Improve the code generation by inlining more let-bindings

3 files changed, 204 insertions, 146 deletions

diff --git a/src/PureMicroPasses.ml b/src/PureMicroPasses.ml
index dd2401b9..9b9107d1 100644
--- a/src/PureMicroPasses.ml
+++ b/src/PureMicroPasses.ml
@@ -327,60 +327,108 @@ let remove_meta (def : fun_def) : fun_def =
   let body = obj#visit_texpression () def.body in
   { def with body }
 
-(** Inline the useless variable reassignments (a lot of variable assignments
-    like `let x = y in ...ÿ` are introduced through the compilation to MIR
-    and by the translation, and the variable used on the left is often unnamed.
+(** Inline the useless variable (re-)assignments:
+
+    A lot of intermediate variable assignments are introduced through the
+    compilation to MIR and by the translation itself (and the variable used
+    on the left is often unnamed).
+
+    Note that many of them are just variable "reassignments": `let x = y in ...`.
+    Some others come from ??
+    
+    TODO: how do we call that when we introduce intermediate variable assignments
+    for the arguments of a function call?
 
     [inline_named]: if `true`, inline all the assignments of the form
     `let VAR = VAR in ...`, otherwise inline only the ones where the variable
     on the left is anonymous.
+    
+    [inline_pure]: if `true`, inline all the pure assignments where the variable
+    on the left is anonymous, but the assignments where the r-expression is
+    a non-primitive function call (i.e.: inline the binops, ADT constructions,
+    etc.).
+
+    TODO: we have a smallish issue which is that rvalues should be merged with
+    expressions... For now, this forces us to substitute whenever we can, but
+    leave the let-bindings where they are, and eliminated them in a subsequent
+    pass (if they are useless).
  *)
-let inline_useless_var_reassignments (inline_named : bool) (def : fun_def) :
-    fun_def =
-  (* Register a substitution.
-     When registering that we need to substitute v0 with v1, we check
-     if v1 is itself substituted by v2, in which case we register:
-     `v0 --> v2` instead of `v0 --> v1`
-  *)
-  let add_subst v0 v1 m =
-    match VarId.Map.find_opt v1 m with
-    | None -> VarId.Map.add v0 v1 m
-    | Some v2 -> VarId.Map.add v0 v2 m
-  in
-
+let inline_useless_var_reassignments (inline_named : bool) (inline_pure : bool)
+    (def : fun_def) : fun_def =
   let obj =
-    object
+    object (self)
       inherit [_] map_expression as super
 
       method! visit_Let env monadic lv re e =
         (* Check that:
          * - the let-binding is not monadic
          * - the left-value is a variable
-         * - the assigned expression is a value *)
-        match (monadic, lv.value, re.e) with
-        | false, LvVar (Var (lv_var, _)), Value (rv, _) -> (
-            (* Check that:
-             * - the left variable is unnamed or that [inline_named] is true
-             * - the right-value is a variable
+         *)
+        match (monadic, lv.value) with
+        | false, LvVar (Var (lv_var, _)) ->
+            (* Check that: *)
+            let filter = false in
+            (* 1. Either:
+             *   - the left variable is unnamed or [inline_named] is true
+             *   - the right-expression is a variable
+             *)
+            let filter =
+              match (inline_named, lv_var.basename) with
+              | true, _ | _, None -> is_var re
+              | _ -> filter
+            in
+            (* 2. Or:
+             *   - the left variable is an unnamed variable
+             *   - the right-expression is a value or a primitive function call
              *)
-            match ((inline_named, lv_var.basename), rv.value) with
-            | (true, _ | false, None), RvPlace { var; projection = [] } ->
-                (* Update the environment and explore the next expression
-                 * (dropping the currrent let) *)
-                let env = add_subst lv_var.id var env in
-                super#visit_expression env e.e
-            | _ -> super#visit_Let env monadic lv re e)
+            let filter =
+              if inline_pure then
+                match re.e with
+                | Value _ -> true
+                | Call call -> (
+                    match call.func with
+                    | Regular _ -> false
+                    | Unop _ | Binop _ -> true)
+                | _ -> filter
+              else false
+            in
+
+            (* Update the environment and continue the exploration *)
+            let re = self#visit_texpression env re in
+            (* TODO: once rvalues and expressions are merged, filter the
+             * let-binding (note that for now we leave it, expect it to
+             * become useless, and wait for a subsequent pass to filter it) *)
+            (* let env = add_subst lv_var.id re env in *)
+            let env = if filter then VarId.Map.add lv_var.id re env else env in
+            let e = self#visit_texpression env e in
+            Let (monadic, lv, re, e)
         | _ -> super#visit_Let env monadic lv re e
       (** Visit the let-bindings to filter the useless ones (and update
           the substitution map while doing so *)
 
