compound assignment

compiler/hir/hir.odin

@@ -102,6 +102,9 @@ Expr_Kind :: enum u8 {
 	Negate,
 	Not,
 	Add,
+	Sub,
+	Mul,
+	Div,
 	Pointer_Add,
 	Eq,
 	Ne,
@@ -151,6 +154,15 @@ Stmt_Kind :: enum u8 {
 	For,
 }
 
+Assignment_Op :: enum u8 {
+	Set,
+	Add,
+	Sub,
+	Mul,
+	Div,
+	Pointer_Add,
+}
+
 Stmt :: struct {
 	kind:       Stmt_Kind,
 	span:       source.Span,
@@ -160,6 +172,10 @@ Stmt :: struct {
 	expr:       Expr_Id,
 	iterator_type: types.Type,
 	pointer_capture: bool,
+	// Assignments carry their operation explicitly. Arithmetic operations lower
+	// by computing the target address once, loading its current value, applying
+	// the operation to `expr`, and storing through the original address.
+	assignment_op: Assignment_Op,
 	// Boolean `If` statements use `expr` as the condition. Conditional unwraps
 	// use `unwraps` for the ordered optional expressions and capture locals, and
 	// `guard` for the optional boolean checked after every unwrap succeeds.