1/* Function log vectorized with AVX2.
2 Copyright (C) 2014-2024 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <sysdep.h>
20#include "svml_d_log_data.h"
21
22 .section .text.avx2, "ax", @progbits
23ENTRY (_ZGVdN4v_log_avx2)
24/* ALGORITHM DESCRIPTION:
25
26 log(x) = -log(Rcp) + log(Rcp*x),
27 where Rcp ~ 1/x (accuracy ~9 bits, obtained by rounding
28 HW approximation to 1+9 mantissa bits)
29
30 Reduced argument R=Rcp*x-1 is used to approximate log(1+R) as polynomial
31
32 log(Rcp) = exponent_Rcp*log(2) + log(mantissa_Rcp)
33 -log(mantissa_Rcp) is obtained from a lookup table,
34 accessed by a 9-bit index
35 */
36 pushq %rbp
37 cfi_adjust_cfa_offset (8)
38 cfi_rel_offset (%rbp, 0)
39 movq %rsp, %rbp
40 cfi_def_cfa_register (%rbp)
41 andq $-64, %rsp
42 subq $448, %rsp
43 movq __svml_dlog_data@GOTPCREL(%rip), %rax
44 vmovdqa %ymm0, %ymm5
45
46/* isolate exponent bits */
47 vpsrlq $20, %ymm5, %ymm0
48
49/* preserve mantissa, set input exponent to 2^(-10) */
50 vandpd _ExpMask(%rax), %ymm5, %ymm6
51 vorpd _Two10(%rax), %ymm6, %ymm4
52
53/* reciprocal approximation good to at least 11 bits */
54 vcvtpd2ps %ymm4, %xmm7
55 vrcpps %xmm7, %xmm1
56 vcmplt_oqpd _MinNorm(%rax), %ymm5, %ymm7
57 vcvtps2pd %xmm1, %ymm3
58 vcmpnle_uqpd _MaxNorm(%rax), %ymm5, %ymm1
59 vextracti128 $1, %ymm0, %xmm2
60 vshufps $221, %xmm2, %xmm0, %xmm6
61
62/* round reciprocal to nearest integer, will have 1+9 mantissa bits */
63 vroundpd $0, %ymm3, %ymm2
64
65/* convert biased exponent to DP format */
66 vcvtdq2pd %xmm6, %ymm0
67
68/* combine and get argument value range mask */
69 vorpd %ymm1, %ymm7, %ymm3
70 vmovupd _One(%rax), %ymm1
71 vmovmskpd %ymm3, %ecx
72
73/* calculate index for table lookup */
74 vpsrlq $40, %ymm2, %ymm3
75
76/* argument reduction started: R = Mantissa*Rcp - 1 */
77 vfmsub213pd %ymm1, %ymm2, %ymm4
78 vcmpgt_oqpd _Threshold(%rax), %ymm2, %ymm2
79 vpcmpeqd %ymm6, %ymm6, %ymm6
80 vxorpd %ymm1, %ymm1, %ymm1
81 vgatherqpd %ymm6, _LogRcp_lookup(%rax,%ymm3), %ymm1
82
83/* exponent*log(2.0) */
84 vmovupd _poly_coeff_1(%rax), %ymm6
85 vmulpd %ymm4, %ymm4, %ymm3
86
87/* polynomial computation */
88 vfmadd213pd _poly_coeff_2(%rax), %ymm4, %ymm6
89 vandpd _Bias(%rax), %ymm2, %ymm7
90 vorpd _Bias1(%rax), %ymm7, %ymm2
91
92/*
93 Table stores -log(0.5*mantissa) for larger mantissas,
94 adjust exponent accordingly
95 */
96 vsubpd %ymm2, %ymm0, %ymm0
97 vmovupd _poly_coeff_3(%rax), %ymm2
98 vfmadd213pd _poly_coeff_4(%rax), %ymm4, %ymm2
