diff --git a/libc/Android.bp b/libc/Android.bp
index 570e785..6c1a2ac 100644
--- a/libc/Android.bp
+++ b/libc/Android.bp
@@ -271,6 +271,7 @@
                 "upstream-freebsd/lib/libc/string/wcscat.c",
                 "upstream-freebsd/lib/libc/string/wcscpy.c",
                 "upstream-freebsd/lib/libc/string/wmemcmp.c",
+                "upstream-freebsd/lib/libc/string/wmemset.c",
             ],
         },
     },
@@ -899,6 +900,7 @@
                 "arch-x86/generic/string/wcscat.c",
                 "arch-x86/generic/string/wcscpy.c",
                 "arch-x86/generic/string/wmemcmp.c",
+                "arch-x86/generic/string/wmemset.c",
 
                 "arch-x86/atom/string/sse2-memchr-atom.S",
                 "arch-x86/atom/string/sse2-memrchr-atom.S",
@@ -947,6 +949,9 @@
                 "arch-x86/atom/string/ssse3-strcpy-atom.S",
                 "arch-x86/atom/string/ssse3-strncpy-atom.S",
                 "arch-x86/atom/string/ssse3-wmemcmp-atom.S",
+
+                // avx2 functions
+                "arch-x86/kabylake/string/avx2-wmemset-kbl.S",
             ],
 
             exclude_srcs: [
@@ -969,6 +974,7 @@
                 "arch-x86_64/string/sse4-memcmp-slm.S",
                 "arch-x86_64/string/ssse3-strcmp-slm.S",
                 "arch-x86_64/string/ssse3-strncmp-slm.S",
+                "arch-x86_64/string/avx2-wmemset-kbl.S",
 
                 "arch-x86_64/bionic/__bionic_clone.S",
                 "arch-x86_64/bionic/_exit_with_stack_teardown.S",
diff --git a/libc/arch-x86/dynamic_function_dispatch.cpp b/libc/arch-x86/dynamic_function_dispatch.cpp
index 70f4b3e..370b372 100644
--- a/libc/arch-x86/dynamic_function_dispatch.cpp
+++ b/libc/arch-x86/dynamic_function_dispatch.cpp
@@ -107,6 +107,13 @@
     RETURN_FUNC(wmemcmp_func, wmemcmp_freebsd);
 }
 
+typedef int wmemset_func(const wchar_t* __lhs, const wchar_t* __rhs, size_t __n);
+DEFINE_IFUNC_FOR(wmemset) {
+    __builtin_cpu_init();
+    if (__builtin_cpu_supports("avx2")) RETURN_FUNC(wmemset_func, wmemset_avx2);
+    RETURN_FUNC(wmemset_func, wmemset_freebsd);
+}
+
 typedef int strcmp_func(const char* __lhs, const char* __rhs);
 DEFINE_IFUNC_FOR(strcmp) {
     __builtin_cpu_init();
diff --git a/libc/arch-x86/generic/string/wmemset.c b/libc/arch-x86/generic/string/wmemset.c
new file mode 100644
index 0000000..6247bfd
--- /dev/null
+++ b/libc/arch-x86/generic/string/wmemset.c
@@ -0,0 +1,17 @@
+// Copyright (C) 2019 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#define wmemset wmemset_freebsd
+
+#include <upstream-freebsd/lib/libc/string/wmemset.c>
diff --git a/libc/arch-x86/kabylake/string/avx2-wmemset-kbl.S b/libc/arch-x86/kabylake/string/avx2-wmemset-kbl.S
new file mode 100644
index 0000000..69b66c7
--- /dev/null
+++ b/libc/arch-x86/kabylake/string/avx2-wmemset-kbl.S
@@ -0,0 +1,148 @@
+/*
+Copyright (C) 2019 The Android Open Source Project
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+ * Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+ * 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 COPYRIGHT HOLDERS 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
+COPYRIGHT OWNER 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.
