From 53d092d34c1e9924151d8d3a228c04620c1baf5c Mon Sep 17 00:00:00 2001
From: Derek Lamberti <derek.lamberti@arm.com>
Date: Wed, 19 Feb 2020 13:40:56 +0000
Subject: IVGCVSW-4486 Introduce numeric_cast implementation

Change-Id: I3e64bca4a1709ac199513676579cf3c9a3090f26
Signed-off-by: Derek Lamberti <derek.lamberti@arm.com>
---
 CMakeLists.txt                        |   1 +
 include/armnn/utility/NumericCast.hpp | 124 ++++++++++++++++++++++++++++++++++
 src/armnn/test/UtilityTests.cpp       |  47 +++++++++++++
 3 files changed, 172 insertions(+)
 create mode 100644 include/armnn/utility/NumericCast.hpp

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8d63e43c04..5002eb4e0b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -249,6 +249,7 @@ list(APPEND armnn_sources
     include/armnn/profiling/ISendTimelinePacket.hpp
     include/armnn/utility/Assert.hpp
     include/armnn/utility/IgnoreUnused.hpp
+    include/armnn/utility/NumericCast.hpp
     include/armnn/utility/PolymorphicDowncast.hpp
     profiling/common/include/SocketConnectionException.hpp
     src/armnn/layers/LayerCloneBase.hpp
diff --git a/include/armnn/utility/NumericCast.hpp b/include/armnn/utility/NumericCast.hpp
new file mode 100644
index 0000000000..62c7d11543
--- /dev/null
+++ b/include/armnn/utility/NumericCast.hpp
@@ -0,0 +1,124 @@
+//
+// Copyright © 2020 Arm Ltd. All rights reserved.
+// SPDX-License-Identifier: MIT
+//
+
+#pragma once
+
+#include "Assert.hpp"
+
+#include <type_traits>
+#include <limits>
+
+namespace armnn
+{
+
+#if !defined(NDEBUG) || defined(ARMNN_NUMERIC_CAST_TESTABLE)
+#define ENABLE_NUMERIC_CAST_CHECKS 1
+#else
+#define ENABLE_NUMERIC_CAST_CHECKS 0
+#endif
+
+#if defined(ARMNN_NUMERIC_CAST_TESTABLE)
+#   define ARMNN_NUMERIC_CAST_CHECK(cond, msg) ConditionalThrow<std::bad_cast>(cond)
+#else
+#   define ARMNN_NUMERIC_CAST_CHECK(cond, msg) ARMNN_ASSERT_MSG(cond, msg)
+#endif
+
+template<typename Dest, typename Source>
+typename std::enable_if_t<
+    std::is_unsigned<Source>::value &&
+    std::is_unsigned<Dest>::value
+    , Dest>
+numeric_cast(Source source)
+{
+#if ENABLE_NUMERIC_CAST_CHECKS
+    if (source > std::numeric_limits<Dest>::max())
+    {
+        ARMNN_NUMERIC_CAST_CHECK(false, "numeric_cast failed casting unsigned type to "
+                                        "narrower unsigned type. Overflow detected.");
+    }
+#endif // ENABLE_NUMERIC_CAST_CHECKS
+
+    return static_cast<Dest>(source);
+}
+
+template<typename Dest, typename Source>
+typename std::enable_if_t<
+    std::is_signed<Source>::value &&
+    std::is_signed<Dest>::value
+    , Dest>
+numeric_cast(Source source)
+{
+    static_assert(!std::is_floating_point<Source>::value && !std::is_floating_point<Dest>::value,
+        "numeric_cast doesn't cast float.");
+
+#if ENABLE_NUMERIC_CAST_CHECKS
+    if (source > std::numeric_limits<Dest>::max())
+    {
+        ARMNN_NUMERIC_CAST_CHECK(false, "numeric_cast failed casting signed type to narrower signed type. "
+                                        "Overflow detected.");
+    }
+
+    if (source < std::numeric_limits<Dest>::lowest())
+    {
+        ARMNN_NUMERIC_CAST_CHECK(false, "numeric_cast failed casting signed type to narrower signed type. "
+                                        "Underflow detected.");
+    }
+#endif // ENABLE_NUMERIC_CAST_CHECKS
+
+    return static_cast<Dest>(source);
+}
+
+// numeric cast from unsigned to signed checked for narrowing overflows
+template<typename Dest, typename Source>
+typename std::enable_if_t<
+    std::is_signed<Dest>::value &&
+    std::is_unsigned<Source>::value
+    , Dest>
+numeric_cast(Source sValue)
+{
+    static_assert(!std::is_floating_point<Dest>::value, "numeric_cast doesn't cast to float.");
+
+#if ENABLE_NUMERIC_CAST_CHECKS
+    if (sValue > static_cast< typename std::make_unsigned<Dest>::type >(std::numeric_limits<Dest>::max()))
+    {
+        ARMNN_NUMERIC_CAST_CHECK(false, "numeric_cast failed casting unsigned type to signed type. "
+                                        "Overflow detected.");
+    }
+#endif // ENABLE_NUMERIC_CAST_CHECKS
+
+    return static_cast<Dest>(sValue);
+}
+
+// numeric cast from signed to unsigned checked for underflows and narrowing overflows
+template<typename Dest, typename Source>
+typename std::enable_if_t<
+    std::is_unsigned<Dest>::value &&
+    std::is_signed<Source>::value
+    , Dest>
+numeric_cast(Source sValue)
+{
+    static_assert(!std::is_floating_point<Source>::value && !std::is_floating_point<Dest>::value,
+        "numeric_cast doesn't cast floats.");
+
+#if ENABLE_NUMERIC_CAST_CHECKS
+    if (sValue < 0)
+    {
+        ARMNN_NUMERIC_CAST_CHECK(false, "numeric_cast failed casting negative value to unsigned type. "
+                                        "Underflow detected.");
+    }
+
+    if (static_cast< typename std::make_unsigned<Source>::type >(sValue) > std::numeric_limits<Dest>::max())
+    {
+        ARMNN_NUMERIC_CAST_CHECK(false, "numeric_cast failed casting signed type to unsigned type. "
+                                        "Overflow detected.");
+    }
+
+#endif // ENABLE_NUMERIC_CAST_CHECKS
+    return static_cast<Dest>(sValue);
+}
+
+#undef ENABLE_NUMERIC_CAST_CHECKS
+
+} //namespace armnn
\ No newline at end of file
diff --git a/src/armnn/test/UtilityTests.cpp b/src/armnn/test/UtilityTests.cpp
index 5309d82ce4..7be5c9518a 100644
--- a/src/armnn/test/UtilityTests.cpp
+++ b/src/armnn/test/UtilityTests.cpp
@@ -8,9 +8,11 @@
 #include <boost/polymorphic_cast.hpp>
 
