Suboptimal assignment

[Domagoj Šarić]

Hi, we're using your MP library, with the cpp_int_backend and fixed sized numbers, along with the "Maybe Boost Hash" library to implement lightweight RSA signature verification (previously done with LibTomCrypt+LibTomMath), so first of all thanks for making this possible ;)

Unless otherwise stated, always assume I'm using MSVC10 32bit (with /Oxs /GL /LTCG) with the above use case (fixed sized, unchecked, unsigned cpp_ints)...

Now, onto the issues ;D

I would expect do_assign() to simply evaluate to simply std::memcpy, however it does not:

• it seems that the this->resize(other.size(), other.size()); call fails to resolve to a nop (check your code)
• why are you using "checked std::copy" instead of a straigh std::memcpy?

ps. MSVC has a very nice debugger and disassembly window so I'll refrain from posting codegen in any of my tickets.

[John Maddock]

(In [86258]) Optimize copying of allocator-free cpp_int's via memcpy. Fix consistency of checks for exponents < 0 in powm. Fixes #9231. Refs #9236.

[anonymous]

Thanks... ps. did you check why this->resize(other.size(), other.size()); does not evaluate to a nop (I forgot to add that this happens in powm when it copy-constructs the double_type)_?