-      method! visit_place env p =
+      method! visit_Value env v mp =
         (* Check if we need to substitute *)
-        match VarId.Map.find_opt p.var env with
-        | None -> (* No substitution *) p
-        | Some nv ->
-            (* Substitute *)
-            { p with var = nv }
+        match v.value with
+        | RvPlace p -> (
+            match VarId.Map.find_opt p.var env with
+            | None -> (* No substitution *) super#visit_Value env v mp
+            | Some ne ->
+                (* Substitute - note that we need to reexplore, because
+                 * there may be stacked substitutions, if we have:
+                 * var0 --> var1
+                 * var1 --> var2.
+                 *
+                 * Also: we can always substitute if we substitute with
+                 * a variable. If we substitute with a value we need to
+                 * check the path is empty (TODO: actually do a projection) *)
+                if is_var ne then
+                  let var = as_var ne in
+                  let p = { p with var } in
+                  let nv = { v with value = RvPlace p } in
+                  self#visit_Value env nv mp
+                else if p.projection = [] then self#visit_expression env ne.e
+                else super#visit_Value env v mp)
+        | _ -> (* No substitution *) super#visit_Value env v mp
       (** Visit the places used as rvalues, to substitute them if necessary *)
     end
   in
@@ -901,7 +949,9 @@ let apply_passes_to_def (config : config) (ctx : trans_ctx) (def : fun_def) :
 
   (* TODO: reorder the branches of the matches/switches *)
 
-  (* The meta-information is now useless: remove it *)
+  (* The meta-information is now useless: remove it.
+   * Rk.: some passes below use the fact that we removed the meta-data
+   * (otherwise we would have to "unmeta" expressions before matching) *)
   let def = remove_meta def in
   log#ldebug (lazy ("remove_meta:\n\n" ^ fun_def_to_string ctx def ^ "\n"));
 
@@ -929,7 +979,10 @@ let apply_passes_to_def (config : config) (ctx : trans_ctx) (def : fun_def) :
 
       (* Inline the useless variable reassignments *)
       let inline_named_vars = true in
-      let def = inline_useless_var_reassignments inline_named_vars def in
+      let inline_pure = true in
+      let def =
+        inline_useless_var_reassignments inline_named_vars inline_pure def
+      in
       log#ldebug
         (lazy
           ("inline_useless_var_assignments:\n\n" ^ fun_def_to_string ctx def
diff --git a/src/PureUtils.ml b/src/PureUtils.ml
index 1ed072e9..f51f9415 100644
--- a/src/PureUtils.ml
+++ b/src/PureUtils.ml
@@ -347,3 +347,26 @@ module TypeCheck = struct
             check_typed_rvalue ctx v)
           av.variant_id av.field_values v.ty
 end
+
+let is_value (e : texpression) : bool =
+  match e.e with Value _ -> true | _ -> false
+
+let is_var (e : texpression) : bool =
+  match e.e with
+  | Value (v, _) -> (
+      match v.value with
+      | RvPlace { var = _; projection = [] } -> true
+      | _ -> false)
+  | _ -> false
+
+let as_var (e : texpression) : VarId.id =
+  match e.e with
+  | Value (v, _) -> (
+      match v.value with
+      | RvPlace { var; projection = [] } -> var
+      | _ -> raise (Failure "Unreachable"))
+  | _ -> raise (Failure "Unreachable")
+
+(** Remove the external occurrences of [Meta] *)
+let rec unmeta (e : texpression) : texpression =
+  match e.e with Meta (_, e) -> unmeta e | _ -> e
diff --git a/tests/hashmap/Hashmap.Funs.fst b/tests/hashmap/Hashmap.Funs.fst
index d3d09765..4aa6f02c 100644
--- a/tests/hashmap/Hashmap.Funs.fst
+++ b/tests/hashmap/Hashmap.Funs.fst
@@ -8,7 +8,7 @@ include Hashmap.Clauses
 #set-options "--z3rlimit 50 --fuel 0 --ifuel 1"
 
