SDL: atomic: Use DMB ISHLD for aarch64 acquire barrier

SDL Commits
1 
From f2206974b098d2fbd61fdaf1a01513b6831b60d9 Mon Sep 17 00:00:00 2001
From: Cameron Gutman <[EMAIL REDACTED]>
Date: Thu, 23 Apr 2026 20:57:35 -0500
Subject: [PATCH] atomic: Use DMB ISHLD for aarch64 acquire barrier

This is a little more efficient than a DMB ISH and matches what
GCC, Clang, and MSVC generate for a C++11 acquire fence.
---
 include/SDL3/SDL_atomic.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/SDL3/SDL_atomic.h b/include/SDL3/SDL_atomic.h
index bbd5828df3c1e..91de8128288eb 100644
--- a/include/SDL3/SDL_atomic.h
+++ b/include/SDL3/SDL_atomic.h
@@ -283,7 +283,7 @@ extern SDL_DECLSPEC void SDLCALL SDL_MemoryBarrierAcquireFunction(void);
 #define SDL_MemoryBarrierAcquire()   __asm__ __volatile__ ("lwsync" : : : "memory")
 #elif defined(__GNUC__) && defined(__aarch64__)
 #define SDL_MemoryBarrierRelease()   __asm__ __volatile__ ("dmb ish" : : : "memory")
-#define SDL_MemoryBarrierAcquire()   __asm__ __volatile__ ("dmb ish" : : : "memory")
+#define SDL_MemoryBarrierAcquire()   __asm__ __volatile__ ("dmb ishld" : : : "memory")
 #elif defined(__GNUC__) && defined(__arm__)
 #if 0 /* defined(SDL_PLATFORM_LINUX) || defined(SDL_PLATFORM_ANDROID) */
 /* Information from: