From 6985150e0b61be4a32e5746e893609323c95d7e7 Mon Sep 17 00:00:00 2001
From: Gustavo Massaccesi <gustavo@oma.org.ar>
Date: Mon, 14 Dec 2015 17:46:44 -0300
Subject: [PATCH] Don't drop expressions with side effects in eq? reduction

The expression (eq? x y) is reduced to #f when the types of
x and y are known. Reduce this to (begin x y #f) when they
have side effects.
---
 pkgs/racket-test-core/tests/racket/optimize.rktl | 6 ++++++
 racket/src/racket/src/optimize.c                 | 8 +++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/pkgs/racket-test-core/tests/racket/optimize.rktl b/pkgs/racket-test-core/tests/racket/optimize.rktl
index 72366f37f0..f1eb1b85a4 100644
--- a/pkgs/racket-test-core/tests/racket/optimize.rktl
+++ b/pkgs/racket-test-core/tests/racket/optimize.rktl
@@ -1494,6 +1494,12 @@
            '(lambda (x y) (car x) (unbox y) (eq? x y)))
 (test-comp '(lambda (x) (car x) #f)
            '(lambda (x) (car x) (eq? x (box 0))))
+(test-comp '(lambda (x) (car x) #f)
+           '(lambda (x) (car x) (eq? (begin (newline) x) (box 0)))
+           #f)
+(test-comp '(lambda (x) (car x) #f)
+           '(lambda (x) (car x) (eq? x (begin (newline) (box 0))))
+           #f)
 
 (test-comp '(lambda (w) (car w) (mcar w))
            '(lambda (w) (car w) (mcar w) (random)))
diff --git a/racket/src/racket/src/optimize.c b/racket/src/racket/src/optimize.c
index c3fdc6493a..8040c496e5 100644
--- a/racket/src/racket/src/optimize.c
+++ b/racket/src/racket/src/optimize.c
@@ -3698,7 +3698,13 @@ static Scheme_Object *finish_optimize_application3(Scheme_App3_Rec *app, Optimiz
         if (!SAME_OBJ(pred1, pred2)) {
           info->preserves_marks = 1;
           info->single_result = 1;
-          return scheme_false;
+          return do_make_discarding_sequence(app->rand1,
+                                             do_make_discarding_sequence(app->rand2,
+                                                                         scheme_false,
+                                                                         info, 0,
+                                                                         1, 0),
+                                             info, 0,
+                                             1, 0);
         }
       }
     }