 (** [hashmap::hash_key] *)
-let hash_key_fwd (k : usize) : result usize = Return k
+let hash_key_fwd (k : usize) : result usize = let i = k in Return i
 
 (** [hashmap::HashMap::allocate_slots] *)
 let rec hash_map_allocate_slots_fwd
@@ -68,8 +68,7 @@ let rec hash_map_clear_slots_fwd_back
   (decreases (hash_map_clear_slots_decreases t slots i))
   =
   let i0 = vec_len (list_t t) slots in
-  let b = i < i0 in
-  if b
+  if i < i0
   then
     begin match vec_index_mut_back (list_t t) slots i ListNil with
     | Fail -> Fail
@@ -79,21 +78,20 @@ let rec hash_map_clear_slots_fwd_back
       | Return i1 ->
         begin match hash_map_clear_slots_fwd_back t v i1 with
         | Fail -> Fail
-        | Return v0 -> Return v0
+        | Return v0 -> let slots0 = v0 in Return slots0
         end
       end
     end
-  else Return slots
+  else let slots0 = slots in Return slots0
 
 (** [hashmap::HashMap::clear] *)
 let hash_map_clear_fwd_back
   (t : Type0) (self : hash_map_t t) : result (hash_map_t t) =
   let p = self.hash_map_max_load_factor in
   let i = self.hash_map_max_load in
-  let v = self.hash_map_slots in
-  begin match hash_map_clear_slots_fwd_back t v 0 with
+  begin match hash_map_clear_slots_fwd_back t self.hash_map_slots 0 with
   | Fail -> Fail
-  | Return v0 -> let self0 = Mkhash_map_t 0 p i v0 in Return self0
+  | Return v -> let self0 = Mkhash_map_t 0 p i v in Return self0
   end
 
 (** [hashmap::HashMap::len] *)
@@ -108,13 +106,12 @@ let rec hash_map_insert_in_list_fwd
   =
   begin match ls with
   | ListCons ckey cvalue ls0 ->
-    let b = ckey = key in
-    if b
+    if ckey = key
     then Return false
     else
       begin match hash_map_insert_in_list_fwd t key value ls0 with
       | Fail -> Fail
-      | Return b0 -> Return b0
+      | Return b -> Return b
       end
   | ListNil -> Return true
   end
@@ -127,8 +124,7 @@ let rec hash_map_insert_in_list_back
   =
   begin match ls with
   | ListCons ckey cvalue ls0 ->
-    let b = ckey = key in
-    if b
+    if ckey = key
     then let ls1 = ListCons ckey value ls0 in Return ls1
     else
       begin match hash_map_insert_in_list_back t key value ls0 with
@@ -149,12 +145,12 @@ let hash_map_insert_no_resize_fwd_back
     let i0 = self.hash_map_num_entries in
     let p = self.hash_map_max_load_factor in
     let i1 = self.hash_map_max_load in
-    let v = self.hash_map_slots in
-    let i2 = vec_len (list_t t) v in
+    let i2 = vec_len (list_t t) self.hash_map_slots in
     begin match usize_rem i i2 with
     | Fail -> Fail
     | Return hash_mod ->
-      begin match vec_index_mut_fwd (list_t t) v hash_mod with
+      begin match vec_index_mut_fwd (list_t t) self.hash_map_slots hash_mod
+        with
       | Fail -> Fail
       | Return l ->
         begin match hash_map_insert_in_list_fwd t key value l with
@@ -162,16 +158,18 @@ let hash_map_insert_no_resize_fwd_back
         | Return b ->
           if b
           then
-            begin match usize_add i0 1 with
+            begin match usize_add self.hash_map_num_entries 1 with
             | Fail -> Fail
             | Return i3 ->
               begin match hash_map_insert_in_list_back t key value l with
               | Fail -> Fail
               | Return l0 ->
-                begin match vec_index_mut_back (list_t t) v hash_mod l0 with
+                begin match
+                  vec_index_mut_back (list_t t) self.hash_map_slots hash_mod l0
+                  with
                 | Fail -> Fail
-                | Return v0 ->
-                  let self0 = Mkhash_map_t i3 p i1 v0 in Return self0
+                | Return v ->
+                  let self0 = Mkhash_map_t i3 p i1 v in Return self0
                 end
               end
             end
@@ -179,10 +177,11 @@ let hash_map_insert_no_resize_fwd_back
             begin match hash_map_insert_in_list_back t key value l with
             | Fail -> Fail
             | Return l0 ->
-              begin match vec_index_mut_back (list_t t) v hash_mod l0 with
+              begin match
+                vec_index_mut_back (list_t t) self.hash_map_slots hash_mod l0
+                with
               | Fail -> Fail
-              | Return v0 ->
-                let self0 = Mkhash_map_t i0 p i1 v0 in Return self0
+              | Return v -> let self0 = Mkhash_map_t i0 p i1 v in Return self0
               end
             end
         end
@@ -203,10 +202,10 @@ let rec hash_map_move_elements_from_list_fwd_back
     | Return h ->
       begin match hash_map_move_elements_from_list_fwd_back t h tl with
       | Fail -> Fail
-      | Return h0 -> Return h0
+      | Return h0 -> let ntable0 = h0 in Return ntable0
       end
     end
-  | ListNil -> Return ntable
+  | ListNil -> let ntable0 = ntable in Return ntable0
   end
 
