Index: head/lib/libc/amd64/string/memset.S
===================================================================
--- head/lib/libc/amd64/string/memset.S	(revision 339205)
+++ head/lib/libc/amd64/string/memset.S	(revision 339206)
@@ -1,77 +1,131 @@
 /*-
  * Copyright (c) 2018 The FreeBSD Foundation
  *
  * This software was developed by Mateusz Guzik <mjg@FreeBSD.org>
  * under sponsorship from the FreeBSD Foundation.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
  * $FreeBSD$
  */
 
 #include <machine/asm.h>
 __FBSDID("$FreeBSD$");
 
-.macro MEMSET bzero
+.macro MEMSET bzero erms
 .if \bzero == 1
 	movq	%rsi,%rcx
 	movq	%rsi,%rdx
 	xorl	%eax,%eax
 .else
 	movq	%rdi,%r9
 	movq	%rdx,%rcx
 	movzbq	%sil,%r8
 	movabs	$0x0101010101010101,%rax
 	imulq	%r8,%rax
 .endif
-	cmpq	$15,%rcx
-	jbe	1f
-	shrq	$3,%rcx
-	rep
-	stosq
-	movq	%rdx,%rcx
-	andq	$7,%rcx
-	jne	1f
+
+	cmpq	$32,%rcx
+	jb	1016f
+
+	cmpq	$256,%rcx
+	ja	1256f
+
+1032:
+	movq	%rax,(%rdi)
+	movq	%rax,8(%rdi)
+	movq	%rax,16(%rdi)
+	movq	%rax,24(%rdi)
+	leaq	32(%rdi),%rdi
+	subq	$32,%rcx
+	cmpq	$32,%rcx
+	jae	1032b
+	cmpb	$0,%cl
+	je	1000f
+1016:
+	cmpb	$16,%cl
+	jl	1008f
+	movq	%rax,(%rdi)
+	movq	%rax,8(%rdi)
+	subb	$16,%cl
+	jz	1000f
+	leaq	16(%rdi),%rdi
+1008:
+	cmpb	$8,%cl
+	jl	1004f
+	movq	%rax,(%rdi)
+	subb	$8,%cl
+	jz	1000f
+	leaq	8(%rdi),%rdi
+1004:
+	cmpb	$4,%cl
+	jl	1002f
+	movl	%eax,(%rdi)
+	subb	$4,%cl
+	jz	1000f
+	leaq	4(%rdi),%rdi
+1002:
+	cmpb	$2,%cl
+	jl	1001f
+	movw	%ax,(%rdi)
+	subb	$2,%cl
+	jz	1000f
+	leaq	2(%rdi),%rdi
+1001:
+	cmpb	$1,%cl
+	jl	1000f
+	movb	%al,(%rdi)
+1000:
 .if \bzero == 0
 	movq	%r9,%rax
 .endif
 	ret
-1:
+
+1256:
+.if \erms == 1
 	rep
 	stosb
+.else
+	shrq	$3,%rcx
+	rep
+	stosq
+	movq	%rdx,%rcx
+	andb	$7,%cl
+	jne	1004b
+.endif
 .if \bzero == 0
 	movq	%r9,%rax
 .endif
 	ret
 .endm
 
 #ifndef BZERO
 ENTRY(memset)
-	MEMSET bzero=0
+	MEMSET bzero=0 erms=0
 END(memset)
 #else
 ENTRY(bzero)
-	MEMSET bzero=1
+	MEMSET bzero=1 erms=0
 END(bzero)
 #endif
 
 	.section .note.GNU-stack,"",%progbits