This is the mail archive of the libc-ports@sources.redhat.com mailing list for the libc-ports project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

[PATCH 22/26] arm: Implement armv6t2 optimized strchr, strrchr, rawmemchr


Not specifically speed tested against the byte-by-byte versions,
but expected to be about as fast as the new strlen.
---
	* sysdeps/arm/armv6t2/strchr.S: New file.
	* sysdeps/arm/armv6t2/strrchr.S: New file.
	* sysdeps/arm/armv6t2/rawmemchr.S: New file.
---
 ports/sysdeps/arm/armv6t2/rawmemchr.S |  81 ++++++++++++++++++++
 ports/sysdeps/arm/armv6t2/strchr.S    | 138 ++++++++++++++++++++++++++++++++++
 ports/sysdeps/arm/armv6t2/strrchr.S   | 137 +++++++++++++++++++++++++++++++++
 3 files changed, 356 insertions(+)
 create mode 100644 ports/sysdeps/arm/armv6t2/rawmemchr.S
 create mode 100644 ports/sysdeps/arm/armv6t2/strchr.S
 create mode 100644 ports/sysdeps/arm/armv6t2/strrchr.S

diff --git a/ports/sysdeps/arm/armv6t2/rawmemchr.S b/ports/sysdeps/arm/armv6t2/rawmemchr.S
new file mode 100644
index 0000000..eea7707
--- /dev/null
+++ b/ports/sysdeps/arm/armv6t2/rawmemchr.S
@@ -0,0 +1,81 @@
+/* Copyright (C) 2013 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>
+
+	.syntax unified
+	.text
+
+ENTRY(__rawmemchr)
+	@ r0 = start of string
+	@ r1 = character to match
+	@ returns a pointer to the match, which must be present.
+	uxtb	r1, r1
+
+	@ Loop until we find ...
+1:	ldrb	r2, [r0], #1
+	cmp	r2, r1			@ ... the character
+	it	ne
+	tstne	r0, #7			@ ... the aligment point
+	bne	1b
+
+	@ Disambiguate the exit possibilites above
+	cmp	r2, r1			@ Found the character
+	itt	eq
+	subeq	r0, r0, #1
+	bxeq	lr
+
+	@ So now we're aligned.
+	orr	r1, r1, r1, lsl #8	@ Replicate C to all bytes
+	movw	ip, #0xfefe
+	orr	r1, r1, r1, lsl #16
+	movt	ip, #0xfefe
+
+	@ Loop searching for EOS or C, 8 bytes at a time.
+	@ Adding (unsigned saturating) 0xfe means result of 0xfe for any byte
+	@ that was originally zero and 0xff otherwise.  Therefore we consider
+	@ the lsb of each byte the "found" bit, with 0 for a match.
+2:	ldrd	r2, r3, [r0], #8
+	s(eor)	r2, r2, r1		@ Convert C bytes to 0
+	s(eor)	r3, r3, r1
+	uqadd8	r2, r2, ip		@ Find C
+	uqadd8	r3, r3, ip
+	s(and)	r3, r3, r2		@ Combine the two words
+	mvns	r3, r3			@ Test for any found bit true
+	beq	2b
+
+	@ Found something.  Disambiguate between first and second words.
+	@ Adjust r0 to point to the word containing the match.
+	@ Adjust r2 to the found bits for the word containing the match.
+	mvns	r2, r2
+	itee	ne
+	subne	r0, r0, #8
+	subeq	r0, r0, #4
+	moveq	r2, r3
+
+	@ Find the bit-offset of the match within the word.
+#ifdef __ARMEL__
+	rbit	r2, r2			@ For LE we need count-trailing-zeros
+#endif
+	clz	r2, r2
+	add	r0, r0, r2, lsr #3	@ Adjust the pointer to the found byte
+	bx	lr
+
+END(__rawmemchr)
+
+weak_alias (__rawmemchr, rawmemchr)
+libc_hidden_def (__rawmemchr)
diff --git a/ports/sysdeps/arm/armv6t2/strchr.S b/ports/sysdeps/arm/armv6t2/strchr.S
new file mode 100644
index 0000000..e7f5acf
--- /dev/null
+++ b/ports/sysdeps/arm/armv6t2/strchr.S
@@ -0,0 +1,138 @@
+/* Copyright (C) 2013 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>
+
+	.syntax unified
+	.text
+
+ENTRY(strchr)
+	@ r0 = start of string
+	@ r1 = character to match
+	@ returns NULL for no match, or a pointer to the match
+
+	@ To cater to long strings, we want to search through a few
+	@ characters until we reach an aligned pointer.  To cater to
+	@ small strings, we don't want to start doing word operations
+	@ immediately.  The compromise is a maximum of 32 bytes less
+	@ whatever is required to end with an aligned pointer.