 (** [hashmap::HashMap::move_elements] *)
@@ -216,8 +215,7 @@ let rec hash_map_move_elements_fwd_back
   (decreases (hash_map_move_elements_decreases t ntable slots i))
   =
   let i0 = vec_len (list_t t) slots in
-  let b = i < i0 in
-  if b
+  if i < i0
   then
     begin match vec_index_mut_fwd (list_t t) slots i with
     | Fail -> Fail
@@ -235,31 +233,30 @@ let rec hash_map_move_elements_fwd_back
           | Return i1 ->
             begin match hash_map_move_elements_fwd_back t h v i1 with
             | Fail -> Fail
-            | Return (h0, v0) -> Return (h0, v0)
+            | Return (h0, v0) ->
+              let ntable0 = h0 in let slots0 = v0 in Return (ntable0, slots0)
             end
           end
         end
       end
     end
-  else Return (ntable, slots)
+  else let ntable0 = ntable in let slots0 = slots in Return (ntable0, slots0)
 
 (** [hashmap::HashMap::try_resize] *)
 let hash_map_try_resize_fwd_back
   (t : Type0) (self : hash_map_t t) : result (hash_map_t t) =
   let i = self.hash_map_num_entries in
-  let p = self.hash_map_max_load_factor in
   let i0 = self.hash_map_max_load in
   let v = self.hash_map_slots in
-  let i1 = vec_len (list_t t) v in
+  let i1 = vec_len (list_t t) self.hash_map_slots in
   begin match usize_div 4294967295 2 with
   | Fail -> Fail
   | Return n1 ->
-    let (i2, i3) = p in
+    let (i2, i3) = self.hash_map_max_load_factor in
     begin match usize_div n1 i2 with
     | Fail -> Fail
     | Return i4 ->
-      let b = i1 <= i4 in
-      if b
+      if i1 <= i4
       then
         begin match usize_mul i1 2 with
         | Fail -> Fail
@@ -267,13 +264,14 @@ let hash_map_try_resize_fwd_back
           begin match hash_map_new_with_capacity_fwd t i5 i2 i3 with
           | Fail -> Fail
           | Return h ->
-            begin match hash_map_move_elements_fwd_back t h v 0 with
+            begin match
+              hash_map_move_elements_fwd_back t h self.hash_map_slots 0 with
             | Fail -> Fail
             | Return (h0, v0) ->
               let i6 = h0.hash_map_max_load in
-              let v1 = h0.hash_map_slots in
-              let v2 = mem_replace_back (vec (list_t t)) v0 v1 in
-              let self0 = Mkhash_map_t i (i2, i3) i6 v2 in
+              let v1 = mem_replace_back (vec (list_t t)) v0 h0.hash_map_slots
+                in
+              let self0 = Mkhash_map_t i (i2, i3) i6 v1 in
               Return
               self0
             end
@@ -298,13 +296,12 @@ let hash_map_insert_fwd_back
       let p = h.hash_map_max_load_factor in
       let i1 = h.hash_map_max_load in
       let v = h.hash_map_slots in
-      let b = i > i1 in
-      if b
+      if i > h.hash_map_max_load
       then
         begin match hash_map_try_resize_fwd_back t (Mkhash_map_t i0 p i1 v)
           with
         | Fail -> Fail
-        | Return h0 -> Return h0
+        | Return h0 -> let self0 = h0 in Return self0
         end
       else let self0 = Mkhash_map_t i0 p i1 v in Return self0
     end
@@ -318,13 +315,12 @@ let rec hash_map_contains_key_in_list_fwd
   =
   begin match ls with
   | ListCons ckey x ls0 ->
-    let b = ckey = key in
-    if b
+    if ckey = key
     then Return true
     else
       begin match hash_map_contains_key_in_list_fwd t key ls0 with
       | Fail -> Fail
-      | Return b0 -> Return b0
+      | Return b -> Return b
       end
   | ListNil -> Return false
   end
@@ -335,12 +331,11 @@ let hash_map_contains_key_fwd
   begin match hash_key_fwd key with
   | Fail -> Fail
   | Return i ->
-    let v = self.hash_map_slots in
-    let i0 = vec_len (list_t t) v in
+    let i0 = vec_len (list_t t) self.hash_map_slots in
