IVGCVSW-798 Add Softmax NEON support for QASYMM8

Change-Id: I4f2cca52caf210fdb7d6bb7e9436ac51cb5088b4
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/112398
Reviewed-by: Anthony Barbier <anthony.barbier@arm.com>
Tested-by: Jenkins <bsgcomp@arm.com>

15 files changed, 133 insertions, 159 deletions

diff --git a/arm_compute/core/AccessWindowAutoPadding.h b/arm_compute/core/AccessWindowAutoPadding.h
index 0a3344b115..0003bb26cd 100644
--- a/arm_compute/core/AccessWindowAutoPadding.h
+++ b/arm_compute/core/AccessWindowAutoPadding.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017 ARM Limited.
+ * Copyright (c) 2017-2018 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -66,7 +66,7 @@ public:
 
     // Inherited methods overridden:
     bool update_window_if_needed(Window &window) const override;
-    bool update_padding_if_needed(const Window &window) const override;
+    bool update_padding_if_needed(const Window &window) override;
     ValidRegion compute_valid_region(const Window &window, ValidRegion input_valid_region, bool border_undefined, BorderSize border_size) const override;
 
 private:
diff --git a/arm_compute/core/AccessWindowStatic.h b/arm_compute/core/AccessWindowStatic.h
index 6dcba072c4..a0ceeda273 100644
--- a/arm_compute/core/AccessWindowStatic.h
+++ b/arm_compute/core/AccessWindowStatic.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017 ARM Limited.
+ * Copyright (c) 2017-2018 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -79,7 +79,7 @@ public:
 
     // Inherited methods overriden:
     bool update_window_if_needed(Window &window) const override;
-    bool update_padding_if_needed(const Window &window) const override;
+    bool update_padding_if_needed(const Window &window) override;
     ValidRegion compute_valid_region(const Window &window, ValidRegion input_valid_region, bool border_undefined, BorderSize border_size) const override;
 
     ITensorInfo *_info;
diff --git a/arm_compute/core/AccessWindowTranspose.h b/arm_compute/core/AccessWindowTranspose.h
index 102860f9d8..4e59e58dce 100644
--- a/arm_compute/core/AccessWindowTranspose.h
+++ b/arm_compute/core/AccessWindowTranspose.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017 ARM Limited.
+ * Copyright (c) 2017-2018 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -40,7 +40,7 @@ class AccessWindowTranspose : public AccessWindowRectangle
 public:
     using AccessWindowRectangle::AccessWindowRectangle;
     bool update_window_if_needed(Window &window) const override;
-    bool update_padding_if_needed(const Window &window) const override;
+    bool update_padding_if_needed(const Window &window) override;
     using AccessWindowRectangle::compute_valid_region;
     ValidRegion compute_valid_region(const Window &window, ValidRegion input_valid_region, bool border_undefined, BorderSize border_size) const override;
 };
diff --git a/arm_compute/core/Error.h b/arm_compute/core/Error.h
index 97dbba3fab..56c7ccdd93 100644
--- a/arm_compute/core/Error.h
+++ b/arm_compute/core/Error.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2017 ARM Limited.
+ * Copyright (c) 2016-2018 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -86,7 +86,7 @@ public:
         return _error_description;
     }
     /** Throws a runtime exception in case it contains a valid error status */
-    void throw_if_error()
+    void throw_if_error() const
     {
         if(!bool(*this))
         {
@@ -96,7 +96,7 @@ public:
 
 private:
     /** Internal throwing function */
-    [[noreturn]] void internal_throw_on_error();
+    [[noreturn]] void internal_throw_on_error() const;
 
 private:
     ErrorCode   _code;
diff --git a/arm_compute/core/FixedPoint.inl b/arm_compute/core/FixedPoint.inl
index 5ea0f6c825..9c7e35ab16 100644
--- a/arm_compute/core/FixedPoint.inl
+++ b/arm_compute/core/FixedPoint.inl
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017 ARM Limited.
+ * Copyright (c) 2017-2018 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -22,27 +22,11 @@
  * SOFTWARE.
  */
 #include "arm_compute/core/Error.h"
+#include "arm_compute/core/utils/misc/utility.h"
 
