From fb3bfdf1862ea5ef6ddeec1d44d355a064f6be08 Mon Sep 17 00:00:00 2001
From: Warner Losh <imp@FreeBSD.org>
Date: Thu, 24 May 2018 21:11:33 +0000
Subject: [PATCH] Make memmove and bcopy share code

Make memmove the primary interface, but have bcopy be an alternative
entry point that jumps into memmove. This will slightly pessimize
bcopy calls, but those are about to get much rarer. Return dst always,
but it will be ignored by bcopy callers. We can remove just the alt
entry point if we ever remove bcopy entirely.

Differential Revision: https://reviews.freebsd.org/D15374
---
 sys/conf/files.i386     |  1 -
 sys/i386/i386/support.s | 12 ++++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/sys/conf/files.i386 b/sys/conf/files.i386
index 9fe32a20eb6..e06c4f6fb57 100644
--- a/sys/conf/files.i386
+++ b/sys/conf/files.i386
@@ -553,7 +553,6 @@ kern/subr_sfbuf.c		standard
 libkern/divdi3.c		standard
 libkern/ffsll.c			standard
 libkern/flsll.c			standard
-libkern/memmove.c		standard
 libkern/memset.c		standard
 libkern/moddi3.c		standard
 libkern/qdivrem.c		standard
diff --git a/sys/i386/i386/support.s b/sys/i386/i386/support.s
index ca4ce8abcda..5fa2aa7131f 100644
--- a/sys/i386/i386/support.s
+++ b/sys/i386/i386/support.s
@@ -146,6 +146,7 @@ ENTRY(fillw)
 END(fillw)
 
 /*
+ * memmove(dst, src, cnt) (return dst)
  * bcopy(src, dst, cnt)
  *  ws@tools.de     (Wolfgang Solfrank, TooLs GmbH) +49-228-985800
  */
@@ -156,6 +157,15 @@ ENTRY(bcopy)
 	pushl	%edi
 	movl	8(%ebp),%esi
 	movl	12(%ebp),%edi
+	jmp	1f
+ALTENTRY(memmove)
+	pushl	%ebp
+	movl	%esp,%ebp
+	pushl	%esi
+	pushl	%edi
+	movl	8(%ebp),%edi
+	movl	12(%ebp),%esi
+1:
 	movl	16(%ebp),%ecx
 
 	movl	%edi,%eax
@@ -172,6 +182,7 @@ ENTRY(bcopy)
 	movsb
 	popl	%edi
 	popl	%esi
+	movl	8(%ebp),%eax			/* return dst for memmove */
 	popl	%ebp
 	ret
 
@@ -194,6 +205,7 @@ ENTRY(bcopy)
 	popl	%edi
 	popl	%esi
 	cld
+	movl	8(%ebp),%eax			/* return dst for memmove */
 	popl	%ebp
 	ret
 END(bcopy)