strcmp.S

/*-
 * Copyright (c) 2018 Instituto de Pesquisas Eldorado
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <machine/asm.h>
__FBSDID("$FreeBSD$");

#if 0
	RCSID("$NetBSD: strcmp.S,v 1.0 2018/05/10 12:33:02 alexandre Exp $")
#endif

#ifdef USE_VSX
#define STRCMP_BUILD_FUNCTION_NAME(name) name ## _vsx

/* Define VSX instructions. */
#define XX1_A(a) ((a & 0x1f) << 16)
#define XX1_B(b) ((b & 0x1f) << 11)
#define XX1_T(t) ((((t & 0x1f) << 21) | ((t & 0x20) >> 5)))
#define XX1_S(s) XX1_T(s)
#define XX3_T(t) XX1_T(t)
#define XX3_A(a) ((((a & 0x1f) << 16) | ((a & 0x20) >> 3)))
#define XX3_B(b) ((((b & 0x1f) << 11) | ((b & 0x20) >> 4)))
#define XX3_BF(bf) ((bf & 0x3f) << 23)
#define XX3_DM(dm) ((dm & 0x3) << 8)

#define LXVD2X_INST ((31 << 26) | (844 << 1))
#define XXLOR_INST ((15 << 28) | (73 << 4))
#define XXLXOR_INST ((15 << 28) | (77 << 4))
#define XSCMPODP_INST ((15 << 28) | (43 << 3))
#define XXPERMDI_INST ((15 << 28) | (5 << 4))
#define MFVSRD_INST ((31 << 26) | 0x66)

#define LXVD2X(t, a, b) .long (LXVD2X_INST | XX1_A(a) | XX1_B(b) | XX1_T(t))
#define XXLOR(t, a, b) .long (XXLOR_INST | XX3_A(a) | XX3_B(b) | XX3_T(t))
#define XXLXOR(t, a, b) .long (XXLXOR_INST | XX3_A(a) | XX3_B(b) | XX3_T(t))
#define XSCMPODP(bf, a, b) .long (XSCMPODP_INST | XX3_A(a) | XX3_B(b) | \
					XX3_BF(bf))
#define XXPERMDI(t, a, b, dm) .long (XXPERMDI_INST | XX3_A(a) | \
					XX3_B(b) | XX3_T(t) | XX3_DM(dm))
#define MFVSRD(a, s) .long (MFVSRD_INST | XX1_A(a) | XX1_S(s))

#define STRCMP_MULTI_ALIGNMENT_BYTES 16
#else
#define STRCMP_BUILD_FUNCTION_NAME(name) name ## _plain
#define STRCMP_MULTI_ALIGNMENT_BYTES 8
#endif

/* Alignment mask. */
#define STRCMP_MULTI_ALIGNMENT_MASK (STRCMP_MULTI_ALIGNMENT_BYTES - 1)

ENTRY(STRCMP_FUNCTION_NAME)
	/* Check alignment of parameter 1. */
	andi.	%r7,%r3,STRCMP_MULTI_ALIGNMENT_MASK
	beq	.Lstrcmp_param1_aligned
	lbz	%r5,0(%r3)		/* Load chars. */
	lbz	%r6,0(%r4)
	cmpdi	%r5,0			/* Check if char is zero. */
	beq+	.Lstrcmp_end
	cmpd	%r5,%r6			/* Check if chars are different. */
	bne+	.Lstrcmp_end

.Lstrcmp_param1_align_loop:
	lbzu	%r5,1(%r3)     		/* Load chars. */
	lbzu	%r6,1(%r4)
	cmpdi	%r5,0	 		/* Check if char is zero. */
	beq+	.Lstrcmp_end
	cmpd	%r5,%r6       		/* Check if chars are different. */
	bne+	.Lstrcmp_end
	andi.	%r7,%r3,STRCMP_MULTI_ALIGNMENT_MASK	/* Check alignment. */
	bne+	.Lstrcmp_param1_align_loop

.Lstrcmp_param1_aligned:
	/* If parameter 2 is aligned compare by qword/word,
	 * else compare by byte. */
	andi.	%r7,%r4,STRCMP_MULTI_ALIGNMENT_MASK

#ifdef USE_VSX
	beq	.Lstrcmp_compare_by_qword
#else
	beq	.Lstrcmp_compare_by_word
#endif
	lbz	%r5,0(%r3)	/* Load chars. */
	lbz	%r6,0(%r4)
	cmpdi	%r5,0		/* Check if char is zero. */
	beq+	.Lstrcmp_end
	cmpd	%r5,%r6		/* Check if chars are different. */
	bne+	.Lstrcmp_end

