| // Copyright (c) Facebook, Inc. and its affiliates. |
| // All rights reserved. |
| // |
| // Copyright 2019 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 <stdint.h> |
| |
| #include <psimd.h> |
| |
| #include <xnnpack/requantization-stubs.h> |
| |
| |
| void xnn_requantize_fp32__psimd( |
| size_t n, |
| const int32_t* input, |
| float scale, |
| uint8_t zero_point, |
| uint8_t qmin, |
| uint8_t qmax, |
| uint8_t* output) |
| { |
| assert(n % 16 == 0); |
| assert(scale < 1.0f); |
| assert(scale >= 0x1.0p-32f); |
| |
| const psimd_f32 vscale = psimd_splat_f32(scale); |
| const psimd_f32 vfmin = psimd_splat_f32((float) ((int32_t)(uint32_t) qmin - (int32_t)(uint32_t) zero_point)); |
| const psimd_f32 vfmax = psimd_splat_f32((float) ((int32_t)(uint32_t) qmax - (int32_t)(uint32_t) zero_point)); |
| const psimd_f32 vfmagic = psimd_splat_f32(12582912.0f); |
| const psimd_s32 vimagic = psimd_splat_s32(INT32_C(0x4B400000) - (int32_t)(uint32_t) zero_point); |
| for (; n != 0; n -= 16) { |
| const psimd_s32 x = psimd_load_s32(input); |
| const psimd_s32 y = psimd_load_s32(input + 4); |
| const psimd_s32 z = psimd_load_s32(input + 8); |
| const psimd_s32 w = psimd_load_s32(input + 12); |
| input += 16; |
| |
| // Convert int32_t input to FP32 and multiply by FP32 scale. |
| // Both operations involve roundings: |
| // - Large int32_t values can't be exactly represented as FP32. We expect that conversion instruction would |
| // round it to nearest FP32 value with ties to even, but Clang documentation for __builtin_convertvector does |
| // not guaratee that. |
| // - Product of two FP32 values is generally not exactly representation as an FP32 value, and will be rounded |
| // to nearest FP32 value with ties to even. |
| const psimd_f32 x_scaled = psimd_cvt_s32_f32(x) * vscale; |
| const psimd_f32 y_scaled = psimd_cvt_s32_f32(y) * vscale; |
| const psimd_f32 z_scaled = psimd_cvt_s32_f32(z) * vscale; |
| const psimd_f32 w_scaled = psimd_cvt_s32_f32(w) * vscale; |
| |
| // Clang/gcc vector extension does not provide an intrinsics for a floating-point to integer conversion |
| // operation with rounding-to-nearest-even. In lieu of such intrinsic, we use a magic trick of adding a large |
| // number (1.5 * 2**23) to scaled value to cause rounding to integer, and then substracing this magic number as |
| // integer. This trick works only in a limited range (absolute value of input must be less than 2**22), so |
| // generally we have to clamp input to this range before using the magic. However, clamping to any smaller range |
| // works just as well, and thus we clamp to [qmin - zero point, qmax - zero point] range so that after we add |
| // zero point to the result, it gets into target [qmin, qmax] range. |
| const psimd_f32 x_clamped = psimd_min_f32(psimd_max_f32(x_scaled, vfmin), vfmax); |
| const psimd_f32 y_clamped = psimd_min_f32(psimd_max_f32(y_scaled, vfmin), vfmax); |
| const psimd_f32 z_clamped = psimd_min_f32(psimd_max_f32(z_scaled, vfmin), vfmax); |
| const psimd_f32 w_clamped = psimd_min_f32(psimd_max_f32(w_scaled, vfmin), vfmax); |
| |
| // Conversion to integer using the "magic trick". Rounding is performed in the output of addition operation, |
| // and result is rounded to nearest even integer with ties to even. |
| const psimd_s32 x_biased = (psimd_s32)(x_clamped + vfmagic) - vimagic; |
| const psimd_s32 y_biased = (psimd_s32)(y_clamped + vfmagic) - vimagic; |
| const psimd_s32 z_biased = (psimd_s32)(z_clamped + vfmagic) - vimagic; |
| const psimd_s32 w_biased = (psimd_s32)(w_clamped + vfmagic) - vimagic; |
| |
| // Select low 8 bits of each 32-bit integer in the vectors for the output. |
| // Since result is already clamped to [qmin, qmax] subrange of [0, 255], saturation is not needed. |
| const psimd_u16 xy_packed = psimd_concat_even_u16((psimd_u16) x_biased, (psimd_u16) y_biased); |
| const psimd_u16 zw_packed = psimd_concat_even_u16((psimd_u16) z_biased, (psimd_u16) w_biased); |
| |
| const psimd_u8 xyzw_packed = psimd_concat_even_u8((psimd_u8) xy_packed, (psimd_u8) zw_packed); |
| |
| psimd_store_u8(output, xyzw_packed); |
| output += 16; |
| } |
| } |