src/qu8-requantization/fp32-neon.c - platform/external/XNNPACK - Gitiles

 // 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 <stddef.h>

 #include <arm_neon.h>

 #include <xnnpack/requantization-stubs.h>


 void xnn_qu8_requantize_fp32__neon(
     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 float32x4_t vscale = vdupq_n_f32(scale);
 #ifdef __aarch64__
   const int16x8_t vzero_point = vdupq_n_s16((int16_t)(uint16_t) zero_point);
   const uint8x16_t vqmin = vdupq_n_u8(qmin);
   const uint8x16_t vqmax = vdupq_n_u8(qmax);
 #else
   const float32x4_t vfmin = vdupq_n_f32((float) ((int32_t)(uint32_t) qmin - (int32_t)(uint32_t) zero_point));
   const float32x4_t vfmax = vdupq_n_f32((float) ((int32_t)(uint32_t) qmax - (int32_t)(uint32_t) zero_point));
   const float32x4_t vfmagic = vdupq_n_f32(12582912.0f);
   const int32x4_t vimagic = vdupq_n_s32(INT32_C(0x4B400000) - (int32_t)(uint32_t) zero_point);
 #endif
   for (; n != 0; n -= 16) {
     const int32x4_t x = vld1q_s32(input);
     const int32x4_t y = vld1q_s32(input + 4);
     const int32x4_t z = vld1q_s32(input + 8);
     const int32x4_t w = vld1q_s32(input + 12);
     input += 16;

     // Convert int32_t input to FP32 and multiply by FP32 scale.
     // Both operations involve statistically unbiased roundings:
     // - Large int32_t values can't be exactly represented as FP32. The conversion instruction in ARM NEON would
     //   round it to nearest FP32 value with ties to even.
     // - 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 float32x4_t x_scaled = vmulq_f32(vcvtq_f32_s32(x), vscale);
     const float32x4_t y_scaled = vmulq_f32(vcvtq_f32_s32(y), vscale);
     const float32x4_t z_scaled = vmulq_f32(vcvtq_f32_s32(z), vscale);
     const float32x4_t w_scaled = vmulq_f32(vcvtq_f32_s32(w), vscale);

 #ifdef __aarch64__
     // Leverage "Floating-point Convert to Signed integer, rouding to nearest with ties to even" instruction.
     // This is an ARMv8 instruction (always available in AArch64), which saturates result on overflow.
     // We don't need to specifically consider saturated results, they will be clamped at the last stage.
     const int32x4_t x_rounded = vcvtnq_s32_f32(x_scaled);
     const int32x4_t y_rounded = vcvtnq_s32_f32(y_scaled);
     const int32x4_t z_rounded = vcvtnq_s32_f32(z_scaled);
     const int32x4_t w_rounded = vcvtnq_s32_f32(w_scaled);

     // Standard final sequence on ARM NEON:
     // - Pack to int16_t and saturate
     // - Add zero point
     // - Pack to uint8_t and saturate
     // - Clamp between qmin and qmax
     const int16x8_t xy_packed = vqaddq_s16(vqmovn_high_s32(vqmovn_s32(x_rounded), y_rounded), vzero_point);
     const int16x8_t zw_packed = vqaddq_s16(vqmovn_high_s32(vqmovn_s32(z_rounded), w_rounded), vzero_point);
     const uint8x16_t xyzw_packed = vqmovun_high_s16(vqmovun_s16(xy_packed), zw_packed);
     const uint8x16_t xyzw_clamped = vmaxq_u8(vminq_u8(xyzw_packed, vqmax), vqmin);

     vst1q_u8(output, xyzw_clamped);
     output += 16;
 #else
     // ARMv7 NEON offers only a floating-point to integer conversion instruction with rounding towards zero.
     // In lieu of conversion instruction with rounding-to-nearest-even, 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 float32x4_t x_clamped = vminq_f32(vmaxq_f32(x_scaled, vfmin), vfmax);
     const float32x4_t y_clamped = vminq_f32(vmaxq_f32(y_scaled, vfmin), vfmax);
     const float32x4_t z_clamped = vminq_f32(vmaxq_f32(z_scaled, vfmin), vfmax);
     const float32x4_t w_clamped = vminq_f32(vmaxq_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 int32x4_t x_biased = vsubq_s32(vreinterpretq_s32_f32(vaddq_f32(x_clamped, vfmagic)), vimagic);
     const int32x4_t y_biased = vsubq_s32(vreinterpretq_s32_f32(vaddq_f32(y_clamped, vfmagic)), vimagic);
     const int32x4_t z_biased = vsubq_s32(vreinterpretq_s32_f32(vaddq_f32(z_clamped, vfmagic)), vimagic);
     const int32x4_t w_biased = vsubq_s32(vreinterpretq_s32_f32(vaddq_f32(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 int16x8_t xy_packed = vcombine_s16(vmovn_s32(x_biased), vmovn_s32(y_biased));
     const int16x8_t zw_packed = vcombine_s16(vmovn_s32(z_biased), vmovn_s32(w_biased));
     const uint8x16_t xyzw_packed = vreinterpretq_u8_s8(vcombine_s8(vmovn_s16(xy_packed), vmovn_s16(zw_packed)));

     // AArch32 version:
     //   4x VCVT.F32.S32 Qd, Qm
     //   4x VMUL.F32 Qd, Qm, Qn
     //   4x VMIN.F32 Qd, Qm, Qn
     //   4x VMAX.F32 Qd, Qm, Qn
     //   4x VADD.F32 Qd, Qm, Qn
     //   4x VSUB.S32 Qd, Qm, Qn
     //   4x VMOVN.I32 Dd, Qm
     //   2x VMOVN.I16 Dd, Qm
     // ---------------------
     // 30 instructions total
     //
     // AArch64 version:
     //   4x SCVTF Vd.4S, Vn.4S
     //   4x FMUL Vd.4S, Vn.4S, Vm.4S
     //   4x FCVTNS Vd.4S, Vn.4S
     //   2x SQXTN Vd.4H, Vn.4S
     //   2x SQXTN2 Vd.8H, Vn.4S
     //   2x ADD Vd.8H, Vn.8H, Vm.8H
     //   1x SQXTUN Vd.8B, Vn.8H
     //   1x SQXTUN2 Vd.16B, Vn.8H
     //   1x UMIN Vd.16B, Vn.16B, Vm.16B
     //   1x UMAX Vd.16B, Vn.16B, Vm.16B
     // ---------------------
     // 22 instructions total

     vst1q_u8(output, xyzw_packed);
     output += 16;
 #endif
   }
 }
	// 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 <stddef.h>

	#include <arm_neon.h>

	#include <xnnpack/requantization-stubs.h>


	void xnn_qu8_requantize_fp32__neon(
	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 float32x4_t vscale = vdupq_n_f32(scale);
	#ifdef __aarch64__
	const int16x8_t vzero_point = vdupq_n_s16((int16_t)(uint16_t) zero_point);
	const uint8x16_t vqmin = vdupq_n_u8(qmin);
	const uint8x16_t vqmax = vdupq_n_u8(qmax);
	#else
	const float32x4_t vfmin = vdupq_n_f32((float) ((int32_t)(uint32_t) qmin - (int32_t)(uint32_t) zero_point));
	const float32x4_t vfmax = vdupq_n_f32((float) ((int32_t)(uint32_t) qmax - (int32_t)(uint32_t) zero_point));
	const float32x4_t vfmagic = vdupq_n_f32(12582912.0f);
	const int32x4_t vimagic = vdupq_n_s32(INT32_C(0x4B400000) - (int32_t)(uint32_t) zero_point);
	#endif
	for (; n != 0; n -= 16) {
	const int32x4_t x = vld1q_s32(input);
	const int32x4_t y = vld1q_s32(input + 4);
	const int32x4_t z = vld1q_s32(input + 8);
	const int32x4_t w = vld1q_s32(input + 12);
	input += 16;

	// Convert int32_t input to FP32 and multiply by FP32 scale.
	// Both operations involve statistically unbiased roundings:
	// - Large int32_t values can't be exactly represented as FP32. The conversion instruction in ARM NEON would
	// round it to nearest FP32 value with ties to even.
	// - 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 float32x4_t x_scaled = vmulq_f32(vcvtq_f32_s32(x), vscale);
	const float32x4_t y_scaled = vmulq_f32(vcvtq_f32_s32(y), vscale);
	const float32x4_t z_scaled = vmulq_f32(vcvtq_f32_s32(z), vscale);
	const float32x4_t w_scaled = vmulq_f32(vcvtq_f32_s32(w), vscale);

	#ifdef __aarch64__
	// Leverage "Floating-point Convert to Signed integer, rouding to nearest with ties to even" instruction.
	// This is an ARMv8 instruction (always available in AArch64), which saturates result on overflow.
	// We don't need to specifically consider saturated results, they will be clamped at the last stage.
	const int32x4_t x_rounded = vcvtnq_s32_f32(x_scaled);
	const int32x4_t y_rounded = vcvtnq_s32_f32(y_scaled);
	const int32x4_t z_rounded = vcvtnq_s32_f32(z_scaled);
	const int32x4_t w_rounded = vcvtnq_s32_f32(w_scaled);

	// Standard final sequence on ARM NEON:
	// - Pack to int16_t and saturate
	// - Add zero point
	// - Pack to uint8_t and saturate
	// - Clamp between qmin and qmax
	const int16x8_t xy_packed = vqaddq_s16(vqmovn_high_s32(vqmovn_s32(x_rounded), y_rounded), vzero_point);
	const int16x8_t zw_packed = vqaddq_s16(vqmovn_high_s32(vqmovn_s32(z_rounded), w_rounded), vzero_point);
	const uint8x16_t xyzw_packed = vqmovun_high_s16(vqmovun_s16(xy_packed), zw_packed);
	const uint8x16_t xyzw_clamped = vmaxq_u8(vminq_u8(xyzw_packed, vqmax), vqmin);

	vst1q_u8(output, xyzw_clamped);
	output += 16;
	#else
	// ARMv7 NEON offers only a floating-point to integer conversion instruction with rounding towards zero.
	// In lieu of conversion instruction with rounding-to-nearest-even, 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 float32x4_t x_clamped = vminq_f32(vmaxq_f32(x_scaled, vfmin), vfmax);
	const float32x4_t y_clamped = vminq_f32(vmaxq_f32(y_scaled, vfmin), vfmax);
	const float32x4_t z_clamped = vminq_f32(vmaxq_f32(z_scaled, vfmin), vfmax);
	const float32x4_t w_clamped = vminq_f32(vmaxq_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 int32x4_t x_biased = vsubq_s32(vreinterpretq_s32_f32(vaddq_f32(x_clamped, vfmagic)), vimagic);
	const int32x4_t y_biased = vsubq_s32(vreinterpretq_s32_f32(vaddq_f32(y_clamped, vfmagic)), vimagic);
	const int32x4_t z_biased = vsubq_s32(vreinterpretq_s32_f32(vaddq_f32(z_clamped, vfmagic)), vimagic);
	const int32x4_t w_biased = vsubq_s32(vreinterpretq_s32_f32(vaddq_f32(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 int16x8_t xy_packed = vcombine_s16(vmovn_s32(x_biased), vmovn_s32(y_biased));
	const int16x8_t zw_packed = vcombine_s16(vmovn_s32(z_biased), vmovn_s32(w_biased));
	const uint8x16_t xyzw_packed = vreinterpretq_u8_s8(vcombine_s8(vmovn_s16(xy_packed), vmovn_s16(zw_packed)));

	// AArch32 version:
	// 4x VCVT.F32.S32 Qd, Qm
	// 4x VMUL.F32 Qd, Qm, Qn
	// 4x VMIN.F32 Qd, Qm, Qn
	// 4x VMAX.F32 Qd, Qm, Qn
	// 4x VADD.F32 Qd, Qm, Qn
	// 4x VSUB.S32 Qd, Qm, Qn
	// 4x VMOVN.I32 Dd, Qm
	// 2x VMOVN.I16 Dd, Qm
	// ---------------------
	// 30 instructions total
	//
	// AArch64 version:
	// 4x SCVTF Vd.4S, Vn.4S
	// 4x FMUL Vd.4S, Vn.4S, Vm.4S
	// 4x FCVTNS Vd.4S, Vn.4S
	// 2x SQXTN Vd.4H, Vn.4S
	// 2x SQXTN2 Vd.8H, Vn.4S
	// 2x ADD Vd.8H, Vn.8H, Vm.8H
	// 1x SQXTUN Vd.8B, Vn.8H
	// 1x SQXTUN2 Vd.16B, Vn.8H
	// 1x UMIN Vd.16B, Vn.16B, Vm.16B
	// 1x UMAX Vd.16B, Vn.16B, Vm.16B
	// ---------------------
	// 22 instructions total

	vst1q_u8(output, xyzw_packed);
	output += 16;
	#endif
	}
	}