########################################################################
# Implement fast CRC-T10DIF computation with SSE and PCLMULQDQ instructions
#
# Copyright (c) 2013, Intel Corporation
#
# Authors:
#     Erdinc Ozturk <erdinc.ozturk@intel.com>
#     Vinodh Gopal <vinodh.gopal@intel.com>
#     James Guilford <james.guilford@intel.com>
#     Tim Chen <tim.c.chen@linux.intel.com>
#
# This software is available to you under a choice of one of two
# licenses.  You may choose to be licensed under the terms of the GNU
# General Public License (GPL) Version 2, available from the file
# COPYING in the main directory of this source tree, or the
# OpenIB.org BSD license below:
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
# * Redistributions of source code must retain the above copyright
#   notice, this list of conditions and the following disclaimer.
#
# * 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.
#
# * Neither the name of the Intel Corporation nor the names of its
#   contributors may be used to endorse or promote products derived from
#   this software without specific prior written permission.
#
#
# THIS SOFTWARE IS PROVIDED BY INTEL CORPORATION ""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 INTEL CORPORATION 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.
########################################################################
#       Function API:
#       UINT16 crc_t10dif_pcl(
#               UINT16 init_crc, //initial CRC value, 16 bits
#               const unsigned char *buf, //buffer pointer to calculate CRC on
#               UINT64 len //buffer length in bytes (64-bit data)
#       );
#
#       Reference paper titled "Fast CRC Computation for Generic
#       Polynomials Using PCLMULQDQ Instruction"
#       URL: http://www.intel.com/content/dam/www/public/us/en/documents
#  /white-papers/fast-crc-computation-generic-polynomials-pclmulqdq-paper.pdf
#
#

#include <linux/linkage.h>

.text

#define        arg1 %rdi
#define        arg2 %rsi
#define        arg3 %rdx

#define        arg1_low32 %edi

ENTRY(crc_t10dif_pcl)
.align 16

        # adjust the 16-bit initial_crc value, scale it to 32 bits
        shl     $16, arg1_low32

        # Allocate Stack Space
        mov     %rsp, %rcx
        sub     $16*2, %rsp
        # align stack to 16 byte boundary
        and     $~(0x10 - 1), %rsp

        # check if smaller than 256
        cmp     $256, arg3

        # for sizes less than 128, we can't fold 64B at a time...
        jl      _less_than_128


        # load the initial crc value
        movd    arg1_low32, %xmm10      # initial crc

        # crc value does not need to be byte-reflected, but it needs
        # to be moved to the high part of the register.
        # because data will be byte-reflected and will align with
        # initial crc at correct place.
        pslldq  $12, %xmm10

        movdqa  SHUF_MASK(%rip), %xmm11
        # receive the initial 64B data, xor the initial crc value
        movdqu  16*0(arg2), %xmm0
        movdqu  16*1(arg2), %xmm1
        movdqu  16*2(arg2), %xmm2
        movdqu  16*3(arg2), %xmm3
        movdqu  16*4(arg2), %xmm4
        movdqu  16*5(arg2), %xmm5
        movdqu  16*6(arg2), %xmm6
        movdqu  16*7(arg2), %xmm7

        pshufb  %xmm11, %xmm0
        # XOR the initial_crc value
        pxor    %xmm10, %xmm0
        pshufb  %xmm11, %xmm1
        pshufb  %xmm11, %xmm2
        pshufb  %xmm11, %xmm3
        pshufb  %xmm11, %xmm4
        pshufb  %xmm11, %xmm5
        pshufb  %xmm11, %xmm6
        pshufb  %xmm11, %xmm7

        movdqa  rk3(%rip), %xmm10       #xmm10 has rk3 and rk4
                                        #imm value of pclmulqdq instruction
                                        #will determine which constant to use

        #################################################################
        # we subtract 256 instead of 128 to save one instruction from the loop
        sub     $256, arg3

        # at this section of the code, there is 64*x+y (0<=y<64) bytes of
        # buffer. The _fold_64_B_loop will fold 64B at a time
        # until we have 64+y Bytes of buffer


