/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*
 * The ascii_strcasecmp() function is a case insensitive versions of strcmp().
 * It assumes the ASCII character set and ignores differences in case
 * when comparing lower and upper case characters. In other words, it
 * behaves as if both strings had been converted to lower case using
 * tolower() in the "C" locale on each byte, and the results had then
 * been compared using strcmp().
 *
 * The assembly code below is an optimized version of the following C
 * reference:
 *
 * static const char charmap[] = {
 *      '\000', '\001', '\002', '\003', '\004', '\005', '\006', '\007',
 *      '\010', '\011', '\012', '\013', '\014', '\015', '\016', '\017',
 *      '\020', '\021', '\022', '\023', '\024', '\025', '\026', '\027',
 *      '\030', '\031', '\032', '\033', '\034', '\035', '\036', '\037',
 *      '\040', '\041', '\042', '\043', '\044', '\045', '\046', '\047',
 *      '\050', '\051', '\052', '\053', '\054', '\055', '\056', '\057',
 *      '\060', '\061', '\062', '\063', '\064', '\065', '\066', '\067',
 *      '\070', '\071', '\072', '\073', '\074', '\075', '\076', '\077',
 *      '\100', '\141', '\142', '\143', '\144', '\145', '\146', '\147',
 *      '\150', '\151', '\152', '\153', '\154', '\155', '\156', '\157',
 *      '\160', '\161', '\162', '\163', '\164', '\165', '\166', '\167',
 *      '\170', '\171', '\172', '\133', '\134', '\135', '\136', '\137',
 *      '\140', '\141', '\142', '\143', '\144', '\145', '\146', '\147',
 *      '\150', '\151', '\152', '\153', '\154', '\155', '\156', '\157',
 *      '\160', '\161', '\162', '\163', '\164', '\165', '\166', '\167',
 *      '\170', '\171', '\172', '\173', '\174', '\175', '\176', '\177',
 *      '\200', '\201', '\202', '\203', '\204', '\205', '\206', '\207',
 *      '\210', '\211', '\212', '\213', '\214', '\215', '\216', '\217',
 *      '\220', '\221', '\222', '\223', '\224', '\225', '\226', '\227',
 *      '\230', '\231', '\232', '\233', '\234', '\235', '\236', '\237',
 *      '\240', '\241', '\242', '\243', '\244', '\245', '\246', '\247',
 *      '\250', '\251', '\252', '\253', '\254', '\255', '\256', '\257',
 *      '\260', '\261', '\262', '\263', '\264', '\265', '\266', '\267',
 *      '\270', '\271', '\272', '\273', '\274', '\275', '\276', '\277',
 *      '\300', '\301', '\302', '\303', '\304', '\305', '\306', '\307',
 *      '\310', '\311', '\312', '\313', '\314', '\315', '\316', '\317',
 *      '\320', '\321', '\322', '\323', '\324', '\325', '\326', '\327',
 *      '\330', '\331', '\332', '\333', '\334', '\335', '\336', '\337',
 *      '\340', '\341', '\342', '\343', '\344', '\345', '\346', '\347',
 *      '\350', '\351', '\352', '\353', '\354', '\355', '\356', '\357',
 *      '\360', '\361', '\362', '\363', '\364', '\365', '\366', '\367',
 *      '\370', '\371', '\372', '\373', '\374', '\375', '\376', '\377',
 * };
 *
 * int
 * ascii_strcasecmp(const char *s1, const char *s2)
 * {
 *      const unsigned char     *cm = (const unsigned char *)charmap;
 *      const unsigned char     *us1 = (const unsigned char *)s1;
 *      const unsigned char     *us2 = (const unsigned char *)s2;
 *
 *      while (cm[*us1] == cm[*us2++])
 *              if (*us1++ == '\0')
 *                      return (0);
 *      return (cm[*us1] - cm[*(us2 - 1)]);
 * }
 *
 * The following algorithm, from a 1987 news posting by Alan Mycroft, is
 * used for finding null bytes in a word:
 *
 * #define has_null(word) ((word - 0x01010101) & (~word & 0x80808080))
 *
 * The following algorithm is used for a wordwise tolower() operation:
 *
 * unsigned int
 * parallel_tolower (unsigned int x)
 * {
 *      unsigned int p;
 *      unsigned int q;
 *
 *      unsigned int m1 = 0x80808080;
 *      unsigned int m2 = 0x3f3f3f3f;
 *      unsigned int m3 = 0x25252525;
 *
 *      q = x & ~m1;// newb = byte & 0x7F
 *      p = q + m2; // newb > 0x5A --> MSB set
 *      q = q + m3; // newb < 0x41 --> MSB clear
 *      p = p & ~q; // newb > 0x40 && newb < 0x5B --> MSB set
 *      q = m1 & ~x;//  byte < 0x80 --> 0x80
 *      q = p & q;  // newb > 0x40 && newb < 0x5B && byte < 0x80 -> 0x80,else 0
 *      q = q >> 2; // newb > 0x40 && newb < 0x5B && byte < 0x80 -> 0x20,else 0
 *      return (x + q); // translate uppercase characters to lowercase
 * }
 *
 * Both algorithms have been tested exhaustively for all possible 2^32 inputs.
 */

