commit 8aa14b8b5b4bd8a65015c638812ae19af6f79980
Author: Mateusz Guzik <mjguzik@gmail.com>
Date:   Mon Oct 1 23:38:22 2018 +0200

    demo ifuncs for libc

diff --git a/lib/libc/amd64/Makefile.inc b/lib/libc/amd64/Makefile.inc
index cd8f0f121ea..d590353ee7e 100644
--- a/lib/libc/amd64/Makefile.inc
+++ b/lib/libc/amd64/Makefile.inc
@@ -7,3 +7,5 @@
 GDTOASRCS+=strtorx.c
 SRCS+=machdep_ldisx.c
 SYM_MAPS+=${LIBC_SRCTOP}/amd64/Symbol.map
+
+SRCS+=amd64/ifunc.c
diff --git a/lib/libc/amd64/ifunc.c b/lib/libc/amd64/ifunc.c
new file mode 100644
index 00000000000..4338a78762a
--- /dev/null
+++ b/lib/libc/amd64/ifunc.c
@@ -0,0 +1,48 @@
+#include <sys/types.h>
+#include <x86/ifunc.h>
+#include <x86/specialreg.h>
+
+void	*memset_std(void *buf, int c, size_t len);
+void	*memset_erms(void *buf, int c, size_t len);
+DEFINE_UIFUNC(, void *, memset, (void *, int, size_t), static)
+{
+
+	return ((cpu_stdext_feature & CPUID_STDEXT_ERMS) != 0 ?
+		memset_erms : memset_std);
+}
+
+void	bzero_std(void *buf, size_t len);
+void	bzero_erms(void *buf, size_t len);
+DEFINE_UIFUNC(, void , bzero, (void *, size_t), static)
+{
+
+	return ((cpu_stdext_feature & CPUID_STDEXT_ERMS) != 0 ?
+		bzero_erms : bzero_std);
+}
+
+void    *memmove_std(void * _Nonnull dst, const void * _Nonnull src, size_t len);
+void    *memmove_erms(void * _Nonnull dst, const void * _Nonnull src, size_t len);
+DEFINE_UIFUNC(, void *, memmove, (void * _Nonnull, const void * _Nonnull, size_t), static)
+{
+
+	return ((cpu_stdext_feature & CPUID_STDEXT_ERMS) != 0 ?
+		memmove_erms : memmove_std);
+}
+
+void    *memcpy_std(void * _Nonnull dst, const void * _Nonnull src, size_t len);
+void    *memcpy_erms(void * _Nonnull dst, const void * _Nonnull src, size_t len);
+DEFINE_UIFUNC(, void *, memcpy, (void * _Nonnull, const void * _Nonnull, size_t), static)
+{
+
+	return ((cpu_stdext_feature & CPUID_STDEXT_ERMS) != 0 ?
+		memcpy_erms : memcpy_std);
+}
+
+void    *bcopy_std(void * _Nonnull src, const void * _Nonnull dst, size_t len);
+void    *bcopy_erms(void * _Nonnull src, const void * _Nonnull dst, size_t len);
+DEFINE_UIFUNC(, void *, bcopy, (void * _Nonnull, const void * _Nonnull, size_t), static)
+{
+
+	return ((cpu_stdext_feature & CPUID_STDEXT_ERMS) != 0 ?
+		bcopy_erms : bcopy_std);
+}
diff --git a/lib/libc/amd64/string/bcopy.S b/lib/libc/amd64/string/bcopy.S
index 9446e75b805..c1dc3a34de8 100644
--- a/lib/libc/amd64/string/bcopy.S
+++ b/lib/libc/amd64/string/bcopy.S
@@ -42,12 +42,16 @@ __FBSDID("$FreeBSD$");
 	 */
 
 #ifdef MEMCOPY
-ENTRY(memcpy)
+ENTRY(memcpy_std)
+ENTRY(memcpy_erms)
+
 #else
 #ifdef MEMMOVE
-ENTRY(memmove)
+ENTRY(memmove_std)
+ENTRY(memmove_erms)
 #else
-ENTRY(bcopy)
+ENTRY(bcopy_std)
+ENTRY(bcopy_erms)
 #endif
 #endif
 #if defined(MEMCOPY) || defined(MEMMOVE)
@@ -91,12 +95,15 @@ ENTRY(bcopy)
 	cld
 	ret
 #ifdef MEMCOPY
-END(memcpy)
+END(memcpy_erms)
+END(memcpy_std)
 #else
 #ifdef MEMMOVE
-END(memmove)
+END(memmove_erms)
+END(memmove_std)
 #else
-END(bcopy)
+END(bcopy_std)
+END(bcopy_erms)
 #endif
 #endif
 
diff --git a/lib/libc/amd64/string/memset.S b/lib/libc/amd64/string/memset.S
index 06c9869c2d6..754e3c5d7bf 100644
--- a/lib/libc/amd64/string/memset.S
+++ b/lib/libc/amd64/string/memset.S
@@ -65,13 +65,31 @@ __FBSDID("$FreeBSD$");
 .endm
 
 #ifndef BZERO
-ENTRY(memset)
+ENTRY(memset_std)
 	MEMSET bzero=0
-END(memset)
+END(memset_std)
+
+ENTRY(memset_erms)
+	movq	%rdi,%r9
+	movq	%rdx,%rcx
+	movb	%sil,%al
+	rep
+	stosb
+	movq	%r9,%rax
+	ret
+END(memset_erms)
 #else
-ENTRY(bzero)
+ENTRY(bzero_std)
 	MEMSET bzero=1
-END(bzero)
+END(bzero_std)
+
+ENTRY(bzero_erms)
+	movq	%rsi,%rcx
+	xorl	%eax,%eax
+	rep
+	stosb
+	ret
+END(bzero_erms)
 #endif
 
 	.section .note.GNU-stack,"",%progbits