From 052d5ccf5dc83db14917f4a52329a3bf2465af74 Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Mon, 28 Nov 2022 13:03:47 +0000
Subject: [PATCH] Implement __isb for AArch64

This is necessary for the mutex implementation of libstd when there is
contention. Seems like I hadn't hit this before by sheer luck.
---
 src/intrinsics/llvm_aarch64.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/intrinsics/llvm_aarch64.rs b/src/intrinsics/llvm_aarch64.rs
index 7959176ac85..b431158d269 100644
--- a/src/intrinsics/llvm_aarch64.rs
+++ b/src/intrinsics/llvm_aarch64.rs
@@ -16,6 +16,10 @@ pub(crate) fn codegen_aarch64_llvm_intrinsic_call<'tcx>(
     // llvm.aarch64.neon.sqshl.v*i*
 
     match intrinsic {
+        "llvm.aarch64.isb" => {
+            fx.bcx.ins().fence();
+        }
+
         _ if intrinsic.starts_with("llvm.aarch64.neon.abs.v") => {
             intrinsic_args!(fx, args => (a); intrinsic);