/* Optimized memchr implementation for POWER8.
   Copyright (C) 2017-2018 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>

/* void *[r3] memchr (const void *s [r3], int c [r4], size_t n [r5])  */

/* TODO: change these to the actual instructions when the minimum required
   binutils allows it.  */
#define MTVRD(v, r) .long (0x7c000167 | ((v)<<(32-11)) | ((r)<<(32-16)))
#define MFVRD(r, v) .long (0x7c000067 | ((v)<<(32-11)) | ((r)<<(32-16)))
#define VBPERMQ(t, a, b)  .long (0x1000054c \
				| ((t)<<(32-11)) \
				| ((a)<<(32-16)) \
				| ((b)<<(32-21)) )

#ifndef MEMCHR
# define MEMCHR __memchr
#endif
/* TODO: change this to .machine power8 when the minimum required binutils
   allows it.  */
	.machine  power7
ENTRY_TOCLESS (MEMCHR)
	CALL_MCOUNT 3
	dcbt	0, r3
	clrrdi  r8, r3, 3
	insrdi	r4, r4, 8, 48

	/* Calculate the last acceptable address and check for possible
	   addition overflow by using satured math:
	   r7 = r3 + r5
	   r7 |= -(r7 < x)  */
	add     r7, r3, r5
	subfc   r6, r3, r7
	subfe   r9, r9, r9
	extsw   r6, r9
	or      r7, r7, r6

	insrdi	r4, r4, 16, 32
	cmpldi	r5, 32
	li	r9, -1
	rlwinm	r6, r3, 3, 26, 28 /* Calculate padding.  */
	insrdi  r4, r4, 32, 0
	mr	r10, r7
	addi	r7, r7, -1
#ifdef __LITTLE_ENDIAN__
	sld	r9, r9, r6
#else
	srd	r9, r9, r6
#endif
	ble	L(small_range)
	andi.	r11, r3, 63
	beq	cr0, L(align_qw)
	clrldi	r11, r3, 61
	ld	r12, 0(r8)     /* Load doubleword from memory.  */
	cmpb	r3, r12, r4     /* Check for BYTEs in DWORD1.  */
	and	r3, r3, r9
	clrldi	r6, r7, 61      /* Byte count - 1 in last dword.  */
	clrrdi	r7, r7, 3       /* Address of last doubleword.  */
	cmpldi	cr7, r3, 0      /* Does r3 indicate we got a hit?  */
	bne	cr7, L(done)
	addi	r8, r8, 8
	addi	r5, r5, -8
	add	r5, r5, r11

	/* Are we now aligned to a quadword boundary?  */
	andi.	r11, r8, 15
	beq	cr0, L(align_qw)

	/* Handle DWORD to make it QW aligned.  */
	ld	r12, 0(r8)
	cmpb	r3, r12, r4
	cmpldi	cr7, r3, 0
	bne	cr7, L(done)
	addi	r5, r5, -8
	addi	r8, r8, 8
	/* At this point, r8 is 16B aligned.  */
L(align_qw):
	vspltisb	v0, 0
	/* Precompute vbpermq constant.  */
	vspltisb	v10, 3
	li	r0, 0
	lvsl	v11, r0, r0
	vslb	v10, v11, v10
	MTVRD(v1, r4)
	vspltb	v1, v1, 7
	cmpldi	r5, 64
	ble	L(tail64)
	/* Are we 64-byte aligned? If so, jump to the vectorized loop.
	   Note: aligning to 64-byte will necessarily slow down performance for
	   strings around 64 bytes in length due to the extra comparisons
	   required to check alignment for the vectorized loop.  This is a
	   necessary tradeoff we are willing to take in order to speed up the
	   calculation for larger strings.  */
	andi.	r11, r8, 63
	beq	cr0, L(preloop_64B)
	/* In order to begin the 64B loop, it needs to be 64
	   bytes aligned.  So read until it is 64B aligned.  */
	lvx	v4, 0, r8
	vcmpequb	v6, v1, v4
	vcmpequb.	v11, v0, v6
	bnl	cr6, L(found_16B)
	addi	r8, r8, 16
	addi	r5, r5, -16