     begin match usize_rem i i0 with
     | Fail -> Fail
     | Return hash_mod ->
-      begin match vec_index_fwd (list_t t) v hash_mod with
+      begin match vec_index_fwd (list_t t) self.hash_map_slots hash_mod with
       | Fail -> Fail
       | Return l ->
         begin match hash_map_contains_key_in_list_fwd t key l with
@@ -358,13 +353,12 @@ let rec hash_map_get_in_list_fwd
   =
   begin match ls with
   | ListCons ckey cvalue ls0 ->
-    let b = ckey = key in
-    if b
+    if ckey = key
     then Return cvalue
     else
       begin match hash_map_get_in_list_fwd t key ls0 with
       | Fail -> Fail
-      | Return x -> Return x
+      | Return x -> let x0 = x in Return x0
       end
   | ListNil -> Fail
   end
@@ -375,17 +369,16 @@ let hash_map_get_fwd
   begin match hash_key_fwd key with
   | Fail -> Fail
   | Return i ->
-    let v = self.hash_map_slots in
-    let i0 = vec_len (list_t t) v in
+    let i0 = vec_len (list_t t) self.hash_map_slots in
     begin match usize_rem i i0 with
     | Fail -> Fail
     | Return hash_mod ->
-      begin match vec_index_fwd (list_t t) v hash_mod with
+      begin match vec_index_fwd (list_t t) self.hash_map_slots hash_mod with
       | Fail -> Fail
       | Return l ->
         begin match hash_map_get_in_list_fwd t key l with
         | Fail -> Fail
-        | Return x -> Return x
+        | Return x -> let x0 = x in Return x0
         end
       end
     end
@@ -398,13 +391,12 @@ let rec hash_map_get_mut_in_list_fwd
   =
   begin match ls with
   | ListCons ckey cvalue ls0 ->
-    let b = ckey = key in
-    if b
+    if ckey = key
     then Return cvalue
     else
       begin match hash_map_get_mut_in_list_fwd t key ls0 with
       | Fail -> Fail
-      | Return x -> Return x
+      | Return x -> let x0 = x in Return x0
       end
   | ListNil -> Fail
   end
@@ -417,9 +409,8 @@ let rec hash_map_get_mut_in_list_back
   =
   begin match ls with
   | ListCons ckey cvalue ls0 ->
-    let b = ckey = key in
-    if b
-    then let ls1 = ListCons ckey ret ls0 in Return ls1
+    if ckey = key
+    then let x = ret in let ls1 = ListCons ckey x ls0 in Return ls1
     else
       begin match hash_map_get_mut_in_list_back t key ls0 ret with
       | Fail -> Fail
@@ -434,17 +425,17 @@ let hash_map_get_mut_fwd
   begin match hash_key_fwd key with
   | Fail -> Fail
   | Return i ->
-    let v = self.hash_map_slots in
-    let i0 = vec_len (list_t t) v in
+    let i0 = vec_len (list_t t) self.hash_map_slots in
     begin match usize_rem i i0 with
     | Fail -> Fail
     | Return hash_mod ->
-      begin match vec_index_mut_fwd (list_t t) v hash_mod with
+      begin match vec_index_mut_fwd (list_t t) self.hash_map_slots hash_mod
+        with
       | Fail -> Fail
       | Return l ->
         begin match hash_map_get_mut_in_list_fwd t key l with
         | Fail -> Fail
-        | Return x -> Return x
+        | Return x -> let x0 = x in Return x0
         end
       end
     end
@@ -461,20 +452,21 @@ let hash_map_get_mut_back
     let i0 = self.hash_map_num_entries in
     let p = self.hash_map_max_load_factor in
     let i1 = self.hash_map_max_load in
-    let v = self.hash_map_slots in
-    let i2 = vec_len (list_t t) v in
+    let i2 = vec_len (list_t t) self.hash_map_slots in
     begin match usize_rem i i2 with
     | Fail -> Fail
     | Return hash_mod ->
-      begin match vec_index_mut_fwd (list_t t) v hash_mod with
+      begin match vec_index_mut_fwd (list_t t) self.hash_map_slots hash_mod
+        with
       | Fail -> Fail
       | Return l ->
         begin match hash_map_get_mut_in_list_back t key l ret with