 #include <cmath>
 #include <limits>
 
-namespace
-{
-template <typename TpIn, typename TpSat>
-inline TpSat saturate_convert(TpIn a)
-{
-    if(a > std::numeric_limits<TpSat>::max())
-    {
-        a = std::numeric_limits<TpSat>::max();
-    }
-    if(a < std::numeric_limits<TpSat>::min())
-    {
-        a = std::numeric_limits<TpSat>::min();
-    }
-    return static_cast<TpSat>(a);
-}
-} // namespace
-
 namespace arm_compute
 {
 inline qint8_t sqshl_qs8(qint8_t a, int shift)
@@ -50,7 +34,7 @@ inline qint8_t sqshl_qs8(qint8_t a, int shift)
     qint16_t tmp = static_cast<qint16_t>(a) << shift;
 
     // Saturate the result in case of overflow and cast to qint8_t
-    return saturate_convert<qint16_t, qint8_t>(tmp);
+    return utility::saturate_cast<qint8_t>(tmp);
 }
 
 inline qint16_t sqshl_qs16(qint16_t a, int shift)
@@ -58,7 +42,7 @@ inline qint16_t sqshl_qs16(qint16_t a, int shift)
     qint32_t tmp = static_cast<qint32_t>(a) << shift;
 
     // Saturate the result in case of overflow and cast to qint16_t
-    return saturate_convert<qint32_t, qint16_t>(tmp);
+    return utility::saturate_cast<qint16_t>(tmp);
 }
 
 inline qint8_t sshr_qs8(qint8_t a, int shift)
@@ -101,7 +85,7 @@ inline qint8_t sqadd_qs8(qint8_t a, qint8_t b)
     qint16_t tmp = (static_cast<qint16_t>(a) + static_cast<qint16_t>(b));
 
     // Saturate the result in case of overflow and cast to qint8_t
-    return saturate_convert<qint16_t, qint8_t>(tmp);
+    return utility::saturate_cast<qint8_t>(tmp);
 }
 
 inline qint16_t sqadd_qs16(qint16_t a, qint16_t b)
@@ -110,7 +94,7 @@ inline qint16_t sqadd_qs16(qint16_t a, qint16_t b)
     qint32_t tmp = (static_cast<qint32_t>(a) + static_cast<qint32_t>(b));
 
     // Saturate the result in case of overflow and cast to qint16_t
-    return saturate_convert<qint32_t, qint16_t>(tmp);
+    return utility::saturate_cast<qint16_t>(tmp);
 }
 
 inline qint32_t sqadd_qs32(qint32_t a, qint32_t b)
@@ -119,7 +103,7 @@ inline qint32_t sqadd_qs32(qint32_t a, qint32_t b)
     qint64_t tmp = (static_cast<qint64_t>(a) + static_cast<qint64_t>(b));
 
     // Saturate the result in case of overflow and cast to qint32_t
-    return saturate_convert<qint64_t, qint32_t>(tmp);
+    return utility::saturate_cast<qint32_t>(tmp);
 }
 
 inline qint8_t ssub_qs8(qint8_t a, qint8_t b)
@@ -138,7 +122,7 @@ inline qint8_t sqsub_qs8(qint8_t a, qint8_t b)
     qint16_t tmp = static_cast<qint16_t>(a) - static_cast<qint16_t>(b);
 
     // Saturate the result in case of overflow and cast to qint8_t
-    return saturate_convert<qint16_t, qint8_t>(tmp);
+    return utility::saturate_cast<qint8_t>(tmp);
 }
 
 inline qint16_t sqsub_qs16(qint16_t a, qint16_t b)
@@ -147,7 +131,7 @@ inline qint16_t sqsub_qs16(qint16_t a, qint16_t b)
     qint32_t tmp = static_cast<qint32_t>(a) - static_cast<qint32_t>(b);
 
