COMPMID-2305: NEDepthwiseConvolution 3x3: support for QUANT8_PER_CHANNEL_SYMM

Change-Id: I9a917cff6a089ce6ae16fb4e6066a4194e2e9487
Signed-off-by: Giuseppe Rossini <giuseppe.rossini@arm.com>
Reviewed-on: https://review.mlplatform.org/c/2241
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Michele Di Giorgio <michele.digiorgio@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Pablo Marquez <pablo.tello@arm.com>
diff --git a/src/core/NEON/kernels/convolution/common/qsymm8.cpp b/src/core/NEON/kernels/convolution/common/qsymm8.cpp
new file mode 100644
index 0000000..e50263a
--- /dev/null
+++ b/src/core/NEON/kernels/convolution/common/qsymm8.cpp
@@ -0,0 +1,185 @@
+/*
+ * Copyright (c) 2019 ARM Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
+#include <cmath>
+#include <limits>
+
+#include "qsymm8.hpp"
+
+namespace qsymm8 {
+#if(__ANDROID__ || BARE_METAL)
+template <typename T> T round(T val) {  return ::round(val); }
+template <typename T> T exp2(T val) { return ::exp2(val); }
+template <typename T> T log2(T val) { return ::log2(val); }
+#else  /* (__ANDROID__ || BARE_METAL) */
+template <typename T> T round(T val) { return std::round(val); }
+template <typename T> T exp2(T val) { return std::exp2(val); }
+template <typename T> T log2(T val) { return std::log2(val); }
+#endif  /* (__ANDROID__ || BARE_METAL) */
+
+// Symmetric quantization
+int8_t QSymm8Params::quantize(float value) const
+{
+  const float transformed = value / scale;
+  return static_cast<int8_t>(round(std::max(-128.0f, std::min(127.0f, transformed))));
+}
+
+float QSymm8Params::dequantize(const int8_t value) const
+{
+  return scale * (static_cast<float>(value));
+}
+
+QSymm8RescaleParams QSymm8RescaleParams::make_rescale_params(
+  const QSymm8Params& weight_quant,
+  const QSymm8Params& input_quant,
+  const QSymm8Params& output_quant
+)
+{
+  // Based on the gemmlowp approach: https://github.com/google/gemmlowp/blob/master/doc/quantization_example.cc
+  const float rescale = weight_quant.scale * input_quant.scale / output_quant.scale;
+  const float shiftf = round(log2(0.5f / rescale));
+  const float multf = exp2(31.0f + shiftf)*rescale;
+
+  int64_t shift = static_cast<int64_t>(shiftf);
+  int64_t mult = static_cast<int64_t>(multf);
+
+  if (mult == (1ll << 31))
+  {
+    mult /= 2;
+    shift--;
+  }
+
+  assert(shift >= 0);
+  assert(mult <= std::numeric_limits<int32_t>::max());
+
+  return QSymm8RescaleParams(
+    static_cast<int32_t>(shift),
+    static_cast<int32_t>(mult),
+    rescale
+  );
+}
+
+QSymm8RescaleParams::QSymm8RescaleParams(int32_t shift, int32_t multi, float rescale)
+  : shift(shift), multiplier(multi), rescale(rescale)
+{
+}
+
+// Symmetric per-channel quantization
+int8_t QSymm8PerChannelParams::quantize(float value, float scale) const
+{
+  const float transformed = value / scale;
+  return static_cast<int8_t>(round(std::max(-128.0f, std::min(127.0f, transformed))));
+}
+
+float QSymm8PerChannelParams::dequantize(const int8_t value, float scale) const
+{
+  return scale * (static_cast<float>(value));
+}
+
+QSymm8PerChannelRescaleParams QSymm8PerChannelRescaleParams::make_rescale_params(
+  const QSymm8PerChannelParams& weight_quant,
+  const QSymm8PerChannelParams& input_quant,
+  const QSymm8PerChannelParams& output_quant
+)
+{
+    std::vector<int32_t> shifts;
+    std::vector<int32_t> mults;
+    std::vector<float> rescales;
+
+    for(size_t s = 0; s< input_quant.scales.size(); s++)
+    {
+          // Based on the gemmlowp approach: https://github.com/google/gemmlowp/blob/master/doc/quantization_example.cc
+          const float rescale = weight_quant.scales[s] * input_quant.scales[s] / output_quant.scales[s];
+          const float shiftf = round(log2(0.5f / rescale));
+          const float multf = exp2(31.0f + shiftf)*rescale;
+
+          int64_t shift = static_cast<int64_t>(shiftf);
+          int64_t mult = static_cast<int64_t>(multf);
+
+          if (mult == (1ll << 31))
+          {
+            mult /= 2;
+            shift--;
+          }
+
+          assert(shift >= 0);
+          assert(mult <= std::numeric_limits<int32_t>::max());
+
+          shifts.push_back(static_cast<int32_t>(shift));
+          mults.push_back(static_cast<int32_t>(mult));
+          rescales.push_back(rescale);
+    }
+
+  return QSymm8PerChannelRescaleParams(shifts, mults, rescales);
+
+}
+
+QSymm8PerChannelRescaleParams QSymm8PerChannelRescaleParams::make_rescale_params(
+  const QSymm8PerChannelParams& weight_quant,
+  const qasymm8::QAsymm8Params& input_quant,
+  const qasymm8::QAsymm8Params& output_quant
+)
+{
+    std::vector<int32_t> shifts;
+    std::vector<int32_t> mults;
+    std::vector<float> rescales;
+
+    for(size_t s = 0; s< weight_quant.scales.size(); s++)
+    {
+          // Based on the gemmlowp approach: https://github.com/google/gemmlowp/blob/master/doc/quantization_example.cc
+          const float rescale = weight_quant.scales[s] * input_quant.scale / output_quant.scale;
+          const float shiftf = round(log2(0.5f / rescale));
+          const float multf = exp2(31.0f + shiftf)*rescale;
+
+          int64_t shift = static_cast<int64_t>(shiftf);
+          int64_t mult = static_cast<int64_t>(multf);
+
+          if (mult == (1ll << 31))
+          {
+            mult /= 2;
+            shift--;
+          }
+
+          assert(shift >= 0);
+          assert(mult <= std::numeric_limits<int32_t>::max());
+
+          shifts.push_back(static_cast<int32_t>(shift));
+          mults.push_back(static_cast<int32_t>(mult));
+          rescales.push_back(rescale);
+    }
+
+  return QSymm8PerChannelRescaleParams(shifts, mults, rescales);
+
+}
+
+QSymm8PerChannelRescaleParams::QSymm8PerChannelRescaleParams(std::vector<int32_t>& shifts, std::vector<int32_t>& multipliers, std::vector<float>& rescales)
+  : shifts(shifts), multipliers(multipliers), rescales(rescales)
+{
+}
+
+
+} // namespace qasymm8