        # fold 64B at a time. This section of the code folds 4 xmm
        # registers in parallel
_fold_64_B_loop:

        # update the buffer pointer
        add     $128, arg2              #    buf += 64#

        movdqu  16*0(arg2), %xmm9
        movdqu  16*1(arg2), %xmm12
        pshufb  %xmm11, %xmm9
        pshufb  %xmm11, %xmm12
        movdqa  %xmm0, %xmm8
        movdqa  %xmm1, %xmm13
        pclmulqdq       $0x0 , %xmm10, %xmm0
        pclmulqdq       $0x11, %xmm10, %xmm8
        pclmulqdq       $0x0 , %xmm10, %xmm1
        pclmulqdq       $0x11, %xmm10, %xmm13
        pxor    %xmm9 , %xmm0
        xorps   %xmm8 , %xmm0
        pxor    %xmm12, %xmm1
        xorps   %xmm13, %xmm1

        movdqu  16*2(arg2), %xmm9
        movdqu  16*3(arg2), %xmm12
        pshufb  %xmm11, %xmm9
        pshufb  %xmm11, %xmm12
        movdqa  %xmm2, %xmm8
        movdqa  %xmm3, %xmm13
        pclmulqdq       $0x0, %xmm10, %xmm2
        pclmulqdq       $0x11, %xmm10, %xmm8
        pclmulqdq       $0x0, %xmm10, %xmm3
        pclmulqdq       $0x11, %xmm10, %xmm13
        pxor    %xmm9 , %xmm2
        xorps   %xmm8 , %xmm2
        pxor    %xmm12, %xmm3
        xorps   %xmm13, %xmm3

        movdqu  16*4(arg2), %xmm9
        movdqu  16*5(arg2), %xmm12
        pshufb  %xmm11, %xmm9
        pshufb  %xmm11, %xmm12
        movdqa  %xmm4, %xmm8
        movdqa  %xmm5, %xmm13
        pclmulqdq       $0x0,  %xmm10, %xmm4
        pclmulqdq       $0x11, %xmm10, %xmm8
        pclmulqdq       $0x0,  %xmm10, %xmm5
        pclmulqdq       $0x11, %xmm10, %xmm13
        pxor    %xmm9 ,  %xmm4
        xorps   %xmm8 ,  %xmm4
        pxor    %xmm12,  %xmm5
        xorps   %xmm13,  %xmm5

        movdqu  16*6(arg2), %xmm9
        movdqu  16*7(arg2), %xmm12
        pshufb  %xmm11, %xmm9
        pshufb  %xmm11, %xmm12
        movdqa  %xmm6 , %xmm8
        movdqa  %xmm7 , %xmm13
        pclmulqdq       $0x0 , %xmm10, %xmm6
        pclmulqdq       $0x11, %xmm10, %xmm8
        pclmulqdq       $0x0 , %xmm10, %xmm7
        pclmulqdq       $0x11, %xmm10, %xmm13
        pxor    %xmm9 , %xmm6
        xorps   %xmm8 , %xmm6
        pxor    %xmm12, %xmm7
        xorps   %xmm13, %xmm7

        sub     $128, arg3

        # check if there is another 64B in the buffer to be able to fold
        jge     _fold_64_B_loop
        ##################################################################


        add     $128, arg2
        # at this point, the buffer pointer is pointing at the last y Bytes
        # of the buffer the 64B of folded data is in 4 of the xmm
        # registers: xmm0, xmm1, xmm2, xmm3


        # fold the 8 xmm registers to 1 xmm register with different constants

        movdqa  rk9(%rip), %xmm10
        movdqa  %xmm0, %xmm8
        pclmulqdq       $0x11, %xmm10, %xmm0
        pclmulqdq       $0x0 , %xmm10, %xmm8
        pxor    %xmm8, %xmm7
        xorps   %xmm0, %xmm7

        movdqa  rk11(%rip), %xmm10
        movdqa  %xmm1, %xmm8
        pclmulqdq        $0x11, %xmm10, %xmm1
        pclmulqdq        $0x0 , %xmm10, %xmm8
        pxor    %xmm8, %xmm7
        xorps   %xmm1, %xmm7

        movdqa  rk13(%rip), %xmm10
        movdqa  %xmm2, %xmm8
        pclmulqdq        $0x11, %xmm10, %xmm2
        pclmulqdq        $0x0 , %xmm10, %xmm8
        pxor    %xmm8, %xmm7
        pxor    %xmm2, %xmm7

        movdqa  rk15(%rip), %xmm10
        movdqa  %xmm3, %xmm8
        pclmulqdq       $0x11, %xmm10, %xmm3
        pclmulqdq       $0x0 , %xmm10, %xmm8
        pxor    %xmm8, %xmm7
        xorps   %xmm3, %xmm7

        movdqa  rk17(%rip), %xmm10
        movdqa  %xmm4, %xmm8
        pclmulqdq       $0x11, %xmm10, %xmm4
        pclmulqdq       $0x0 , %xmm10, %xmm8
        pxor    %xmm8, %xmm7
        pxor    %xmm4, %xmm7

