feat: THIS keyword

compiler/plc_ast/src/ast.rs

@@ -861,6 +861,7 @@ pub enum AstStatement {
     ReferenceExpr(ReferenceExpr),
     Identifier(String),
     Super(Option<DerefMarker>),
+    This,
     DirectAccess(DirectAccess),
     HardwareAccess(HardwareAccess),
     BinaryExpression(BinaryExpression),
@@ -931,6 +932,7 @@ impl Debug for AstNode {
             AstStatement::Identifier(name) => f.debug_struct("Identifier").field("name", name).finish(),
             AstStatement::Super(Some(_)) => f.debug_struct("Super(derefed)").finish(),
             AstStatement::Super(_) => f.debug_struct("Super").finish(),
+            AstStatement::This => f.debug_struct("This").finish(),
             AstStatement::BinaryExpression(BinaryExpression { operator, left, right }) => f
                 .debug_struct("BinaryExpression")
                 .field("operator", operator)
@@ -1236,6 +1238,10 @@ impl AstNode {
         )
     }
 
+    pub fn is_this(&self) -> bool {
+        matches!(self.stmt, AstStatement::This)
+    }
+
     pub fn is_paren(&self) -> bool {
         matches!(self.stmt, AstStatement::ParenExpression { .. })
     }
@@ -1282,6 +1288,9 @@ impl AstNode {
         if self.has_super_metadata() {
             return false;
         }
+        if self.is_this() {
+            return false;
+        }
         self.has_direct_access()
             || self.is_flat_reference()
             || self.is_reference()
@@ -1640,6 +1649,13 @@ impl AstFactory {
         AstNode::new(AstStatement::Super(deref), id, location.into())
     }
 
+    pub fn create_this_reference<T>(location: T, id: AstId) -> AstNode
+    where
+        T: Into<SourceLocation>,
+    {
+        AstNode::new(AstStatement::This, id, location.into())
+    }
+
     pub fn create_unary_expression(
         operator: Operator,
         value: AstNode,

compiler/plc_ast/src/mut_visitor.rs

@@ -210,7 +210,10 @@ pub trait AstVisitorMut: Sized {
     fn visit_interface(&mut self, _interface: &mut Interface) {}
 
     fn visit_property(&mut self, _property: &mut PropertyBlock) {}
+
     fn visit_super(&mut self, _node: &mut AstNode) {}
+
+    fn visit_this(&mut self, _node: &mut AstNode) {}
 }
 
 impl WalkerMut for AstLiteral {
@@ -406,6 +409,7 @@ impl WalkerMut for AstNode {
             AstStatement::LabelStatement(_) => visitor.visit_label_statement(self),
             AstStatement::AllocationStatement(_) => visitor.visit_allocation(self),
             AstStatement::Super(_) => visitor.visit_super(self),
+            AstStatement::This => visitor.visit_this(self),
         }
     }
 }

compiler/plc_ast/src/visitor.rs

@@ -611,6 +611,7 @@ impl Walker for AstNode {
             AstStatement::LabelStatement(stmt) => visitor.visit_label_statement(stmt, node),
             AstStatement::AllocationStatement(stmt) => visitor.visit_allocation(stmt, node),
             AstStatement::Super(_) => {}
+            AstStatement::This => {}
         }
     }
 }

compiler/plc_diagnostics/src/diagnostics/diagnostics_registry.rs

@@ -221,6 +221,7 @@ lazy_static! {
         E117,   Error,      include_str!("./error_codes/E117.md"),  // Property with invalid number of GET and/or SET blocks
         E118,   Info,       include_str!("./error_codes/E118.md"),  // Follow-up error to 112
         E119,   Error,      include_str!("./error_codes/E119.md"),  // Invalid use of `SUPER` keyword
+        E120,   Error,      include_str!("./error_codes/E120.md"),  // Invalid use of `THIS` keyword
     );
 }
 

compiler/plc_diagnostics/src/diagnostics/error_codes/E120.md

@@ -0,0 +1,17 @@
+# `THIS` keyword is only allowed in `FUNCTION_BLOCK`
+
+`THIS` is a keyword in IEC 61131-3 that refers to the instance of a `FUNCTION_BLOCK`. It is used to access the instance variables and methods of the `FUNCTION_BLOCK` from within its own methods or body.
+Therefore it cannot be used in `FUNCTION`s or `PROGRAM`s, as these do not have an instance context like `FUNCTION_BLOCK`s do.
+
+Errouneus code example:
+
+```iec61131
+FUNCTION foo
+    VAR
+        someVar : STRING := 'this is the instance var';
+    END_VAR
+
+    // use of `THIS` is not allowed here
+    printf('%s', REF(THIS^.someVar));
+END_FUNCTION
+```

