/* SPDX-License-Identifier: GPL-2.0 */
/*
 * NH - ε-almost-universal hash function, x86_64 AVX2 accelerated
 *
 * Copyright 2018 Google LLC
 *
 * Author: Eric Biggers <ebiggers@google.com>
 */

#include <linux/linkage.h>

#define         PASS0_SUMS      %ymm0
#define         PASS1_SUMS      %ymm1
#define         PASS2_SUMS      %ymm2
#define         PASS3_SUMS      %ymm3
#define         K0              %ymm4
#define         K0_XMM          %xmm4
#define         K1              %ymm5
#define         K1_XMM          %xmm5
#define         K2              %ymm6
#define         K2_XMM          %xmm6
#define         K3              %ymm7
#define         K3_XMM          %xmm7
#define         T0              %ymm8
#define         T1              %ymm9
#define         T2              %ymm10
#define         T2_XMM          %xmm10
#define         T3              %ymm11
#define         T3_XMM          %xmm11
#define         T4              %ymm12
#define         T5              %ymm13
#define         T6              %ymm14
#define         T7              %ymm15
#define         KEY             %rdi
#define         MESSAGE         %rsi
#define         MESSAGE_LEN     %rdx
#define         HASH            %rcx

.macro _nh_2xstride     k0, k1, k2, k3

        // Add message words to key words
        vpaddd          \k0, T3, T0
        vpaddd          \k1, T3, T1
        vpaddd          \k2, T3, T2
        vpaddd          \k3, T3, T3

        // Multiply 32x32 => 64 and accumulate
        vpshufd         $0x10, T0, T4
        vpshufd         $0x32, T0, T0
        vpshufd         $0x10, T1, T5
        vpshufd         $0x32, T1, T1
        vpshufd         $0x10, T2, T6
        vpshufd         $0x32, T2, T2
        vpshufd         $0x10, T3, T7
        vpshufd         $0x32, T3, T3
        vpmuludq        T4, T0, T0
        vpmuludq        T5, T1, T1
        vpmuludq        T6, T2, T2
        vpmuludq        T7, T3, T3
        vpaddq          T0, PASS0_SUMS, PASS0_SUMS
        vpaddq          T1, PASS1_SUMS, PASS1_SUMS
        vpaddq          T2, PASS2_SUMS, PASS2_SUMS
        vpaddq          T3, PASS3_SUMS, PASS3_SUMS
.endm

/*
 * void nh_avx2(const u32 *key, const u8 *message, size_t message_len,
 *              __le64 hash[NH_NUM_PASSES])
 *
 * It's guaranteed that message_len % 16 == 0.
 */
SYM_FUNC_START(nh_avx2)

        vmovdqu         0x00(KEY), K0
        vmovdqu         0x10(KEY), K1
        add             $0x20, KEY
        vpxor           PASS0_SUMS, PASS0_SUMS, PASS0_SUMS
        vpxor           PASS1_SUMS, PASS1_SUMS, PASS1_SUMS
        vpxor           PASS2_SUMS, PASS2_SUMS, PASS2_SUMS
        vpxor           PASS3_SUMS, PASS3_SUMS, PASS3_SUMS

        sub             $0x40, MESSAGE_LEN
        jl              .Lloop4_done
.Lloop4:
        vmovdqu         (MESSAGE), T3
        vmovdqu         0x00(KEY), K2
        vmovdqu         0x10(KEY), K3
        _nh_2xstride    K0, K1, K2, K3

        vmovdqu         0x20(MESSAGE), T3
        vmovdqu         0x20(KEY), K0
        vmovdqu         0x30(KEY), K1
        _nh_2xstride    K2, K3, K0, K1

        add             $0x40, MESSAGE
        add             $0x40, KEY
        sub             $0x40, MESSAGE_LEN
        jge             .Lloop4

.Lloop4_done:
        and             $0x3f, MESSAGE_LEN
        jz              .Ldone

        cmp             $0x20, MESSAGE_LEN
        jl              .Llast

        // 2 or 3 strides remain; do 2 more.
        vmovdqu         (MESSAGE), T3
        vmovdqu         0x00(KEY), K2
        vmovdqu         0x10(KEY), K3
        _nh_2xstride    K0, K1, K2, K3
        add             $0x20, MESSAGE
        add             $0x20, KEY
        sub             $0x20, MESSAGE_LEN
        jz              .Ldone
        vmovdqa         K2, K0
        vmovdqa         K3, K1
.Llast:
        // Last stride.  Zero the high 128 bits of the message and keys so they
        // don't affect the result when processing them like 2 strides.
        vmovdqu         (MESSAGE), T3_XMM
        vmovdqa         K0_XMM, K0_XMM
        vmovdqa         K1_XMM, K1_XMM
        vmovdqu         0x00(KEY), K2_XMM
        vmovdqu         0x10(KEY), K3_XMM
        _nh_2xstride    K0, K1, K2, K3

.Ldone:
        // Sum the accumulators for each pass, then store the sums to 'hash'

        // PASS0_SUMS is (0A 0B 0C 0D)
        // PASS1_SUMS is (1A 1B 1C 1D)
        // PASS2_SUMS is (2A 2B 2C 2D)
        // PASS3_SUMS is (3A 3B 3C 3D)
        // We need the horizontal sums:
        //     (0A + 0B + 0C + 0D,
        //      1A + 1B + 1C + 1D,
        //      2A + 2B + 2C + 2D,
        //      3A + 3B + 3C + 3D)
        //

        vpunpcklqdq     PASS1_SUMS, PASS0_SUMS, T0      // T0 = (0A 1A 0C 1C)
        vpunpckhqdq     PASS1_SUMS, PASS0_SUMS, T1      // T1 = (0B 1B 0D 1D)
        vpunpcklqdq     PASS3_SUMS, PASS2_SUMS, T2      // T2 = (2A 3A 2C 3C)
        vpunpckhqdq     PASS3_SUMS, PASS2_SUMS, T3      // T3 = (2B 3B 2D 3D)

        vinserti128     $0x1, T2_XMM, T0, T4            // T4 = (0A 1A 2A 3A)
        vinserti128     $0x1, T3_XMM, T1, T5            // T5 = (0B 1B 2B 3B)
        vperm2i128      $0x31, T2, T0, T0               // T0 = (0C 1C 2C 3C)
        vperm2i128      $0x31, T3, T1, T1               // T1 = (0D 1D 2D 3D)

        vpaddq          T5, T4, T4
        vpaddq          T1, T0, T0
        vpaddq          T4, T0, T0
        vmovdqu         T0, (HASH)
        vzeroupper
        RET
SYM_FUNC_END(nh_avx2)