#include <sys/asm_linkage.h>

        ! The first part of this algorithm walks through the beginning of
        ! both strings a byte at a time until the source ptr is  aligned to
        ! a word boundary. During these steps, the bytes are translated to
        ! lower-case if they are upper-case, and are checked against
        ! the source string.

        ENTRY(ascii_strcasecmp)

        .align 32

        save    %sp, -SA(WINDOWSIZE), %sp
        subcc   %i0, %i1, %i2           ! s1 == s2 ?
        bz      .stringsequal           ! yup, done, strings equal
        andcc   %i0, 3, %i3             ! s1 word-aligned ?
        bz      .s1aligned1             ! yup
        sethi   %hi(0x80808080), %i4    ! start loading Mycroft's magic1

        ldub    [%i1 + %i2], %i0        ! s1[0]
        ldub    [%i1], %g1              ! s2[0]
        sub     %i0, 'A', %l0           ! transform for faster uppercase check
        sub     %g1, 'A', %l1           ! transform for faster uppercase check
        cmp     %l0, ('Z' - 'A')        ! s1[0] uppercase?
        bleu,a  .noxlate11              ! yes
        add     %i0, ('a' - 'A'), %i0   ! s1[0] = tolower(s1[0])
.noxlate11:
        cmp     %l1, ('Z' - 'A')        ! s2[0] uppercase?
        bleu,a  .noxlate12              ! yes
        add     %g1, ('a' - 'A'), %g1   ! s2[0] = tolower(s2[0])
.noxlate12:
        subcc   %i0, %g1, %i0           ! tolower(s1[0]) != tolower(s2[0]) ?
        bne     .done                   ! yup, done
        inc     %i1                     ! s1++, s2++
        addcc   %i0, %g1, %i0           ! s1[0] == 0 ?
        bz      .done                   ! yup, done, strings equal
        cmp     %i3, 3                  ! s1 aligned now?
        bz      .s1aligned2             ! yup
        sethi   %hi(0x01010101), %i5    ! start loading Mycroft's magic2

        ldub    [%i1 + %i2], %i0        ! s1[1]
        ldub    [%i1], %g1              ! s2[1]
        sub     %i0, 'A', %l0           ! transform for faster uppercase check
        sub     %g1, 'A', %l1           ! transform for faster uppercase check
        cmp     %l0, ('Z' - 'A')        ! s1[1] uppercase?
        bleu,a  .noxlate21              ! yes
        add     %i0, ('a' - 'A'), %i0   ! s1[1] = tolower(s1[1])
.noxlate21:
        cmp     %l1, ('Z' - 'A')        ! s2[1] uppercase?
        bleu,a  .noxlate22              ! yes
        add     %g1, ('a' - 'A'), %g1   ! s2[1] = tolower(s2[1])
.noxlate22:
        subcc   %i0, %g1, %i0           ! tolower(s1[1]) != tolower(s2[1]) ?
        bne     .done                   ! yup, done
        inc     %i1                     ! s1++, s2++
        addcc   %i0, %g1, %i0           ! s1[1] == 0 ?
        bz      .done                   ! yup, done, strings equal
        cmp     %i3, 2                  ! s1 aligned now?
        bz      .s1aligned3             ! yup
        or      %i4, %lo(0x80808080),%i4! finish loading Mycroft's magic1

        ldub    [%i1 + %i2], %i0        ! s1[2]
        ldub    [%i1], %g1              ! s2[2]
        sub     %i0, 'A', %l0           ! transform for faster uppercase check
        sub     %g1, 'A', %l1           ! transform for faster uppercase check
        cmp     %l0, ('Z' - 'A')        ! s1[2] uppercase?
        bleu,a  .noxlate31              ! yes
        add     %i0, ('a' - 'A'), %i0   ! s1[2] = tolower(s1[2])
.noxlate31:
        cmp     %l1, ('Z' - 'A')        ! s2[2] uppercase?
        bleu,a  .noxlate32              ! yes
        add     %g1, ('a' - 'A'), %g1   ! s2[2] = tolower(s2[2])
.noxlate32:
        subcc   %i0, %g1, %i0           ! tolower(s1[2]) != tolower(s2[2]) ?
        bne     .done                   ! yup, done
        inc     %i1                     ! s1++, s2++
        addcc   %i0, %g1, %i0           ! s1[2] == 0 ?
        bz      .done                   ! yup, done, strings equal
        or      %i5, %lo(0x01010101),%i5! finish loading Mycroft's magic2
        ba      .s1aligned4             ! s1 aligned now
        andcc   %i1, 3, %i3             ! s2 word-aligned ?