+*/
+
+#include <private/bionic_asm.h>
+
+#ifndef WMEMSET
+ #define WMEMSET wmemset_avx2
+#endif
+
+ENTRY(WMEMSET)
+# BB#0:
+	pushl	%ebp
+	pushl	%ebx
+	pushl	%edi
+	pushl	%esi
+	pushl	%eax
+	movl	32(%esp), %ecx
+	movl	24(%esp), %eax
+	testl	%ecx, %ecx
+	je	.LBB0_12
+# BB#1:
+	movl	28(%esp), %edx
+	xorl	%edi, %edi
+	movl	%eax, %esi
+	cmpl	$32, %ecx
+	jb	.LBB0_10
+# BB#2:
+	movl	%ecx, %eax
+	andl	$-32, %eax
+	vmovd	%edx, %xmm0
+	vpbroadcastd	%xmm0, %ymm0
+	movl	%eax, (%esp)            # 4-byte Spill
+	leal	-32(%eax), %esi
+	movl	%esi, %eax
+	shrl	$5, %eax
+	leal	1(%eax), %edi
+	andl	$7, %edi
+	xorl	%ebx, %ebx
+	cmpl	$224, %esi
+	jb	.LBB0_5
+# BB#3:
+	movl	24(%esp), %esi
+	leal	992(%esi), %ebp
+	leal	-1(%edi), %esi
+	subl	%eax, %esi
+	xorl	%ebx, %ebx
+	.p2align	4, 0x90
+.LBB0_4:                                # =>This Inner Loop Header: Depth=1
+	vmovdqu	%ymm0, -992(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -960(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -928(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -896(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -864(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -832(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -800(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -768(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -736(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -704(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -672(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -640(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -608(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -576(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -544(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -512(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -480(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -448(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -416(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -384(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -352(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -320(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -288(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -256(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -224(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -192(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -160(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -128(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -96(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -64(%ebp,%ebx,4)
+	vmovdqu	%ymm0, -32(%ebp,%ebx,4)
+	vmovdqu	%ymm0, (%ebp,%ebx,4)
+	addl	$256, %ebx              # imm = 0x100
+	addl	$8, %esi
+	jne	.LBB0_4
+.LBB0_5:
+	testl	%edi, %edi
+	movl	24(%esp), %eax
+	je	.LBB0_8
+# BB#6:
+	leal	(%eax,%ebx,4), %esi
+	addl	$96, %esi
+	negl	%edi
+	.p2align	4, 0x90
+.LBB0_7:                                # =>This Inner Loop Header: Depth=1
+	vmovdqu	%ymm0, -96(%esi)
+	vmovdqu	%ymm0, -64(%esi)
+	vmovdqu	%ymm0, -32(%esi)
+	vmovdqu	%ymm0, (%esi)
+	subl	$-128, %esi
+	addl	$1, %edi
+	jne	.LBB0_7
+.LBB0_8:
+	movl	(%esp), %edi            # 4-byte Reload
+	cmpl	%ecx, %edi
+	je	.LBB0_12
+# BB#9:
+	leal	(%eax,%edi,4), %esi
+.LBB0_10:
+	subl	%edi, %ecx
+	.p2align	4, 0x90
+.LBB0_11:                               # =>This Inner Loop Header: Depth=1
+	movl	%edx, (%esi)
+	addl	$4, %esi
+	addl	$-1, %ecx
+	jne	.LBB0_11
+.LBB0_12:
+	addl	$4, %esp
+	popl	%esi
+	popl	%edi
+	popl	%ebx
+	popl	%ebp
+	vzeroupper
+	retl
+END(WMEMSET)
diff --git a/libc/arch-x86/static_function_dispatch.S b/libc/arch-x86/static_function_dispatch.S
index 7e8e63d..1560c04 100644
--- a/libc/arch-x86/static_function_dispatch.S
+++ b/libc/arch-x86/static_function_dispatch.S
@@ -45,6 +45,7 @@
 FUNCTION_DELEGATE(strncmp, strncmp_generic)
 FUNCTION_DELEGATE(strcat, strcat_generic)
 FUNCTION_DELEGATE(wmemcmp, wmemcmp_freebsd)
+FUNCTION_DELEGATE(wmemset, wmemset_freebsd)
 FUNCTION_DELEGATE(wcscat, wcscat_freebsd)
 FUNCTION_DELEGATE(strncat, strncat_openbsd)
 FUNCTION_DELEGATE(strlcat, strlcat_openbsd)
diff --git a/libc/arch-x86_64/string/avx2-wmemset-kbl.S b/libc/arch-x86_64/string/avx2-wmemset-kbl.S
new file mode 100644
index 0000000..7c485cf
--- /dev/null
+++ b/libc/arch-x86_64/string/avx2-wmemset-kbl.S
@@ -0,0 +1,140 @@
+/*
+Copyright (C) 2019 The Android Open Source Project
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions
+are met:
+ * Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+ * 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 COPYRIGHT HOLDERS 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
+COPYRIGHT OWNER 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.
