[Mlir-commits] [mlir] [mlir][emitc] Add a `declare_func` operation (PR #80297)

[Marius Brehler]

================
@@ -460,6 +460,48 @@ def EmitC_CallOp : EmitC_Op<"call",
   }];
 }
 
+def EmitC_DeclareFuncOp : EmitC_Op<"declare_func", [
+  DeclareOpInterfaceMethods<SymbolUserOpInterface>
+]> {
+  let summary = "An operation to declare a function";
+  let description = [{
+    The `declare_func` operation allows to insert a function declaration for an
+    `emitc.func` at a specific position. The operation only requires the `callee`
+    of the `emitc.func` to be specified as an attribute.
+
+    Example:
+
+    ```mlir
+    emitc.declare_func @bar
+    emitc.func @foo(%arg0: i32) -> i32 {
+      %0 = emitc.call @bar(%arg0) : (i32) -> (i32)
+      emitc.return %0 : i32
+    }
+
+    emitc.func @bar(%arg0: i32) -> i32 {
+      emitc.return %arg0 : i32
+    }
+    ```
+
+    ```c++
+    // Code emitted for the operations above.
+    int32_t bar(int32_t v1);
+    int32_t foo(int32_t v1) {
+      int32_t v2 = bar(v1);
+      return v2;
+    }
+
+    int32_t bar(int32_t v1) {
+      return v1;
+    }
+    ```
+  }];
+  let arguments = (ins FlatSymbolRefAttr:$callee);
----------------
marbre wrote:

Yeah, I need to correct my previous statement as i was wrong and the corresponding attribute is named `sym_name` in `emitc.func`. I will adopt this for the `FlatSymbolRefAttr`of the `emitc.declare_func`op.

https://github.com/llvm/llvm-project/pull/80297