From a8e2ecc8b188f4f6c8529477392e344243ce40bd Mon Sep 17 00:00:00 2001
From: Mauri de Souza Meneguzzo <mauri870@gmail.com>
Date: Thu, 17 Oct 2024 12:57:26 +0000
Subject: [PATCH] internal/runtime/atomic: add Xchg8 for 386

For #69735

Change-Id: I5b9f57315d693d613dc88dc02c10bee39aeeef76
GitHub-Last-Rev: 690337e5b81a48bdcb808526d0c5f4837e8912b7
GitHub-Pull-Request: golang/go#69923
Reviewed-on: https://go-review.googlesource.com/c/go/+/620756
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
---
 src/internal/runtime/atomic/atomic_386.go | 3 +++
 src/internal/runtime/atomic/atomic_386.s  | 8 ++++++++
 src/internal/runtime/atomic/xchg8_test.go | 2 +-
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/internal/runtime/atomic/atomic_386.go b/src/internal/runtime/atomic/atomic_386.go
index a023baddb7..b6cdea61ab 100644
--- a/src/internal/runtime/atomic/atomic_386.go
+++ b/src/internal/runtime/atomic/atomic_386.go
@@ -53,6 +53,9 @@ func Xchg64(ptr *uint64, new uint64) uint64
 //go:noescape
 func Xchg(ptr *uint32, new uint32) uint32
 
+//go:noescape
+func Xchg8(ptr *uint8, new uint8) uint8
+
 //go:noescape
 func Xchguintptr(ptr *uintptr, new uintptr) uintptr
 
diff --git a/src/internal/runtime/atomic/atomic_386.s b/src/internal/runtime/atomic/atomic_386.s
index 08812c37ec..58a56e63c0 100644
--- a/src/internal/runtime/atomic/atomic_386.s
+++ b/src/internal/runtime/atomic/atomic_386.s
@@ -153,6 +153,14 @@ addloop:
 	MOVL	CX, ret_hi+16(FP)
 	RET
 
+// uint8 Xchg8(uint8 *ptr, uint8 new)
+TEXT ·Xchg8(SB), NOSPLIT, $0-9
+	MOVL	ptr+0(FP), BX
+	MOVB	new+4(FP), AX
+	XCHGB	AX, 0(BX)
+	MOVB	AX, ret+8(FP)
+	RET
+
 TEXT ·Xchg(SB), NOSPLIT, $0-12
 	MOVL	ptr+0(FP), BX
 	MOVL	new+4(FP), AX
diff --git a/src/internal/runtime/atomic/xchg8_test.go b/src/internal/runtime/atomic/xchg8_test.go
index a04fcfc4bd..d9f1d8854e 100644
--- a/src/internal/runtime/atomic/xchg8_test.go
+++ b/src/internal/runtime/atomic/xchg8_test.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build amd64 || arm64 || ppc64 || ppc64le
+//go:build 386 || amd64 || arm64 || ppc64 || ppc64le
 
 package atomic_test
 
-- 
2.48.1