powerpc: Optimized stpcpy for POWER9

Add stpcpy support to the POWER9 strcpy. This is up to 40% faster on
small strings and up to 90% faster on long relatively unaligned strings,
compared to the POWER8 version. A few examples:

                                        __stpcpy_power9  __stpcpy_power8
Length   20, alignments in bytes  4/ 4:  2.58246          4.8788
Length 1024, alignments in bytes  1/ 6: 24.8186          47.8528

2 files changed, 82 insertions, 15 deletions

diff --git a/sysdeps/powerpc/powerpc64/le/power9/stpcpy.S b/sysdeps/powerpc/powerpc64/le/power9/stpcpy.S
new file mode 100644
index 0000000000..44425cb1e8
--- /dev/null
+++ b/sysdeps/powerpc/powerpc64/le/power9/stpcpy.S
@@ -0,0 +1,24 @@
+/* Optimized stpcpy implementation for PowerPC64/POWER9.
+   Copyright (C) 2015-2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#define USE_AS_STPCPY
+#include <sysdeps/powerpc/powerpc64/le/power9/strcpy.S>
+
+weak_alias (__stpcpy, stpcpy)
+libc_hidden_def (__stpcpy)
+libc_hidden_builtin_def (stpcpy)
diff --git a/sysdeps/powerpc/powerpc64/le/power9/strcpy.S b/sysdeps/powerpc/powerpc64/le/power9/strcpy.S
index 5749228054..ce8f503291 100644
--- a/sysdeps/powerpc/powerpc64/le/power9/strcpy.S
+++ b/sysdeps/powerpc/powerpc64/le/power9/strcpy.S
@@ -18,19 +18,35 @@
 
 #include <sysdep.h>
 
-#ifndef STRCPY
-# define STRCPY strcpy
-#endif
+#ifdef USE_AS_STPCPY
+# ifndef STPCPY
+#   define FUNC_NAME __stpcpy
+# else
+#   define FUNC_NAME STPCPY
+# endif
+#else
+# ifndef STRCPY
+#  define FUNC_NAME strcpy
+# else
+#  define FUNC_NAME STRCPY
+# endif
+#endif  /* !USE_AS_STPCPY  */
 
 /* Implements the function
 
    char * [r3] strcpy (char *dest [r3], const char *src [r4])
 
+   or
+
+   char * [r3] stpcpy (char *dest [r3], const char *src [r4])
+
+   if USE_AS_STPCPY is defined.
+
    The implementation can load bytes past a null terminator, but only
    up to the next 16B boundary, so it never crosses a page.  */
 
 .machine power9
-ENTRY_TOCLESS (STRCPY, 4)
+ENTRY_TOCLESS (FUNC_NAME, 4)
 	CALL_MCOUNT 2
 
 	/* NULL string optimisation  */
@@ -53,8 +69,8 @@ ENTRY_TOCLESS (STRCPY, 4)
 	vperm	v0,v18,v0,v1
 
 	vcmpequb v6,v0,v18	/* 0xff if byte is NULL, 0x00 otherwise  */
-	vctzlsbb r8,v6		/* Number of trailing zeroes  */
-	addi	r8,r8,1		/* Add null terminator  */
+	vctzlsbb r7,v6		/* Number of trailing zeroes  */
+	addi	r8,r7,1		/* Add null terminator  */
 
 	/* r8 = bytes including null
 	   r9 = bytes to get source 16B aligned
@@ -68,6 +84,11 @@ ENTRY_TOCLESS (STRCPY, 4)
 	sldi	r10,r8,56	/* stxvl wants size in top 8 bits  */
 	stxvl	32+v0,r11,r10	/* Partial store  */
 
+#ifdef USE_AS_STPCPY
+	/* stpcpy returns the dest address plus the size not counting the
+	   final '\0'.  */
+	add	r3,r11,r7
+#endif
 	blr
 
 L(no_null):
@@ -106,28 +127,43 @@ L(loop):
 
 L(tail1):
 	vctzlsbb r8,v6
-	addi	r8,r8,1
-	sldi	r9,r8,56	/* stxvl wants size in top 8 bits  */
+	addi	r9,r8,1
+	sldi	r9,r9,56	/* stxvl wants size in top 8 bits  */
 	stxvl	32+v0,r11,r9
+#ifdef USE_AS_STPCPY
+	/* stpcpy returns the dest address plus the size not counting the
+	   final '\0'.  */
+	add	r3,r11,r8
+#endif
 	blr
 
 L(tail2):
 	stxv	32+v0,0(r11)
 	vctzlsbb r8,v6		/* Number of trailing zeroes  */
-	addi	r8,r8,1		/* Add null terminator  */
-	sldi	r10,r8,56	/* stxvl wants size in top 8 bits  */
+	addi	r9,r8,1		/* Add null terminator  */
+	sldi	r10,r9,56	/* stxvl wants size in top 8 bits  */
 	addi	r11,r11,16
 	stxvl	32+v1,r11,r10	/* Partial store  */
+#ifdef USE_AS_STPCPY
+	/* stpcpy returns the dest address plus the size not counting the
+	   final '\0'.  */
+	add	r3,r11,r8
+#endif
 	blr
 
 L(tail3):
 	stxv	32+v0,0(r11)
 	stxv	32+v1,16(r11)
 	vctzlsbb r8,v6		/* Number of trailing zeroes  */
-	addi	r8,r8,1		/* Add null terminator  */
-	sldi	r10,r8,56	/* stxvl wants size in top 8 bits  */
+	addi	r9,r8,1		/* Add null terminator  */
+	sldi	r10,r9,56	/* stxvl wants size in top 8 bits  */
 	addi	r11,r11,32
 	stxvl	32+v2,r11,r10	/* Partial store  */
+#ifdef USE_AS_STPCPY
+	/* stpcpy returns the dest address plus the size not counting the
+	   final '\0'.  */
+	add	r3,r11,r8
+#endif
 	blr
 
 L(tail4):
@@ -135,10 +171,17 @@ L(tail4):
 	stxv	32+v1,16(r11)
 	stxv	32+v2,32(r11)
 	vctzlsbb r8,v6		/* Number of trailing zeroes  */
-	addi	r8,r8,1		/* Add null terminator  */
-	sldi	r10,r8,56	/* stxvl wants size in top 8 bits  */
+	addi	r9,r8,1		/* Add null terminator  */
+	sldi	r10,r9,56	/* stxvl wants size in top 8 bits  */
 	addi	r11,r11,48
 	stxvl	32+v3,r11,r10	/* Partial store  */
+#ifdef USE_AS_STPCPY
+	/* stpcpy returns the dest address plus the size not counting the
+	   final '\0'.  */
+	add	r3,r11,r8
+#endif
 	blr
-END (STRCPY)
+END (FUNC_NAME)
+#ifndef USE_AS_STPCPY
 libc_hidden_builtin_def (strcpy)
+#endif