     // Saturate the result in case of overflow and cast to qint16_t
-    return saturate_convert<qint32_t, qint16_t>(tmp);
+    return utility::saturate_cast<qint16_t>(tmp);
 }
 
 inline qint8_t smul_qs8(qint8_t a, qint8_t b, int fixed_point_position)
@@ -183,7 +167,7 @@ inline qint8_t sqmul_qs8(qint8_t a, qint8_t b, int fixed_point_position)
     // Rounding up
     tmp += round_up_const;
 
-    return saturate_convert<qint16_t, qint8_t>(tmp >> fixed_point_position);
+    return utility::saturate_cast<qint8_t>(tmp >> fixed_point_position);
 }
 
 inline qint16_t sqmul_qs16(qint16_t a, qint16_t b, int fixed_point_position)
@@ -195,7 +179,7 @@ inline qint16_t sqmul_qs16(qint16_t a, qint16_t b, int fixed_point_position)
     // Rounding up
     tmp += round_up_const;
 
-    return saturate_convert<qint32_t, qint16_t>(tmp >> fixed_point_position);
+    return utility::saturate_cast<qint16_t>(tmp >> fixed_point_position);
 }
 
 inline qint16_t sqmull_qs8(qint8_t a, qint8_t b, int fixed_point_position)
@@ -394,7 +378,7 @@ inline float scvt_f32_qs8(qint8_t a, int fixed_point_position)
 inline qint8_t sqcvt_qs8_f32(float a, int fixed_point_position)
 {
     // round_nearest_integer(a * 2^(fixed_point_position))
-    return saturate_convert<float, qint8_t>(a * (1 << fixed_point_position) + ((a >= 0) ? 0.5 : -0.5));
+    return utility::saturate_cast<qint8_t>(a * (1 << fixed_point_position) + ((a >= 0) ? 0.5 : -0.5));
 }
 
 inline float scvt_f32_qs16(qint16_t a, int fixed_point_position)
@@ -405,18 +389,18 @@ inline float scvt_f32_qs16(qint16_t a, int fixed_point_position)
 inline qint16_t sqcvt_qs16_f32(float a, int fixed_point_position)
 {
     // round_nearest_integer(a * 2^(fixed_point_position))
-    return saturate_convert<float, qint16_t>(a * (1 << fixed_point_position) + ((a >= 0) ? 0.5 : -0.5));
+    return utility::saturate_cast<qint16_t>(a * (1 << fixed_point_position) + ((a >= 0) ? 0.5 : -0.5));
 }
 
 inline qint8_t sqmovn_qs16(qint16_t a)
 {
     // Saturate the result in case of overflow and cast to qint8_t
-    return saturate_convert<qint16_t, qint8_t>(a);
+    return utility::saturate_cast<qint8_t>(a);
 }
 
 inline qint16_t sqmovn_qs32(qint32_t a)
 {
     // Saturate the result in case of overflow and cast to qint16_t
-    return saturate_convert<qint32_t, qint16_t>(a);
+    return utility::saturate_cast<qint16_t>(a);
 }
 }
diff --git a/arm_compute/core/Helpers.h b/arm_compute/core/Helpers.h
index e01e4baa6b..c6a7db4f96 100644
--- a/arm_compute/core/Helpers.h
+++ b/arm_compute/core/Helpers.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2018 ARM Limited.
+ * Copyright (c) 2016-2018 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -350,7 +350,7 @@ bool update_window_and_padding(Window &win, Ts &&... patterns)
 
     bool padding_changed = false;
 
-    utility::for_each([&](const IAccessWindow & w)
+    utility::for_each([&](IAccessWindow & w)
     {
         padding_changed |= w.update_padding_if_needed(win);
     },
diff --git a/arm_compute/core/IAccessWindow.h b/arm_compute/core/IAccessWindow.h
index cf7490d53e..583041a48b 100644
--- a/arm_compute/core/IAccessWindow.h
+++ b/arm_compute/core/IAccessWindow.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017 ARM Limited.
+ * Copyright (c) 2017-2018 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -85,7 +85,7 @@ public:
      *
      * @return True if the padding has been changed.
      */
-    virtual bool update_padding_if_needed(const Window &window) const = 0;
+    virtual bool update_padding_if_needed(const Window &window) = 0;
     /** Compute the valid region based on access pattern and valid region of the inputs.
      *
      * @note This method assumes that there is no border.
@@ -168,7 +168,7 @@ public:
     ValidRegion compute_valid_region(const Window &window, ValidRegion input_valid_region, bool border_undefined, BorderSize border_size) const override;
 
