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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.
This commit is contained in:
riastradh 2022-04-09 12:07:17 +00:00
parent e0c914a79b
commit 3066bbbbf8
2 changed files with 12 additions and 6 deletions
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9
common/lib/libc/arch/i386/atomic/atomic.S
View File

@ -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)

9
common/lib/libc/arch/x86_64/atomic/atomic.S
View File

@ -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)