;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;  Copyright(c) 2011-2020 Intel Corporation All rights reserved.
;
;  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 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 THE COPYRIGHT HOLDERS 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 COPYRIGHT
;  OWNER 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:
;       UINT32 crc16_t10dif_by16_10(
;               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)
;       );
;
;       Authors:
;               Erdinc Ozturk
;               Vinodh Gopal
;               James Guilford
;
;       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 "reg_sizes.asm"

%ifndef FUNCTION_NAME
%define FUNCTION_NAME crc16_t10dif_by16_10
%endif

%if (AS_FEATURE_LEVEL) >= 10

[bits 64]
default rel

section .text


%ifidn __OUTPUT_FORMAT__, win64
	%xdefine	arg1 rcx
	%xdefine	arg2 rdx
	%xdefine	arg3 r8

	%xdefine	arg1_low32 ecx
%else
	%xdefine	arg1 rdi
	%xdefine	arg2 rsi
	%xdefine	arg3 rdx

	%xdefine	arg1_low32 edi
%endif

%define TMP 16*0
%ifidn __OUTPUT_FORMAT__, win64
	%define XMM_SAVE 16*2
	%define VARIABLE_OFFSET 16*12+8
%else
	%define VARIABLE_OFFSET 16*2+8
%endif

align 16
mk_global FUNCTION_NAME, function
FUNCTION_NAME:
	endbranch

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

	; After this point, code flow is exactly same as a 32-bit CRC.
	; The only difference is before returning eax, we will shift it right 16 bits, to scale back to 16 bits.

	sub		rsp, VARIABLE_OFFSET

%ifidn __OUTPUT_FORMAT__, win64
	; push the xmm registers into the stack to maintain
	vmovdqa		[rsp + XMM_SAVE + 16*0], xmm6
	vmovdqa		[rsp + XMM_SAVE + 16*1], xmm7
	vmovdqa		[rsp + XMM_SAVE + 16*2], xmm8
	vmovdqa		[rsp + XMM_SAVE + 16*3], xmm9
	vmovdqa		[rsp + XMM_SAVE + 16*4], xmm10
	vmovdqa		[rsp + XMM_SAVE + 16*5], xmm11
	vmovdqa		[rsp + XMM_SAVE + 16*6], xmm12
	vmovdqa		[rsp + XMM_SAVE + 16*7], xmm13
	vmovdqa		[rsp + XMM_SAVE + 16*8], xmm14
	vmovdqa		[rsp + XMM_SAVE + 16*9], xmm15
%endif

	vbroadcasti32x4 zmm18, [SHUF_MASK]
	cmp		arg3, 256
	jl		.less_than_256

	; load the initial crc value
	vmovd		xmm10, arg1_low32      ; 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.
	vpslldq		xmm10, 12

	; receive the initial 64B data, xor the initial crc value
	vmovdqu8	zmm0, [arg2+16*0]
	vmovdqu8	zmm4, [arg2+16*4]
	vpshufb		zmm0, zmm0, zmm18
	vpshufb		zmm4, zmm4, zmm18
	vpxorq		zmm0, zmm10
	vbroadcasti32x4	zmm10, [rk3]	;xmm10 has rk3 and rk4
					;imm value of pclmulqdq instruction will determine which constant to use

	sub		arg3, 256
	cmp		arg3, 256
	jl		.fold_128_B_loop

	vmovdqu8	zmm7, [arg2+16*8]
	vmovdqu8	zmm8, [arg2+16*12]
	vpshufb		zmm7, zmm7, zmm18
	vpshufb		zmm8, zmm8, zmm18
	vbroadcasti32x4 zmm16, [rk_1]	;zmm16 has rk-1 and rk-2
	sub		arg3, 256