        movdqa  rk19(%rip), %xmm10
        movdqa  %xmm5, %xmm8
        pclmulqdq       $0x11, %xmm10, %xmm5
        pclmulqdq       $0x0 , %xmm10, %xmm8
        pxor    %xmm8, %xmm7
        xorps   %xmm5, %xmm7

        movdqa  rk1(%rip), %xmm10       #xmm10 has rk1 and rk2
                                        #imm value of pclmulqdq instruction
                                        #will determine which constant to use
        movdqa  %xmm6, %xmm8
        pclmulqdq       $0x11, %xmm10, %xmm6
        pclmulqdq       $0x0 , %xmm10, %xmm8
        pxor    %xmm8, %xmm7
        pxor    %xmm6, %xmm7


        # instead of 64, we add 48 to the loop counter to save 1 instruction
        # from the loop instead of a cmp instruction, we use the negative
        # flag with the jl instruction
        add     $128-16, arg3
        jl      _final_reduction_for_128

        # now we have 16+y bytes left to reduce. 16 Bytes is in register xmm7
        # and the rest is in memory. We can fold 16 bytes at a time if y>=16
        # continue folding 16B at a time

_16B_reduction_loop:
        movdqa  %xmm7, %xmm8
        pclmulqdq       $0x11, %xmm10, %xmm7
        pclmulqdq       $0x0 , %xmm10, %xmm8
        pxor    %xmm8, %xmm7
        movdqu  (arg2), %xmm0
        pshufb  %xmm11, %xmm0
        pxor    %xmm0 , %xmm7
        add     $16, arg2
        sub     $16, arg3
        # instead of a cmp instruction, we utilize the flags with the
        # jge instruction equivalent of: cmp arg3, 16-16
        # check if there is any more 16B in the buffer to be able to fold
        jge     _16B_reduction_loop

        #now we have 16+z bytes left to reduce, where 0<= z < 16.
        #first, we reduce the data in the xmm7 register


_final_reduction_for_128:
        # check if any more data to fold. If not, compute the CRC of
        # the final 128 bits
        add     $16, arg3
        je      _128_done

        # here we are getting data that is less than 16 bytes.
        # since we know that there was data before the pointer, we can
        # offset the input pointer before the actual point, to receive
        # exactly 16 bytes. after that the registers need to be adjusted.
_get_last_two_xmms:
        movdqa  %xmm7, %xmm2

        movdqu  -16(arg2, arg3), %xmm1
        pshufb  %xmm11, %xmm1

        # get rid of the extra data that was loaded before
        # load the shift constant
        lea     pshufb_shf_table+16(%rip), %rax
        sub     arg3, %rax
        movdqu  (%rax), %xmm0

        # shift xmm2 to the left by arg3 bytes
        pshufb  %xmm0, %xmm2

        # shift xmm7 to the right by 16-arg3 bytes
        pxor    mask1(%rip), %xmm0
        pshufb  %xmm0, %xmm7
        pblendvb        %xmm2, %xmm1    #xmm0 is implicit

        # fold 16 Bytes
        movdqa  %xmm1, %xmm2
        movdqa  %xmm7, %xmm8
        pclmulqdq       $0x11, %xmm10, %xmm7
        pclmulqdq       $0x0 , %xmm10, %xmm8
        pxor    %xmm8, %xmm7
        pxor    %xmm2, %xmm7

_128_done:
        # compute crc of a 128-bit value
        movdqa  rk5(%rip), %xmm10       # rk5 and rk6 in xmm10
        movdqa  %xmm7, %xmm0

        #64b fold
        pclmulqdq       $0x1, %xmm10, %xmm7
        pslldq  $8   ,  %xmm0
        pxor    %xmm0,  %xmm7

        #32b fold
        movdqa  %xmm7, %xmm0

        pand    mask2(%rip), %xmm0

        psrldq  $12, %xmm7
        pclmulqdq       $0x10, %xmm10, %xmm7
        pxor    %xmm0, %xmm7

        #barrett reduction
_barrett:
        movdqa  rk7(%rip), %xmm10       # rk7 and rk8 in xmm10
        movdqa  %xmm7, %xmm0
        pclmulqdq       $0x01, %xmm10, %xmm7
        pslldq  $4, %xmm7
        pclmulqdq       $0x11, %xmm10, %xmm7

        pslldq  $4, %xmm7
        pxor    %xmm0, %xmm7
        pextrd  $1, %xmm7, %eax

_cleanup:
        # scale the result back to 16 bits
        shr     $16, %eax
        mov     %rcx, %rsp
        ret

