From d61f56c77f6f498398ab2d0294b53439e5abdee7 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Tue, 9 Apr 2019 04:41:14 -0600
Subject: [PATCH] cs: imprve fixnum hashing

Avoid collision for 0 and -1, for example.
---
 racket/src/cs/rumble/hash-code.ss | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/racket/src/cs/rumble/hash-code.ss b/racket/src/cs/rumble/hash-code.ss
index 9546776fe0..7b7777b2a5 100644
--- a/racket/src/cs/rumble/hash-code.ss
+++ b/racket/src/cs/rumble/hash-code.ss
@@ -41,7 +41,7 @@
 (define number-hash
   (lambda (z)
     (cond
-     [(fixnum? z) (if (fx< z 0) (fxnot z) z)]
+     [(fixnum? z) (if (fx< z 0) (fxand z (most-positive-fixnum)) z)]
      [(flonum? z) (#3%$flhash z)]
      [(bignum? z) (modulo z (most-positive-fixnum))]
      [(ratnum? z) (number-hash (+ (* (numerator z) 5) (denominator z)))]