+	@ r3 = number of characters to search in alignment loop
+	and	r3, r0, #7
+	uxtb	r1, r1
+	rsb	r3, r3, #32
+
+	@ Loop until we find ...
+1:	ldrb	r2, [r0], #1
+	subs	r3, r3, #1		@ ... the aligment point
+	it	ne
+	cmpne	r2, r1			@ ... or the character
+	it	ne
+	cmpne	r2, #0			@ ... or EOS
+	bne	1b
+
+	@ Disambiguate the exit possibilites above
+	cmp	r2, r1			@ Found the character
+	itt	eq
+	subeq	r0, r0, #1
+	bxeq	lr
+
+	cmp	r2, #0			@ Found EOS
+	itt	eq
+	moveq	r0, #0
+	bxeq	lr
+
+	@ So now we're aligned.  Now we actually need a stack frame.
+	push	{ r4, r5, r6, r7 }
+	cfi_adjust_cfa_offset (16)
+	cfi_rel_offset (r4, 0)
+	cfi_rel_offset (r5, 4)
+	cfi_rel_offset (r6, 8)
+	cfi_rel_offset (r7, 12)
+
+	orr	r1, r1, r1, lsl #8	@ Replicate C to all bytes
+	movw	ip, #0xfefe
+	orr	r1, r1, r1, lsl #16
+	movt	ip, #0xfefe
+
+	@ Loop searching for EOS or C, 8 bytes at a time.
+2:	ldrd	r2, r3, [r0], #8
+	@ Adding (unsigned saturating) 0xfe means result of 0xfe for any byte
+	@ that was originally zero and 0xff otherwise.  Therefore we consider
+	@ the lsb of each byte the "found" bit, with 0 for a match.
+	uqadd8	r4, r2, ip		@ Find EOS
+	uqadd8	r5, r3, ip
+	eor	r6, r2, r1		@ Convert C bytes to 0
+	eor	r7, r3, r1
+	uqadd8	r6, r6, ip		@ Find C
+	uqadd8	r7, r7, ip
+	s(and)	r4, r4, r6		@ Combine found for EOS and C
+	s(and)	r5, r5, r7
+	and	r6, r4, r5		@ Combine the two words
+	mvns	r6, r6			@ Test for any found bit true
+	beq	2b
+
+	@ Invert the sense of the found bits.  After this we have 1 in
+	@ any byte that contains a match, and 0 otherwise.
+	s(mvn)	r5, r5
+	mvns	r4, r4
+
+	@ Found something.  Disambiguate between first and second words.
+	@ Adjust r0 to point to the word containing the match.
+	@ Adjust r2 to the contents of the word containing the match.
+	@ Adjust r4 to the found bits for the word containing the match.
+	iteee	ne
+	subne	r0, r0, #8
+	subeq	r0, r0, #4
+	moveq	r4, r5
+	moveq	r2, r3
+
+	@ Find the bit-offset of the match within the word.
+#ifdef __ARMEL__
+	@ For little-endian, we only need to reverse the bits so that
+	@ count-leading-zeros becomes in effect count-trailing-zeros.
+	rbit	r4, r4
+	clz	r3, r4
+#else
+	@ For big-endian, we're matching 0x01 (not 0x80), and so the
+	@ bit offset is 7 too high.  Also, we byte-swap the word so
+	@ that we can shift down to extract the found byte.
+	clz	r3, r4
+	rev	r2, r2
+	s(sub)	r3, r3, #7
+#endif
+	s(lsr)	r2, r2, r3		@ Shift down found byte
+	add	r0, r0, r3, lsr #3	@ Adjust the pointer to the found byte
+	uxtb	r2, r2			@ Extract found byte
+	uxtb	r1, r1			@ Undo replication of C
+
+	pop	{ r4, r5, r6, r7 }
+	cfi_adjust_cfa_offset (-16)
+	cfi_restore (r4)
+	cfi_restore (r5)
+	cfi_restore (r6)
+	cfi_restore (r7)
+
+	@ Disambiguate between EOS and C.
+	cmp	r2, r1
+	it	ne
+	movne	r0, #0			@ Found EOS, return NULL
+	bx	lr
+
+END(strchr)
+
+weak_alias (strchr, index)
+libc_hidden_builtin_def (strchr)
diff --git a/ports/sysdeps/arm/armv6t2/strrchr.S b/ports/sysdeps/arm/armv6t2/strrchr.S
new file mode 100644
index 0000000..483e52a
--- /dev/null
+++ b/ports/sysdeps/arm/armv6t2/strrchr.S
@@ -0,0 +1,137 @@
+/* Copyright (C) 2013 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>
+
+	.syntax unified
+	.text
+
+ENTRY(strrchr)
+	@ r0 = start of string
+	@ r1 = character to match
+	@ returns NULL for no match, or a pointer to the match
+
+	mov	r3, r0
+	s(mov)	r0, #0
+	uxtb	r1, r1
+
+	@ Loop a few times until we're aligned.