	andi.	r11, r8, 63
	beq	cr0, L(preloop_64B)
	lvx	v4, 0, r8
	vcmpequb	v6, v1, v4
	vcmpequb.	v11, v0, v6
	bnl	cr6, L(found_16B)
	addi	r8, r8, 16
	addi	r5, r5, -16

	andi.	r11, r8, 63
	beq	cr0, L(preloop_64B)
	lvx	v4, 0, r8
	vcmpequb	v6, v1, v4
	vcmpequb.	v11, v0, v6
	bnl	cr6, L(found_16B)
	addi	r8, r8, 16
	addi	r5, r5, -16
	/* At this point it should be 64B aligned.
	   Prepare for the 64B loop.  */
L(preloop_64B):
	cmpldi	r5, 64		/* Check if r5 < 64.  */
	ble	L(tail64)
	sub	r6, r10, r8
	srdi	r9, r6, 6	/* Number of loop iterations.  */
	mtctr	r9		/* Setup the counter.  */
	li	r11, 16		/* Load required offsets.  */
	li	r9, 32
	li	r7, 48

	/* Handle r5 > 64.  Loop over the bytes in strides of 64B.  */
	.align 4
L(loop):
	lvx	v2, 0, r8	/* Load 4 quadwords.  */
	lvx	v3, r8, r11
	lvx	v4, v8, r9
	lvx	v5, v8, r7
	vcmpequb	v6, v1, v2
	vcmpequb	v7, v1, v3
	vcmpequb	v8, v1, v4
	vcmpequb	v9, v1, v5
	vor	v11, v6, v7
	vor	v12, v8, v9
	vor	v11, v11, v12	/* Compare and merge into one VR for speed.  */
	vcmpequb.	v11, v0, v11
	bnl	cr6, L(found)
	addi	r8, r8, 64	/* Adjust address for the next iteration.  */
	bdnz	L(loop)
	clrldi	r5, r6, 58

	/* Handle remainder of 64B loop or r5 > 64.  */
	.align	4
L(tail64):
	cmpldi	r5, 0
	beq	L(null)
	lvx	v4, 0, r8
	vcmpequb	v6, v1, v4
	vcmpequb.	v11, v0, v6
	bnl	cr6, L(found_16B)
	addi	r8, r8, 16
	cmpldi	cr6, r5, 16
	ble	cr6, L(null)
	addi	r5, r5, -16

	lvx	v4, 0, r8
	vcmpequb	v6, v1, v4
	vcmpequb.	v11, v0, v6
	bnl	cr6, L(found_16B)
	addi	r8, r8, 16
	cmpldi	cr6, r5, 16
	ble	cr6, L(null)
	addi	r5, r5, -16

	lvx	v4, 0, r8
	vcmpequb	v6, v1, v4
	vcmpequb.	v11, v0, v6
	bnl	cr6, L(found_16B)
	addi	r8, r8, 16
	cmpldi	cr6, r5, 16
	ble	cr6, L(null)
	addi	r5, r5, -16

	lvx	v4, 0, r8
	vcmpequb	v6, v1, v4
	vcmpequb.	v11, v0, v6
	bnl	cr6, L(found_16B)
	li	r3, 0
	blr