        ! Here, we initialize our checks for a zero byte and decide
        ! whether or not we can optimize further if we're fortunate
        ! enough to have a word aligned desintation

.s1aligned1:
        sethi   %hi(0x01010101), %i5    ! start loading Mycroft's magic2
.s1aligned2:
        or      %i4, %lo(0x80808080),%i4! finish loading Mycroft's magic1
.s1aligned3:
        or      %i5, %lo(0x01010101),%i5! finish loading Mycroft's magic2
        andcc   %i1, 3, %i3             ! s2 word aligned ?
.s1aligned4:
        sethi   %hi(0x3f3f3f3f), %l2    ! load m2 for parallel tolower()
        sethi   %hi(0x25252525), %l3    ! load m3 for parallel tolower()
        or      %l2, %lo(0x3f3f3f3f),%l2! finish loading m2
        bz      .word4                  ! yup, s2 word-aligned
        or      %l3, %lo(0x25252525),%l3! finish loading m3

        add     %i2, %i3, %i2           ! start adjusting offset s1-s2
        sll     %i3, 3, %l6             ! shift factor for left shifts
        andn    %i1, 3, %i1             ! round s1 pointer down to next word
        sub     %g0, %l6, %l7           ! shift factor for right shifts
        orn     %i3, %g0, %i3           ! generate all ones
        lduw    [%i1], %i0              ! new lower word from s2
        srl     %i3, %l6, %i3           ! mask for fixing up bytes
        sll     %i0, %l6, %g1           ! partial unaligned word from s2
        orn     %i0, %i3, %i0           ! force start bytes to non-zero
        nop                             ! pad to align loop to 16-byte boundary
        nop                             ! pad to align loop to 16-byte boundary

        ! This is the comparision procedure used if the destination is not
        ! word aligned, if it is, we use word4 & cmp4

.cmp:
        andn    %i4, %i0, %l4           ! ~word & 0x80808080
        sub     %i0, %i5, %l5           ! word - 0x01010101
        andcc   %l5, %l4, %g0           ! (word - 0x01010101) & ~word & 0x80808080
        bz,a    .doload                 ! null byte in previous aligned s2 word
        lduw    [%i1 + 4], %i0          ! load next aligned word from s2
.doload:
        srl     %i0, %l7, %i3           ! byte(s) from new aligned word from s2
        or      %g1, %i3, %g1           ! merge to get unaligned word from s2
        lduw    [%i1 + %i2], %i3        ! x1 = word from s1
        andn    %i3, %i4, %l0           ! q1 = x1 & ~m1
        andn    %g1, %i4, %l4           ! q2 = x2 & ~m1
        add     %l0, %l2, %l1           ! p1 = q1 + m2
        add     %l4, %l2, %l5           ! p2 = q2 + m2
        add     %l0, %l3, %l0           ! q1 = q1 + m3
        add     %l4, %l3, %l4           ! q2 = q2 + m3
        andn    %l1, %l0, %l1           ! p1 = p1 & ~q1
        andn    %l5, %l4, %l5           ! p2 = p2 & ~q2
        andn    %i4, %i3, %l0           ! q1 = m1 & ~x1
        andn    %i4, %g1, %l4           ! q2 = m1 & ~x2
        and     %l0, %l1, %l0           ! q1 = p1 & q1
        and     %l4, %l5, %l4           ! q2 = p2 & q2
        srl     %l0, 2, %l0             ! q1 = q1 >> 2
        srl     %l4, 2, %l4             ! q2 = q2 >> 2
        add     %l0, %i3, %i3           ! lowercase word from s1
        add     %l4, %g1, %g1           ! lowercase word from s2
        cmp     %i3, %g1                ! tolower(*s1) != tolower(*s2) ?
        bne     .wordsdiffer            ! yup, now find byte that is different
        add     %i1, 4, %i1             ! s1+=4, s2+=4
        andn    %i4, %i3, %l4           ! ~word & 0x80808080
        sub     %i3, %i5, %l5           ! word - 0x01010101
        andcc   %l5, %l4, %g0           ! (word - 0x01010101) & ~word & 0x80808080
        bz      .cmp                    ! no null-byte in s1 yet
        sll     %i0, %l6, %g1           ! bytes from old aligned word from s2

        ! words are equal but the end of s1 has been reached
        ! this means the strings must be equal
.stringsequal:
        ret                             ! return
        restore %g0, %g0, %o0           ! return 0, i.e. strings are equal
        nop                             ! pad

        ! we have a word aligned source and destination!  This means
        ! things get to go fast!

