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More efficient implementations of sign_extend

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This commit is contained in:
John Wellbelove 2018-04-16 19:17:41 +01:00
parent e3b40c1eb4
commit ea9a1e51c9
1 changed files with 18 additions and 38 deletions
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56
include/etl/binary.h
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@ -270,16 +270,12 @@ namespace etl
STATIC_ASSERT(etl::is_signed<TReturn>::value, "TReturn not a signed type");
STATIC_ASSERT(NBITS <= std::numeric_limits<TReturn>::digits, "NBITS too large for return type");
const TReturn negative = (TReturn(1) << (NBITS - 1));
TReturn signed_value = value & ((1 << NBITS) - 1);
if ((signed_value & negative) != 0)
struct S
{
const TReturn sign_bits = ~((TReturn(1) << NBITS) - 1);
signed_value |= sign_bits;
}
signed value : NBITS;
} s;
return signed_value;
return (s.value = value);
}
//***************************************************************************
@ -290,22 +286,18 @@ namespace etl
template <typename TReturn, const size_t NBITS, const size_t SHIFT, typename TValue>
TReturn sign_extend(TValue value)
{
STATIC_ASSERT(etl::is_integral<TValue>::value, "TValue not an integral type");
STATIC_ASSERT(etl::is_integral<TValue>::value, "TValue not an integral type");
STATIC_ASSERT(etl::is_integral<TReturn>::value, "TReturn not an integral type");
STATIC_ASSERT(etl::is_signed<TReturn>::value, "TReturn not a signed type");
STATIC_ASSERT(etl::is_signed<TReturn>::value, "TReturn not a signed type");
STATIC_ASSERT(NBITS <= std::numeric_limits<TReturn>::digits, "NBITS too large for return type");
STATIC_ASSERT(SHIFT <= std::numeric_limits<TReturn>::digits, "SHIFT too large");
const TReturn negative = (TReturn(1) << (NBITS - 1));
TReturn signed_value = (value >> SHIFT) & ((1 << NBITS) - 1);
if ((signed_value & negative) != 0)
struct S
{
const TReturn sign_bits = ~((TReturn(1) << NBITS) - 1);
signed_value |= sign_bits;
}
signed value : NBITS;
} s;
return signed_value;
return (s.value = (value >> SHIFT));
}
//***************************************************************************
@ -320,16 +312,10 @@ namespace etl
STATIC_ASSERT(etl::is_signed<TReturn>::value, "TReturn not a signed type");
assert(NBITS <= std::numeric_limits<TReturn>::digits);
const TReturn negative = (TReturn(1) << (NBITS - 1));
TReturn signed_value = value & ((1 << NBITS) - 1);
TReturn mask = TReturn(1U) << (NBITS - 1);
value = value & ((1U << NBITS) - 1);
if ((signed_value & negative) != 0)
{
const TReturn sign_bits = ~((TReturn(1) << NBITS) - 1);
signed_value |= sign_bits;
}
return signed_value;
return TReturn((value ^ mask) - mask);
}
//***************************************************************************
@ -340,21 +326,15 @@ namespace etl
template <typename TReturn, typename TValue>
TReturn sign_extend(TValue value, const size_t NBITS, const size_t SHIFT)
{
STATIC_ASSERT(etl::is_integral<TValue>::value, "TValue not an integral type");
STATIC_ASSERT(etl::is_integral<TValue>::value, "TValue not an integral type");
STATIC_ASSERT(etl::is_integral<TReturn>::value, "TReturn not an integral type");
STATIC_ASSERT(etl::is_signed<TReturn>::value, "TReturn not a signed type");
STATIC_ASSERT(etl::is_signed<TReturn>::value, "TReturn not a signed type");
assert(NBITS <= std::numeric_limits<TReturn>::digits);
const TReturn negative = (TReturn(1) << (NBITS - 1));
TReturn signed_value = (value >> SHIFT) & ((1 << NBITS) - 1);
TReturn mask = TReturn(1U) << (NBITS - 1);
value = (value >> SHIFT) & ((1U << NBITS) - 1);
if ((signed_value & negative) != 0)
{
const TReturn sign_bits = ~((TReturn(1) << NBITS) - 1);
signed_value |= sign_bits;
}
return signed_value;
return TReturn((value ^ mask) - mask);
}
//***************************************************************************