From a31ded07977e2229ceec22b326b4b82cb3802851 Mon Sep 17 00:00:00 2001
From: Paul Fd <paul@ferrand.cc>
Date: Tue, 10 Mar 2020 14:30:27 +0100
Subject: [PATCH] Tentative atomic_queue patch

---
 src/external/atomic_queue/atomic_queue.h | 33 +++++++++++-------------
 1 file changed, 15 insertions(+), 18 deletions(-)

diff --git a/src/external/atomic_queue/atomic_queue.h b/src/external/atomic_queue/atomic_queue.h
index 19fdb40d..bcbd29a9 100644
--- a/src/external/atomic_queue/atomic_queue.h
+++ b/src/external/atomic_queue/atomic_queue.h
@@ -95,27 +95,24 @@ constexpr T& map(T* elements, unsigned index) noexcept {
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
 
+template<class T>
+constexpr T decrement(T x) { return x - 1; }
+template<class T>
+constexpr T increment(T x) { return x + 1; }
+template<class T>
+constexpr T or_equal(T x, unsigned u) { return (x | x >> u); }
+template<class T, class... Args>
+constexpr T or_equal(T x, unsigned u, Args... rest)
+{
+    return or_equal(or_equal(x, u), rest...);
+}
+
 constexpr uint32_t round_up_to_power_of_2(uint32_t a) noexcept {
-    --a;
-    a |= a >> 1;
-    a |= a >> 2;
-    a |= a >> 4;
-    a |= a >> 8;
-    a |= a >> 16;
-    ++a;
-    return a;
+    return increment(or_equal(decrement(a), 1, 2, 4, 8, 16));
 }
 
 constexpr uint64_t round_up_to_power_of_2(uint64_t a) noexcept {
-    --a;
-    a |= a >> 1;
-    a |= a >> 2;
-    a |= a >> 4;
-    a |= a >> 8;
-    a |= a >> 16;
-    a |= a >> 32;
-    ++a;
-    return a;
+    return increment(or_equal(decrement(a), 1, 2, 4, 8, 16, 32));
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
@@ -304,7 +301,7 @@ public:
         static_cast<Derived&>(*this).do_push(std::forward<T>(element), head);
     }
 
-    auto pop() noexcept {
+    Derived& pop() noexcept {
         unsigned tail;
         if(Derived::spsc_) {
             tail = tail_.load(X);