[PATCH] powerpc: Optimized strncat for POWER7/PPC64

[Adhemerval Zanella <azanella at linux dot vnet dot ibm dot com>]

Hi

The commit 3eb38795dbbbd816 (Simplify strncat) implements a new 
strncat algorithm that uses strlen, strnlen, and memcpy.  This is 
faster than POWER7 current implementation, especially for unaligned 
strings (where POWER7 code uses byte-byte operations).

This patch removes the assembly implementation and uses a multiarch
especialization based on default algorithm calling optimized POWER7
symbols. Benchtests results in attachments (ran on a POWER8 machine).

Tested on powerpc64 and powerpc64le.

--

	* sysdeps/powerpc/powerpc64/multiarch/strncat-power7.c: New file.
	* sysdeps/powerpc/powerpc64/multiarch/strncat-power7.S: Remove file.
	* sysdeps/powerpc/powerpc64/power7/strncat.S: Likewise.

--

diff --git a/sysdeps/powerpc/powerpc64/multiarch/strncat-power7.S b/sysdeps/powerpc/powerpc64/multiarch/strncat-power7.S
deleted file mode 100644
index ead4a9a..0000000
--- a/sysdeps/powerpc/powerpc64/multiarch/strncat-power7.S
+++ /dev/null
@@ -1,42 +0,0 @@
-/* Optimized strncat implementation for POWER7.
-   Copyright (C) 2014 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
-   <http://www.gnu.org/licenses/>.  */
-
-#include <sysdep.h>
-
-#undef EALIGN
-#define EALIGN(name, alignt, words)				\
-  .section ".text";						\
-  ENTRY_2(__strncat_power7)					\
-  .align ALIGNARG(alignt);					\
-  EALIGN_W_##words;						\
-  BODY_LABEL(__strncat_power7):					\
-  cfi_startproc;						\
-  LOCALENTRY(__strncat_power7)
-
-#undef END
-#define END(name)						\
-  cfi_endproc;							\
-  TRACEBACK(__strncat_power7)					\
-  END_2(__strncat_power7)
-
-#undef libc_hidden_builtin_def
-#define libc_hidden_builtin_def(name)
-
-#define STRLEN __strlen_power7
-
-#include <sysdeps/powerpc/powerpc64/power7/strncat.S>
diff --git a/sysdeps/powerpc/powerpc64/multiarch/strncat-power7.c b/sysdeps/powerpc/powerpc64/multiarch/strncat-power7.c
new file mode 100644
index 0000000..fff28bf
--- /dev/null
+++ b/sysdeps/powerpc/powerpc64/multiarch/strncat-power7.c
@@ -0,0 +1,31 @@
+/* Copyright (C) 2014 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
+   <http://www.gnu.org/licenses/ >.  */
+
+#include <string.h>
+
+#define STRNCAT __strncat_power7
+
+extern __typeof (strncat) __strncat_power7 attribute_hidden;
+extern __typeof (strlen) __strlen_power7 attribute_hidden;
+extern __typeof (strnlen) __strnlen_power7 attribute_hidden;
+extern __typeof (memcpy) __memcpy_power7 attribute_hidden;
+
+#define strlen    __strlen_power7
+#define __strnlen __strnlen_power7
+#define memcpy    __memcpy_power7
+
+#include <string/strncat.c>
diff --git a/sysdeps/powerpc/powerpc64/power7/strncat.S b/sysdeps/powerpc/powerpc64/power7/strncat.S
deleted file mode 100644
index f5ea52d..0000000
--- a/sysdeps/powerpc/powerpc64/power7/strncat.S
+++ /dev/null
@@ -1,228 +0,0 @@
-/* Optimized strncat implementation for PowerPC64/POWER7.
-
-   Copyright (C) 2014 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
-   <http://www.gnu.org/licenses/>.  */
-
-/* The algorithm is as follows for aligned memory access :
-
