Prepare for radical source tree reorganization. zack/build-layout-experiment

All top-level files and directories are moved into a temporary storage
directory, REORG.TODO, except for files that will certainly still
exist in their current form at top level when we're done (COPYING,
COPYING.LIB, LICENSES, NEWS, README), all old ChangeLog files (which
are moved to the new directory OldChangeLogs, instead), and the
generated file INSTALL (which is just deleted; in the new order, there
will be no generated files checked into version control).

1 files changed, 143 insertions, 0 deletions

diff --git a/REORG.TODO/sysdeps/arm/armv6/strchr.S b/REORG.TODO/sysdeps/arm/armv6/strchr.S
new file mode 100644
index 0000000000..bfd0a6b237
--- /dev/null
+++ b/REORG.TODO/sysdeps/arm/armv6/strchr.S
@@ -0,0 +1,143 @@
+/* strchr -- find the first instance of C in a nul-terminated string.
+   Copyright (C) 2013-2017 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
+	ldrb	r2, [r0]		@ load the first byte asap
+	uxtb	r1, r1
+
+	@ 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 16 bytes less
+	@ whatever is required to end with an aligned pointer.
+	@ r3 = number of characters to search in alignment loop
+	and	r3, r0, #7
+	rsb	r3, r3, #15		@ 16 - 1 peeled loop iteration
+	cmp	r2, r1			@ Found C?
+	it	ne
+	cmpne	r2, #0			@ Found EOS?
+	beq	99f
+
+	@ 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
+	it	ne
+	cmpne	r2, #0			@ Found EOS
+	beq	99f
+	add	r0, r0, #1
+
+	@ 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)
+
+	ldrd	r2, r3, [r0], #8
+	orr	r1, r1, r1, lsl #8	@ Replicate C to all bytes
+#ifdef ARCH_HAS_T2
+	movw	ip, #0x0101
+	pld	[r0, #64]
+	movt	ip, #0x0101
+#else
+	ldr	ip, =0x01010101
+	pld	[r0, #64]
+#endif
+	orr	r1, r1, r1, lsl #16
+
+	@ Loop searching for EOS or C, 8 bytes at a time.
+2:
+	@ Subtracting (unsigned saturating) from 1 means result of 1 for
+	@ any byte that was originally zero and 0 otherwise.  Therefore
+	@ we consider the lsb of each byte the "found" bit.
+	uqsub8	r4, ip, r2		@ Find EOS
+	eor	r6, r2, r1		@ Convert C bytes to 0
+	uqsub8	r5, ip, r3
+	eor	r7, r3, r1
+	uqsub8	r6, ip, r6		@ Find C
+	pld	[r0, #128]		@ Prefetch 2 lines ahead
+	uqsub8	r7, ip, r7
+	orr	r4, r4, r6		@ Combine found for EOS and C
+	orr	r5, r5, r7
+	orrs	r6, r4, r5		@ Combine the two words
+	it	eq
+	ldrdeq	r2, r3, [r0], #8
+	beq	2b
+
+	@ 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.
+	cmp	r4, #0
+	sub	r0, r0, #4
+	itte	eq
+	moveq	r4, r5
+	moveq	r2, r3
+	subne	r0, r0, #4
+
+	@ Find the bit-offset of the match within the word.
+#if defined(__ARMEL__)
+	@ For LE, swap the found word so clz searches from the little end.
+	rev	r4, r4
+#else
+	@ For BE, byte swap the word to make it easier to extract the byte.
+	rev	r2, r2
+#endif
+	@ We're counting 0x01 (not 0x80), so the bit offset is 7 too high.
+	clz	r3, r4
+	sub	r3, r3, #7
+	lsr	r2, r2, r3		@ Shift down found byte
+	uxtb	r1, r1			@ Undo replication of C
+	uxtb	r2, r2			@ Extract found byte
+	add	r0, r0, r3, lsr #3	@ Adjust the pointer to the found byte
+
+	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.
+99:
+	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)