src/codegen/generators/expression_generator.rs

@@ -217,6 +217,22 @@ impl<'ink, 'b> ExpressionCodeGenerator<'ink, 'b> {
 
         // generate the expression
         match expression.get_stmt() {
+            AstStatement::This => {
+                // TODO: #THIS can we expect to have context here?
+                self.function_context.ok_or_else(|| {
+                    Diagnostic::codegen_error("Cannot use 'this' without context", expression)
+                })?;
+                let Some(this_name) = self.annotations.get_call_name(expression) else {
+                    // TODO: is this correct?
+                    unreachable!("this should have a name");
+                };
+                let this_value =
+                    self.llvm_index.find_loaded_associated_variable_value(this_name).ok_or_else(|| {
+                        let message = format!("Cannot find '{}' in associated variable values", this_name);
+                        Diagnostic::codegen_error(message, expression)
+                    })?;
+                Ok(ExpressionValue::LValue(this_value))
+            }
             AstStatement::ReferenceExpr(data) => {
                 let res =
                     self.generate_reference_expression(&data.access, data.base.as_deref(), expression)?;

src/codegen/generators/pou_generator.rs

@@ -699,6 +699,17 @@ impl<'ink, 'cg> PouGenerator<'ink, 'cg> {
                 location.get_column(),
             );
         }
+
+        if ((function_context.linking_context.is_method() || function_context.linking_context.is_action())
+            && self.index.find_pou(type_name).is_some_and(|it| it.is_function_block()))
+            || function_context.linking_context.get_implementation_type()
+                == &ImplementationType::FunctionBlock
+        {
+            let alloca = self.llvm.builder.build_alloca(param_pointer.get_type(), "this");
+            self.llvm.builder.build_store(alloca, param_pointer);
+            index.associate_loaded_local_variable(type_name, "__THIS", alloca)?;
+        }
+
         //Generate reference to parameter
         // cannot use index from members because return and temp variables may not be considered for index in build_struct_gep
         let mut var_count = 0;

src/codegen/tests/code_gen_tests.rs

@@ -1114,13 +1114,17 @@ fn fb_method_called_locally() {
 
     define void @foo(%foo* %0) {
     entry:
+      %this = alloca %foo*, align 8
+      store %foo* %0, %foo** %this, align 8
       %bar = getelementptr inbounds %foo, %foo* %0, i32 0, i32 0
       %call = call i32 @foo_addToBar(%foo* %0, i16 42)
       ret void
     }
 
     define i32 @foo_addToBar(%foo* %0, i16 %1) {
     entry:
+      %this = alloca %foo*, align 8
+      store %foo* %0, %foo** %this, align 8
       %bar = getelementptr inbounds %foo, %foo* %0, i32 0, i32 0
       %foo.addToBar = alloca i32, align 4
       %in = alloca i16, align 2
@@ -1197,13 +1201,17 @@ fn fb_local_method_var_shadows_parent_var() {
 
     define void @foo(%foo* %0) {
     entry:
+      %this = alloca %foo*, align 8
+      store %foo* %0, %foo** %this, align 8
       %bar = getelementptr inbounds %foo, %foo* %0, i32 0, i32 0
       %call = call i32 @foo_addToBar(%foo* %0, i16 42)
       ret void
     }
 
     define i32 @foo_addToBar(%foo* %0, i16 %1) {
     entry:
+      %this = alloca %foo*, align 8
+      store %foo* %0, %foo** %this, align 8
       %bar = getelementptr inbounds %foo, %foo* %0, i32 0, i32 0
       %foo.addToBar = alloca i32, align 4
       %in = alloca i16, align 2
@@ -3969,6 +3977,8 @@ fn variables_in_var_external_block_are_not_generated() {
 
     define void @bar(%bar* %0) {
     entry:
+      %this = alloca %bar*, align 8
+      store %bar* %0, %bar** %this, align 8
       ret void
     }
 

src/codegen/tests/debug_tests.rs

@@ -361,12 +361,16 @@ fn dbg_declare_has_valid_metadata_references_for_methods() {
     define void @fb(%fb* %0) !dbg !9 {
     entry:
       call void @llvm.dbg.declare(metadata %fb* %0, metadata !12, metadata !DIExpression()), !dbg !13
+      %this = alloca %fb*, align 8
+      store %fb* %0, %fb** %this, align 8
       ret void, !dbg !13
     }
 
     define void @fb_foo(%fb* %0) !dbg !14 {
     entry:
       call void @llvm.dbg.declare(metadata %fb* %0, metadata !15, metadata !DIExpression()), !dbg !16
+      %this = alloca %fb*, align 8
+      store %fb* %0, %fb** %this, align 8
       ret void, !dbg !16
     }
 

src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__implementation_added_as_subroutine.snap

@@ -1,7 +1,6 @@
 ---
 source: src/codegen/tests/debug_tests/expression_debugging.rs
 expression: result
-snapshot_kind: text
 ---
 ; ModuleID = '<internal>'
 source_filename = "<internal>"
@@ -30,6 +29,8 @@ entry:
 define void @myFb(%myFb* %0) !dbg !25 {
 entry:
   call void @llvm.dbg.declare(metadata %myFb* %0, metadata !28, metadata !DIExpression()), !dbg !29
+  %this = alloca %myFb*, align 8
+  store %myFb* %0, %myFb** %this, align 8
   ret void, !dbg !29
 }
 

src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__non_function_pous_have_struct_as_param.snap

