1 // Auto-generated file. Do not edit!
2 // Template: src/f32-vscaleexpminusmax/avx2-p5.c.in
3 // Generator: tools/xngen
4 //
5 // Copyright 2019 Google LLC
6 //
7 // This source code is licensed under the BSD-style license found in the
8 // LICENSE file in the root directory of this source tree.
9
10 #include <assert.h>
11
12 #include <immintrin.h>
13
14 #include <xnnpack/common.h>
15 #include <xnnpack/vscaleexpminusmax.h>
16
17
18 static const int32_t mask_table[14] = {-1, -1, -1, -1, -1, -1, -1, 0, 0, 0, 0, 0, 0, 0};
19
xnn_f32_vscaleexpminusmax_ukernel__avx2_p5_x8(size_t elements,const float * input,float * output,float scale,float max)20 void xnn_f32_vscaleexpminusmax_ukernel__avx2_p5_x8(
21 size_t elements,
22 const float* input,
23 float* output,
24 float scale,
25 float max)
26 {
27 assert(elements % sizeof(float) == 0);
28
29 const __m256 vmagic_bias = _mm256_set1_ps(0x1.8000FEp23f);
30 // The smallest x for which expf(x) is normalized.
31 const __m256 vdenorm_cutoff = _mm256_set1_ps(-0x1.5D589Ep6f);
32 const __m256 vlog2e = _mm256_set1_ps(0x1.715476p+0f);
33 const __m256 vminus_ln2_hi = _mm256_set1_ps(-0x1.62E43p-1f);
34 const __m256 vminus_ln2_lo = _mm256_set1_ps(0x1.05C61p-29f);
35
36 const __m256 vc1 = _mm256_set1_ps(0x1.FFFFF6p-1f);
37 const __m256 vc2 = _mm256_set1_ps(0x1.FFFDC6p-2f);
38 const __m256 vc3 = _mm256_set1_ps(0x1.555A80p-3f);
39 const __m256 vc4 = _mm256_set1_ps(0x1.573A1Ap-5f);
40 const __m256 vc5 = _mm256_set1_ps(0x1.0F9F9Cp-7f);
41
42 const __m256 vscale = _mm256_set1_ps(scale);
43 const __m256 vi_max = _mm256_set1_ps(max);
44
45 for (; elements >= 8 * sizeof(float); elements -= 8 * sizeof(float)) {
46 // Load 8 (1x8) inputs at a time.
47 const __m256 vi0 = _mm256_loadu_ps(input);
48 input += 8;
49
50 // Subtract maximum input x := i - i_max. This implies x <= 0.
51 const __m256 vx0 = _mm256_sub_ps(vi0, vi_max);
52
53 // Compute reduced argument elements := round(x / log(2)).
54 __m256 vn0 = _mm256_fmadd_ps(vx0, vlog2e, vmagic_bias);
55
56 // Create a floating-point number s (scale) such that s == 2**elements for inputs which don't cause underflow, i.e.
57 // -87.33642 <= x <= 0.0, and -126 <= elements <= 0 accordingly.
58 const __m256 vs0 = _mm256_castsi256_ps(_mm256_slli_epi32(_mm256_castps_si256(vn0), 23));
59
60 // Subtract the large number back to get final elements := round(x / log(2)).
61 vn0 = _mm256_sub_ps(vn0, vmagic_bias);
62
63 // Compute reduced argument t := x - elements * log(2).
64 // Use Cody-Waite range reduction method (note two constants to represent log(2)) to improve accuracy.
65 __m256 vt0 = _mm256_fmadd_ps(vn0, vminus_ln2_hi, vx0);
66
67 vt0 = _mm256_fmadd_ps(vn0, vminus_ln2_lo, vt0);
68
69 // Compute degree-5 polynomial approximation for exp(t) on [-log(2)/2, log(2)/2].
70 __m256 vp0 = _mm256_fmadd_ps(vc5, vt0, vc4);
71
72 vp0 = _mm256_fmadd_ps(vp0, vt0, vc3);
73
74 vp0 = _mm256_fmadd_ps(vp0, vt0, vc2);
75
76 vp0 = _mm256_fmadd_ps(vp0, vt0, vc1);
77
78 // Reconstruct the final f value:
79 // f = s * (1 + t * (c1 + t * (c2 + t * (c3 + t * (c4 + t * c5)))))
80 // = s + (t * s) * (c1 + t * (c2 + t * (c3 + t * (c4 + t * c5))))
81 // = s + (t * s) * p
82 vt0 = _mm256_mul_ps(vt0, vs0);
83
84 __m256 vf0 = _mm256_fmadd_ps(vt0, vp0, vs0);
85
86 // For inputs below zero cutoff, replace output with +0.0f.
87 // Note that for NaN inputs, comparison result is false, and outputs are left unchanged.
88 vf0 = _mm256_andnot_ps(_mm256_cmp_ps(vx0, vdenorm_cutoff, _CMP_LT_OS), vf0);
89
90 // Multiply by scale.
91 vf0 = _mm256_mul_ps(vf0, vscale);
92
93 // Store 8 (1x8) outputs at a time.
94 _mm256_storeu_ps(output, vf0);
95 output += 8;
96 }
97 for (; elements >= 8 * sizeof(float); elements -= 8 * sizeof(float)) {
98 // Load 8 inputs at a time.
99 const __m256 vi = _mm256_loadu_ps(input);
100 input += 8;
101
102 // Subtract maximum input x := i - i_max. This implies x <= 0.
