github.com/code-reading/golang@v0.0.0-20220303082512-ba5bc0e589a3/go/src/hash/crc32/crc32_s390x.s (about) 1 // Copyright 2016 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 #include "textflag.h" 6 7 // Vector register range containing CRC-32 constants 8 9 #define CONST_PERM_LE2BE V9 10 #define CONST_R2R1 V10 11 #define CONST_R4R3 V11 12 #define CONST_R5 V12 13 #define CONST_RU_POLY V13 14 #define CONST_CRC_POLY V14 15 16 17 // The CRC-32 constant block contains reduction constants to fold and 18 // process particular chunks of the input data stream in parallel. 19 // 20 // Note that the constant definitions below are extended in order to compute 21 // intermediate results with a single VECTOR GALOIS FIELD MULTIPLY instruction. 22 // The rightmost doubleword can be 0 to prevent contribution to the result or 23 // can be multiplied by 1 to perform an XOR without the need for a separate 24 // VECTOR EXCLUSIVE OR instruction. 25 // 26 // The polynomials used are bit-reflected: 27 // 28 // IEEE: P'(x) = 0x0edb88320 29 // Castagnoli: P'(x) = 0x082f63b78 30 31 32 // IEEE polynomial constants 33 DATA ·crclecons+0(SB)/8, $0x0F0E0D0C0B0A0908 // LE-to-BE mask 34 DATA ·crclecons+8(SB)/8, $0x0706050403020100 35 DATA ·crclecons+16(SB)/8, $0x00000001c6e41596 // R2 36 DATA ·crclecons+24(SB)/8, $0x0000000154442bd4 // R1 37 DATA ·crclecons+32(SB)/8, $0x00000000ccaa009e // R4 38 DATA ·crclecons+40(SB)/8, $0x00000001751997d0 // R3 39 DATA ·crclecons+48(SB)/8, $0x0000000000000000 40 DATA ·crclecons+56(SB)/8, $0x0000000163cd6124 // R5 41 DATA ·crclecons+64(SB)/8, $0x0000000000000000 42 DATA ·crclecons+72(SB)/8, $0x00000001F7011641 // u' 43 DATA ·crclecons+80(SB)/8, $0x0000000000000000 44 DATA ·crclecons+88(SB)/8, $0x00000001DB710641 // P'(x) << 1 45 46 GLOBL ·crclecons(SB),RODATA, $144 47 48 // Castagonli Polynomial constants 49 DATA ·crcclecons+0(SB)/8, $0x0F0E0D0C0B0A0908 // LE-to-BE mask 50 DATA ·crcclecons+8(SB)/8, $0x0706050403020100 51 DATA ·crcclecons+16(SB)/8, $0x000000009e4addf8 // R2 52 DATA ·crcclecons+24(SB)/8, $0x00000000740eef02 // R1 53 DATA ·crcclecons+32(SB)/8, $0x000000014cd00bd6 // R4 54 DATA ·crcclecons+40(SB)/8, $0x00000000f20c0dfe // R3 55 DATA ·crcclecons+48(SB)/8, $0x0000000000000000 56 DATA ·crcclecons+56(SB)/8, $0x00000000dd45aab8 // R5 57 DATA ·crcclecons+64(SB)/8, $0x0000000000000000 58 DATA ·crcclecons+72(SB)/8, $0x00000000dea713f1 // u' 59 DATA ·crcclecons+80(SB)/8, $0x0000000000000000 60 DATA ·crcclecons+88(SB)/8, $0x0000000105ec76f0 // P'(x) << 1 61 62 GLOBL ·crcclecons(SB),RODATA, $144 63 64 // The CRC-32 function(s) use these calling conventions: 65 // 66 // Parameters: 67 // 68 // R2: Initial CRC value, typically ~0; and final CRC (return) value. 69 // R3: Input buffer pointer, performance might be improved if the 70 // buffer is on a doubleword boundary. 71 // R4: Length of the buffer, must be 64 bytes or greater. 72 // 73 // Register usage: 74 // 75 // R5: CRC-32 constant pool base pointer. 76 // V0: Initial CRC value and intermediate constants and results. 77 // V1..V4: Data for CRC computation. 78 // V5..V8: Next data chunks that are fetched from the input buffer. 79 // 80 // V9..V14: CRC-32 constants. 81 82 // func vectorizedIEEE(crc uint32, p []byte) uint32 83 TEXT ·vectorizedIEEE(SB),NOSPLIT,$0 84 MOVWZ crc+0(FP), R2 // R2 stores the CRC value 85 MOVD p+8(FP), R3 // data pointer 86 MOVD p_len+16(FP), R4 // len(p) 87 88 MOVD $·crclecons(SB), R5 89 BR vectorizedBody<>(SB) 90 91 // func vectorizedCastagnoli(crc uint32, p []byte) uint32 92 TEXT ·vectorizedCastagnoli(SB),NOSPLIT,$0 93 MOVWZ crc+0(FP), R2 // R2 stores the CRC value 94 MOVD p+8(FP), R3 // data pointer 95 MOVD p_len+16(FP), R4 // len(p) 96 97 // R5: crc-32 constant pool base pointer, constant is used to reduce crc 98 MOVD $·crcclecons(SB), R5 99 BR vectorizedBody<>(SB) 100 101 TEXT vectorizedBody<>(SB),NOSPLIT,$0 102 XOR $0xffffffff, R2 // NOTW R2 103 VLM 0(R5), CONST_PERM_LE2BE, CONST_CRC_POLY 104 105 // Load the initial CRC value into the rightmost word of V0 106 VZERO V0 107 VLVGF $3, R2, V0 108 109 // Crash if the input size is less than 64-bytes. 