From 38e66d6f91d8e04d3735d14ada0d98019404734a Mon Sep 17 00:00:00 2001
From: Timotej Kapus <kapust@fb.com>
Date: Mon, 1 Jul 2019 07:39:12 -0700
Subject: [PATCH] [sledge] [summaries] Fix issues with multiple calls

Summary:
This fixes two issues with function summarization when calling a
function multiple times.

* Previously on return, the actuals wouldn't get added back in, so
  their name would be "lost" (that is existentially quantified out),
  this patch adds the formals to actuals equalities back on return,
  before quantifying the formals out.

* Previously the entry state of the function would be lost if there were
  multiple calls to other functions.

Reviewed By: jberdine

Differential Revision: D16071656

fbshipit-source-id: 9df7b1d4b
---
 sledge/src/symbheap/domain.ml       |  5 ++---
 sledge/src/symbheap/state_domain.ml | 22 +++++++++++++++-------
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/sledge/src/symbheap/domain.ml b/sledge/src/symbheap/domain.ml
index 0c11ff88b..9dfa200df 100644
--- a/sledge/src/symbheap/domain.ml
+++ b/sledge/src/symbheap/domain.ml
@@ -53,7 +53,7 @@ let jump actuals formals ?temps (entry, current) =
   let current, _ = State_domain.jump actuals formals ?temps current in
   (entry, current)
 
-let call ~summaries actuals formals locals globals_vec (_, current) =
+let call ~summaries actuals formals locals globals_vec (entry, current) =
   let globals =
     Var.Set.of_vector
       (Vector.map globals_vec ~f:(fun (g : Global.t) -> g.var))
@@ -69,8 +69,7 @@ let call ~summaries actuals formals locals globals_vec (_, current) =
   let caller_current, state_from_call =
     State_domain.call ~summaries actuals formals locals globals current
   in
-  ( (caller_current, caller_current)
-  , {state_from_call; caller_entry= current} ))
+  ((caller_current, caller_current), {state_from_call; caller_entry= entry}))
   |>
   [%Trace.retn fun {pf} (reln, _) -> pf "@,%a" pp reln]
 
diff --git a/sledge/src/symbheap/state_domain.ml b/sledge/src/symbheap/state_domain.ml
index 3738686e8..c616254fa 100644
--- a/sledge/src/symbheap/state_domain.ml
+++ b/sledge/src/symbheap/state_domain.ml
@@ -66,7 +66,8 @@ let garbage_collect (q : t) ~wrt =
   |>
   [%Trace.retn fun {pf} -> pf "%a" pp]
 
-type from_call = {subst: Var.Subst.t; frame: Sh.t}
+type from_call =
+  {subst: Var.Subst.t; frame: Sh.t; actuals_to_formals: (Exp.t * Var.t) list}
 [@@deriving compare, equal, sexp]
 
 (** Express formula in terms of formals instead of actuals, and enter scope
@@ -89,7 +90,7 @@ let jump actuals formals ?temps q =
   in
   ( Option.fold ~f:(Fn.flip Sh.exists) temps
       ~init:(and_eqs formals actuals q')
-  , {subst= freshen_locals; frame= Sh.emp} )
+  , {subst= freshen_locals; frame= Sh.emp; actuals_to_formals= []} )
   |>
   [%Trace.retn fun {pf} (q', {subst}) ->
     pf "@[<hv>subst: %a@ q': %a@]" Var.Subst.pp subst Sh.pp q']
@@ -116,7 +117,8 @@ let call ~summaries actuals formals locals globals q =
   let q'', subst =
     (Sh.extend_us locals (and_eqs formals actuals q'), freshen_locals)
   in
-  ( if not summaries then (q'', {subst; frame= Sh.emp})
+  ( if not summaries then
+    (q'', {subst; frame= Sh.emp; actuals_to_formals= []})
   else
     let formals_set = Var.Set.of_list formals in
     let non_function_specific_vars =
@@ -144,7 +146,8 @@ let call ~summaries actuals formals locals globals q =
     let frame =
       Option.value ~default:Sh.emp (Solver.infer_frame pre xs foot)
     in
-    (function_summary_pre, {subst; frame}) )
+    ( function_summary_pre
+    , {subst; frame; actuals_to_formals= List.zip_exn actuals formals} ) )
   |>
   [%Trace.retn fun {pf} (q', {subst; frame}) ->
     pf "@[<v>subst: %a@ frame: %a@ q': %a@]" Var.Subst.pp subst pp frame pp
@@ -162,11 +165,16 @@ let post locals q =
 (** Express in terms of actuals instead of formals: existentially quantify
     formals, and apply inverse of fresh variables for formals renaming to
     restore the shadowed variables. *)
-let retn formals {subst; frame} q =
+let retn formals {subst; frame; actuals_to_formals} q =
   [%Trace.call fun {pf} ->
-    pf "@[<v>formals: {@[%a@]}@ subst: %a@ q: %a@]" (List.pp ", " Var.pp)
-      formals Var.Subst.pp (Var.Subst.invert subst) pp q]
+    pf "@[<v>formals: {@[%a@]}@ subst: %a@ q: %a@ frame: %a@]"
+      (List.pp ", " Var.pp) formals Var.Subst.pp (Var.Subst.invert subst) pp
+      q pp frame]
   ;
+  let and_eq q (actual, formal) =
+    Sh.and_ (Exp.eq (Exp.var formal) actual) q
+  in
+  let q = List.fold ~f:and_eq actuals_to_formals ~init:q in
   let func_post =
     Sh.rename (Var.Subst.invert subst)
       (Sh.exists (Var.Set.of_list formals) q)