.fold_256_B_loop:
	add		arg2, 256
	vmovdqu8	zmm3, [arg2+16*0]
	vpshufb		zmm3, zmm3, zmm18
	vpclmulqdq	zmm1, zmm0, zmm16, 0x00
	vpclmulqdq	zmm2, zmm0, zmm16, 0x11
	vpxorq		zmm0, zmm1, zmm2
	vpxorq		zmm0, zmm0, zmm3

	vmovdqu8	zmm9, [arg2+16*4]
	vpshufb		zmm9, zmm9, zmm18
	vpclmulqdq	zmm5, zmm4, zmm16, 0x00
	vpclmulqdq	zmm6, zmm4, zmm16, 0x11
	vpxorq		zmm4, zmm5, zmm6
	vpxorq		zmm4, zmm4, zmm9

	vmovdqu8	zmm11, [arg2+16*8]
	vpshufb		zmm11, zmm11, zmm18
	vpclmulqdq	zmm12, zmm7, zmm16, 0x00
	vpclmulqdq	zmm13, zmm7, zmm16, 0x11
	vpxorq		zmm7, zmm12, zmm13
	vpxorq		zmm7, zmm7, zmm11

	vmovdqu8	zmm17, [arg2+16*12]
	vpshufb		zmm17, zmm17, zmm18
	vpclmulqdq	zmm14, zmm8, zmm16, 0x00
	vpclmulqdq	zmm15, zmm8, zmm16, 0x11
	vpxorq		zmm8, zmm14, zmm15
	vpxorq		zmm8, zmm8, zmm17

	sub		arg3, 256
	jge     	.fold_256_B_loop

	;; Fold 256 into 128
	add		arg2, 256
	vpclmulqdq	zmm1, zmm0, zmm10, 0x00
	vpclmulqdq	zmm2, zmm0, zmm10, 0x11
	vpternlogq	zmm7, zmm1, zmm2, 0x96	; xor ABC

	vpclmulqdq	zmm5, zmm4, zmm10, 0x00
	vpclmulqdq	zmm6, zmm4, zmm10, 0x11
	vpternlogq	zmm8, zmm5, zmm6, 0x96	; xor ABC

	vmovdqa32	zmm0, zmm7
	vmovdqa32	zmm4, zmm8

	add		arg3, 128
	jmp		.fold_128_B_register



	; at this section of the code, there is 128*x+y (0<=y<128) bytes of buffer. The fold_128_B_loop
	; loop will fold 128B at a time until we have 128+y Bytes of buffer

	; fold 128B at a time. This section of the code folds 8 xmm registers in parallel
.fold_128_B_loop:
	add		arg2, 128
	vmovdqu8	zmm8, [arg2+16*0]
	vpshufb		zmm8, zmm8, zmm18
	vpclmulqdq	zmm2, zmm0, zmm10, 0x00
	vpclmulqdq	zmm1, zmm0, zmm10, 0x11
	vpxorq		zmm0, zmm2, zmm1
	vpxorq		zmm0, zmm0, zmm8

	vmovdqu8	zmm9, [arg2+16*4]
	vpshufb		zmm9, zmm9, zmm18
	vpclmulqdq	zmm5, zmm4, zmm10, 0x00
	vpclmulqdq	zmm6, zmm4, zmm10, 0x11
	vpxorq		zmm4, zmm5, zmm6
	vpxorq		zmm4, zmm4, zmm9

	sub		arg3, 128
	jge		.fold_128_B_loop
	;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

	add		arg2, 128
	; at this point, the buffer pointer is pointing at the last y Bytes of the buffer, where 0 <= y < 128
	; the 128B of folded data is in 8 of the xmm registers: xmm0, xmm1, xmm2, xmm3, xmm4, xmm5, xmm6, xmm7

.fold_128_B_register:
	; fold the 8 128b parts into 1 xmm register with different constants
	vmovdqu8	zmm16, [rk9]		; multiply by rk9-rk16
	vmovdqu8	zmm11, [rk17]		; multiply by rk17-rk20, rk1,rk2, 0,0
	vpclmulqdq	zmm1, zmm0, zmm16, 0x00
	vpclmulqdq	zmm2, zmm0, zmm16, 0x11
	vextracti64x2	xmm7, zmm4, 3		; save last that has no multiplicand

	vpclmulqdq	zmm5, zmm4, zmm11, 0x00
	vpclmulqdq	zmm6, zmm4, zmm11, 0x11
	vmovdqa		xmm10, [rk1]		; Needed later in reduction loop
	vpternlogq	zmm1, zmm2, zmm5, 0x96	; xor ABC
	vpternlogq	zmm1, zmm6, zmm7, 0x96	; xor ABC

	vshufi64x2      zmm8, zmm1, zmm1, 0x4e ; Swap 1,0,3,2 - 01 00 11 10
	vpxorq          ymm8, ymm8, ymm1
	vextracti64x2   xmm5, ymm8, 1
	vpxorq          xmm7, xmm5, xmm8