     bool update_window_if_needed(Window &window) const override;
-    bool update_padding_if_needed(const Window &window) const override;
+    bool update_padding_if_needed(const Window &window) override;
 
 protected:
     ITensorInfo *_info;
diff --git a/arm_compute/core/ITensorInfo.h b/arm_compute/core/ITensorInfo.h
index 9a67712f3d..9112f3ea18 100644
--- a/arm_compute/core/ITensorInfo.h
+++ b/arm_compute/core/ITensorInfo.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2017 ARM Limited.
+ * Copyright (c) 2016-2018 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -79,7 +79,7 @@ public:
      *
      * @return Reference to this ITensorInfo object
      */
-    virtual ITensorInfo &set_tensor_shape(TensorShape shape) = 0;
+    virtual ITensorInfo &set_tensor_shape(const TensorShape &shape) = 0;
     /** Set the fixed point position to the specified value
      *
      * @warning The fixed point position must be set once the data type has been configured
@@ -95,7 +95,7 @@ public:
      *
      * @return Reference to this ITensorInfo object
      */
-    virtual ITensorInfo &set_quantization_info(QuantizationInfo quantization_info) = 0;
+    virtual ITensorInfo &set_quantization_info(const QuantizationInfo &quantization_info) = 0;
     /** Resets the padding settings of the tensor.
     *
     * @return Reference to this ITensorInfo object
@@ -214,7 +214,7 @@ public:
      *
      * @param[in] valid_region Valid region to set.
      */
-    virtual void set_valid_region(ValidRegion valid_region) = 0;
+    virtual void set_valid_region(const ValidRegion &valid_region) = 0;
 
     /** Get the quantization settings (scale and offset) of the tensor.
     *
diff --git a/arm_compute/core/NEON/kernels/NESoftmaxLayerKernel.h b/arm_compute/core/NEON/kernels/NESoftmaxLayerKernel.h
index bd0e642d76..c30a4cd23d 100644
--- a/arm_compute/core/NEON/kernels/NESoftmaxLayerKernel.h
+++ b/arm_compute/core/NEON/kernels/NESoftmaxLayerKernel.h
@@ -43,13 +43,13 @@ public:
     NELogits1DMaxKernel();
     /** Set the input and output tensors.
      *
-     * @param[in]  input  Source tensor. Data types supported: QS8/QS16/F16/F32.
+     * @param[in]  input  Source tensor. Data types supported: QASYMM8/QS8/QS16/F16/F32.
      * @param[out] output Destination tensor. Data types supported: same as @p input
      */
     void configure(const ITensor *input, ITensor *output);
     /** Static function to check if given info will lead to a valid configuration of @ref NELogits1DMaxKernel
      *
-     * @param[in] input  Source tensor. Data types supported: QS8/QS16/F16/F32
+     * @param[in] input  Source tensor. Data types supported: QASYMM8/QS8/QS16/F16/F32.
      * @param[in] output Destination tensor. Data types supported: same as @p input
      *
      * @return a status
@@ -61,117 +61,71 @@ public:
     BorderSize border_size() const override;
 
 private:
-    using Logits1DMaxFunction = void(const ITensor *in, ITensor *out, const Window &window);
+    using Logits1DMaxFunction = void(const ITensor &in, ITensor &out, const Window &window);
 
 private:
     Logits1DMaxFunction *_func;
     BorderSize           _border_size;
 };
 
