----------------------------------------------------------------------===//
+
+namespace {
+class CallOpConversion final : public OpConversionPattern<func::CallOp> {
+public:
+  using OpConversionPattern<func::CallOp>::OpConversionPattern;
+
+  LogicalResult
+  matchAndRewrite(func::CallOp callOp, OpAdaptor adaptor,
+                  ConversionPatternRewriter &rewriter) const override {
+    // multiple results func was not converted to spirv.func
+    if (callOp.getNumResults() > 1)
+      return rewriter.notifyMatchFailure(
+          callOp, "Only functions with zero or one result can be converted");
+
+    rewriter.replaceOpWithNewOp<emitc::CallOp>(
+        callOp,
+        callOp.getNumResults() ? callOp.getResult(0).getType() : nullptr,
+        adaptor.getOperands(), callOp->getAttrs());
+
+    return success();
+  }
+};
+
+class FuncOpConversion final : public OpConversionPattern<func::FuncOp> {
+public:
+  using OpConversionPattern<func::FuncOp>::OpConversionPattern;
+
+  LogicalResult
+  matchAndRewrite(func::FuncOp funcOp, OpAdaptor adaptor,
+                  ConversionPatternRewriter &rewriter) const override {
+
+    if (funcOp.getFunctionType().getNumResults() > 1)
+      return rewriter.notifyMatchFailure(
+          funcOp, "Only functions with zero or one result can be converted");
+
+    if (funcOp.isDeclaration())
+      return rewriter.notifyMatchFailure(funcOp,
+                                         "Declarations cannot be converted");
+
+    // Create the converted emitc.func op.
+    emitc::FuncOp newFuncOp = rewriter.create<emitc::FuncOp>(
+        funcOp.getLoc(), funcOp.getName(), funcOp.getFunctionType());
+
+    // Copy over all attributes other than the function name and type.
+    for (const auto &namedAttr : funcOp->getAttrs()) {
+      if (namedAttr.getName() != funcOp.getFunctionTypeAttrName() &&
+          namedAttr.getName() != SymbolTable::getSymbolAttrName())
+        newFuncOp->setAttr(namedAttr.getName(), namedAttr.getValue());
+    }
+
+    // Create add `static` to specifiers if `func.func` is private.
+    if (funcOp.isPrivate()) {
+      StringAttr specifier = rewriter.getStringAttr("static");
+      ArrayAttr specifiers = rewriter.getArrayAttr(specifier);
+      newFuncOp.setSpecifiersAttr(specifiers);
+    }
+
+    rewriter.inlineRegionBefore(funcOp.getBody(), newFuncOp.getBody(),
+                                newFuncOp.end());
+    rewriter.eraseOp(funcOp);
+
+    return success();
+  }
+};
+
+class ReturnOpConversion final : public OpConversionPattern<func::ReturnOp> {
+public:
+  using OpConversionPattern<func::ReturnOp>::OpConversionPattern;
+
+  LogicalResult
+  matchAndRewrite(func::ReturnOp returnOp, OpAdaptor adaptor,
+                  ConversionPatternRewriter &rewriter) const override {
+    if (returnOp.getNumOperands() > 1)
+      return rewriter.notifyMatchFailure(
+          returnOp, "Only zero or one operand is supported");
+
+    rewriter.replaceOpWithNewOp<emitc::ReturnOp>(
+        returnOp,
+        returnOp.getNumOperands() ? adaptor.getOperands()[0] : nullptr);
+    return success();
+  }
+};
+} // namespace
+
+//===----------------------------------------------------------------------===//
+// Pattern population
+//===----------------------------------------------------------------------===//
+
+void mlir::populateFuncToEmitCPatterns(RewritePatternSet &patterns) {
+  MLIRContext *ctx = patterns.getContext();
+
+  patterns.add<CallOpConversion>(ctx);
+  patterns.add<FuncOpConversion>(ctx);
+  patterns.add<ReturnOpConversion>(ctx);
+}