.Lstrcmp_compare_by_byte_loop:
	/* Check 1st byte. */
	lbzu	%r5,1(%r3)
	lbzu	%r6,1(%r4)
	cmpdi	%r5,0
	beq	.Lstrcmp_end
	cmpd	%r5,%r6
	bne	.Lstrcmp_end

	/* Check 2nd byte. */
	lbzu	%r5,1(%r3)
	lbzu	%r6,1(%r4)
	cmpdi	%r5,0
	beq	.Lstrcmp_end
	cmpd	%r5,%r6
	bne	.Lstrcmp_end

	/* Check 3rd byte. */
	lbzu	%r5,1(%r3)
	lbzu	%r6,1(%r4)
	cmpdi	%r5,0
	beq	.Lstrcmp_end
	cmpd	%r5,%r6
	bne	.Lstrcmp_end

	/* Check 4th byte. */
	lbzu	%r5,1(%r3)
	lbzu	%r6,1(%r4)
	cmpdi	%r5,0
	beq	.Lstrcmp_end
	cmpd	%r5,%r6
	bne	.Lstrcmp_end

	/* Check 5th byte. */
	lbzu	%r5,1(%r3)
	lbzu	%r6,1(%r4)
	cmpdi	%r5,0
	beq	.Lstrcmp_end
	cmpd	%r5,%r6
	bne	.Lstrcmp_end

	/* Check 6th byte. */
	lbzu	%r5,1(%r3)
	lbzu	%r6,1(%r4)
	cmpdi	%r5,0
	beq	.Lstrcmp_end
	cmpd	%r5,%r6
	bne	.Lstrcmp_end

	/* Check 7th byte. */
	lbzu	%r5,1(%r3)
	lbzu	%r6,1(%r4)
	cmpdi	%r5,0
	beq	.Lstrcmp_end
	cmpd	%r5,%r6
	bne	.Lstrcmp_end

	/* Check 8th byte. */
	lbzu	%r5,1(%r3)
	lbzu	%r6,1(%r4)
	cmpdi	%r5,0
	beq	.Lstrcmp_end
	cmpd	%r5,%r6
	beq+	.Lstrcmp_compare_by_byte_loop

.Lstrcmp_end:
	sub	%r3,%r5,%r6
	blr

#ifdef USE_VSX
.Lstrcmp_compare_by_qword:
	.align 5
	XXLXOR(32,32,32)	/* VS32 (VR0) <- Zero */

	/* Load qwords. */
	LXVD2X(33,0,3)		/* VS33 (VR1) <- Parameter_1 */
	LXVD2X(34,0,4)		/* VS34 (VR2) <- Parameter_2 */

	/* Check if qwords are different. */
	XXLXOR(35,33,34)	/* VS35 (VR3) <- xor(Parameter_1, Parameter_2) */

	/* Check if qwords contain zero. */
	vcmpequb	4,1,0	/* VS36 (VR4) <- cmpb(Parameter_1, Zero) */

	/*
	 * If qwords are different or contain zero,
	 * find what byte is different or contains zero,
	 * else load next double words.
	 */
	XXLOR(2,35,36)		/* VS2 <- or(VS35 (VR3), VS36 (VR4)) */
	XSCMPODP(7,2,32)	/* cmp(VS2:0:32, Zero) */
	bne	cr7, .Lstrcmp_compare_by_qword_found_zero_difference
	XXPERMDI(2,2,2,2)	/* Swap bytes. */
	XSCMPODP(7,2,32)	/* cmp(VS2:0:32, Zero) */
	bne	cr7,.Lstrcmp_compare_by_qword_found_zero_difference_increment

.Lstrcmp_compare_by_qword_loop:
	/* Increment data addresses. */
	addi	%r3,%r3,16
	addi	%r4,%r4,16

	/* Load qwords. */
	LXVD2X(33,0,3)		/* VS33 (VR1) <- Parameter_1 */
	LXVD2X(34,0,4)		/* VS34 (VR2) <- Parameter_2 */

	/* Check if qwords are different. */
	XXLXOR(35,33,34)	/* VS35 (VR3) <- xor(Parameter_1, Parameter_2) */

	/* Check if qwords contain zero. */
	vcmpequb	4,1,0	/* VS36 (VR4) <- cmpb(Parameter_1, Zero) */

	/*
	 * If qwords are different or contain zero,
	 * find what byte is different or contains zero,
	 * else load next double words.
	 */
	XXLOR(2,35,36)		/* VS2 <- or(VS35 (VR3), VS36 (VR4)) */
	XSCMPODP(7,2,32)	/* cmp(VS2:0:32, Zero) */
	bne	cr7, .Lstrcmp_compare_by_qword_found_zero_difference
	XXPERMDI(2,2,2,2)	/* Swap bytes. */
	XSCMPODP(7,2,32)	/* cmp(VS2:0:32, Zero) */
	beq	cr7, .Lstrcmp_compare_by_qword_loop