-/** Interface for shifting the logits values around the max value and exponentiating the result */
-class NELogits1DShiftExpSumKernel : public INEKernel
+/** Interface for softmax computation for QASYMM8 with pre-computed max. */
+class NELogits1DSoftmaxKernel : public INEKernel
 {
 public:
     const char *name() const override
     {
-        return "NELogits1DShiftExpSumKernel";
+        return "NELogits1DSoftmaxKernel";
     }
     /** Default constructor */
-    NELogits1DShiftExpSumKernel();
+    NELogits1DSoftmaxKernel();
     /** Prevent instances of this class from being copied (As this class contains pointers) */
-    NELogits1DShiftExpSumKernel(const NELogits1DShiftExpSumKernel &) = delete;
+    NELogits1DSoftmaxKernel(const NELogits1DSoftmaxKernel &) = delete;
     /** Prevent instances of this class from being copied (As this class contains pointers) */
-    NELogits1DShiftExpSumKernel &operator=(const NELogits1DShiftExpSumKernel &) = delete;
+    NELogits1DSoftmaxKernel &operator=(const NELogits1DSoftmaxKernel &) = delete;
     /** Allow instances of this class to be moved */
-    NELogits1DShiftExpSumKernel(NELogits1DShiftExpSumKernel &&) = default;
+    NELogits1DSoftmaxKernel(NELogits1DSoftmaxKernel &&) = default;
     /** Allow instances of this class to be moved */
-    NELogits1DShiftExpSumKernel &operator=(NELogits1DShiftExpSumKernel &&) = default;
+    NELogits1DSoftmaxKernel &operator=(NELogits1DSoftmaxKernel &&) = default;
     /** Default destructor */
-    ~NELogits1DShiftExpSumKernel() = default;
+    ~NELogits1DSoftmaxKernel() = default;
     /** Set the input and output tensors.
      *
-     * @param[in]  input  Source tensor. Data types supported: QS8/QS16/F16/F32.
-     * @param[in]  max    Max values tensor. Data types supported: same as @p input.
+     * @param[in]  input  Source tensor. Data types supported: QASYMM8/QS8/QS16/F16/F32.
+     * @param[in]  max    Max values tensor. Same shape as input with dimension 0 set to 1.
+     *                    Data types supported: same as @p input.
      * @param[out] output Destination tensor. Data types supported: same as @p input.
-     * @param[out] sum    Sum of 1D logits tensor. Data types supported: same as @p input.
-     * @param[in]  beta   (Optional) A scaling factor for the exponent. QS8/QS16 only support a beta value of 1.
-     */
-    void configure(const ITensor *input, const ITensor *max, ITensor *output, ITensor *sum, float beta = 1.0f);
-    /** Static function to check if given info will lead to a valid configuration of @ref NELogits1DShiftExpSumKernel
-     *
-     * @param[in] input  Source tensor. Data types supported: QS8/QS16/F16/F32
-     * @param[in] max    Max values tensor. Data types supported: same as @p input
-     * @param[in] output Destination tensor. Data types supported: same as @p input.
-     * @param[in] sum    Sum of 1D logits tensor. Data types supported: same as @p input.
-     * @param[in] beta   (Optional) A scaling factor for the exponent. QS8/QS16 only support a beta value of 1.
-     *
-     * @return a status
-     */
-    static Status validate(const ITensorInfo *input, const ITensorInfo *max, const ITensorInfo *output, const ITensorInfo *sum, float beta = 1.0f);
-
-    // Inherited methods overridden:
-    void run(const Window &window, const ThreadInfo &info) override;
-
-private:
-    using Logits1DShiftExpSumFunction = void(const ITensor *in, const ITensor *max, ITensor *out, ITensor *sum, const Window &window, float beta);
-
-private:
-    Logits1DShiftExpSumFunction *_func;
-    const ITensor               *_input;
-    const ITensor               *_max;
-    ITensor                     *_output;
-    ITensor                     *_sum;
-    float                        _beta;
-};
-
-/** Interface for calculating the final step of the Softmax Layer where each logit value is multiplied by the inverse of the sum of the logits. */
-class NELogits1DNormKernel : public INEKernel
-{
-public:
-    const char *name() const override
-    {
-        return "NELogits1DNormKernel";
-    }
-    /** Default constructor */
-    NELogits1DNormKernel();
-    /** Prevent instances of this class from being copied (As this class contains pointers) */
-    NELogits1DNormKernel(const NELogits1DNormKernel &) = delete;
-    /** Prevent instances of this class from being copied (As this class contains pointers) */
-    NELogits1DNormKernel &operator=(const NELogits1DNormKernel &) = delete;
-    /** Allow instances of this class to be moved */
-    NELogits1DNormKernel(NELogits1DNormKernel &&) = default;
-    /** Allow instances of this class to be moved */
-    NELogits1DNormKernel &operator=(NELogits1DNormKernel &&) = default;
-    /** Default destructor */
-    ~NELogits1DNormKernel() = default;
-    /** Set the input and output tensors.
+     * @param[in]  beta   A scaling factor for the exponent.
      *
-     * @param[in]  input  Source tensor. Data types supported: QS8/QS16/F16/F32.
-     * @param[in]  sum    Sum tensor. The number of dimensions should be dim(input)-1. Data types supported: same as @p input.
-     * @param[out] output Destination tensor. Data types supported: same as @p input.
+     * @param      tmp    Auxiliary tensor. Must be type F32 and same shape as the input.
      */
-    void configure(const ITensor *input, const ITensor *sum, ITensor *output);
-    /** Static function to check if given info will lead to a valid configuration of @ref NELogits1DNormKernel
+    void configure(const ITensor *input, const ITensor *max, ITensor *output, const float beta, ITensor *tmp);
+    /** Static function to check if given info will lead to a valid configuration of @ref NELogits1DSoftmaxKernel
      *
-     * @param[in] input  Source tensor. Data types supported: QS8/QS16/S32/F16/F32
-     * @param[in] sum    Sum tensor. The number of dimensions should be dim(input)-1. Data types supported: same as @p input.
-     * @param[in] output Destination tensor. Data types supported: same as @p input.
+     * @param[in] input  Source tensor info. Data types supported: QASYMM8/QS8/QS16/F16/F32.
+     * @param[in] max    Max values tensor info. Same shape as input with dimension 0 set to 1.
+     *                   Data types supported: same as @p input.
+     * @param[in] output Destination tensor info. Data types supported: same as @p input.
+     * @param[in] beta   A scaling factor for the exponent.
+     * @param[in] tmp    Tensor info of auxiliary. Must be type F32 and same shape as the input.
      *
      * @return a status
      */
-    static Status validate(const ITensorInfo *input, const ITensorInfo *sum, const ITensorInfo *output);
+    static Status validate(const ITensorInfo *input, const ITensorInfo *max,
+                           const ITensorInfo *output, const float beta, const ITensorInfo *tmp);
 