110 CMP R4, $64 111 BLT crash 112 113 // Load a 64-byte data chunk and XOR with CRC 114 VLM 0(R3), V1, V4 // 64-bytes into V1..V4 115 116 // Reflect the data if the CRC operation is in the bit-reflected domain 117 VPERM V1, V1, CONST_PERM_LE2BE, V1 118 VPERM V2, V2, CONST_PERM_LE2BE, V2 119 VPERM V3, V3, CONST_PERM_LE2BE, V3 120 VPERM V4, V4, CONST_PERM_LE2BE, V4 121 122 VX V0, V1, V1 // V1 ^= CRC 123 ADD $64, R3 // BUF = BUF + 64 124 ADD $(-64), R4 125 126 // Check remaining buffer size and jump to proper folding method 127 CMP R4, $64 128 BLT less_than_64bytes 129 130 fold_64bytes_loop: 131 // Load the next 64-byte data chunk into V5 to V8 132 VLM 0(R3), V5, V8 133 VPERM V5, V5, CONST_PERM_LE2BE, V5 134 VPERM V6, V6, CONST_PERM_LE2BE, V6 135 VPERM V7, V7, CONST_PERM_LE2BE, V7 136 VPERM V8, V8, CONST_PERM_LE2BE, V8 137 138 139 // Perform a GF(2) multiplication of the doublewords in V1 with 140 // the reduction constants in V0. The intermediate result is 141 // then folded (accumulated) with the next data chunk in V5 and 142 // stored in V1. Repeat this step for the register contents 143 // in V2, V3, and V4 respectively. 144 145 VGFMAG CONST_R2R1, V1, V5, V1 146 VGFMAG CONST_R2R1, V2, V6, V2 147 VGFMAG CONST_R2R1, V3, V7, V3 148 VGFMAG CONST_R2R1, V4, V8 ,V4 149 150 // Adjust buffer pointer and length for next loop 151 ADD $64, R3 // BUF = BUF + 64 152 ADD $(-64), R4 // LEN = LEN - 64 153 154 CMP R4, $64 155 BGE fold_64bytes_loop 156 157 less_than_64bytes: 158 // Fold V1 to V4 into a single 128-bit value in V1 159 VGFMAG CONST_R4R3, V1, V2, V1 160 VGFMAG CONST_R4R3, V1, V3, V1 161 VGFMAG CONST_R4R3, V1, V4, V1 162 163 // Check whether to continue with 64-bit folding 164 CMP R4, $16 165 BLT final_fold 166 167 fold_16bytes_loop: 168 VL 0(R3), V2 // Load next data chunk 169 VPERM V2, V2, CONST_PERM_LE2BE, V2 170 171 VGFMAG CONST_R4R3, V1, V2, V1 // Fold next data chunk 172 173 // Adjust buffer pointer and size for folding next data chunk 174 ADD $16, R3 175 ADD $-16, R4 176 177 // Process remaining data chunks 178 CMP R4 ,$16 179 BGE fold_16bytes_loop 180 181 final_fold: 182 VLEIB $7, $0x40, V9 183 VSRLB V9, CONST_R4R3, V0 184 VLEIG $0, $1, V0 185 186 VGFMG V0, V1, V1 187 188 VLEIB $7, $0x20, V9 // Shift by words 189 VSRLB V9, V1, V2 // Store remaining bits in V2 190 VUPLLF V1, V1 // Split rightmost doubleword 191 VGFMAG CONST_R5, V1, V2, V1 // V1 = (V1 * R5) XOR V2 192 193 194 // The input values to the Barret reduction are the degree-63 polynomial 195 // in V1 (R(x)), degree-32 generator polynomial, and the reduction 196 // constant u. The Barret reduction result is the CRC value of R(x) mod 197 // P(x). 198 // 199 // The Barret reduction algorithm is defined as: 200 // 201 // 1. T1(x) = floor( R(x) / x^32 ) GF2MUL u 202 // 2. T2(x) = floor( T1(x) / x^32 ) GF2MUL P(x) 203 // 3. C(x) = R(x) XOR T2(x) mod x^32 204 // 205 // Note: To compensate the division by x^32, use the vector unpack 206 // instruction to move the leftmost word into the leftmost doubleword 207 // of the vector register. The rightmost doubleword is multiplied 208 // with zero to not contribute to the intermediate results. 209 210 211 // T1(x) = floor( R(x) / x^32 ) GF2MUL u 212 VUPLLF V1, V2 213 VGFMG CONST_RU_POLY, V2, V2 214 215 216 // Compute the GF(2) product of the CRC polynomial in VO with T1(x) in 217 // V2 and XOR the intermediate result, T2(x), with the value in V1. 218 // The final result is in the rightmost word of V2. 219 220 VUPLLF V2, V2 221 VGFMAG CONST_CRC_POLY, V2, V1, V2 222 223 done: 224 VLGVF $2, V2, R2 225 XOR $0xffffffff, R2 // NOTW R2 226 MOVWZ R2, ret + 32(FP) 227 RET 228 229 crash: 230 MOVD $0, (R0) // input size is less than 64-bytes