	; instead of 128, we add 128-16 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		arg3, 128-16
	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:
	vpclmulqdq	xmm8, xmm7, xmm10, 0x11
	vpclmulqdq	xmm7, xmm7, xmm10, 0x00
	vpxor		xmm7, xmm8
	vmovdqu		xmm0, [arg2]
	vpshufb		xmm0, xmm0, xmm18
	vpxor		xmm7, xmm0
	add		arg2, 16
	sub		arg3, 16
	; 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:
	add		arg3, 16
	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:

	vmovdqa		xmm2, xmm7
	vmovdqu		xmm1, [arg2 - 16 + arg3]
	vpshufb		xmm1, xmm18

	; get rid of the extra data that was loaded before
	; load the shift constant
	lea		rax, [pshufb_shf_table + 16]
	sub		rax, arg3
	vmovdqu		xmm0, [rax]

	vpshufb		xmm2, xmm0
	vpxor		xmm0, [mask1]
	vpshufb		xmm7, xmm0
	vpblendvb	xmm1, xmm1, xmm2, xmm0

	vpclmulqdq	xmm8, xmm7, xmm10, 0x11
	vpclmulqdq	xmm7, xmm7, xmm10, 0x00
	vpxor		xmm7, xmm8
	vpxor		xmm7, xmm1

.128_done:
	; compute crc of a 128-bit value
	vmovdqa		xmm10, [rk5]
	vmovdqa		xmm0, xmm7

	;64b fold
	vpclmulqdq	xmm7, xmm10, 0x01	; H*L
	vpslldq		xmm0, 8
	vpxor		xmm7, xmm0

	;32b fold
	vmovdqa		xmm0, xmm7
	vpand		xmm0, [mask2]
	vpsrldq		xmm7, 12
	vpclmulqdq	xmm7, xmm10, 0x10
	vpxor		xmm7, xmm0

	;barrett reduction
.barrett:
	vmovdqa		xmm10, [rk7]	; rk7 and rk8 in xmm10
	vmovdqa		xmm0, xmm7
	vpclmulqdq	xmm7, xmm10, 0x01
	vpslldq		xmm7, 4
	vpclmulqdq	xmm7, xmm10, 0x11

	vpslldq		xmm7, 4
	vpxor		xmm7, xmm0
	vpextrd		eax, xmm7, 1

.cleanup:
	; scale the result back to 16 bits
	shr		eax, 16

%ifidn __OUTPUT_FORMAT__, win64
	vmovdqa		xmm6, [rsp + XMM_SAVE + 16*0]
	vmovdqa		xmm7, [rsp + XMM_SAVE + 16*1]
	vmovdqa		xmm8, [rsp + XMM_SAVE + 16*2]
	vmovdqa		xmm9, [rsp + XMM_SAVE + 16*3]
	vmovdqa		xmm10, [rsp + XMM_SAVE + 16*4]
	vmovdqa		xmm11, [rsp + XMM_SAVE + 16*5]
	vmovdqa		xmm12, [rsp + XMM_SAVE + 16*6]
	vmovdqa		xmm13, [rsp + XMM_SAVE + 16*7]
	vmovdqa		xmm14, [rsp + XMM_SAVE + 16*8]
	vmovdqa		xmm15, [rsp + XMM_SAVE + 16*9]
%endif
	add		rsp, VARIABLE_OFFSET
	ret


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

align 16
.less_than_256:

	; check if there is enough buffer to be able to fold 16B at a time
	cmp	arg3, 32
	jl	.less_than_32