         | Fail -> Fail
         | Return l0 ->
-          begin match vec_index_mut_back (list_t t) v hash_mod l0 with
+          begin match
+            vec_index_mut_back (list_t t) self.hash_map_slots hash_mod l0 with
           | Fail -> Fail
-          | Return v0 -> let self0 = Mkhash_map_t i0 p i1 v0 in Return self0
+          | Return v -> let self0 = Mkhash_map_t i0 p i1 v in Return self0
           end
         end
       end
@@ -489,8 +481,7 @@ let rec hash_map_remove_from_list_fwd
   =
   begin match ls with
   | ListCons ckey x tl ->
-    let b = ckey = key in
-    if b
+    if ckey = key
     then
       let mv_ls = mem_replace_fwd (list_t t) (ListCons ckey x tl) ListNil in
       begin match mv_ls with
@@ -513,12 +504,11 @@ let rec hash_map_remove_from_list_back
   =
   begin match ls with
   | ListCons ckey x tl ->
-    let b = ckey = key in
-    if b
+    if ckey = key
     then
       let mv_ls = mem_replace_fwd (list_t t) (ListCons ckey x tl) ListNil in
       begin match mv_ls with
-      | ListCons i cvalue tl0 -> Return tl0
+      | ListCons i cvalue tl0 -> let ls0 = tl0 in Return ls0
       | ListNil -> Fail
       end
     else
@@ -535,13 +525,12 @@ let hash_map_remove_fwd
   begin match hash_key_fwd key with
   | Fail -> Fail
   | Return i ->
-    let i0 = self.hash_map_num_entries in
-    let v = self.hash_map_slots in
-    let i1 = vec_len (list_t t) v in
-    begin match usize_rem i i1 with
+    let i0 = vec_len (list_t t) self.hash_map_slots in
+    begin match usize_rem i i0 with
     | Fail -> Fail
     | Return hash_mod ->
-      begin match vec_index_mut_fwd (list_t t) v hash_mod with
+      begin match vec_index_mut_fwd (list_t t) self.hash_map_slots hash_mod
+        with
       | Fail -> Fail
       | Return l ->
         begin match hash_map_remove_from_list_fwd t key l with
@@ -550,7 +539,7 @@ let hash_map_remove_fwd
           begin match x with
           | None -> Return None
           | Some x0 ->
-            begin match usize_sub i0 1 with
+            begin match usize_sub self.hash_map_num_entries 1 with
             | Fail -> Fail
             | Return _ -> Return (Some x0)
             end
@@ -569,12 +558,12 @@ let hash_map_remove_back
     let i0 = self.hash_map_num_entries in
     let p = self.hash_map_max_load_factor in
     let i1 = self.hash_map_max_load in
-    let v = self.hash_map_slots in
-    let i2 = vec_len (list_t t) v in
+    let i2 = vec_len (list_t t) self.hash_map_slots in
     begin match usize_rem i i2 with
     | Fail -> Fail
     | Return hash_mod ->
-      begin match vec_index_mut_fwd (list_t t) v hash_mod with
+      begin match vec_index_mut_fwd (list_t t) self.hash_map_slots hash_mod
+        with
       | Fail -> Fail
       | Return l ->
         begin match hash_map_remove_from_list_fwd t key l with
@@ -585,23 +574,26 @@ let hash_map_remove_back
             begin match hash_map_remove_from_list_back t key l with
             | Fail -> Fail
             | Return l0 ->
-              begin match vec_index_mut_back (list_t t) v hash_mod l0 with
+              begin match
+                vec_index_mut_back (list_t t) self.hash_map_slots hash_mod l0
+                with
               | Fail -> Fail
-              | Return v0 ->
-                let self0 = Mkhash_map_t i0 p i1 v0 in Return self0
+              | Return v -> let self0 = Mkhash_map_t i0 p i1 v in Return self0
               end
             end
           | Some x0 ->
-            begin match usize_sub i0 1 with
+            begin match usize_sub self.hash_map_num_entries 1 with
             | Fail -> Fail
             | Return i3 ->
