From ebcfae388a0cad4bd2bd8633a5e39327e0240e7b Mon Sep 17 00:00:00 2001
From: Sam Blackshear <shb@fb.com>
Date: Thu, 5 May 2016 10:01:31 -0700
Subject: [PATCH] handling Set(Var, _,) as read of var in liveness analysis

Reviewed By: jvillard

Differential Revision: D3264597

fb-gh-sync-id: efe1982
fbshipit-source-id: efe1982
---
 infer/src/checkers/liveness.ml  |  3 +--
 infer/src/unit/livenessTests.ml | 10 ++++++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/infer/src/checkers/liveness.ml b/infer/src/checkers/liveness.ml
index a006d7277..7b11295e7 100644
--- a/infer/src/checkers/liveness.ml
+++ b/infer/src/checkers/liveness.ml
@@ -32,8 +32,7 @@ module TransferFunctions = struct
     IList.fold_left (fun astate_acc pvar -> Domain.add (ProgramVar pvar) astate_acc) astate' pvars
 
   let exec_instr astate _ = function
-    | Sil.Letderef (lhs_id, rhs_exp, _, _)
-    | Sil.Set (Sil.Var lhs_id, _, rhs_exp, _) ->
+    | Sil.Letderef (lhs_id, rhs_exp, _, _) ->
         Domain.remove (LogicalVar lhs_id) astate
         |> exp_add_live rhs_exp
     | Sil.Set (Lvar lhs_pvar, _, rhs_exp, _) ->
diff --git a/infer/src/unit/livenessTests.ml b/infer/src/unit/livenessTests.ml
index 080049112..6793ac05a 100644
--- a/infer/src/unit/livenessTests.ml
+++ b/infer/src/unit/livenessTests.ml
@@ -30,6 +30,11 @@ let tests =
   let unknown_cond =
     (* don't want to use AnalyzerTest.unknown_exp because we'll treat it as a live var! *)
     Sil.exp_zero in
+  let id_set_id lhs_id rhs_id =
+    let lhs_exp = Sil.Var (ident_of_str lhs_id) in
+    let rhs_exp = Sil.Var (ident_of_str rhs_id) in
+    let rhs_typ = dummy_typ in
+    make_set ~rhs_typ ~lhs_exp ~rhs_exp in
   let test_list = [
     "basic_live",
     [
@@ -73,6 +78,11 @@ let tests =
       invariant "{ y$0 }";
       id_assign_id "x" "y"
     ];
+    "set_id",
+    [
+      invariant "{ x$0, y$0 }";
+      id_set_id "x" "y" (* this is *x = y, which is a read of both x and y *)
+    ];
     "if_exp_live",
     [
       assert_empty;