[sledge] Add type for instruction pointers and use in Control

Summary:
In the sequential analysis there is no control-flow within a basic
block. This changes in the concurrent analyis as context switches can
occur within basic blocks. To support this, this diff adds a notion of
"instruction pointer" to Llair and adjusts Control to use it to
iterate blocks.

Differential Revision: D29441164

fbshipit-source-id: b9c977545

sledge/src/control.ml

@@ -650,32 +650,28 @@ module Make (Config : Config) (D : Domain) (Queue : Queue) = struct
     | Throw {exc} -> exec_throw stk state block exc
     | Unreachable -> Work.skip
 
-  let exec_inst : Llair.block -> Llair.inst -> D.t -> D.t Or_alarm.t =
-   fun block inst state ->
+  let rec exec_ip : Llair.program -> Stack.t -> D.t -> Llair.ip -> Work.x =
+   fun pgm stk state ip ->
+    match Llair.IP.inst ip with
+    | Some inst -> (
         [%Trace.info "@\n@[%a@]@\n%a" D.pp state Llair.Inst.pp inst] ;
-    Report.step_inst block inst ;
-    D.exec_inst inst state
+        Report.step_inst ip ;
+        match D.exec_inst inst state with
+        | Ok state ->
+            let ip = Llair.IP.succ ip in
+            exec_ip pgm stk state ip
+        | Error alarm ->
+            Report.alarm alarm ;
+            Work.skip )
+    | None -> exec_term pgm stk state (Llair.IP.block ip)
 
   let exec_block : Llair.program -> Stack.t -> D.t -> Llair.block -> Work.x
       =
    fun pgm stk state block ->
     [%trace]
-      ~call:(fun {pf} ->
-        pf "@ #%i %%%s in %a" block.sort_index block.lbl Llair.Function.pp
-          block.parent.name )
-      ~retn:(fun {pf} _ ->
-        pf "#%i %%%s in %a" block.sort_index block.lbl Llair.Function.pp
-          block.parent.name )
-    @@ fun () ->
-    match
-      Iter.fold_result ~f:(exec_inst block)
-        (IArray.to_iter block.cmnd)
-        state
-    with
-    | Ok state -> exec_term pgm stk state block
-    | Error alarm ->
-        Report.alarm alarm ;
-        Work.skip
+      ~call:(fun {pf} -> pf "@ %a" Llair.Block.pp block)
+      ~retn:(fun {pf} _ -> pf "%a" Llair.Block.pp block)
+    @@ fun () -> exec_ip pgm stk state (Llair.IP.mk block)
 
   let call_entry_point : Llair.program -> Work.t option =
    fun pgm ->

sledge/src/llair/llair.ml

@@ -370,10 +370,6 @@ and dummy_func =
 module Inst = struct
   type t = inst [@@deriving compare, equal, hash, sexp]
 
-  module Tbl = HashTable.Make (struct
-    type t = block * inst [@@deriving equal, hash]
-  end)
-
   let pp = pp_inst
   let move ~reg_exps ~loc = Move {reg_exps; loc}
   let load ~reg ~ptr ~len ~loc = Load {reg; ptr; len; loc}
@@ -538,6 +534,26 @@ module Block = struct
     ; sort_index= dummy_block.sort_index }
 end
 
+type ip = {block: block; index: int} [@@deriving equal, hash]
+
+module IP = struct
+  type t = ip
+
+  let mk block = {block; index= 0}
+  let succ {block; index} = {block; index= index + 1}
+
+  let inst {block; index} =
+    if index < IArray.length block.cmnd then
+      Some (IArray.get block.cmnd index)
+    else None
+
+  let block ip = ip.block
+
+  module Tbl = HashTable.Make (struct
+    type t = ip [@@deriving equal, hash]
+  end)
+end
+
 (* Blocks compared by label, which are unique within a function, used to
    compute unique sort_index ids *)
 module Block_label = struct

sledge/src/llair/llair.mli

@@ -106,6 +106,7 @@ and func = private
   ; entry: block
   ; loc: Loc.t }
 
+type ip
 type functions = func Function.Map.t
 
 type program = private
@@ -134,8 +135,6 @@ module Inst : sig
   val loc : inst -> Loc.t
   val locals : inst -> Reg.Set.t
   val fold_exps : inst -> 's -> f:(Exp.t -> 's -> 's) -> 's
-
-  module Tbl : HashTable.S with type key := block * t
 end
 
 module Jump : sig
@@ -197,6 +196,17 @@ module Block : sig
   module Tbl : HashTable.S with type key := t
 end
 
+module IP : sig
+  type t = ip
+
+  val mk : block -> t
+  val block : t -> block
+  val inst : t -> inst option
+  val succ : t -> t
+
+  module Tbl : HashTable.S with type key := t
+end
+
 module Func : sig
   type t = func [@@deriving compare, equal, hash]
 

sledge/src/report.ml

@@ -33,11 +33,11 @@ let unknown_call call =
 let solver_steps = ref 0
 let step_solver () = Int.incr solver_steps
 let steps = ref 0
-let hit_insts = Llair.Inst.Tbl.create ()
+let hit_insts = Llair.IP.Tbl.create ()
 let hit_terms = Llair.Block.Tbl.create ()
 
-let step_inst b i =
-  Llair.Inst.Tbl.incr hit_insts (b, i) ;
+let step_inst ip =
+  Llair.IP.Tbl.incr hit_insts ip ;
   Int.incr steps
 
 let step_term b =
@@ -162,7 +162,7 @@ let coverage (pgm : Llair.program) =
             n + IArray.length blk.cmnd + 1 ) )
   in
   let hit =
-    Llair.Inst.Tbl.length hit_insts + Llair.Block.Tbl.length hit_terms
+    Llair.IP.Tbl.length hit_insts + Llair.Block.Tbl.length hit_terms
   in
   let fraction = Float.(of_int hit /. of_int size) in
   output

sledge/src/report.mli

@@ -9,7 +9,7 @@
 
 val init : ?append:bool -> string -> unit
 val step_solver : unit -> unit
-val step_inst : Llair.block -> Llair.inst -> unit
+val step_inst : Llair.ip -> unit
 val step_term : Llair.block -> unit
 val hit_bound : int -> unit
 val unknown_call : Llair.term -> unit