svn commit: r353270 - head/sys/cddl/contrib/opensolaris/common/atomic/i386

[Andriy Gapon]

Author: avg
Date: Mon Oct  7 12:53:27 2019
New Revision: 353270
URL: https://svnweb.freebsd.org/changeset/base/353270

Log:
  fix up r353168, add atomic_swap_64 to i386 version of opensolaris_atomic.S
  
  The compatibility code for the atomic operations in ZFS code is a bit
  messy.  In some cases the native definitions are directly made
  available, in some cases there are emulated operations in
  opensolaris_atomic.c and in yet other cases there are atomic operations
  implemented in assembly that were obtained from OpenSolaris / illumos.
  
  This commit adds atomic_swap_64 for use with i386 userland.
  The code is copied from illumos.
  
  I am not sure why FreeBSD does not provide that operation natively.
  Maybe because we try (or pretend) to support processors that did not
  have the necessary instructions.
  
  While here I also added atomic_load_64 for the same reasons.
  This is original code based on iilumos atomic_swap_64 and FreeBSD
  atomic_load_acq_64_i586.
  
  Pointyhat to:	avg
  MFC after:	1 week

Modified:
  head/sys/cddl/contrib/opensolaris/common/atomic/i386/opensolaris_atomic.S

Modified: head/sys/cddl/contrib/opensolaris/common/atomic/i386/opensolaris_atomic.S
==============================================================================
--- head/sys/cddl/contrib/opensolaris/common/atomic/i386/opensolaris_atomic.S	Mon Oct  7 12:51:36 2019	(r353269)
+++ head/sys/cddl/contrib/opensolaris/common/atomic/i386/opensolaris_atomic.S	Mon Oct  7 12:53:27 2019	(r353270)
@@ -126,6 +126,34 @@
 	ret
 	SET_SIZE(atomic_cas_64)
 
+	ENTRY(atomic_swap_64)
+	pushl	%esi
+	pushl	%ebx
+	movl	12(%esp), %esi
+	movl	16(%esp), %ebx
+	movl	20(%esp), %ecx
+	movl	(%esi), %eax
+	movl	4(%esi), %edx	// %edx:%eax = old value
+1:
+	lock
+	cmpxchg8b (%esi)
+	jne	1b
+	popl	%ebx
+	popl	%esi
+	ret
+	SET_SIZE(atomic_swap_64)
+
+	ENTRY(atomic_load_64)
+	pushl	%esi
+	movl	8(%esp), %esi
+	movl	%ebx, %eax	// make old and new values equal, so that
+	movl	%ecx, %edx	// destination is never changed
+	lock
+	cmpxchg8b (%esi)
+	popl	%esi
+	ret
+	SET_SIZE(atomic_load_64)
+
 	ENTRY(membar_producer)
 	lock
 	xorl	$0, (%esp)