SDL: atomic: Use DMB ISHLD for aarch64 acquire barrier (34742)

SDL Commits
1 
From 34742887ef54288c650dcd2aa0b6490fd1128d9b Mon Sep 17 00:00:00 2001
From: Cameron Gutman <[EMAIL REDACTED]>
Date: Thu, 23 Apr 2026 21:18:05 -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.

(cherry picked from commit 77514941604212337976574531fa4398938d204d)
---
 include/SDL_atomic.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/SDL_atomic.h b/include/SDL_atomic.h
index 064276fefda18..970ec97dc7c35 100644
--- a/include/SDL_atomic.h
+++ b/include/SDL_atomic.h
@@ -182,7 +182,7 @@ extern 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(__LINUX__) || defined(__ANDROID__) */
 /* Information from: