IVGCVSW-1898 : Ref backend folder structure

* Reference backend is renamed to backends/reference as per
  https://confluence.arm.com/display/MLENG/Pluggable+backends

Change-Id: I27a13c274eb60995dfb459e3c49c0e2f60bcd32c

1 files changed, 71 insertions, 0 deletions

diff --git a/src/backends/reference/workloads/ConvImpl.cpp b/src/backends/reference/workloads/ConvImpl.cpp
new file mode 100644
index 0000000000..8743a2bd0d
--- /dev/null
+++ b/src/backends/reference/workloads/ConvImpl.cpp
@@ -0,0 +1,71 @@
+//
+// Copyright © 2017 Arm Ltd. All rights reserved.
+// SPDX-License-Identifier: MIT
+//
+
+#include "ConvImpl.hpp"
+
+#include <boost/assert.hpp>
+
+#include <cmath>
+#include <limits>
+
+namespace armnn
+{
+
+QuantizedMultiplierSmallerThanOne::QuantizedMultiplierSmallerThanOne(float multiplier)
+{
+    BOOST_ASSERT(multiplier >= 0.0f && multiplier < 1.0f);
+    if (multiplier == 0.0f)
+    {
+        m_Multiplier = 0;
+        m_RightShift = 0;
+    }
+    else
+    {
+        const double q = std::frexp(multiplier, &m_RightShift);
+        m_RightShift = -m_RightShift;
+        int64_t qFixed = static_cast<int64_t>(std::round(q * (1ll << 31)));
+        BOOST_ASSERT(qFixed <= (1ll << 31));
+        if (qFixed == (1ll << 31))
+        {
+            qFixed /= 2;
+            --m_RightShift;
+        }
+        BOOST_ASSERT(m_RightShift >= 0);
+        BOOST_ASSERT(qFixed <= std::numeric_limits<int32_t>::max());
+        m_Multiplier = static_cast<int32_t>(qFixed);
+    }
+}
+
+int32_t QuantizedMultiplierSmallerThanOne::operator*(int32_t rhs) const
+{
+    int32_t x = SaturatingRoundingDoublingHighMul(rhs, m_Multiplier);
+    return RoundingDivideByPOT(x, m_RightShift);
+}
+
+int32_t QuantizedMultiplierSmallerThanOne::SaturatingRoundingDoublingHighMul(int32_t a, int32_t b)
+{
+    // Check for overflow.
+    if (a == b && a == std::numeric_limits<int32_t>::min())
+    {
+        return std::numeric_limits<int32_t>::max();
+    }
+    int64_t a_64(a);
+    int64_t b_64(b);
+    int64_t ab_64 = a_64 * b_64;
+    int32_t nudge = ab_64 >= 0 ? (1 << 30) : (1 - (1 << 30));
+    int32_t ab_x2_high32 = static_cast<std::int32_t>((ab_64 + nudge) / (1ll << 31));
+    return ab_x2_high32;
+}
+
+int32_t QuantizedMultiplierSmallerThanOne::RoundingDivideByPOT(int32_t x, int exponent)
+{
+    BOOST_ASSERT(exponent >= 0 && exponent <= 31);
+    int32_t mask = (1 << exponent) - 1;
+    int32_t remainder = x & mask;
+    int32_t threshold = (mask >> 1) + (x < 0 ? 1 : 0);
+    return (x >> exponent) + (remainder > threshold ? 1 : 0);
+}
+
+} //namespace armnn