99 vfmadd213pd %ymm2, %ymm3, %ymm6
100
101/*
102 reconstruction:
103 (exponent*log(2)) + (LogRcp + (R+poly))
104 */
105 vfmadd213pd %ymm4, %ymm3, %ymm6
106 vaddpd %ymm1, %ymm6, %ymm4
107 vfmadd132pd _L2(%rax), %ymm4, %ymm0
108 testl %ecx, %ecx
109 jne .LBL_1_3
110
111.LBL_1_2:
112 cfi_remember_state
113 movq %rbp, %rsp
114 cfi_def_cfa_register (%rsp)
115 popq %rbp
116 cfi_adjust_cfa_offset (-8)
117 cfi_restore (%rbp)
118 ret
119
120.LBL_1_3:
121 cfi_restore_state
122 vmovupd %ymm5, 320(%rsp)
123 vmovupd %ymm0, 384(%rsp)
124 je .LBL_1_2
125
126 xorb %dl, %dl
127 xorl %eax, %eax
128 vmovups %ymm8, 224(%rsp)
129 vmovups %ymm9, 192(%rsp)
130 vmovups %ymm10, 160(%rsp)
131 vmovups %ymm11, 128(%rsp)
132 vmovups %ymm12, 96(%rsp)
133 vmovups %ymm13, 64(%rsp)
134 vmovups %ymm14, 32(%rsp)
135 vmovups %ymm15, (%rsp)
136 movq %rsi, 264(%rsp)
137 movq %rdi, 256(%rsp)
138 movq %r12, 296(%rsp)
139 cfi_offset_rel_rsp (12, 296)
140 movb %dl, %r12b
141 movq %r13, 288(%rsp)
142 cfi_offset_rel_rsp (13, 288)
143 movl %ecx, %r13d
144 movq %r14, 280(%rsp)
145 cfi_offset_rel_rsp (14, 280)
146 movl %eax, %r14d
147 movq %r15, 272(%rsp)
148 cfi_offset_rel_rsp (15, 272)
149 cfi_remember_state
150
151.LBL_1_6:
152 btl %r14d, %r13d
153 jc .LBL_1_12
154
155.LBL_1_7:
156 lea 1(%r14), %esi
157 btl %esi, %r13d
158 jc .LBL_1_10
159
160.LBL_1_8:
161 incb %r12b
162 addl $2, %r14d
163 cmpb $16, %r12b
164 jb .LBL_1_6
165
166 vmovups 224(%rsp), %ymm8
167 vmovups 192(%rsp), %ymm9
168 vmovups 160(%rsp), %ymm10
169 vmovups 128(%rsp), %ymm11
170 vmovups 96(%rsp), %ymm12
171 vmovups 64(%rsp), %ymm13
172 vmovups 32(%rsp), %ymm14
173 vmovups (%rsp), %ymm15
174 vmovupd 384(%rsp), %ymm0
175 movq 264(%rsp), %rsi
176 movq 256(%rsp), %rdi
177 movq 296(%rsp), %r12
178 cfi_restore (%r12)
179 movq 288(%rsp), %r13
180 cfi_restore (%r13)
181 movq 280(%rsp), %r14
182 cfi_restore (%r14)
183 movq 272(%rsp), %r15
184 cfi_restore (%r15)
185 jmp .LBL_1_2
186
187.LBL_1_10:
188 cfi_restore_state
189 movzbl %r12b, %r15d
190 shlq $4, %r15
191 vmovsd 328(%rsp,%r15), %xmm0
192 vzeroupper
193
194 call JUMPTARGET(log)
195
196 vmovsd %xmm0, 392(%rsp,%r15)
197 jmp .LBL_1_8
198
199.LBL_1_12:
200 movzbl %r12b, %r15d
201 shlq $4, %r15
202 vmovsd 320(%rsp,%r15), %xmm0
203 vzeroupper
204
205 call JUMPTARGET(log)
206
207 vmovsd %xmm0, 384(%rsp,%r15)
208 jmp .LBL_1_7
209
210END (_ZGVdN4v_log_avx2)
211

source code of glibc/sysdeps/x86_64/fpu/multiarch/svml_d_log4_core_avx2.S