103 const __m256 vx = _mm256_sub_ps(vi, vi_max);
104
105 // Compute reduced argument elements := round(x / log(2)).
106 __m256 vn = _mm256_fmadd_ps(vx, vlog2e, vmagic_bias);
107
108 // Create a floating-point number s (scale) such that s == 2**elements for inputs which don't cause underflow, i.e.
109 // -87.33642 <= x <= 0.0, and -126 <= elements <= 0 accordingly.
110 const __m256 vs = _mm256_castsi256_ps(_mm256_slli_epi32(_mm256_castps_si256(vn), 23));
111
112 // Subtract the large number back to get final elements := round(x / log(2)).
113 vn = _mm256_sub_ps(vn, vmagic_bias);
114
115 // Compute reduced argument t := x - elements * log(2).
116 // Use Cody-Waite range reduction method (note two constants to represent log(2)) to improve accuracy.
117 __m256 vt = _mm256_fmadd_ps(vn, vminus_ln2_hi, vx);
118 vt = _mm256_fmadd_ps(vn, vminus_ln2_lo, vt);
119
120 // Compute degree-5 polynomial approximation for exp(t) on [-log(2)/2, log(2)/2].
121 __m256 vp = _mm256_fmadd_ps(vc5, vt, vc4);
122 vp = _mm256_fmadd_ps(vp, vt, vc3);
123 vp = _mm256_fmadd_ps(vp, vt, vc2);
124 vp = _mm256_fmadd_ps(vp, vt, vc1);
125
126 // Reconstruct the final f value:
127 // f = s * (1 + t * (c1 + t * (c2 + t * (c3 + t * (c4 + t * c5)))))
128 // = s + (t * s) * (c1 + t * (c2 + t * (c3 + t * (c4 + t * c5))))
129 // = s + (t * s) * p
130 vt = _mm256_mul_ps(vt, vs);
131 __m256 vf = _mm256_fmadd_ps(vt, vp, vs);
132
133 // For inputs below zero cutoff, replace output with +0.0f.
134 // Note that for NaN inputs, comparison result is false, and outputs are left unchanged.
135 vf = _mm256_andnot_ps(_mm256_cmp_ps(vx, vdenorm_cutoff, _CMP_LT_OS), vf);
136
137 // Multiply by scale.
138 vf = _mm256_mul_ps(vf, vscale);
139
140 // Store 64 (8x8) outputs at a time.
141 _mm256_storeu_ps(output, vf);
142 output += 8;
143 }
144 if (elements != 0) {
145 assert(elements >= 1 * sizeof(float));
146 assert(elements <= 7 * sizeof(float));
147 const __m256i vmask = _mm256_loadu_si256((const __m256i*) ((uintptr_t) &mask_table[7] - elements));
148
149 // Load up to 7 inputs at a time.
150 const __m256 vi = _mm256_maskload_ps(input, vmask);
151
152 // Subtract maximum input x := i - i_max. This implies x <= 0.
153 const __m256 vx = _mm256_sub_ps(vi, vi_max);
154
155 // Compute reduced argument elements := round(x / log(2)).
156 __m256 vn = _mm256_fmadd_ps(vx, vlog2e, vmagic_bias);
157
158 // Create a floating-point number s (scale) such that s == 2**elements for inputs which don't cause underflow, i.e.
159 // -87.33642 <= x <= 0.0, and -126 <= elements <= 0 accordingly.
160 const __m256 vs = _mm256_castsi256_ps(_mm256_slli_epi32(_mm256_castps_si256(vn), 23));
161
162 // Subtract the large number back to get final elements := round(x / log(2)).
163 vn = _mm256_sub_ps(vn, vmagic_bias);
164
165 // Compute reduced argument t := x - elements * log(2).
166 // Use Cody-Waite range reduction method (note two constants to represent log(2)) to improve accuracy.
167 __m256 vt = _mm256_fmadd_ps(vn, vminus_ln2_hi, vx);
168 vt = _mm256_fmadd_ps(vn, vminus_ln2_lo, vt);
169
170 // Compute degree-5 polynomial approximation for exp(t) on [-log(2)/2, log(2)/2].
171 __m256 vp = _mm256_fmadd_ps(vc5, vt, vc4);
172 vp = _mm256_fmadd_ps(vp, vt, vc3);
173 vp = _mm256_fmadd_ps(vp, vt, vc2);
174 vp = _mm256_fmadd_ps(vp, vt, vc1);
175
176 // Reconstruct the final f value:
177 // f = s * (1 + t * (c1 + t * (c2 + t * (c3 + t * (c4 + t * c5)))))
178 // = s + (t * s) * (c1 + t * (c2 + t * (c3 + t * (c4 + t * c5))))
179 // = s + (t * s) * p
180 vt = _mm256_mul_ps(vt, vs);
181 __m256 vf = _mm256_fmadd_ps(vt, vp, vs);
182
183 // For inputs below zero cutoff, replace output with +0.0f.
184 // Note that for NaN inputs, comparison result is false, and outputs are left unchanged.
185 vf = _mm256_andnot_ps(_mm256_cmp_ps(vx, vdenorm_cutoff, _CMP_LT_OS), vf);
186
187 // Multiply by scale.
188 vf = _mm256_mul_ps(vf, vscale);
189
190 // Store up to 7 outputs at a time.
191 _mm256_maskstore_ps(output, vmask, vf);
192 }
193 }
194