On 16/04/12 01:10, Michael Kochetkov wrote:
boost uses the following comparison operator: inline bool operator==(uuid const& lhs, uuid const& rhs) /* throw() */ { return std::equal(lhs.begin(), lhs.end(), rhs.begin()); }
which end up with the following code: lea edx, DWORD PTR _id2$[esp+92] lea ecx, DWORD PTR _id1$[esp+108] lea eax, DWORD PTR _id1$[esp+92] call ?_Equal@std@@YA_NPBE00@Z ; std::_Equal
A good implementation of std::equal would call memcmp here, which would already be optimized. That doesn't seem to be the case. Can you try replacing this by memcmp(lhs.begin(), rhs.begin(), lhs.size()) ?
inline bool comp(const boost::uuids::uuid& l, const boost::uuids::uuid& r) { return *reinterpret_cast<const uint32_t*>(l.data) == *reinterpret_cast<const uint32_t*>(r.data) && *reinterpret_cast<const uint32_t*>(l.data+4) == *reinterpret_cast<const uint32_t*>(r.data+4) && *reinterpret_cast<const uint32_t*>(l.data+8) == *reinterpret_cast<const uint32_t*>(r.data+8) && *reinterpret_cast<const uint32_t*>(l.data+12) == *reinterpret_cast<const uint32_t*>(r.data+12); }
This code is specific to 32-bit architectures and also breaks the strict-aliasing rule.