.Lstrcmp_compare_by_qword_found_zero_difference_increment:
	addi	%r3,%r3,8	/* Increment data addresses. */
	addi	%r4,%r4,8
.Lstrcmp_compare_by_qword_found_zero_difference:
	MFVSRD(9,2)	/* %r9 <- %VS2:0:32 */
#else
.Lstrcmp_compare_by_word:
	ld	%r5,0(%r3)	/* Load double words. */
	ld	%r6,0(%r4)
	xor	%r8,%r8,%r8	/* %r8 <- Zero. */
	xor	%r0,%r5,%r6	/* Check if double words are different. */
	cmpb	%r7,%r5,%r8	/* Check if double words contain zero. */

	/*
	 * If double words are different or contain zero,
	 * find what byte is different or contains zero,
	 * else load next double words.
	 */
	or.	%r9,%r7,%r0
	bne	.Lstrcmp_check_zeros_differences

.Lstrcmp_compare_by_word_loop:
	addi	%r3,%r3,8	/* Increment data addresses. */
	addi	%r4,%r4,8
	ld	%r5,0(%r3)	/* Load double words. */
	ld	%r6,0(%r4)
	xor	%r0,%r5,%r6	/* Check if double words are different. */
	cmpb	%r7,%r5,%r8	/* Check if double words contain zero. */

	/*
	 * If double words are different or contain zero,
	 * find what byte is different or contains zero,
	 * else load next double words.
	 */
	or.	%r9,%r7,%r0
	beq	.Lstrcmp_compare_by_word_loop
#endif

.Lstrcmp_check_zeros_differences:
	/* Find what byte is different or contains zero. */

	/* Check 1st byte. */
	rldicr.	%r0,%r9,0,7
	bne	.Lstrcmp_found_zero_difference_in_1

	/* Check 2nd byte. */
	rldicr.	%r0,%r9,8,7
	bne	.Lstrcmp_found_zero_difference_in_2

	/* Check 3rd byte. */
	rldicr.	%r0,%r9,16,7
	bne	.Lstrcmp_found_zero_difference_in_3

	/* Check 4th byte. */
	rldicr.	%r0,%r9,24,7
	bne	.Lstrcmp_found_zero_difference_in_4

	/* Check 5th byte. */
	andis.	%r0,%r9,0xff00
	bne	.Lstrcmp_found_zero_difference_in_5

	/* Check 6th byte. */
	andis.	%r0,%r9,0xff
	bne	.Lstrcmp_found_zero_difference_in_6

	/* Check 7th byte. */
	andi.	%r0,%r9,0xff00
	bne	.Lstrcmp_found_zero_difference_in_7

.Lstrcmp_found_zero_difference_in_8:
	/* 8th byte is different or contains zero. */
#ifdef USE_VSX
	lbz	%r5,7(%r3)
	lbz	%r6,7(%r4)
#else
	andi.	%r5,%r5,0xff
	andi.	%r6,%r6,0xff
#endif
	sub	%r3,%r5,%r6
	blr

.Lstrcmp_found_zero_difference_in_1:
	/* 1st byte is different or contains zero. */
	lbz	%r5,0(%r3)
	lbz	%r6,0(%r4)
	sub	%r3,%r5,%r6
	blr

.Lstrcmp_found_zero_difference_in_2:
	/* 2nd byte is different or contains zero. */
	lbz	%r5,1(%r3)
	lbz	%r6,1(%r4)
	sub	%r3,%r5,%r6
	blr

.Lstrcmp_found_zero_difference_in_3:
	/* 3rd byte is different or contains zero. */
	lbz	%r5,2(%r3)
	lbz	%r6,2(%r4)
	sub	%r3,%r5,%r6
	blr

.Lstrcmp_found_zero_difference_in_4:
	/* 4th byte is different or contains zero. */
	lbz	%r5,3(%r3)
	lbz	%r6,3(%r4)
	sub	%r3,%r5,%r6
	blr

.Lstrcmp_found_zero_difference_in_5:
	/* 5th byte is different or contains zero. */
	lbz	%r5,4(%r3)
	lbz	%r6,4(%r4)
	sub	%r3,%r5,%r6
	blr

.Lstrcmp_found_zero_difference_in_6:
	/* 6th byte is different or contains zero. */
	lbz	%r5,5(%r3)
	lbz	%r6,5(%r4)
	sub	%r3,%r5,%r6
	blr

.Lstrcmp_found_zero_difference_in_7:
	/* 7th byte is different or contains zero. */
	lbz	%r5,6(%r3)
	lbz	%r6,6(%r4)
	sub	%r3,%r5,%r6
	blr

END(STRCMP_FUNCTION_NAME)

	.section .note.GNU-stack,"",%progbits