Text file
src/hash/crc32/crc32_s390x.s
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
231
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