From 7ac04fa46a4745c4c39700d4cceb68ffd5736a54 Mon Sep 17 00:00:00 2001
From: Josh Berdine <jjb@fb.com>
Date: Tue, 28 May 2019 14:22:07 -0700
Subject: [PATCH] [sledge] Optimize finding functions by name

Summary: Replace the naive linear scan with a map lookup.

Reviewed By: ngorogiannis

Differential Revision: D15512746

fbshipit-source-id: d103ffdc7
---
 sledge/src/control.ml      |  5 +----
 sledge/src/llair/exp.ml    | 11 ++++++++++
 sledge/src/llair/exp.mli   |  7 +++++++
 sledge/src/llair/llair.ml  | 43 ++++++++++++++++----------------------
 sledge/src/llair/llair.mli |  6 ++++--
 5 files changed, 41 insertions(+), 31 deletions(-)

diff --git a/sledge/src/control.ml b/sledge/src/control.ml
index c595406d7..07beee755 100644
--- a/sledge/src/control.ml
+++ b/sledge/src/control.ml
@@ -364,10 +364,7 @@ let exec_block : Llair.t -> Stack.t -> Domain.t -> Llair.block -> Work.x =
 let harness : Llair.t -> (int -> Work.t) option =
  fun pgm ->
   List.find_map ["__llair_main"; "_Z12__llair_mainv"; "main"]
-    ~f:(fun name ->
-      Vector.find_map pgm.functions ~f:(fun func ->
-          Option.some_if (String.equal name (Var.name func.name.var)) func
-      ) )
+    ~f:(fun name -> Llair.Func.find pgm.functions (Var.program name))
   |> function
   | Some {entry= {params= []} as block} ->
       Some
diff --git a/sledge/src/llair/exp.ml b/sledge/src/llair/exp.ml
index 70b58feb1..60d33859f 100644
--- a/sledge/src/llair/exp.ml
+++ b/sledge/src/llair/exp.ml
@@ -504,6 +504,17 @@ module Var = struct
     let of_vector = Set.of_vector (module T)
   end
 
+  module Map = struct
+    include (
+      Map :
+        module type of Map
+        with type ('key, 'value, 'cmp) t := ('key, 'value, 'cmp) Map.t )
+
+    type 'v t = 'v Map.M(T).t [@@deriving compare, equal, sexp]
+
+    let empty = Map.empty (module T)
+  end
+
   let demangle =
     let open Ctypes in
     let cxa_demangle =
diff --git a/sledge/src/llair/exp.mli b/sledge/src/llair/exp.mli
index 2ce055b02..eee3b1caf 100644
--- a/sledge/src/llair/exp.mli
+++ b/sledge/src/llair/exp.mli
@@ -101,6 +101,13 @@ module Var : sig
     val of_vector : var vector -> t
   end
 
+  module Map : sig
+    type 'a t = (var, 'a, comparator_witness) Map.t
+    [@@deriving compare, equal, sexp]
+
+    val empty : 'a t
+  end
+
   val pp : t pp
   val pp_demangled : t pp
 
diff --git a/sledge/src/llair/llair.ml b/sledge/src/llair/llair.ml
index b99042850..bdc09f230 100644
--- a/sledge/src/llair/llair.ml
+++ b/sledge/src/llair/llair.ml
@@ -108,7 +108,9 @@ let sexp_of_func {name; entry; cfg} =
 let compare_block x y = Int.compare x.sort_index y.sort_index
 let equal_block x y = Int.equal x.sort_index y.sort_index
 
-type t = {globals: Global.t vector; functions: func vector}
+type functions = func Var.Map.t [@@deriving sexp_of]
+
+type t = {globals: Global.t vector; functions: functions}
 [@@deriving sexp_of]
 
 let pp_inst fs inst =
@@ -411,8 +413,7 @@ module Func = struct
         iter_term func ~f:(fun term -> Term.invariant term)
     | _ -> assert false
 
