[cost] Fix control variables to pick up global vars in prune instructions

Reviewed By: ngorogiannis

Differential Revision: D13322062

fbshipit-source-id: 4e8081103

infer/src/checkers/control.ml

@@ -73,10 +73,18 @@ module TransferFunctionsControlDeps (CFG : ProcCfg.S) = struct
 
 
   let get_vars_in_exp exp prune_node loop_head =
-    assert (Exp.program_vars exp |> Sequence.is_empty) ;
+    let global_control_vars =
-    (* We should never have program variables in prune nodes *)
+      Exp.program_vars exp
+      |> Sequence.fold ~init:ControlDepSet.empty ~f:(fun global_acc pvar ->
+             let cvar = Var.of_pvar pvar in
+             if Pvar.is_global pvar then ControlDepSet.add {cvar; loop_head} global_acc
+             else
+               Logging.die InternalError
+                 "We should never have non-global program variables in prune nodes: %a@." Var.pp
+                 cvar )
+    in
     Exp.free_vars exp
-    |> Sequence.fold ~init:ControlDepSet.empty ~f:(fun acc id ->
+    |> Sequence.fold ~init:global_control_vars ~f:(fun acc id ->
            match
              Procdesc.Node.find_in_node_or_preds prune_node ~f:(find_vars_in_decl id loop_head)
            with

infer/tests/codetoanalyze/c/performance/issues.exp

@@ -160,6 +160,9 @@ codetoanalyze/c/performance/loops.c, larger_state_FN, 3, EXPENSIVE_EXECUTION_TIM
 codetoanalyze/c/performance/loops.c, larger_state_FN, 4, EXPENSIVE_EXECUTION_TIME_CALL, no_bucket, ERROR, [with estimated cost 1006, degree = 0]
 codetoanalyze/c/performance/loops.c, larger_state_FN, 5, EXPENSIVE_EXECUTION_TIME_CALL, no_bucket, ERROR, [with estimated cost 1006, degree = 0]
 codetoanalyze/c/performance/loops.c, larger_state_FN, 7, EXPENSIVE_EXECUTION_TIME_CALL, no_bucket, ERROR, [with estimated cost 1006, degree = 0]
+codetoanalyze/c/performance/loops.c, loop_use_global_vars, 1, EXPENSIVE_EXECUTION_TIME_CALL, no_bucket, ERROR, [with estimated cost 4 + 4 ⋅ x.ub + 2 ⋅ (1+max(0, x.ub)), degree = 1]
+codetoanalyze/c/performance/loops.c, loop_use_global_vars, 1, EXPENSIVE_EXECUTION_TIME_CALL, no_bucket, ERROR, [with estimated cost 3 + 4 ⋅ x.ub + 2 ⋅ (1+max(0, x.ub)), degree = 1]
+codetoanalyze/c/performance/loops.c, loop_use_global_vars, 1, EXPENSIVE_EXECUTION_TIME_CALL, no_bucket, ERROR, [with estimated cost 3 + 4 ⋅ x.ub + 2 ⋅ (1+max(0, x.ub)), degree = 1]
 codetoanalyze/c/performance/purity.c, loop, 2, EXPENSIVE_EXECUTION_TIME_CALL, no_bucket, ERROR, [with estimated cost 7006, degree = 0]
 codetoanalyze/c/performance/purity.c, loop, 2, EXPENSIVE_EXECUTION_TIME_CALL, no_bucket, ERROR, [with estimated cost 7006, degree = 0]
 codetoanalyze/c/performance/purity.c, loop, 3, EXPENSIVE_EXECUTION_TIME_CALL, no_bucket, ERROR, [with estimated cost 7006, degree = 0]

infer/tests/codetoanalyze/c/performance/loops.c

@@ -59,3 +59,14 @@ void larger_state_FN() {
     }
   }
 }
+
+static int array1[] = {1, 2, 3};
+static int array2[] = {};
+
+// Cvars will initially contain array1 and array2 but will be removed
+// since they are invariant
+void loop_use_global_vars(int x) {
+  for (int i = 0; i < x && array1 != array2; i++) {
+    // do something
+  }
+}