               begin match hash_map_remove_from_list_back t key l with
               | Fail -> Fail
               | Return l0 ->
-                begin match vec_index_mut_back (list_t t) v hash_mod l0 with
+                begin match
+                  vec_index_mut_back (list_t t) self.hash_map_slots hash_mod l0
+                  with
                 | Fail -> Fail
-                | Return v0 ->
-                  let self0 = Mkhash_map_t i3 p i1 v0 in Return self0
+                | Return v ->
+                  let self0 = Mkhash_map_t i3 p i1 v in Return self0
                 end
               end
             end
@@ -631,9 +623,7 @@ let test1_fwd : result unit =
             begin match hash_map_get_fwd u64 h3 128 with
             | Fail -> Fail
             | Return i ->
-              let b = i = 18 in
-              let b0 = not b in
-              if b0
+              if not (i = 18)
               then Fail
               else
                 begin match hash_map_get_mut_back u64 h3 1024 56 with
@@ -642,9 +632,7 @@ let test1_fwd : result unit =
                   begin match hash_map_get_fwd u64 h4 1024 with
                   | Fail -> Fail
                   | Return i0 ->
-                    let b1 = i0 = 56 in
-                    let b2 = not b1 in
-                    if b2
+                    if not (i0 = 56)
                     then Fail
                     else
                       begin match hash_map_remove_fwd u64 h4 1024 with
@@ -653,9 +641,7 @@ let test1_fwd : result unit =
                         begin match x with
                         | None -> Fail
                         | Some x0 ->
-                          let b3 = x0 = 56 in
-                          let b4 = not b3 in
-                          if b4
+                          if not (x0 = 56)
                           then Fail
                           else
                             begin match hash_map_remove_back u64 h4 1024 with
@@ -664,26 +650,22 @@ let test1_fwd : result unit =
                               begin match hash_map_get_fwd u64 h5 0 with
                               | Fail -> Fail
                               | Return i1 ->
-                                let b5 = i1 = 42 in
-                                let b6 = not b5 in
-                                if b6
+                                if not (i1 = 42)
                                 then Fail
                                 else
                                   begin match hash_map_get_fwd u64 h5 128 with
                                   | Fail -> Fail
                                   | Return i2 ->
-                                    let b7 = i2 = 18 in
-                                    let b8 = not b7 in
-                                    if b8
+                                    if not (i2 = 18)
                                     then Fail
                                     else
                                       begin match hash_map_get_fwd u64 h5 1056
                                         with
                                       | Fail -> Fail
                                       | Return i3 ->
-                                        let b9 = i3 = 256 in
-                                        let b10 = not b9 in
-                                        if b10 then Fail else Return ()
+                                        if not (i3 = 256)
+                                        then Fail
+                                        else Return ()
                                       end
                                   end
                               end