From fcac8617b4e3c8fcb3a8c888fe77fa8bff1c2057 Mon Sep 17 00:00:00 2001
From: Lukas Lalinsky <lukas@lalinsky.com>
Date: Thu, 9 Oct 2025 08:52:52 +0200
Subject: [PATCH] Add missing clobbers to context switching

This only shows in release mode, the compiler tries to preserve some
value in rdi, but that gets replaced inside the fiber. This would not
happen in the C calling convention, but in these normal Zig functions,
it can happen.
---
 lib/std/Io/EventLoop.zig | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/std/Io/EventLoop.zig b/lib/std/Io/EventLoop.zig
index d1d7799907..4cb5745e31 100644
--- a/lib/std/Io/EventLoop.zig
+++ b/lib/std/Io/EventLoop.zig
@@ -644,6 +644,7 @@ inline fn contextSwitch(message: *const SwitchMessage) *const SwitchMessage {
             : [received_message] "={x1}" (-> *const @FieldType(SwitchMessage, "contexts")),
             : [message_to_send] "{x1}" (&message.contexts),
             : .{
+              .x0 = true,
               .x1 = true,
               .x2 = true,
               .x3 = true,
@@ -745,6 +746,7 @@ inline fn contextSwitch(message: *const SwitchMessage) *const SwitchMessage {
               .rdx = true,
               .rbx = true,
               .rsi = true,
+              .rdi = true,
               .r8 = true,
               .r9 = true,
               .r10 = true,