@@ -1,7 +1,6 @@
 ---
 source: src/codegen/tests/debug_tests/expression_debugging.rs
 expression: result
-snapshot_kind: text
 ---
 ; ModuleID = '<internal>'
 source_filename = "<internal>"
@@ -25,6 +24,8 @@ entry:
 define void @fb(%fb* %0) !dbg !24 {
 entry:
   call void @llvm.dbg.declare(metadata %fb* %0, metadata !27, metadata !DIExpression()), !dbg !28
+  %this = alloca %fb*, align 8
+  store %fb* %0, %fb** %this, align 8
   %x = getelementptr inbounds %fb, %fb* %0, i32 0, i32 0
   %load_x = load i32, i32* %x, align 4, !dbg !28
   %tmpVar = add i32 %load_x, 2, !dbg !28

src/codegen/tests/debug_tests/snapshots/rusty__codegen__tests__debug_tests__expression_debugging__var_and_vartemp_variables_in_pous_added_as_local.snap

@@ -1,7 +1,6 @@
 ---
 source: src/codegen/tests/debug_tests/expression_debugging.rs
 expression: result
-snapshot_kind: text
 ---
 ; ModuleID = '<internal>'
 source_filename = "<internal>"
@@ -48,6 +47,8 @@ entry:
 define void @myFb(%myFb* %0) !dbg !37 {
 entry:
   call void @llvm.dbg.declare(metadata %myFb* %0, metadata !40, metadata !DIExpression()), !dbg !41
+  %this = alloca %myFb*, align 8
+  store %myFb* %0, %myFb** %this, align 8
   %a = alloca i32, align 4
   %b = alloca i32, align 4
   %c = alloca i32, align 4

src/codegen/tests/directaccess_test.rs

@@ -141,7 +141,7 @@ fn direct_acess_in_output_assignment_implicit_explicit_and_mixed() {
         ",
     );
 
-    assert_snapshot!(ir, @r###"
+    assert_snapshot!(ir, @r#"
     ; ModuleID = '<internal>'
     source_filename = "<internal>"
 
@@ -151,6 +151,8 @@ fn direct_acess_in_output_assignment_implicit_explicit_and_mixed() {
 
     define void @FOO(%FOO* %0) {
     entry:
+      %this = alloca %FOO*, align 8
+      store %FOO* %0, %FOO** %this, align 8
       %X = getelementptr inbounds %FOO, %FOO* %0, i32 0, i32 0
       %Y = getelementptr inbounds %FOO, %FOO* %0, i32 0, i32 1
       ret void
@@ -218,7 +220,7 @@ fn direct_acess_in_output_assignment_implicit_explicit_and_mixed() {
     declare void @llvm.memcpy.p0i8.p0i8.i64(i8* noalias nocapture writeonly, i8* noalias nocapture readonly, i64, i1 immarg) #0
 
     attributes #0 = { argmemonly nofree nounwind willreturn }
-    "###);
+    "#);
 }
 
 #[test]
@@ -252,6 +254,8 @@ fn direct_acess_in_output_assignment_with_simple_expression() {
 
     define void @FOO(%FOO* %0) {
     entry:
+      %this = alloca %FOO*, align 8
+      store %FOO* %0, %FOO** %this, align 8
       %Q = getelementptr inbounds %FOO, %FOO* %0, i32 0, i32 0
       ret void
     }
@@ -305,7 +309,7 @@ fn direct_acess_in_output_assignment_with_simple_expression_implicit() {
         ",
     );
 
-    assert_snapshot!(ir, @r###"
+    assert_snapshot!(ir, @r#"
     ; ModuleID = '<internal>'
     source_filename = "<internal>"
 
@@ -315,6 +319,8 @@ fn direct_acess_in_output_assignment_with_simple_expression_implicit() {
 
     define void @FOO(%FOO* %0) {
     entry:
+      %this = alloca %FOO*, align 8
+      store %FOO* %0, %FOO** %this, align 8
       %Q = getelementptr inbounds %FOO, %FOO* %0, i32 0, i32 0
       ret void
     }
@@ -344,7 +350,7 @@ fn direct_acess_in_output_assignment_with_simple_expression_implicit() {
     declare void @llvm.memcpy.p0i8.p0i8.i64(i8* noalias nocapture writeonly, i8* noalias nocapture readonly, i64, i1 immarg) #0
 
     attributes #0 = { argmemonly nofree nounwind willreturn }
-    "###);
+    "#);
 }
 
 #[test]
@@ -391,6 +397,8 @@ fn direct_acess_in_output_assignment_with_complexe_expression() {
 
     define void @QUUX(%QUUX* %0) {
     entry:
+      %this = alloca %QUUX*, align 8
+      store %QUUX* %0, %QUUX** %this, align 8
       %Q = getelementptr inbounds %QUUX, %QUUX* %0, i32 0, i32 0
       ret void
     }