[pulse] perf win: separate edges from attrs in memory

Summary:
Before: the abstract state represents heap addresses as a single map
from addresses to edges + attributes.

After: the heap is made of 2 maps: one mapping addresses to edges, and
one mapping an address to its attributes.

It turns out that edges and attributes are often not updated at the same
time, so keeping them in the same map was causing pressure on the OCaml
gc.

Reviewed By: mbouaziz

Differential Revision: D14147991

fbshipit-source-id: 6713eeb3c

infer/src/checkers/PulseDomain.ml

@@ -102,7 +102,7 @@ module Memory : sig
 
   val empty : t
 
-  val filter : (AbstractAddress.t -> cell -> bool) -> t -> t
+  val filter : (AbstractAddress.t -> bool) -> t -> t
 
   val find_opt : AbstractAddress.t -> t -> cell option
 
@@ -142,23 +142,21 @@ end = struct
 
   module Graph = PrettyPrintable.MakePPMap (AbstractAddress)
 
-  type t = cell Graph.t [@@deriving compare]
+  type t = edges Graph.t * Attributes.t Graph.t [@@deriving compare]
 
   let pp =
-    Graph.pp ~pp_value:(Pp.pair ~fst:(Edges.pp ~pp_value:AddrTracePair.pp) ~snd:Attributes.pp)
+    Pp.pair
+      ~fst:(Graph.pp ~pp_value:(Edges.pp ~pp_value:AddrTracePair.pp))
+      ~snd:(Graph.pp ~pp_value:Attributes.pp)
 
 
   (* {3 Helper functions to traverse the two maps at once } *)
 
   let add_edge addr_src access value memory =
-    let edges, attrs =
-      match Graph.find_opt addr_src memory with
-      | Some cell ->
-          cell
-      | None ->
-          (Edges.empty, Attributes.empty)
-    in
-    Graph.add addr_src (Edges.add access value edges, attrs) memory
+    let old_edges = Graph.find_opt addr_src (fst memory) |> Option.value ~default:Edges.empty in
+    let new_edges = Edges.add access value old_edges in
+    if phys_equal old_edges new_edges then memory
+    else (Graph.add addr_src new_edges (fst memory), snd memory)
 
 
   (** [Dereference] edges induce a [TakeAddress] back edge and vice-versa, because
@@ -176,29 +174,24 @@ end = struct
 
   let find_edge_opt addr access memory =
     let open Option.Monad_infix in
-    Graph.find_opt addr memory >>| fst >>= Edges.find_opt access
+    Graph.find_opt addr (fst memory) >>= Edges.find_opt access
 
 
+  (* TODO: maybe sets for attributes is overkill and a list would be better? *)
   let add_attributes addr attrs memory =
-    let edges, old_attrs =
-      match Graph.find_opt addr memory with
-      | Some edges_old_attrs ->
-          edges_old_attrs
-      | None ->
-          (Edges.empty, Attributes.empty)
-    in
+    if Attributes.is_empty attrs then memory
+    else
+      let old_attrs = Graph.find_opt addr (snd memory) |> Option.value ~default:Attributes.empty in
       if phys_equal old_attrs attrs then memory
-    else Graph.add addr (edges, Attributes.union attrs old_attrs) memory
+      else
+        let new_attrs = Attributes.union attrs old_attrs in
+        if phys_equal new_attrs old_attrs then
+          (* unlikely as [union] makes no effort to preserve physical equality *) memory
+        else (fst memory, Graph.add addr new_attrs (snd memory))
 
 
   let add_attribute address attribute memory =
-    Graph.update address
-      (function
-        | Some (edges, old_attributes) ->
-            Some (edges, Attributes.add attribute old_attributes)
-        | None ->
-            Some (Edges.empty, Attributes.singleton attribute))
-      memory
+    add_attributes address (Attributes.singleton attribute) memory
 
 
   let invalidate address invalidation memory =
@@ -206,9 +199,7 @@ end = struct
 
 
   let check_valid address memory =
-    match
-      Graph.find_opt address memory |> Option.map ~f:snd |> Option.bind ~f:Attributes.get_invalid
-    with
+    match Graph.find_opt address (snd memory) |> Option.bind ~f:Attributes.get_invalid with
     | Some invalidation ->
         Error invalidation
     | None ->
@@ -218,20 +209,33 @@ end = struct
   let std_vector_reserve address memory = add_attribute address Attribute.StdVectorReserve memory
 
   let is_std_vector_reserved address memory =
-    Graph.find_opt address memory |> Option.map ~f:snd
+    Graph.find_opt address (snd memory)
     |> Option.value_map ~default:false ~f:(fun attributes ->
            Attributes.mem Attribute.StdVectorReserve attributes )
 
 
   (* {3 Monomorphic {!PPMap} interface as needed } *)
 
-  let empty = Graph.empty
+  let empty = (Graph.empty, Graph.empty)
+
+  let find_opt addr memory =
+    match (Graph.find_opt addr (fst memory), Graph.find_opt addr (snd memory)) with
+    | None, None ->
+        None
+    | edges_opt, attrs_opt ->
+        let edges = Option.value edges_opt ~default:Edges.empty in
+        let attrs = Option.value attrs_opt ~default:Attributes.empty in
+        Some (edges, attrs)
+
 
-  let find_opt = Graph.find_opt
+  let set_cell addr (edges, attrs) memory =
+    (Graph.add addr edges (fst memory), Graph.add addr attrs (snd memory))
 
-  let set_cell = Graph.add
 
-  let filter = Graph.filter
+  let filter f memory =
+    let heap = Graph.filter (fun address _ -> f address) (fst memory) in
+    let attrs = Graph.filter (fun address _ -> f address) (snd memory) in
+    if phys_equal heap (fst memory) && phys_equal attrs (snd memory) then memory else (heap, attrs)
 end
 
 (** Stacks: map addresses of variables to values and initialisation location.
@@ -493,7 +497,7 @@ end = struct
 
   let minimize astate =
     let visited = visit_stack astate AddressSet.empty in
-    let heap = Memory.filter (fun address _ -> AddressSet.mem address visited) astate.heap in
+    let heap = Memory.filter (fun address -> AddressSet.mem address visited) astate.heap in
     if phys_equal heap astate.heap then astate else {astate with heap}
 end