	/* Found a match in 64B loop.  */
	.align	4
L(found):
	/* Permute the first bit of each byte into bits 48-63.  */
	VBPERMQ(v6, v6, v10)
	VBPERMQ(v7, v7, v10)
	VBPERMQ(v8, v8, v10)
	VBPERMQ(v9, v9, v10)
	/* Shift each component into its correct position for merging.  */
#ifdef __LITTLE_ENDIAN__
	vsldoi	v7, v7, v7, 2
	vsldoi	v8, v8, v8, 4
	vsldoi	v9, v9, v9, 6
#else
	vsldoi	v6, v6, v6, 6
	vsldoi	v7, v7, v7, 4
	vsldoi	v8, v8, v8, 2
#endif
	/* Merge the results and move to a GPR.  */
	vor	v11, v6, v7
	vor	v4, v9, v8
	vor	v4, v11, v4
	MFVRD(r5, v4)
#ifdef __LITTLE_ENDIAN__
	addi	r6, r5, -1
	andc	r6, r6, r5
	popcntd	r6, r6
#else
	cntlzd	r6, r5	/* Count leading zeros before the match.  */
#endif
	add	r3, r8, r6	/* Compute final length.  */
	blr

	/* Found a match in last 16 bytes.  */
	.align	4
L(found_16B):
	/* Permute the first bit of each byte into bits 48-63.  */
	VBPERMQ(v6, v6, v10)
	/* Shift each component into its correct position for merging.  */
#ifdef __LITTLE_ENDIAN__
	MFVRD(r7, v6)
	addi	r6, r7, -1
	andc	r6, r6, r7
	popcntd	r6, r6
#else
	vsldoi	v6, v6, v6, 6
	MFVRD(r7, v6)
	cntlzd	r6, r7	/* Count leading zeros before the match.  */
#endif
	add	r3, r8, r6	/* Compute final length.  */
	cmpld	r6, r5
	bltlr
	li	r3, 0
	blr

	.align	4
	/* r3 has the output of the cmpb instruction, that is, it contains
	   0xff in the same position as BYTE in the original
	   doubleword from the string.  Use that to calculate the pointer.
	   We need to make sure BYTE is *before* the end of the range.  */
L(done):
#ifdef __LITTLE_ENDIAN__
	addi	r0, r3, -1
	andc	r0, r0, r3
	popcntd	r0, r0	      /* Count trailing zeros.  */
#else
	cntlzd	r0, r3	      /* Count leading zeros before the match.  */
#endif
	cmpld	r8, r7         /* Are we on the last dword?  */
	srdi	r0, r0, 3	/* Convert leading/trailing zeros to bytes.  */
	add	r3, r8, r0
	cmpld	cr7, r0, r6     /* If on the last dword, check byte offset.  */
	bnelr
	blelr	cr7
	li	r3, 0
	blr

	.align	4
L(null):
	li	r3, 0
	blr

/* Deals with size <= 32.  */
	.align	4
L(small_range):
	cmpldi	r5, 0
	beq	L(null)
	ld	r12, 0(r8)     /* Load word from memory.  */
	cmpb	r3, r12, r4     /* Check for BYTE in DWORD1.  */
	and	r3, r3, r9
	cmpldi	cr7, r3, 0
	clrldi	r6, r7, 61      /* Byte count - 1 in last dword.  */
	clrrdi	r7, r7, 3       /* Address of last doubleword.  */
	cmpld	r8, r7         /* Are we done already?  */
	bne	cr7, L(done)
	beqlr

	ldu	r12, 8(r8)
	cmpb	r3, r12, r4
	cmpldi	cr6, r3, 0
	cmpld	r8, r7
	bne	cr6, L(done)   /* Found something.  */
	beqlr		      /* Hit end of string (length).  */

	ldu	r12, 8(r8)
	cmpb	r3, r12, r4
	cmpldi	cr6, r3, 0
	cmpld	r8, r7
	bne	cr6, L(done)
	beqlr

	ldu	r12, 8(r8)
	cmpb	r3, r12, r4
	cmpldi	cr6, r3, 0
	cmpld	r8, r7
	bne	cr6, L(done)
	beqlr

	ldu	r12, 8(r8)
	cmpb	r3, r12, r4
	cmpldi	cr6, r3, 0
	bne	cr6, L(done)
	blr

END (MEMCHR)
weak_alias (__memchr, memchr)
libc_hidden_builtin_def (memchr)