[mlir][EmitC] Add func, call and return operations

This adds a `func`, `call` and `return` operation to the EmitC dialect,
closely related to the corresponding operations of the Func dialect. In
contrast to the operations of the Func dialect, the EmitC operations do
not support multiple results. The `emitc.func` op features a
`specifiers` argument that for example allows, with corresponding
support in the emitter, to emit `inline static` functions.

Author: marbre

mlir/include/mlir/Dialect/EmitC/IR/EmitC.h

@@ -20,6 +20,7 @@
 #include "mlir/IR/Dialect.h"
 #include "mlir/Interfaces/CastInterfaces.h"
 #include "mlir/Interfaces/ControlFlowInterfaces.h"
+#include "mlir/Interfaces/FunctionInterfaces.h"
 #include "mlir/Interfaces/SideEffectInterfaces.h"
 
 #include "mlir/Dialect/EmitC/IR/EmitCDialect.h.inc"

mlir/include/mlir/Dialect/EmitC/IR/EmitC.td

@@ -16,8 +16,10 @@
 include "mlir/Dialect/EmitC/IR/EmitCAttributes.td"
 include "mlir/Dialect/EmitC/IR/EmitCTypes.td"
 
+include "mlir/Interfaces/CallInterfaces.td"
 include "mlir/Interfaces/CastInterfaces.td"
 include "mlir/Interfaces/ControlFlowInterfaces.td"
+include "mlir/Interfaces/FunctionInterfaces.td"
 include "mlir/Interfaces/SideEffectInterfaces.td"
 include "mlir/IR/RegionKindInterface.td"
 
@@ -386,6 +388,190 @@ def EmitC_ForOp : EmitC_Op<"for",
   let hasRegionVerifier = 1;
 }
 