+	tst	r3, #7
+	beq	2f
+1:	ldrb	r2, [r3], #1
+	cmp	r2, r1			@ Find the character
+	it	eq
+	subeq	r0, r3, #1
+	cmp	r2, #0			@ Find EOS
+	it	eq
+	bxeq	lr
+	tst	r3, #7			@ Find the aligment point
+	bne	1b
+
+	@ So now we're aligned.  Now we actually need a stack frame.
+2:	push	{ r4, r5, r6, r7 }
+	cfi_adjust_cfa_offset (16)
+	cfi_rel_offset (r4, 0)
+	cfi_rel_offset (r5, 4)
+	cfi_rel_offset (r6, 8)
+	cfi_rel_offset (r7, 12)
+
+	orr	r1, r1, r1, lsl #8	@ Replicate C to all bytes
+	movw	ip, #0xfefe
+	orr	r1, r1, r1, lsl #16
+	movt	ip, #0xfefe
+	s(mov)	r2, #0			@ No found bits yet
+
+	@ Loop searching for EOS and C, 8 bytes at a time.
+	@ Any time we find a match in a word, we copy the address of
+	@ the word to r0, and the found bits to r2.
+3:	ldrd	r4, r5, [r3], #8
+	@ Adding (unsigned saturating) 0xfe means result of 0xfe for any byte
+	@ that was originally zero and 0xff otherwise.  Therefore we consider
+	@ the lsb of each byte the "found" bit, with 0 for a match.
+	uqadd8	r6, r4, ip		@ Find EOS
+	uqadd8	r7, r5, ip
+	s(eor)	r4, r4, r1		@ Convert C bytes to 0
+	s(eor)	r5, r5, r1
+	uqadd8	r4, r4, ip		@ Find C
+	uqadd8	r5, r5, ip
+	mvns	r6, r6			@ Found EOS, first word
+	bne	4f
+	mvns	r4, r4			@ Handle C, first word
+	itt	ne
+	subne	r0, r3, #8
+	movne	r2, r4
+	mvns	r7, r7			@ Found EOS, second word
+	bne	5f
+	mvns	r5, r5			@ Handle C, second word
+	itt	ne
+	subne	r0, r3, #4
+	movne	r2, r5
+	b	3b
+
+	@ Found EOS in second word; fold to first word.
+5:	s(add)	r3, r3, #4		@ Dec pointer to 2nd word, with below
+	mov	r4, r5			@ Overwrite first word C found
+	mov	r6, r7			@ Overwrite first word EOS found
+
+	@ Found EOS.  Zap found C after EOS.
+4:	s(sub)	r3, r3, #8		@ Decrement pointer to first word
+	s(mvn)	r4, r4			@ Positive found bit for C
+#ifdef __ARMEL__
+	sub	r7, r6, #1		@ Toggle EOS lsb and below
+	s(eor)	r6, r6, r7		@ All bits below and including lsb
+	ands	r4, r4, r6		@ Zap C above EOS
+#else
+	clz	r6, r6			@ Find highest EOS bit set.
+	s(mvn)	r7, #0
+	s(add)	r6, r6, #1
+	s(lsr)	r7, r7, r6		@ All bits below msb
+	bics	r4, r4, r7		@ Zap C below EOS
+#endif
+	itt	ne
+	movne	r2, r4			@ Copy to result, if still non-zero
+	movne	r0, r3
+
+	pop	{ r4, r5, r6, r7 }
+	cfi_adjust_cfa_offset (-16)
+	cfi_restore (r4)
+	cfi_restore (r5)
+	cfi_restore (r6)
+	cfi_restore (r7)
+
+	@ Adjust the result pointer if we found a word containing C.
+	@ Rather than fight with thumb IT insn about how many insns
+	@ we'd like to conditionally execute, just jump over them here.
+#ifdef __thumb2__
+#define ne(insn)  insn
+	cbz	r2, 6f			@ Did we find any C?
+#else
+#define ne(insn)  insn##ne
+	cmp	r2, #0
+#endif
+#ifdef __ARMEB__
+	ne(rbit) r2, r2			@ BE needs count-trailing-zeros
+#endif
+	ne(clz)	r2, r2			@ Find the bit offset of the last C
+	ne(rsb)	r2, r2, #32		@ Convert to a count from the right
+	ne(add)	r0, r0, r2, lsr #3	@ Convert to byte offset and add.
+6:	bx	lr
+
+END(strrchr)
+
+weak_alias (strrchr, rindex)
+libc_hidden_builtin_def (strrchr)
-- 
1.8.1.2


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]