-  let find functions name =
-    Vector.find functions ~f:(fun {name= {var}} -> Var.equal name var)
+  let find functions name = Map.find functions name
 
   let mk ~name ~entry ~cfg =
     let func = {name; entry; cfg} in
@@ -479,9 +480,9 @@ module FuncQ = Hash_queue.Make (Var)
 let set_derived_metadata functions =
   let compute_roots functions =
     let roots = FuncQ.create () in
-    Array.iter functions ~f:(fun func ->
+    Map.iter functions ~f:(fun func ->
         FuncQ.enqueue_back_exn roots func.name.var func ) ;
-    Array.iter functions ~f:(fun func ->
+    Map.iter functions ~f:(fun func ->
         Func.fold_term func ~init:() ~f:(fun () -> function
           | Call {call= {dst}} -> (
             match Var.of_exp dst with
@@ -507,9 +508,7 @@ let set_derived_metadata functions =
             jump els
         | Iswitch {tbl} -> Vector.iter tbl ~f:jump
         | Call {call= {dst} as call; return; throw} ->
-            ( match
-                Var.of_exp dst >>= Func.find (Vector.of_array functions)
-              with
+            ( match Var.of_exp dst >>= Func.find functions with
             | Some func ->
                 if Set.mem ancestors func.entry then call.retreating <- true
                 else visit ancestors func func.entry
@@ -531,36 +530,28 @@ let set_derived_metadata functions =
         index := !index - 1 )
   in
   let sort_cfgs functions =
-    Array.iter functions ~f:(fun {cfg} ->
+    Map.iter functions ~f:(fun {cfg} ->
         Array.sort
           ~compare:(fun x y -> Int.compare x.sort_index y.sort_index)
           (Vector.to_array cfg) )
   in
-  let sort_functions functions =
-    Array.sort
-      ~compare:(fun x y -> Int.compare x.entry.sort_index y.entry.sort_index)
-      functions
+  let functions =
+    List.fold functions ~init:Var.Map.empty ~f:(fun m func ->
+        Map.add_exn m ~key:func.name.var ~data:func )
   in
-  let functions = Array.of_list functions in
   let roots = compute_roots functions in
   let tips_to_roots = topsort functions roots in
   set_sort_indices tips_to_roots ;
   sort_cfgs functions ;
-  sort_functions functions ;
-  Vector.of_array functions
+  functions
 
 let invariant pgm =
   Invariant.invariant [%here] pgm [%sexp_of: t]
   @@ fun () ->
-  let {globals; functions} = pgm in
-  assert (
-    not
-      (Vector.contains_dup globals ~compare:(fun g1 g2 ->
-           Var.compare g1.Global.var g2.Global.var )) ) ;
   assert (
     not
-      (Vector.contains_dup functions ~compare:(fun f1 f2 ->
-           Var.compare f1.name.var f2.name.var )) )
+      (Vector.contains_dup pgm.globals ~compare:(fun g1 g2 ->
+           Var.compare g1.Global.var g2.Global.var )) )
 
 let mk ~globals ~functions =
   { globals= Vector.of_list_rev globals
@@ -571,5 +562,7 @@ let pp fs {globals; functions} =
   Format.fprintf fs "@[<v>@[%a@]@ @ @ @[%a@]@]"
     (Vector.pp "@\n@\n" Global.pp_defn)
     globals
-    (Vector.pp "@\n@\n" Func.pp)
-    functions
+    (List.pp "@\n@\n" Func.pp)
+    ( Map.data functions
+    |> List.sort ~compare:(fun x y ->
+           Int.compare x.entry.sort_index y.entry.sort_index ) )
diff --git a/sledge/src/llair/llair.mli b/sledge/src/llair/llair.mli
index 38343e1dd..9be5956b2 100644
--- a/sledge/src/llair/llair.mli
+++ b/sledge/src/llair/llair.mli
@@ -109,9 +109,11 @@ and cfg
     parameters are the function parameters. *)
 and func = private {name: Global.t; entry: block; cfg: cfg}
 
+type functions
+
 type t = private
   { globals: Global.t vector  (** Global variable definitions. *)
-  ; functions: func vector  (** (Global) function definitions. *) }
+  ; functions: functions  (** (Global) function definitions. *) }
 
 val pp : t pp
 
@@ -197,7 +199,7 @@ module Func : sig
   val mk : name:Global.t -> entry:block -> cfg:block vector -> func
   val mk_undefined : name:Global.t -> params:Var.t list -> t
 
-  val find : func vector -> Var.t -> func option
+  val find : functions -> Var.t -> func option
   (** Look up a function of the given name in the given functions. *)
 
   val is_undefined : func -> bool