     // Inherited methods overridden:
     void run(const Window &window, const ThreadInfo &info) override;
 
 private:
-    using Logits1DNormFunction = void(const ITensor *in, const ITensor *sum, ITensor *out, const Window &window);
+    using LogitsSoftmaxFunction = void(const ITensor &in, const ITensor &max, void *const tmp, ITensor &out, const float beta,
+                                       const Window &window);
 
-private:
-    Logits1DNormFunction *_func;
-    const ITensor        *_input;
-    const ITensor        *_sum;
-    ITensor              *_output;
+    LogitsSoftmaxFunction *_func;
+    const ITensor         *_input;
+    const ITensor         *_max;
+    ITensor               *_output;
+    float                  _beta;
+    ITensor               *_tmp; //Temporary. Used internally
 };
 } // namespace arm_compute
 #endif /*__ARM_COMPUTE_NESOFTMAXLAYERKERNEL_H__ */
diff --git a/arm_compute/core/SubTensorInfo.h b/arm_compute/core/SubTensorInfo.h
index 67574f1326..7f4239d49b 100644
--- a/arm_compute/core/SubTensorInfo.h
+++ b/arm_compute/core/SubTensorInfo.h
@@ -98,8 +98,8 @@ public:
         _parent->set_fixed_point_position(fixed_point_position);
         return *this;
     };
-    ITensorInfo &set_tensor_shape(TensorShape shape) override;
-    ITensorInfo &set_quantization_info(QuantizationInfo quantization_info) override
+    ITensorInfo &set_tensor_shape(const TensorShape &shape) override;
+    ITensorInfo &set_quantization_info(const QuantizationInfo &quantization_info) override
     {
         ARM_COMPUTE_ERROR_ON(_parent == nullptr);
         _parent->set_quantization_info(quantization_info);
@@ -196,7 +196,7 @@ public:
     {
         return _valid_region;
     }
-    void set_valid_region(ValidRegion valid_region) override
+    void set_valid_region(const ValidRegion &valid_region) override
     {
         ARM_COMPUTE_ERROR_ON(_parent == nullptr);
         // Check if subtensor is valid if parent is configured
@@ -204,7 +204,7 @@ public:
         {
             ARM_COMPUTE_ERROR_ON_INVALID_SUBTENSOR_VALID_REGION(_parent->valid_region(), valid_region);
         }
-        _valid_region = std::move(valid_region);
+        _valid_region = valid_region;
     }
     QuantizationInfo quantization_info() const override
     {
diff --git a/arm_compute/core/TensorInfo.h b/arm_compute/core/TensorInfo.h
index 80ef7f8d5a..0b8989f942 100644
--- a/arm_compute/core/TensorInfo.h
+++ b/arm_compute/core/TensorInfo.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2017 ARM Limited.
+ * Copyright (c) 2016-2018 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -217,9 +217,9 @@ public:
     ITensorInfo &set_data_type(DataType data_type) override;
     ITensorInfo &set_num_channels(int num_channels) override;
     ITensorInfo &set_format(Format format) override;
-    ITensorInfo &set_tensor_shape(TensorShape shape) override;
+    ITensorInfo &set_tensor_shape(const TensorShape &shape) override;
     ITensorInfo &set_fixed_point_position(int fixed_point_position) override;
-    ITensorInfo &set_quantization_info(QuantizationInfo quantization_info) override;
+    ITensorInfo &set_quantization_info(const QuantizationInfo &quantization_info) override;
     ITensorInfo &reset_padding() override;
     bool         auto_padding() override;
     bool extend_padding(const PaddingSize &padding) override;
@@ -289,9 +289,9 @@ public:
     {
         return _valid_region;
     }
-    void set_valid_region(ValidRegion valid_region) override
+    void set_valid_region(const ValidRegion &valid_region) override
     {
-        _valid_region = std::move(valid_region);
+        _valid_region = valid_region;
     }
     QuantizationInfo quantization_info() const override
     {
diff --git a/arm_compute/core/TensorShape.h b/arm_compute/core/TensorShape.h
index ad102607e8..50f1211c18 100644
--- a/arm_compute/core/TensorShape.h
+++ b/arm_compute/core/TensorShape.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2017 ARM Limited.
+ * Copyright (c) 2016-2018 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -70,26 +70,30 @@ public:
      *
      * @param[in] dimension Dimension for which the value is set.
      * @param[in] value     Value to be set for the dimension.
+     *
+     * @return *this.
      */
-    void set(size_t dimension, size_t value)
+    TensorShape &set(size_t dimension, size_t value)
     {
         // Clear entire shape if one dimension is zero
         if(value == 0)
         {
             _num_dimensions = 0;
             std::fill(_id.begin(), _id.end(), 0);
-            return;
         }
+        else
+        {
+            // Make sure all empty dimensions are filled with 1
+            std::fill(_id.begin() + _num_dimensions, _id.end(), 1);
 
-        // Make sure all empty dimensions are filled with 1
-        std::fill(_id.begin() + _num_dimensions, _id.end(), 1);
-
-        // Set the specified dimension and increase the number of dimensions if
-        // necessary
-        Dimensions::set(dimension, value);
+            // Set the specified dimension and increase the number of dimensions if
+            // necessary
+            Dimensions::set(dimension, value);
 
-        // Correct number dimensions to ignore trailing dimensions of size 1
-        apply_dimension_correction();
+            // Correct number dimensions to ignore trailing dimensions of size 1
+            apply_dimension_correction();
+        }
+        return *this;
     }
 