+*/
+
+#include <private/bionic_asm.h>
+
+#ifndef WMEMSET
+ #define WMEMSET wmemset_avx2
+#endif
+
+        .section .text.avx2,"ax",@progbits
+
+ENTRY (WMEMSET)
+# BB#0:
+	testq	%rdx, %rdx
+	je	.LBB0_14
+# BB#1:
+	cmpq	$32, %rdx
+	jae	.LBB0_3
+# BB#2:
+	xorl	%r8d, %r8d
+	movq	%rdi, %rax
+	jmp	.LBB0_12
+.LBB0_3:
+	movq	%rdx, %r8
+	andq	$-32, %r8
+	vmovd	%esi, %xmm0
+	vpbroadcastd	%xmm0, %ymm0
+	leaq	-32(%r8), %rcx
+	movq	%rcx, %rax
+	shrq	$5, %rax
+	leal	1(%rax), %r9d
+	andl	$7, %r9d
+	cmpq	$224, %rcx
+	jae	.LBB0_5
+# BB#4:
+	xorl	%eax, %eax
+	testq	%r9, %r9
+	jne	.LBB0_8
+	jmp	.LBB0_10
+.LBB0_5:
+	leaq	992(%rdi), %rcx
+	leaq	-1(%r9), %r10
+	subq	%rax, %r10
+	xorl	%eax, %eax
+	.p2align	4, 0x90
+.LBB0_6:                                # =>This Inner Loop Header: Depth=1
+	vmovdqu	%ymm0, -992(%rcx,%rax,4)
+	vmovdqu	%ymm0, -960(%rcx,%rax,4)
+	vmovdqu	%ymm0, -928(%rcx,%rax,4)
+	vmovdqu	%ymm0, -896(%rcx,%rax,4)
+	vmovdqu	%ymm0, -864(%rcx,%rax,4)
+	vmovdqu	%ymm0, -832(%rcx,%rax,4)
+	vmovdqu	%ymm0, -800(%rcx,%rax,4)
+	vmovdqu	%ymm0, -768(%rcx,%rax,4)
+	vmovdqu	%ymm0, -736(%rcx,%rax,4)
+	vmovdqu	%ymm0, -704(%rcx,%rax,4)
+	vmovdqu	%ymm0, -672(%rcx,%rax,4)
+	vmovdqu	%ymm0, -640(%rcx,%rax,4)
+	vmovdqu	%ymm0, -608(%rcx,%rax,4)
+	vmovdqu	%ymm0, -576(%rcx,%rax,4)
+	vmovdqu	%ymm0, -544(%rcx,%rax,4)
+	vmovdqu	%ymm0, -512(%rcx,%rax,4)
+	vmovdqu	%ymm0, -480(%rcx,%rax,4)
+	vmovdqu	%ymm0, -448(%rcx,%rax,4)
+	vmovdqu	%ymm0, -416(%rcx,%rax,4)
+	vmovdqu	%ymm0, -384(%rcx,%rax,4)
+	vmovdqu	%ymm0, -352(%rcx,%rax,4)
+	vmovdqu	%ymm0, -320(%rcx,%rax,4)
+	vmovdqu	%ymm0, -288(%rcx,%rax,4)
+	vmovdqu	%ymm0, -256(%rcx,%rax,4)
+	vmovdqu	%ymm0, -224(%rcx,%rax,4)
+	vmovdqu	%ymm0, -192(%rcx,%rax,4)
+	vmovdqu	%ymm0, -160(%rcx,%rax,4)
+	vmovdqu	%ymm0, -128(%rcx,%rax,4)
+	vmovdqu	%ymm0, -96(%rcx,%rax,4)
+	vmovdqu	%ymm0, -64(%rcx,%rax,4)
+	vmovdqu	%ymm0, -32(%rcx,%rax,4)
+	vmovdqu	%ymm0, (%rcx,%rax,4)
+	addq	$256, %rax              # imm = 0x100
+	addq	$8, %r10
+	jne	.LBB0_6
+# BB#7:
+	testq	%r9, %r9
+	je	.LBB0_10
+.LBB0_8:
+	leaq	(%rdi,%rax,4), %rax
+	addq	$96, %rax
+	negq	%r9
+	.p2align	4, 0x90
+.LBB0_9:                                # =>This Inner Loop Header: Depth=1
+	vmovdqu	%ymm0, -96(%rax)
+	vmovdqu	%ymm0, -64(%rax)
+	vmovdqu	%ymm0, -32(%rax)
+	vmovdqu	%ymm0, (%rax)
+	subq	$-128, %rax
+	addq	$1, %r9
+	jne	.LBB0_9
+.LBB0_10:
+	cmpq	%rdx, %r8
+	je	.LBB0_14
+# BB#11:
+	leaq	(%rdi,%r8,4), %rax
+.LBB0_12:
+	subq	%r8, %rdx
+	.p2align	4, 0x90
+.LBB0_13:                               # =>This Inner Loop Header: Depth=1
+	movl	%esi, (%rax)
+	addq	$4, %rax
+	addq	$-1, %rdx
+	jne	.LBB0_13
+.LBB0_14:
+	movq	%rdi, %rax
+	vzeroupper
+	retq
+END(WMEMSET)