that has required alignment. This avoids issues that keep coming up with
function pointers being less aligned.
I'm pretty annoyed that we can't take advantage of function alignment
even on platforms where they *are* aligned, but build modes and other
things make taking advantage of it somewhere between hard and
impossible. The best case scenario would still embed various build modes
into the ABI causing really hard to debug issues if you compiled one
object file differently from another. =/
This should at least bring the bots back that were having trouble with
this.
llvm-svn: 336337
It appears that the function pointer we use there isn't reliably 4-byte
aligned. I have no idea why or how we could correct this, so for now we
just regress the Windows performance some.
Someone with access to Windows could try working on a fix. At the very
least we could use a double indirection rather than a table, but maybe
there is some way to fully restore this optimization. I don't want to
play too much with this when I don't have access to the platform and
this at least should restore the last bots.
llvm-svn: 336178
Putting `sizeof(T) <= 16` into the parameter of a `std::conditional`
causes every version of MSVC I've tried to crash:
https://godbolt.org/g/eqVULL
Really frustrating, but an extra layer of indirection through an
instantiated type gives a working way to access this computed constant.
llvm-svn: 336170
introducing llvm::trivially_{copy,move}_constructible type traits.
This uses a completely portable implementation of these traits provided
by Richard Smith. You can see it on compiler explorer in all its glory:
https://godbolt.org/g/QEDZjW
I have transcribed it, clang-formatted it, added some comments, and made
the tests fit into a unittest file.
I have also switched llvm::unique_function over to use these new, much
more portable traits. =D
Hopefully this will fix the build bot breakage from my prior commit.
llvm-svn: 336161
supporting move-only closures.
Most of the core optimizations for std::function are here plus
a potentially novel one that detects trivially movable and destroyable
functors and implements those with fewer indirections.
This is especially useful as we start trying to add concurrency
primitives as those often end up with move-only types (futures,
promises, etc) and wanting them to work through lambdas.
As further work, we could add better support for things like const-qualified
operator()s to support more algorithms, and r-value ref qualified operator()s
to model call-once. None of that is here though.
We can also provide our own llvm::function that has some of the optimizations
used in this class, but with copy semantics instead of move semantics.
This is motivated by increasing usage of things like executors and the task
queue where it is useful to embed move-only types like a std::promise within
a type erased function. That isn't possible without this version of a type
erased function.
Differential Revision: https://reviews.llvm.org/D48349
llvm-svn: 336156
