From b0e6ed8b35c199bdb1fd69a5b2f9596a89a741c5 Mon Sep 17 00:00:00 2001
From: Cristiano Calcagno <cristianoc@fb.com>
Date: Mon, 9 Jan 2017 07:34:22 -0800
Subject: [PATCH] [clang frontend] Eliminate use of expensive list append

Reviewed By: jberdine

Differential Revision: D4387084

fbshipit-source-id: fcc113e
---
 infer/src/clang/cFrontend_utils.ml  |  5 ----
 infer/src/clang/cFrontend_utils.mli |  3 --
 infer/src/clang/cVar_decl.ml        | 46 ++++++++++++++++-------------
 3 files changed, 25 insertions(+), 29 deletions(-)

diff --git a/infer/src/clang/cFrontend_utils.ml b/infer/src/clang/cFrontend_utils.ml
index 25d1ca6f2..abeba5c23 100644
--- a/infer/src/clang/cFrontend_utils.ml
+++ b/infer/src/clang/cFrontend_utils.ml
@@ -537,11 +537,6 @@ struct
     let eq (m1, t1) (m2, t2) = (Mangled.equal m1 m2) && (Typ.equal t1 t2) in
     append_no_duplicates eq list1 list2
 
-  let append_no_duplicateds list1 list2 =
-    let eq (e1, t1) (e2, t2) = (Exp.equal e1 e2) && (Typ.equal t1 t2) in
-    append_no_duplicates eq list1 list2
-
-
   let append_no_duplicates_annotations list1 list2 =
     let eq (annot1, _) (annot2, _) = annot1.Annot.class_name = annot2.Annot.class_name in
     append_no_duplicates eq list1 list2
diff --git a/infer/src/clang/cFrontend_utils.mli b/infer/src/clang/cFrontend_utils.mli
index a71a16ba3..404d0000c 100644
--- a/infer/src/clang/cFrontend_utils.mli
+++ b/infer/src/clang/cFrontend_utils.mli
@@ -193,9 +193,6 @@ sig
   val append_no_duplicated_vars :
     (Mangled.t * Typ.t) list -> (Mangled.t * Typ.t) list -> (Mangled.t * Typ.t) list
 
-  val append_no_duplicateds :
-    (Exp.t * Typ.t) list -> (Exp.t * Typ.t) list -> (Exp.t * Typ.t) list
-
   val sort_fields :
     (Ident.fieldname * Typ.t * Annot.Item.t) list ->
     (Ident.fieldname * Typ.t * Annot.Item.t) list
diff --git a/infer/src/clang/cVar_decl.ml b/infer/src/clang/cVar_decl.ml
index c07e959ac..2ca584d9e 100644
--- a/infer/src/clang/cVar_decl.ml
+++ b/infer/src/clang/cVar_decl.ml
@@ -62,27 +62,31 @@ let add_var_to_locals procdesc var_decl sil_typ pvar =
         Procdesc.append_locals procdesc [(Pvar.get_name pvar, sil_typ)]
   | _ -> assert false
 
-let rec compute_autorelease_pool_vars context stmts =
-  let procname = Procdesc.get_proc_name context.CContext.procdesc in
-  match stmts with
-  | [] -> []
-  | Clang_ast_t.DeclRefExpr (_, _, _, drei):: stmts' ->
-      (let res = compute_autorelease_pool_vars context stmts' in
-       match drei.Clang_ast_t.drti_decl_ref with
-       | Some decl_ref ->
-           (match decl_ref.Clang_ast_t.dr_type_ptr with
-            | Some type_ptr when decl_ref.Clang_ast_t.dr_kind = `Var ->
-                let typ = CType_decl.type_ptr_to_sil_type context.CContext.tenv type_ptr in
-                let pvar = sil_var_of_decl_ref context decl_ref procname in
-                if Pvar.is_local pvar then
-                  General_utils.append_no_duplicateds [(Exp.Lvar pvar, typ)] res
-                else res
-            | _ -> res)
-       | _ -> res)
-  | s :: stmts' ->
-      let sl = snd (Clang_ast_proj.get_stmt_tuple s) in
-      compute_autorelease_pool_vars context (sl @ stmts')
-
+let compute_autorelease_pool_vars context stmts =
+  let rec do_stmts map = function
+    | [] ->
+        map
+    | Clang_ast_t.DeclRefExpr (_, _, _, drei):: stmts' ->
+        let map1 = match drei.Clang_ast_t.drti_decl_ref with
+          | Some decl_ref ->
+              (match decl_ref.Clang_ast_t.dr_type_ptr with
+               | Some type_ptr when decl_ref.Clang_ast_t.dr_kind = `Var ->
+                   let typ = CType_decl.type_ptr_to_sil_type context.CContext.tenv type_ptr in
+                   let procname = Procdesc.get_proc_name context.CContext.procdesc in
+                   let pvar = sil_var_of_decl_ref context decl_ref procname in
+                   if Pvar.is_local pvar then
+                     Exp.Map.add (Exp.Lvar pvar) typ map
+                   else map
+               | _ ->
+                   map)
+          | None ->
+              map in
+        do_stmts map1 stmts'
+    | s :: stmts' ->
+        let sl = snd (Clang_ast_proj.get_stmt_tuple s) in
+        let map1 = do_stmts map sl in
+        do_stmts map1 stmts' in
+  Exp.Map.bindings (do_stmts Exp.Map.empty stmts)
 
 (* Returns a list of captured variables as sil variables. *)
 let captured_vars_from_block_info context cvl =