mlir/lib/Conversion/FuncToEmitC/FuncToEmitCPass.cpp

@@ -0,0 +1,49 @@
+//===- FuncToEmitC.cpp - Func to EmitC Pass ---------------------*- 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 implements a pass to convert the Func dialect to the EmitC dialect.
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Conversion/FuncToEmitC/FuncToEmitCPass.h"
+
+#include "mlir/Conversion/FuncToEmitC/FuncToEmitC.h"
+#include "mlir/Dialect/EmitC/IR/EmitC.h"
+#include "mlir/Dialect/Func/IR/FuncOps.h"
+#include "mlir/Pass/Pass.h"
+#include "mlir/Transforms/DialectConversion.h"
+
+namespace mlir {
+#define GEN_PASS_DEF_CONVERTFUNCTOEMITC
+#include "mlir/Conversion/Passes.h.inc"
+} // namespace mlir
+
+using namespace mlir;
+
+namespace {
+struct ConvertFuncToEmitC
+    : public impl::ConvertFuncToEmitCBase<ConvertFuncToEmitC> {
+  void runOnOperation() override;
+};
+} // namespace
+
+void ConvertFuncToEmitC::runOnOperation() {
+  ConversionTarget target(getContext());
+
+  target.addLegalDialect<emitc::EmitCDialect>();
+  target.addIllegalOp<func::CallOp>();
+  target.addIllegalOp<func::FuncOp>();
+  target.addIllegalOp<func::ReturnOp>();
+
+  RewritePatternSet patterns(&getContext());
+  populateFuncToEmitCPatterns(patterns);
+
+  if (failed(
+          applyPartialConversion(getOperation(), target, std::move(patterns))))
+    signalPassFailure();
+}

mlir/test/Conversion/FuncToEmitC/func-to-emitc.mlir

@@ -0,0 +1,55 @@
+// RUN: mlir-opt -split-input-file -convert-func-to-emitc %s | FileCheck %s
+
+// CHECK-LABEL: emitc.func @foo()
+// CHECK-NEXT: emitc.return
+func.func @foo() {
+  return
+}
+
+// -----
+
+// CHECK-LABEL: emitc.func private @foo() attributes {specifiers = ["static"]}
+// CHECK-NEXT: emitc.return
+func.func private @foo() {
+  return
+}
+
+// -----
+
+// CHECK-LABEL: emitc.func @foo(%arg0: i32)
+func.func @foo(%arg0: i32) {
+  emitc.call_opaque "bar"(%arg0) : (i32) -> ()
+  return
+}
+
+// -----
+
+// CHECK-LABEL: emitc.func @foo(%arg0: i32) -> i32
+// CHECK-NEXT: emitc.return %arg0 : i32
+func.func @foo(%arg0: i32) -> i32 {
+  return %arg0 : i32
+}
+
+// -----
+
+// CHECK-LABEL: emitc.func @foo(%arg0: i32, %arg1: i32) -> i32
+func.func @foo(%arg0: i32, %arg1: i32) -> i32 {
+  %0 = "emitc.add" (%arg0, %arg1) : (i32, i32) -> i32
+  return %0 : i32
+}
+
+// -----
+
+// CHECK-LABEL: emitc.func private @return_i32(%arg0: i32) -> i32 attributes {specifiers = ["static"]}
+// CHECK-NEXT: emitc.return %arg0 : i32
+func.func private @return_i32(%arg0: i32) -> i32 {
+  return %arg0 : i32
+}
+
+// CHECK-LABEL: emitc.func @call(%arg0: i32) -> i32
+// CHECK-NEXT: %0 = emitc.call @return_i32(%arg0) : (i32) -> i32
+// CHECK-NEXT: emitc.return %0 : i32
+func.func @call(%arg0: i32) -> i32 {
+  %0 = call @return_i32(%arg0) : (i32) -> (i32)
+  return %0 : i32
+}