+def EmitC_CallOp : EmitC_Op<"call",
+    [CallOpInterface,
+     DeclareOpInterfaceMethods<SymbolUserOpInterface>]> {
+  let summary = "call operation";
+  let description = [{
+    The `emitc.call` operation represents a direct call to an `emitc.func`
+    that is within the same symbol scope as the call. The operands and result type
+    of the call must match the specified function type. The callee is encoded as a
+    symbol reference attribute named "callee".
+
+    Example:
+
+    ```mlir
+    %2 = emitc.call @my_add(%0, %1) : (f32, f32) -> f32
+    ```
+  }];
+  let arguments = (ins FlatSymbolRefAttr:$callee, Variadic<AnyType>:$operands);
+  let results = (outs Variadic<AnyType>);
+
+  let builders = [
+    OpBuilder<(ins "FuncOp":$callee, CArg<"ValueRange", "{}">:$operands), [{
+      $_state.addOperands(operands);
+      $_state.addAttribute("callee", SymbolRefAttr::get(callee));
+      $_state.addTypes(callee.getFunctionType().getResults());
+    }]>,
+    OpBuilder<(ins "SymbolRefAttr":$callee, "TypeRange":$results,
+      CArg<"ValueRange", "{}">:$operands), [{
+      $_state.addOperands(operands);
+      $_state.addAttribute("callee", callee);
+      $_state.addTypes(results);
+    }]>,
+    OpBuilder<(ins "StringAttr":$callee, "TypeRange":$results,
+      CArg<"ValueRange", "{}">:$operands), [{
+      build($_builder, $_state, SymbolRefAttr::get(callee), results, operands);
+    }]>,
+    OpBuilder<(ins "StringRef":$callee, "TypeRange":$results,
+      CArg<"ValueRange", "{}">:$operands), [{
+      build($_builder, $_state, StringAttr::get($_builder.getContext(), callee),
+            results, operands);
+    }]>];
+
+  let extraClassDeclaration = [{
+    FunctionType getCalleeType();
+
+    /// Get the argument operands to the called function.
+    operand_range getArgOperands() {
+      return {arg_operand_begin(), arg_operand_end()};
+    }
+
+    MutableOperandRange getArgOperandsMutable() {
+      return getOperandsMutable();
+    }
+
+    operand_iterator arg_operand_begin() { return operand_begin(); }
+    operand_iterator arg_operand_end() { return operand_end(); }
+
+    /// Return the callee of this operation.
+    CallInterfaceCallable getCallableForCallee() {
+      return (*this)->getAttrOfType<SymbolRefAttr>("callee");
+    }
+
+    /// Set the callee for this operation.
+    void setCalleeFromCallable(CallInterfaceCallable callee) {
+      (*this)->setAttr("callee", callee.get<SymbolRefAttr>());
+    }
+  }];
+
+  let assemblyFormat = [{
+    $callee `(` $operands `)` attr-dict `:` functional-type($operands, results)
+  }];
+}
+
+def EmitC_FuncOp : EmitC_Op<"func", [
+  AutomaticAllocationScope,
+  FunctionOpInterface, IsolatedFromAbove
+]> {
+  let summary = "An operation with a name containing a single `SSACFG` region";
+  let description = [{
+    Operations within the function cannot implicitly capture values defined
+    outside of the function, i.e. Functions are `IsolatedFromAbove`. All
+    external references must use function arguments or attributes that establish
+    a symbolic connection (e.g. symbols referenced by name via a string
+    attribute like SymbolRefAttr). While the MLIR textual form provides a nice
+    inline syntax for function arguments, they are internally represented as
+    “block arguments” to the first block in the region.
+
+    Only dialect attribute names may be specified in the attribute dictionaries
+    for function arguments, results, or the function itself.
+
+    Example:
+
+    ```mlir
+    // A function with no results:
+    emitc.func @foo(%arg0 : i32) {
+      emitc.call_opaque "bar" (%arg0) : (i32) -> ()
+      emitc.return
+    }
+
+    // A function with its argument as single result:
+    emitc.func @foo(%arg0 : i32) -> i32 {
+      emitc.return %arg0 : i32
+    }
+
+    // A function with specifiers attribute:
+    emitc.func @example_specifiers_fn_attr() -> i32
+                attributes {specifiers = ["static","inline"]} {
+      %0 = emitc.call_opaque "foo" (): () -> i32
+      emitc.return %0 : i32
+    }
+
+    ```
+  }];
+  let arguments = (ins SymbolNameAttr:$sym_name,
+                       TypeAttrOf<FunctionType>:$function_type,
+                       OptionalAttr<StrArrayAttr>:$specifiers,
+                       OptionalAttr<DictArrayAttr>:$arg_attrs,
+                       OptionalAttr<DictArrayAttr>:$res_attrs);
+  let regions = (region AnyRegion:$body);
+
+  let builders = [OpBuilder<(ins
+    "StringRef":$name, "FunctionType":$type,
+    CArg<"ArrayRef<NamedAttribute>", "{}">:$attrs,
+    CArg<"ArrayRef<DictionaryAttr>", "{}">:$argAttrs)
+  >];
+  let extraClassDeclaration = [{
+    /// Create a deep copy of this function and all of its blocks, remapping any
+    /// operands that use values outside of the function using the map that is
+    /// provided (leaving them alone if no entry is present). If the mapper
+    /// contains entries for function arguments, these arguments are not
+    /// included in the new function. Replaces references to cloned sub-values
+    /// with the corresponding value that is copied, and adds those mappings to
+    /// the mapper.
+    FuncOp clone(IRMapping &mapper);
+    FuncOp clone();
+
+    /// Clone the internal blocks and attributes from this function into dest.
+    /// Any cloned blocks are appended to the back of dest. This function
+    /// asserts that the attributes of the current function and dest are
+    /// compatible.
+    void cloneInto(FuncOp dest, IRMapping &mapper);
+
+    //===------------------------------------------------------------------===//
+    // FunctionOpInterface Methods
+    //===------------------------------------------------------------------===//
+
+    /// Returns the region on the current operation that is callable. This may
+    /// return null in the case of an external callable object, e.g. an external
+    /// function.
+    ::mlir::Region *getCallableRegion() { return isExternal() ? nullptr : &getBody(); }
+
+    /// Returns the argument types of this function.
+    ArrayRef<Type> getArgumentTypes() { return getFunctionType().getInputs(); }
+
+    /// Returns the result types of this function.
+    ArrayRef<Type> getResultTypes() { return getFunctionType().getResults(); }
+  }];
+  let hasCustomAssemblyFormat = 1;
+  let hasVerifier = 1;
+}
+
+def EmitC_ReturnOp : EmitC_Op<"return", [Pure, HasParent<"FuncOp">,
+                                ReturnLike, Terminator]> {
+  let summary = "Function return operation";
+  let description = [{
+    The `emitc.return` operation represents a return operation within a function.
+    The operation takes zero or exactly one operand and produces no results.
+    The operand number and type must match the signature of the function
+    that contains the operation.
+
+    Example:
+
+    ```mlir
+    emitc.func @foo() : (i32) {
+      ...
+      emitc.return %0 : i32
+    }
+    ```
+  }];
+  let arguments = (ins Optional<AnyType>:$operand);
+
+  let assemblyFormat = "attr-dict ($operand^ `:` type($operand))?";
+  let hasVerifier = 1;
+}
+
 def EmitC_IncludeOp
     : EmitC_Op<"include", [HasParent<"ModuleOp">]> {
   let summary = "Include operation";

mlir/lib/Dialect/EmitC/IR/CMakeLists.txt

@@ -9,8 +9,10 @@ add_mlir_dialect_library(MLIREmitCDialect
   MLIREmitCAttributesIncGen
 
   LINK_LIBS PUBLIC
+  MLIRCallInterfaces
   MLIRCastInterfaces
   MLIRControlFlowInterfaces
+  MLIRFunctionInterfaces
   MLIRIR
   MLIRSideEffectInterfaces
   )