-   if address of s2 is divisible by 0x7UL,
-       perform aligned doubleword catenation
-   else
-       perform unaligned catenation
-
-   The aligned comparison are made using cmpb instructions.  */
-
-/* char* [r3] strncat (const char *s1 [r3],
-                       const char *s2 [r4],
-                       size_t size [r5])  */
-
-#include <sysdep.h>
-
-#ifndef STRNCAT
-# undef strncat
-# define STRNCAT  strncat
-#endif
-
-#ifndef STRLEN
-/* For builds with no IFUNC support, local calls should be made to internal
-   GLIBC symbol (created by libc_hidden_builtin_def).  */
-# ifdef SHARED
-#  define STRLEN   __GI_strlen
-# else
-#  define STRLEN   strlen
-# endif
-#endif
-
-#define	FRAMESIZE	(FRAME_MIN_SIZE+32)
-
-	.machine  power7
-EALIGN(STRNCAT, 4, 0)
-	CALL_MCOUNT 3
-
-	mflr r0				/* Load link register LR to r0.  */
-
-/* We shall use r29, r30 and r31 non volatile register for retention.
-   Save all the callee registers in the GPR save area.  */
-	std r29, -24(r1)		/* Save callers register r29.  */
-	std r30, -16(r1)		/* Save callers register r30.  */
-	std r31, -8(r1)			/* Save callers register r31.  */
-
-	std r0, 16(r1)			/* Store the link register.  */
-	stdu r1, -FRAMESIZE(r1)		/* Create the stack frame.  */
-
-/* Improve performance with CPU pre-fetch.  */
-	dcbt 0, r3			/* Pre-fetch str to avoid cache
-					   miss.  */
-	dcbt 0, r4			/* Pre-fetch accept to avoid cache
-					   miss.  */
-
-	mr. r29, r5			/* Save "n" in r29.  */
-	mr r30, r3			/* Save "s1" in r30 from r3.  */
-	beq cr0,L(done)
-
-	mr r31, r4			/* Save "s2" in r31 from r4.  */
-	bl STRLEN			/* Call optimized strlen on s1; goto
-					   end of s1.  */
-	nop
-	cmpldi cr7, r29, 7		/* If s2 is <=7 process
-					    byte-by-byte.  */
-	add r3, r30, r3			/* Grab the last character of s1.  */
-	bgt cr7,L(alignment)		/* Process by aligned strings.  */
-
-	cmpldi cr7, r29, 3		/* If n is >= 4, we can
-					   byte-unroll.  */
-	addi r9, r3, -1			/* Make "s1" point before next
-					   character, increment when read.  */
-	bgt cr7, L(bytes_unroll)	/* Process each byte.  */
-
-L(byte_by_byte):
-	lbz r10, 0(r31)
-	addi r8, r9, 1
-	cmpdi cr7, r10, 0		/* Check for NULL in "s2".  */
-	stb r10, 1(r9)
-	beq cr7, L(done)
-	add r9, r9, r29
-	subf r9, r8, r9
-	addi r9, r9, 1
-	mtctr r9
-	b L(branch2)
-	.p2align 4
-L(branch1):
-	lbzu r10, 1(r31)
-	cmpdi cr7, r10, 0
-	stbu r10, 1(r8)
-	beq cr7,L(done)
-L(branch2):
-	mr r9, r8
-	bdnz L(branch1)
-	beq cr7,L(done)
-L(nullTerminate):
-	li r10, 0			/* Load NULL for termination.  */
-	stb r10, 1(r9)			/* Append or terminate s1 with
-					   NULL.  */
-	.p2align 4			/* A small section here.  */
-L(done):				/* We return now.   */
-	addi r1, r1, FRAMESIZE		/* Restore stack pointer.  */
-	mr r3, r30			/* Set the return value length of
-					   string.  */
-	ld r0, 16(r1)			/* Read the saved link register.  */
-	ld r29, -24(r1)			/* Restore save register r29.  */
-	ld r30, -16(r1)			/* Restore save register r30.  */
-	ld r31, -8(r1)			/* Restore save register r31.  */
-	mtlr r0				/* Restore link register.  */
-	blr				/* Branch to link register.  */
-
-	.p2align 4
-L(alignment):
-	rldicl. r9, r31, 0, 61		/* Check if s2 is 8byte aligned  */
