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Use builtins for overflow detection in OverflowSafeInt on gcc/clang

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This commit is contained in:
Jonathan G Rennison
2020-04-20 21:48:04 +01:00
parent be3f03358f
commit 6821c0e945
2 changed files with 47 additions and 1 deletions
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25
src/core/overflowsafe_type.hpp
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@@ -46,12 +46,30 @@ public:
*/
inline OverflowSafeInt& operator += (const OverflowSafeInt& other)
{
#ifdef WITH_OVERFLOW_BUILTINS
if (unlikely(__builtin_add_overflow(this->m_value, other.m_value, &this->m_value))) {
this->m_value = (other.m_value < 0) ? T_MIN : T_MAX;
}
#else
if ((T_MAX - abs(other.m_value)) < abs(this->m_value) &&
(this->m_value < 0) == (other.m_value < 0)) {
this->m_value = (this->m_value < 0) ? T_MIN : T_MAX ;
} else {
this->m_value += other.m_value;
}
#endif
return *this;
}
inline OverflowSafeInt& operator -= (const OverflowSafeInt& other)
{
#ifdef WITH_OVERFLOW_BUILTINS
if (unlikely(__builtin_sub_overflow(this->m_value, other.m_value, &this->m_value))) {
this->m_value = (other.m_value < 0) ? T_MAX : T_MIN;
}
#else
*this += (-other);
#endif
return *this;
}
@@ -59,7 +77,6 @@ public:
inline OverflowSafeInt operator + (const OverflowSafeInt& other) const { OverflowSafeInt result = *this; result += other; return result; }
inline OverflowSafeInt operator + (const int other) const { OverflowSafeInt result = *this; result += (int64)other; return result; }
inline OverflowSafeInt operator + (const uint other) const { OverflowSafeInt result = *this; result += (int64)other; return result; }
inline OverflowSafeInt& operator -= (const OverflowSafeInt& other) { return *this += (-other); }
inline OverflowSafeInt operator - (const OverflowSafeInt& other) const { OverflowSafeInt result = *this; result -= other; return result; }
inline OverflowSafeInt operator - (const int other) const { OverflowSafeInt result = *this; result -= (int64)other; return result; }
inline OverflowSafeInt operator - (const uint other) const { OverflowSafeInt result = *this; result -= (int64)other; return result; }
@@ -77,11 +94,17 @@ public:
*/
inline OverflowSafeInt& operator *= (const int factor)
{
#ifdef WITH_OVERFLOW_BUILTINS
if (unlikely(__builtin_mul_overflow(this->m_value, factor, &this->m_value))) {
this->m_value = ((this->m_value < 0) == (factor < 0)) ? T_MAX : T_MIN;
}
#else
if (factor != 0 && (T_MAX / abs(factor)) < abs(this->m_value)) {
this->m_value = ((this->m_value < 0) == (factor < 0)) ? T_MAX : T_MIN ;
} else {
this->m_value *= factor ;
}
#endif
return *this;
}