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// Auto-generated file. Do not edit!
// Template: src/u32-vlog/scalar.c.in
// Generator: tools/xngen
//
// Copyright 2022 Google LLC
//
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree.
#include <assert.h>
#include <stddef.h>
#include <stdint.h>
#include <xnnpack/math.h>
#include <xnnpack/vlog.h>
extern XNN_INTERNAL const uint16_t xnn_table_vlog[129];
// Calculate integer logarithm, 32 Bit version
static uint32_t xnn_u32_log32(uint32_t x, uint32_t out_scale) {
const uint32_t log_scale = 65536;
const uint32_t log_scale_log2 = 16;
const uint32_t log_coeff = 45426;
const uint32_t log2x = math_clz_nonzero_u32(x) ^ 31; // log2 of x
assert(log2x < 32);
// Number of segments in the log lookup table. The table will be log_segments+1
// in length (with some padding).
const int log_segments_log2 = 7;
// Part 1
uint32_t frac = x - (UINT32_C(1) << log2x);
// Shift the fractional part into msb of 16 bits
frac = XNN_UNPREDICTABLE(log2x < log_scale_log2) ?
(frac << (log_scale_log2 - log2x)) :
(frac >> (log2x - log_scale_log2));
// Part 2
const uint32_t base_seg = frac >> (log_scale_log2 - log_segments_log2);
const uint32_t seg_unit = (UINT32_C(1) << log_scale_log2) >> log_segments_log2;
assert(128 == (UINT32_C(1) << log_segments_log2));
assert(base_seg < (UINT32_C(1) << log_segments_log2));
const uint32_t c0 = xnn_table_vlog[base_seg];
const uint32_t c1 = xnn_table_vlog[base_seg + 1];
const uint32_t seg_base = seg_unit * base_seg;
const uint32_t rel_pos = ((c1 - c0) * (frac - seg_base)) >> log_scale_log2;
const uint32_t fraction = frac + c0 + rel_pos;
const uint32_t log2 = (log2x << log_scale_log2) + fraction;
const uint32_t round = log_scale >> 1;
const uint32_t loge = (math_mulext_u32(log_coeff, log2) + round) >> log_scale_log2;
// Finally scale to our output scale
const uint32_t loge_scaled = (out_scale * loge + round) >> log_scale_log2;
return loge_scaled;
}
void xnn_u32_vlog_ukernel__scalar_x1(
size_t batch,
const uint32_t* input,
uint32_t input_lshift,
uint32_t output_scale,
uint16_t* output) {
assert(batch != 0);
assert(input != NULL);
assert(input_lshift < 32);
assert(output != NULL);
if XNN_UNLIKELY(batch != 0) {
do {
const uint32_t vi = *input++;
const uint32_t scaled = vi << input_lshift;
const uint32_t log_value = scaled ? xnn_u32_log32(scaled, output_scale) : 0;
const uint32_t vout = math_min_u32(log_value, (uint32_t) INT16_MAX);
*output++ = (uint16_t) vout;
} while (--batch != 0);
}
}
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