     /** Accessor to remove the dimension n from the tensor shape.
diff --git a/arm_compute/core/Types.h b/arm_compute/core/Types.h
index 5197000bf9..aa415acebe 100644
--- a/arm_compute/core/Types.h
+++ b/arm_compute/core/Types.h
@@ -190,6 +190,21 @@ struct ValidRegion
         return anchor[d] + shape[d];
     }
 
+    /** Accessor to set the value of anchor and shape for one of the dimensions.
+     *
+     * @param[in] dimension Dimension for which the value is set.
+     * @param[in] start     Value to be set in anchor for the dimension.
+     * @param[in] size      Value to be set in shape for the dimension.
+     *
+     * @return *this.
+     */
+    ValidRegion &set(size_t dimension, int start, size_t size)
+    {
+        anchor.set(dimension, start);
+        shape.set(dimension, size);
+        return *this;
+    }
+
     Coordinates anchor;
     TensorShape shape;
 };
diff --git a/arm_compute/core/Utils.h b/arm_compute/core/Utils.h
index 51967b1762..fc89d97073 100644
--- a/arm_compute/core/Utils.h
+++ b/arm_compute/core/Utils.h
@@ -40,12 +40,19 @@
 
 namespace arm_compute
 {
+/** Calculate the rounded up quotient of val / m. */
+template <typename S, typename T>
+constexpr auto DIV_CEIL(S val, T m) -> decltype((val + m - 1) / m)
+{
+    return (val + m - 1) / m;
+}
+
 /** Computes the smallest number larger or equal to value that is a multiple of divisor. */
 template <typename S, typename T>
 inline auto ceil_to_multiple(S value, T divisor) -> decltype(((value + divisor - 1) / divisor) * divisor)
 {
     ARM_COMPUTE_ERROR_ON(value < 0 || divisor <= 0);
-    return ((value + divisor - 1) / divisor) * divisor;
+    return DIV_CEIL(value, divisor) * divisor;
 }
 
 /** Computes the largest number smaller or equal to value that is a multiple of divisor. */
@@ -56,13 +63,6 @@ inline auto floor_to_multiple(S value, T divisor) -> decltype((value / divisor)
     return (value / divisor) * divisor;
 }
 
-/** Calculate the rounded up quotient of val / m. */
-template <typename S, typename T>
-constexpr auto DIV_CEIL(S val, T m) -> decltype((val + m - 1) / m)
-{
-    return (val + m - 1) / m;
-}
-
 /** Returns the arm_compute library build information
  *
  * Contains the version number and the build options used to build the library
diff --git a/arm_compute/core/utils/misc/utility.h b/arm_compute/core/utils/misc/utility.h
index 45b3b5268e..e8d823b5bc 100644
--- a/arm_compute/core/utils/misc/utility.h
+++ b/arm_compute/core/utils/misc/utility.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017 ARM Limited.
+ * Copyright (c) 2017-2018 ARM Limited.
  *
  * SPDX-License-Identifier: MIT
  *
@@ -25,6 +25,7 @@
 #define __ARM_COMPUTE_MISC_UTILITY_H__
 
 #include <array>
+#include <limits>
 
 namespace arm_compute
 {
@@ -123,6 +124,22 @@ inline auto foldl(F &&func, T &&initial, U &&value, Us &&... values) -> decltype
 {
     return foldl(std::forward<F>(func), func(std::forward<T>(initial), std::forward<U>(value)), std::forward<Us>(values)...);
 }
+
+/** Type cast with saturation.
+ *
+ * @param[in] val Value of type U to cast.
+ *
+ * @return Original value clamped to numeric limits of T and converted to type T.
+ *
+ * @warning Numeric limits of T must be representable without loss in type U.
+ */
+template <typename T, typename U>
+T saturate_cast(U val)
+{
+    const auto low  = static_cast<U>(std::numeric_limits<T>::lowest());
+    const auto high = static_cast<U>(std::numeric_limits<T>::max());
+    return static_cast<T>(clamp(val, low, high));
+}
 } // namespace utility
 } // namespace arm_compute
 #endif /* __ARM_COMPUTE_MISC_UTILITY_H__ */