########################################################################

.align 16
_less_than_128:

        # check if there is enough buffer to be able to fold 16B at a time
        cmp     $32, arg3
        jl      _less_than_32
        movdqa  SHUF_MASK(%rip), %xmm11

        # now if there is, load the constants
        movdqa  rk1(%rip), %xmm10       # rk1 and rk2 in xmm10

        movd    arg1_low32, %xmm0       # get the initial crc value
        pslldq  $12, %xmm0      # align it to its correct place
        movdqu  (arg2), %xmm7   # load the plaintext
        pshufb  %xmm11, %xmm7   # byte-reflect the plaintext
        pxor    %xmm0, %xmm7


        # update the buffer pointer
        add     $16, arg2

        # update the counter. subtract 32 instead of 16 to save one
        # instruction from the loop
        sub     $32, arg3

        jmp     _16B_reduction_loop


.align 16
_less_than_32:
        # mov initial crc to the return value. this is necessary for
        # zero-length buffers.
        mov     arg1_low32, %eax
        test    arg3, arg3
        je      _cleanup

        movdqa  SHUF_MASK(%rip), %xmm11

        movd    arg1_low32, %xmm0       # get the initial crc value
        pslldq  $12, %xmm0      # align it to its correct place

        cmp     $16, arg3
        je      _exact_16_left
        jl      _less_than_16_left

        movdqu  (arg2), %xmm7   # load the plaintext
        pshufb  %xmm11, %xmm7   # byte-reflect the plaintext
        pxor    %xmm0 , %xmm7   # xor the initial crc value
        add     $16, arg2
        sub     $16, arg3
        movdqa  rk1(%rip), %xmm10       # rk1 and rk2 in xmm10
        jmp     _get_last_two_xmms


.align 16
_less_than_16_left:
        # use stack space to load data less than 16 bytes, zero-out
        # the 16B in memory first.

        pxor    %xmm1, %xmm1
        mov     %rsp, %r11
        movdqa  %xmm1, (%r11)

        cmp     $4, arg3
        jl      _only_less_than_4

        # backup the counter value
        mov     arg3, %r9
        cmp     $8, arg3
        jl      _less_than_8_left

        # load 8 Bytes
        mov     (arg2), %rax
        mov     %rax, (%r11)
        add     $8, %r11
        sub     $8, arg3
        add     $8, arg2
_less_than_8_left:

        cmp     $4, arg3
        jl      _less_than_4_left

        # load 4 Bytes
        mov     (arg2), %eax
        mov     %eax, (%r11)
        add     $4, %r11
        sub     $4, arg3
        add     $4, arg2
_less_than_4_left:

        cmp     $2, arg3
        jl      _less_than_2_left

        # load 2 Bytes
        mov     (arg2), %ax
        mov     %ax, (%r11)
        add     $2, %r11
        sub     $2, arg3
        add     $2, arg2
_less_than_2_left:
        cmp     $1, arg3
        jl      _zero_left

        # load 1 Byte
        mov     (arg2), %al
        mov     %al, (%r11)
_zero_left:
        movdqa  (%rsp), %xmm7
        pshufb  %xmm11, %xmm7
        pxor    %xmm0 , %xmm7   # xor the initial crc value

        # shl r9, 4
        lea     pshufb_shf_table+16(%rip), %rax
        sub     %r9, %rax
        movdqu  (%rax), %xmm0
        pxor    mask1(%rip), %xmm0

        pshufb  %xmm0, %xmm7
        jmp     _128_done

.align 16
_exact_16_left:
        movdqu  (arg2), %xmm7
        pshufb  %xmm11, %xmm7
        pxor    %xmm0 , %xmm7   # xor the initial crc value

        jmp     _128_done

_only_less_than_4:
        cmp     $3, arg3
        jl      _only_less_than_3

        # load 3 Bytes
        mov     (arg2), %al
        mov     %al, (%r11)

        mov     1(arg2), %al
        mov     %al, 1(%r11)

        mov     2(arg2), %al
        mov     %al, 2(%r11)

        movdqa   (%rsp), %xmm7
        pshufb   %xmm11, %xmm7
        pxor     %xmm0 , %xmm7  # xor the initial crc value

        psrldq  $5, %xmm7

        jmp     _barrett
_only_less_than_3:
        cmp     $2, arg3
        jl      _only_less_than_2

        # load 2 Bytes
        mov     (arg2), %al
        mov     %al, (%r11)

        mov     1(arg2), %al
        mov     %al, 1(%r11)

        movdqa  (%rsp), %xmm7
        pshufb  %xmm11, %xmm7
        pxor    %xmm0 , %xmm7   # xor the initial crc value

        psrldq  $6, %xmm7

        jmp     _barrett
_only_less_than_2:

        # load 1 Byte
        mov     (arg2), %al
        mov     %al, (%r11)

        movdqa  (%rsp), %xmm7
        pshufb  %xmm11, %xmm7
        pxor    %xmm0 , %xmm7   # xor the initial crc value

        psrldq  $7, %xmm7

        jmp     _barrett

ENDPROC(crc_t10dif_pcl)

.section        .rodata, "a", @progbits
.align 16
# precomputed constants
# these constants are precomputed from the poly:
# 0x8bb70000 (0x8bb7 scaled to 32 bits)
# Q = 0x18BB70000
# rk1 = 2^(32*3) mod Q << 32
# rk2 = 2^(32*5) mod Q << 32
# rk3 = 2^(32*15) mod Q << 32
# rk4 = 2^(32*17) mod Q << 32
# rk5 = 2^(32*3) mod Q << 32
# rk6 = 2^(32*2) mod Q << 32
# rk7 = floor(2^64/Q)
# rk8 = Q
rk1:
.quad 0x2d56000000000000
rk2:
.quad 0x06df000000000000
rk3:
.quad 0x9d9d000000000000
rk4:
.quad 0x7cf5000000000000
rk5:
.quad 0x2d56000000000000
rk6:
.quad 0x1368000000000000
rk7:
.quad 0x00000001f65a57f8
rk8:
.quad 0x000000018bb70000

rk9:
.quad 0xceae000000000000
rk10:
.quad 0xbfd6000000000000
rk11:
.quad 0x1e16000000000000
rk12:
.quad 0x713c000000000000
rk13:
.quad 0xf7f9000000000000
rk14:
.quad 0x80a6000000000000
rk15:
.quad 0x044c000000000000
rk16:
.quad 0xe658000000000000
rk17:
.quad 0xad18000000000000
rk18:
.quad 0xa497000000000000
rk19:
.quad 0x6ee3000000000000
rk20:
.quad 0xe7b5000000000000



.section        .rodata.cst16.mask1, "aM", @progbits, 16
.align 16
mask1:
.octa 0x80808080808080808080808080808080

.section        .rodata.cst16.mask2, "aM", @progbits, 16
.align 16
mask2:
.octa 0x00000000FFFFFFFFFFFFFFFFFFFFFFFF

.section        .rodata.cst16.SHUF_MASK, "aM", @progbits, 16
.align 16
SHUF_MASK:
.octa 0x000102030405060708090A0B0C0D0E0F

.section        .rodata.cst32.pshufb_shf_table, "aM", @progbits, 32
.align 32
pshufb_shf_table:
# use these values for shift constants for the pshufb instruction
# different alignments result in values as shown:
#       DDQ 0x008f8e8d8c8b8a898887868584838281 # shl 15 (16-1) / shr1
#       DDQ 0x01008f8e8d8c8b8a8988878685848382 # shl 14 (16-3) / shr2
#       DDQ 0x0201008f8e8d8c8b8a89888786858483 # shl 13 (16-4) / shr3
#       DDQ 0x030201008f8e8d8c8b8a898887868584 # shl 12 (16-4) / shr4
#       DDQ 0x04030201008f8e8d8c8b8a8988878685 # shl 11 (16-5) / shr5
#       DDQ 0x0504030201008f8e8d8c8b8a89888786 # shl 10 (16-6) / shr6
#       DDQ 0x060504030201008f8e8d8c8b8a898887 # shl 9  (16-7) / shr7
#       DDQ 0x07060504030201008f8e8d8c8b8a8988 # shl 8  (16-8) / shr8
#       DDQ 0x0807060504030201008f8e8d8c8b8a89 # shl 7  (16-9) / shr9
#       DDQ 0x090807060504030201008f8e8d8c8b8a # shl 6  (16-10) / shr10
#       DDQ 0x0a090807060504030201008f8e8d8c8b # shl 5  (16-11) / shr11
#       DDQ 0x0b0a090807060504030201008f8e8d8c # shl 4  (16-12) / shr12
#       DDQ 0x0c0b0a090807060504030201008f8e8d # shl 3  (16-13) / shr13
#       DDQ 0x0d0c0b0a090807060504030201008f8e # shl 2  (16-14) / shr14
#       DDQ 0x0e0d0c0b0a090807060504030201008f # shl 1  (16-15) / shr15
.octa 0x8f8e8d8c8b8a89888786858483828100
.octa 0x000e0d0c0b0a09080706050403020100