	; if there is, load the constants
	vmovdqa	xmm10, [rk1]    ; rk1 and rk2 in xmm10

	vmovd	xmm0, arg1_low32	; get the initial crc value
	vpslldq	xmm0, 12		; align it to its correct place
	vmovdqu	xmm7, [arg2]		; load the plaintext
	vpshufb	xmm7, xmm18		; byte-reflect the plaintext
	vpxor	xmm7, xmm0

	; update the buffer pointer
	add	arg2, 16

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

	jmp	.16B_reduction_loop


align 16
.less_than_32:
	; mov initial crc to the return value. this is necessary for zero-length buffers.
	mov	eax, arg1_low32
	test	arg3, arg3
	je	.cleanup

	vmovd	xmm0, arg1_low32	; get the initial crc value
	vpslldq	xmm0, 12		; align it to its correct place

	cmp	arg3, 16
	je	.exact_16_left
	jl	.less_than_16_left

	vmovdqu	xmm7, [arg2]		; load the plaintext
	vpshufb	xmm7, xmm18
	vpxor	xmm7, xmm0		; xor the initial crc value
	add	arg2, 16
	sub	arg3, 16
	vmovdqa	xmm10, [rk1]		; 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.

	vpxor	xmm1, xmm1
	mov	r11, rsp
	vmovdqa	[r11], xmm1

	cmp	arg3, 4
	jl	.only_less_than_4

	; backup the counter value
	mov	r9, arg3
	cmp	arg3, 8
	jl	.less_than_8_left

	; load 8 Bytes
	mov	rax, [arg2]
	mov	[r11], rax
	add	r11, 8
	sub	arg3, 8
	add	arg2, 8
.less_than_8_left:

	cmp	arg3, 4
	jl	.less_than_4_left

	; load 4 Bytes
	mov	eax, [arg2]
	mov	[r11], eax
	add	r11, 4
	sub	arg3, 4
	add	arg2, 4
.less_than_4_left:

	cmp	arg3, 2
	jl	.less_than_2_left

	; load 2 Bytes
	mov	ax, [arg2]
	mov	[r11], ax
	add	r11, 2
	sub	arg3, 2
	add	arg2, 2
.less_than_2_left:
	cmp	arg3, 1
	jl	.zero_left

	; load 1 Byte
	mov	al, [arg2]
	mov	[r11], al

.zero_left:
	vmovdqa	xmm7, [rsp]
	vpshufb	xmm7, xmm18
	vpxor	xmm7, xmm0	; xor the initial crc value

	lea	rax, [pshufb_shf_table + 16]
	sub	rax, r9
	vmovdqu	xmm0, [rax]
	vpxor	xmm0, [mask1]

	vpshufb	xmm7,xmm0
	jmp	.128_done

align 16
.exact_16_left:
	vmovdqu	xmm7, [arg2]
	vpshufb	xmm7, xmm18
	vpxor	xmm7, xmm0      ; xor the initial crc value
	jmp	.128_done

.only_less_than_4:
	cmp	arg3, 3
	jl	.only_less_than_3

	; load 3 Bytes
	mov	al, [arg2]
	mov	[r11], al

	mov	al, [arg2+1]
	mov	[r11+1], al

	mov	al, [arg2+2]
	mov	[r11+2], al

	vmovdqa	xmm7, [rsp]
	vpshufb	xmm7, xmm18
	vpxor	xmm7, xmm0	; xor the initial crc value

	vpsrldq	xmm7, 5
	jmp	.barrett

.only_less_than_3:
	cmp	arg3, 2
	jl	.only_less_than_2

	; load 2 Bytes
	mov	al, [arg2]
	mov	[r11], al

	mov	al, [arg2+1]
	mov	[r11+1], al

	vmovdqa	xmm7, [rsp]
	vpshufb	xmm7, xmm18
	vpxor	xmm7, xmm0	; xor the initial crc value

	vpsrldq	xmm7, 6
	jmp	.barrett

.only_less_than_2:
	; load 1 Byte
	mov	al, [arg2]
	mov	[r11], al

	vmovdqa	xmm7, [rsp]
	vpshufb	xmm7, xmm18
	vpxor	xmm7, xmm0      ; xor the initial crc value

