Module Name: src
Committed By: riastradh
Date: Sat Apr 9 12:07:18 UTC 2022
Modified Files:
src/common/lib/libc/arch/i386/atomic: atomic.S
src/common/lib/libc/arch/x86_64/atomic: atomic.S
Log Message:
x86: Omit needless store in membar_producer/exit.
On x86, every store is a store-release, so there is no need for any
barrier. But this wasn't a barrier anyway; it was just a store,
which was redundant with the store of the return address to the stack
implied by CALL even if issuing a store made a difference.
To generate a diff of this commit:
cvs rdiff -u -r1.31 -r1.32 src/common/lib/libc/arch/i386/atomic/atomic.S
cvs rdiff -u -r1.24 -r1.25 src/common/lib/libc/arch/x86_64/atomic/atomic.S
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/common/lib/libc/arch/i386/atomic/atomic.S
diff -u src/common/lib/libc/arch/i386/atomic/atomic.S:1.31 src/common/lib/libc/arch/i386/atomic/atomic.S:1.32
--- src/common/lib/libc/arch/i386/atomic/atomic.S:1.31 Sat Apr 9 12:07:00 2022
+++ src/common/lib/libc/arch/i386/atomic/atomic.S Sat Apr 9 12:07:17 2022
@@ -1,4 +1,4 @@
-/* $NetBSD: atomic.S,v 1.31 2022/04/09 12:07:00 riastradh Exp $ */
+/* $NetBSD: atomic.S,v 1.32 2022/04/09 12:07:17 riastradh Exp $ */
/*-
* Copyright (c) 2007 The NetBSD Foundation, Inc.
@@ -188,8 +188,11 @@ ENTRY(_membar_consumer)
END(_membar_consumer)
ENTRY(_membar_producer)
- /* A store is enough */
- movl $0, -4(%esp)
+ /*
+ * Every store to normal memory is a store-release on x86, so
+ * there is never any need for explicit barriers to order
+ * anything-before-store.
+ */
ret
END(_membar_producer)
Index: src/common/lib/libc/arch/x86_64/atomic/atomic.S
diff -u src/common/lib/libc/arch/x86_64/atomic/atomic.S:1.24 src/common/lib/libc/arch/x86_64/atomic/atomic.S:1.25
--- src/common/lib/libc/arch/x86_64/atomic/atomic.S:1.24 Sat Apr 9 12:07:00 2022
+++ src/common/lib/libc/arch/x86_64/atomic/atomic.S Sat Apr 9 12:07:17 2022
@@ -1,4 +1,4 @@
-/* $NetBSD: atomic.S,v 1.24 2022/04/09 12:07:00 riastradh Exp $ */
+/* $NetBSD: atomic.S,v 1.25 2022/04/09 12:07:17 riastradh Exp $ */
/*-
* Copyright (c) 2007 The NetBSD Foundation, Inc.
@@ -263,8 +263,11 @@ ENTRY(_membar_consumer)
END(_membar_consumer)
ENTRY(_membar_producer)
- /* A store is enough */
- movq $0, -8(%rsp)
+ /*
+ * Every store to normal memory is a store-release on x86, so
+ * there is never any need for explicit barriers to order
+ * anything-before-store.
+ */
ret
END(_membar_producer)
