Expand `*e` into `tmp = e; *tmp`

clangml-transforms/for_memcad.ml

@@ -178,6 +178,12 @@ module Applicative =
         let ( + ) = plus_with_warning
       end)))
 
+let rec deref_decl (expr : Clang.Ast.expr) =
+  match expr.desc with
+  | DeclRef _ -> true
+  | UnaryOperator { kind = Deref; operand } -> deref_decl operand
+  | _ -> false
+
 module rec Visitor : Refl.Visit.VisitorS
 with type 'a Applicative.t = 'a Applicative.t = struct
   module Applicative = Applicative
@@ -328,9 +334,17 @@ with type 'a Applicative.t = 'a Applicative.t = struct
       match kind with
       | LNot -> { env with in_condition = true }
       | _ -> { env with in_condition = false } in
-    let operand, operand_value =
+    let operand, delayed_stmts =
       Visit.visit [%refl: Clang.Ast.expr] [] operand operand_env in
-    UnaryOperator { kind; operand }, operand_value
+    let operand, delayed_stmts =
+      match kind with
+      | Deref when not (deref_decl operand) ->
+         let operand, stmts = assign_to_tmp operand in
+         let delayed_stmts =
+           Free_monoid.plus delayed_stmts (Free_monoid.of_list stmts) in
+         operand, delayed_stmts
+      | _ -> operand, delayed_stmts in
+    UnaryOperator { kind; operand }, delayed_stmts
 
   let rec visit_if(cond : Clang.Ast.expr) (then_branch : Clang.Ast.stmt)
       (else_branch : Clang.Ast.stmt option) env
@@ -420,7 +434,7 @@ with type 'a Applicative.t = 'a Applicative.t = struct
     | _ ->
     let (expr : Clang.Ast.expr), delayed_stmts =
       super expr { env with statement_root = false; assign_rhs = false } in
-    let make_assign expr lhs =
+    let make_assign (expr : Clang.Ast.expr) (lhs : Clang.Ast.expr) =
       if env.statement_root then
         expr, delayed_stmts
       else
@@ -642,13 +656,12 @@ with type 'a Applicative.t = 'a Applicative.t = struct
             visit_unary_expr_size_of argument env
         | ArraySubscript { base; index }
             when not (is_array base) ->
-            let x' : Clang.Ast.expr_desc = UnaryOperator {
-              kind = Deref;
-              operand = { base with desc = BinaryOperator {
-                lhs = base;
-                kind = Add;
-                rhs = index; }}} in
-            super x' env
+           let operand : Clang.Ast.expr =
+             { base with desc = BinaryOperator {
+                 lhs = base;
+                 kind = Add;
+                 rhs = index; }} in
+           visit_unary_operator env Deref operand
         | _ -> super x env
         end
     | Clang.Ast.Refl_decl_desc ->