	vpsrldq	xmm7, 7
	jmp	.barrett

section .data
align 32

%ifndef USE_CONSTS
; precomputed constants

rk_1: dq 0xdccf000000000000
rk_2: dq 0x4b0b000000000000
rk1:  dq 0x2d56000000000000
rk2:  dq 0x06df000000000000
rk3:  dq 0x9d9d000000000000
rk4:  dq 0x7cf5000000000000
rk5:  dq 0x2d56000000000000
rk6:  dq 0x1368000000000000
rk7:  dq 0x00000001f65a57f8
rk8:  dq 0x000000018bb70000
rk9:  dq 0xceae000000000000
rk10: dq 0xbfd6000000000000
rk11: dq 0x1e16000000000000
rk12: dq 0x713c000000000000
rk13: dq 0xf7f9000000000000
rk14: dq 0x80a6000000000000
rk15: dq 0x044c000000000000
rk16: dq 0xe658000000000000
rk17: dq 0xad18000000000000
rk18: dq 0xa497000000000000
rk19: dq 0x6ee3000000000000
rk20: dq 0xe7b5000000000000

rk_1b: dq 0x2d56000000000000
rk_2b: dq 0x06df000000000000
	dq 0x0000000000000000
	dq 0x0000000000000000
%else
INCLUDE_CONSTS
%endif

mask1: dq 0x8080808080808080, 0x8080808080808080
mask2: dq 0xFFFFFFFFFFFFFFFF, 0x00000000FFFFFFFF

SHUF_MASK: dq 0x08090A0B0C0D0E0F, 0x0001020304050607

pshufb_shf_table:
; use these values for shift constants for the pshufb instruction
; different alignments result in values as shown:
;       dq 0x8887868584838281, 0x008f8e8d8c8b8a89 ; shl 15 (16-1) / shr1
;       dq 0x8988878685848382, 0x01008f8e8d8c8b8a ; shl 14 (16-3) / shr2
;       dq 0x8a89888786858483, 0x0201008f8e8d8c8b ; shl 13 (16-4) / shr3
;       dq 0x8b8a898887868584, 0x030201008f8e8d8c ; shl 12 (16-4) / shr4
;       dq 0x8c8b8a8988878685, 0x04030201008f8e8d ; shl 11 (16-5) / shr5
;       dq 0x8d8c8b8a89888786, 0x0504030201008f8e ; shl 10 (16-6) / shr6
;       dq 0x8e8d8c8b8a898887, 0x060504030201008f ; shl 9  (16-7) / shr7
;       dq 0x8f8e8d8c8b8a8988, 0x0706050403020100 ; shl 8  (16-8) / shr8
;       dq 0x008f8e8d8c8b8a89, 0x0807060504030201 ; shl 7  (16-9) / shr9
;       dq 0x01008f8e8d8c8b8a, 0x0908070605040302 ; shl 6  (16-10) / shr10
;       dq 0x0201008f8e8d8c8b, 0x0a09080706050403 ; shl 5  (16-11) / shr11
;       dq 0x030201008f8e8d8c, 0x0b0a090807060504 ; shl 4  (16-12) / shr12
;       dq 0x04030201008f8e8d, 0x0c0b0a0908070605 ; shl 3  (16-13) / shr13
;       dq 0x0504030201008f8e, 0x0d0c0b0a09080706 ; shl 2  (16-14) / shr14
;       dq 0x060504030201008f, 0x0e0d0c0b0a090807 ; shl 1  (16-15) / shr15
dq 0x8786858483828100, 0x8f8e8d8c8b8a8988
dq 0x0706050403020100, 0x000e0d0c0b0a0908
dq 0x8080808080808080, 0x0f0e0d0c0b0a0908
dq 0x8080808080808080, 0x8080808080808080

%else  ; Assembler doesn't understand these opcodes. Add empty symbol for windows.
%ifidn __OUTPUT_FORMAT__, win64
global no_ %+ FUNCTION_NAME
no_ %+ FUNCTION_NAME %+ :
%endif
%endif ; (AS_FEATURE_LEVEL) >= 10
