From 8de6f6058e6236ad13ccac933158def70237e946 Mon Sep 17 00:00:00 2001
From: Katelyn Gadd <kg@luminance.org>
Date: Thu, 5 Sep 2024 19:21:52 -0700
Subject: [PATCH] Fix atomic fence encoding

---
 src/mono/browser/runtime/jiterpreter-trace-generator.ts | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/mono/browser/runtime/jiterpreter-trace-generator.ts b/src/mono/browser/runtime/jiterpreter-trace-generator.ts
index 092d721daa2bd..956538ffe5f3c 100644
--- a/src/mono/browser/runtime/jiterpreter-trace-generator.ts
+++ b/src/mono/browser/runtime/jiterpreter-trace-generator.ts
@@ -3977,8 +3977,12 @@ function emit_atomics (
     builder: WasmBuilder, ip: MintOpcodePtr, opcode: number
 ) {
     if (opcode === MintOpcode.MINT_MONO_MEMORY_BARRIER) {
-        if (WasmEnableThreads)
+        if (WasmEnableThreads) {
             builder.appendAtomic(WasmAtomicOpcode.atomic_fence);
+            // The text format and other parts of the spec say atomic.fence has no operands,
+            //  but the binary encoding requires a dummy zero byte for some reason
+            builder.appendU8(0);
+        }
         return true;
     }