-	beq cr0,L(dwordAligned)
-
-	.p2align 4
-/* Unaligned bytes in string, so process byte by byte.
-   POWER7 has performance gains over loop unroll.  */
-L(bytes_unroll):
-	addi r9, r3, -1
-	srdi r10, r29, 2
-	mtctr r10
-	b L(L10)
-	.p2align 4
-L(L44):
-	lbz r10, 1(r31)			/* Load byte.  */
-	cmpdi cr7, r10, 0		/* Compare ; if byte not zero,
-					   continue.  */
-	stb r10, 2(r9)			/* Store byte  */
-	beq cr7, L(done)
-	addi r31, r31, 4
-
-	lbz r10, -2(r31)		/* Perform loop unroll here on byte
-					   load and store.  */
-	cmpdi cr7, r10, 0
-	stb r10, 3(r9)
-	beq cr7, L(done)
-
-	lbz r10, -1(r31)		/* Loop unroll here.  */
-	cmpdi cr7, r10, 0
-	stbu r10, 4(r9)
-	beq cr7, L(done)
-
-	bdz L(leftNbytes)
-
-L(L10):
-	lbz r10, 0(r31)			/* Loop unroll here.  */
-	cmpdi cr7, r10, 0
-	stb r10, 1(r9)
-	bne cr7,L(L44)
-	b L(done)
-	.p2align 4
-/* If s2 is double word aligned, we load and store double word.  */
-L(dwordAligned):
-/* read, write 8 bytes at a time  */
-	srdi r8, r29, 3			/* Compute count for CTR to loop;
-					   count = n/8.  */
-	li r7, 0			/* Load r7 with NULL.  */
-	li r10, 0			/* Load r10 with MASK '0'.  */
-
-	mtctr r8			/* Move count to CTR.  */
-L(loop8):
-	ld r9, 0(r31)			/* Read double word from s2.  */
-	cmpb r6, r9, r10		/* Compare bytes in s2 we read
-					   just now.  */
-	cmpdi r6, 0			/* If cmpb returned NULL,
-					   we continue.  */
-	bne+ L(a8)
-	std r9, 0(r3)			/* Append double word from s2
-					   with s1.  */
-	addi r3, r3, 8			/* Increment s1.  */
-	addi r31, r31, 8		/* Increment s2.  */
-	subi r29, r29, 8		/* Decrement count by 8.  */
-	bdnz L(loop8)			/* Continue until "count" is
-					   non zero.  */
-
-L(a8):
-	cmpdi r29, 0			/* If "n" is already zero, we skip. */
-	beq+ L(align8align)
-
-	mtctr r29			/* Process left over bytes in "n".  */
-L(unaligned0):
-	lbz r9, 0(r31)			/* Read a byte from s2.  */
-	cmpw r9, r7			/* If byte is NULL, we stop here . */
-	beq+ L(align8align)		/* Skip processing further if NULL.  */
-	stb  r9, 0(r3)			/* If not NULL, store byte into s1.  */
-	addi r3, r3, 1			/* Increment s1 by 1.  */
-	addi r31, r31, 1		/* Increment s2 by 1.  */
-	bdnz L(unaligned0)		/* Decrement counter "n" and loop
-					   until non zero.  */
-L(align8align):
-	stb r7, 0(r3)			/* Terminate s1 with NULL.  */
-
-	addi r1, r1, FRAMESIZE		/* Restore stack pointer.  */
-	mr r3, r30			/* Set the return value, length of
-					   string.  */
-	ld r0, 16(r1)			/* Read the saved link register.  */
-	ld r29, -24(r1)			/* Restore save register r29.  */
-	ld r30, -16(r1)			/* Restore save register r30.  */
-	ld r31, -8(r1)			/* Restore save register r31.  */
-	mtlr r0				/* Restore link register.  */
-	blr				/* Branch to link register  */
-
-	.p2align 4
-L(leftNbytes):
-	rldicl. r29, r29, 0, 62		/* Check if n>0 and n < 4 bytes.  */
-	bne cr0,L(byte_by_byte)		/* Process bytes one by one. */
-	b L(nullTerminate)		/* Now, finish catenation with
-					   NULL termination.  */
-END(STRNCAT)

Attachment: bench-strncat.out
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Attachment: bench-strncat-opt.out
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