From 484f870c87266913a26fd680b5b9bc887315ae0e Mon Sep 17 00:00:00 2001
From: Peter du Marchie van Voorthuysen <p.dumarchie@gmail.com>
Date: Tue, 17 Nov 2020 22:33:52 +0100
Subject: [PATCH] Make cas($target, &code) ~10% faster

---
 src/core.c/atomicops.pm6 | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/core.c/atomicops.pm6 b/src/core.c/atomicops.pm6
index 83974aed928..8f2912d2367 100644
--- a/src/core.c/atomicops.pm6
+++ b/src/core.c/atomicops.pm6
@@ -24,12 +24,15 @@ multi sub cas($target is rw, \expected, \value) {
 }
 multi sub cas($target is rw, &code) {
     my $current := nqp::atomicload($target);
-    loop {
-        my $updated := code($current);
-        my $seen := nqp::cas($target, $current, $updated);
-        return $updated if nqp::eqaddr($seen, $current);
-        $current := $seen;
-    }
+    nqp::until(
+      nqp::stmts(
+        (my $updated := code($current)),
+        (my $seen := nqp::cas($target, $current, $updated)),
+        nqp::eqaddr($seen, $current)
+      ),
+      $current := $seen
+    );
+    $updated
 }
 
 #== Native integer atomics only available on MoarVM ==============================