.word4:
        lduw    [%i1 + %i2], %i3        ! x1 = word from s1

.cmp4:
        andn    %i3, %i4, %l0           ! q1 = x1 & ~m1
        lduw    [%i1], %g1              ! x2 = word from s2
        andn    %g1, %i4, %l4           ! q2 = x2 & ~m1
        add     %l0, %l2, %l1           ! p1 = q1 + m2
        add     %l4, %l2, %l5           ! p2 = q2 + m2
        add     %l0, %l3, %l0           ! q1 = q1 + m3
        add     %l4, %l3, %l4           ! q2 = q2 + m3
        andn    %l1, %l0, %l1           ! p1 = p1 & ~q1
        andn    %l5, %l4, %l5           ! p2 = p2 & ~q2
        andn    %i4, %i3, %l0           ! q1 = m1 & ~x1
        andn    %i4, %g1, %l4           ! q2 = m1 & ~x2
        and     %l0, %l1, %l0           ! q1 = p1 & q1
        and     %l4, %l5, %l4           ! q2 = p2 & q2
        srl     %l0, 2, %l0             ! q1 = q1 >> 2
        srl     %l4, 2, %l4             ! q2 = q2 >> 2
        add     %l0, %i3, %i3           ! lowercase word from s1
        add     %l4, %g1, %g1           ! lowercase word from s2
        cmp     %i3, %g1                ! tolower(*s1) != tolower(*s2) ?
        bne     .wordsdiffer            ! yup, now find mismatching character
        add     %i1, 4, %i1             ! s1+=4, s2+=4
        andn    %i4, %i3, %l4           ! ~word & 0x80808080
        sub     %i3, %i5, %l5           ! word - 0x01010101
        andcc   %l5, %l4, %g0           ! (word - 0x01010101) & ~word & 0x80808080
        bz,a    .cmp4                   ! no null-byte in s1 yet
        lduw    [%i1 + %i2], %i3        ! load word from s1

        ! words are equal but the end of s1 has been reached
        ! this means the strings must be equal
.stringsequal4:
        ret                             ! return
        restore %g0, %g0, %o0           ! return 0, i.e. strings are equal

.wordsdiffer:
        srl     %g1, 24, %i2            ! first byte of mismatching word in s2
        srl     %i3, 24, %i1            ! first byte of mismatching word in s1
        subcc   %i1, %i2, %i0           ! *s1-*s2
        bnz     .done                   ! bytes differ, return difference
        srl     %g1, 16, %i2            ! second byte of mismatching word in s2
        andcc   %i1, 0xff, %i0          ! *s1 == 0 ?
        bz      .done                   ! yup, done, strings equal

        ! we know byte 1 is equal, so can compare bytes 1,2 as a group

        srl     %i3, 16, %i1            ! second byte of mismatching word in s1
        subcc   %i1, %i2, %i0           ! *s1-*s2
        bnz     .done                   ! bytes differ, return difference
        srl     %g1, 8, %i2             ! third byte of mismatching word in s2
        andcc   %i1, 0xff, %i0          ! *s1 == 0 ?
        bz      .done                   ! yup, done, strings equal

        ! we know bytes 1, 2 are equal, so can compare bytes 1,2,3 as a group

        srl     %i3, 8, %i1             ! third byte of mismatching word in s1
        subcc   %i1, %i2, %i0           ! *s1-*s2
        bnz     .done                   ! bytes differ, return difference
        andcc   %i1, 0xff, %g0          ! *s1 == 0 ?
        bz      .stringsequal           ! yup, done, strings equal

        ! we know bytes 1,2,3 are equal, so can compare bytes 1,2,3,4 as group

        subcc   %i3, %g1, %i0           ! *s1-*s2
        bz,a    .done                   ! bytes differ, return difference
        andcc   %i3, 0xff, %i0          ! *s1 == 0, strings equal

.done:
        ret                             ! return
        restore %i0, %g0, %o0           ! return 0 or byte difference

        SET_SIZE(ascii_strcasecmp)