This was mention in D150044 and D154995 that this would be useful.
This addresses the last review coment of D150044.
Reviewed By: #libc, ldionne
Differential Revision: https://reviews.llvm.org/D156019
In the event the internal function __init is called with an empty string the code will take unnecessary extra steps, in addition, the code generated might be overall greater because, to my understanding, when initializing a string with an empty `const char*` "" (like in this case), the compiler might be unable to deduce the string is indeed empty at compile time and more code is generated.
The goal of this patch is to make a new internal function that will accept just an error code skipping the empty string argument. It should skip the unnecessary steps and in the event `if (ec)` is `false`, it will return an empty string using the correct ctor, avoiding any extra code generation issues.
After the conversation about this patch matured in the libcxx channel on the LLVM Discord server, the patch was analyzed quickly with "Compiler Explorer" and other tools and it was discovered that it does indeed reduce the amount of code generated when using the latest stable clang version (16) which in turn produces faster code.
This patch targets LLVM 18 as it will break the ABI by addressing https://github.com/llvm/llvm-project/issues/63985
Benchmark tests run on other machines as well show in the best case, that the new version without the extra string as an argument performs 10 times faster.
On the buildkite CI run it shows the new code takes less CPU time as well.
In conclusion, the new code should also just appear cleaner because there are fewer checks to do when there is no message.
Reviewed By: #libc, philnik
Spies: emaste, nemanjai, philnik, libcxx-commits
Differential Revision: https://reviews.llvm.org/D155820
These macros are always defined identically, so we can simplify the code a bit by merging them.
Reviewed By: ldionne, #libc
Spies: libcxx-commits, krytarowski, smeenai
Differential Revision: https://reviews.llvm.org/D152652
We already have a clang-tidy check for making sure that `_LIBCPP_HIDE_FROM_ABI` is on free functions. This patch extends this to class members. The places where we don't check for `_LIBCPP_HIDE_FROM_ABI` are classes for which we have an instantiation in the library.
Reviewed By: ldionne, Mordante, #libc
Spies: jplehr, mikhail.ramalho, sstefan1, libcxx-commits, krytarowski, miyuki, smeenai
Differential Revision: https://reviews.llvm.org/D142332