 #define ARMNN_POLYMORPHIC_CAST_TESTABLE
+#define ARMNN_NUMERIC_CAST_TESTABLE
 
 #include <armnn/utility/IgnoreUnused.hpp>
 #include <armnn/utility/PolymorphicDowncast.hpp>
+#include <armnn/utility/NumericCast.hpp>
 
 #include <armnn/Exceptions.hpp>
 
@@ -53,4 +55,49 @@ BOOST_AUTO_TEST_CASE(PolymorphicDowncast)
     armnn::IgnoreUnused(ptr1, ptr2);
 }
 
+
+BOOST_AUTO_TEST_CASE(NumericCast)
+{
+    using namespace armnn;
+
+    // To 8 bit
+    BOOST_CHECK_THROW(numeric_cast<unsigned char>(-1), std::bad_cast);
+    BOOST_CHECK_THROW(numeric_cast<unsigned char>(1 << 8), std::bad_cast);
+    BOOST_CHECK_THROW(numeric_cast<unsigned char>(1L << 16), std::bad_cast);
+    BOOST_CHECK_THROW(numeric_cast<unsigned char>(1LL << 32), std::bad_cast);
+
+    BOOST_CHECK_THROW(numeric_cast<signed char>((1L << 8)*-1), std::bad_cast);
+    BOOST_CHECK_THROW(numeric_cast<signed char>((1L << 15)*-1), std::bad_cast);
+    BOOST_CHECK_THROW(numeric_cast<signed char>((1LL << 31)*-1), std::bad_cast);
+
+    BOOST_CHECK_NO_THROW(numeric_cast<unsigned char>(1U));
+    BOOST_CHECK_NO_THROW(numeric_cast<unsigned char>(1L));
+    BOOST_CHECK_NO_THROW(numeric_cast<signed char>(-1));
+    BOOST_CHECK_NO_THROW(numeric_cast<signed char>(-1L));
+    BOOST_CHECK_NO_THROW(numeric_cast<signed char>((1 << 7)*-1));
+
+    // To 16 bit
+    BOOST_CHECK_THROW(numeric_cast<uint16_t>(-1), std::bad_cast);
+    BOOST_CHECK_THROW(numeric_cast<uint16_t>(1L << 16), std::bad_cast);
+    BOOST_CHECK_THROW(numeric_cast<uint16_t>(1LL << 32), std::bad_cast);
+
+    BOOST_CHECK_THROW(numeric_cast<int16_t>(1L << 15), std::bad_cast);
+    BOOST_CHECK_THROW(numeric_cast<int16_t>(1LL << 31), std::bad_cast);
+
+    BOOST_CHECK_NO_THROW(numeric_cast<uint16_t>(1L << 8));
+    BOOST_CHECK_NO_THROW(numeric_cast<int16_t>(1L << 7));
+    BOOST_CHECK_NO_THROW(numeric_cast<int16_t>((1L << 15)*-1));
+
+    // To 32 bit
+    BOOST_CHECK_NO_THROW(numeric_cast<uint32_t>(1));
+    BOOST_CHECK_NO_THROW(numeric_cast<uint32_t>(1 << 8));
+    BOOST_CHECK_NO_THROW(numeric_cast<uint32_t>(1L << 16));
+    BOOST_CHECK_NO_THROW(numeric_cast<uint32_t>(1LL << 31));
+
+    BOOST_CHECK_NO_THROW(numeric_cast<int32_t>(-1));
+    BOOST_CHECK_NO_THROW(numeric_cast<int32_t>((1L << 8)*-1));
+    BOOST_CHECK_NO_THROW(numeric_cast<int32_t>((1L << 16)*-1));
+    BOOST_CHECK_NO_THROW(numeric_cast<int32_t>((1LL << 31)*-1));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
-- 
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