[Bug c++/83428] Static initialization and struct with constexpr ctor

[alkondratenko at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83428

Aliaksei Kandratsenka  changed:

   What|Removed |Added

 CC||alkondratenko at gmail dot com

--- Comment #3 from Aliaksei Kandratsenka  ---
constructor is defined after variable in this example. I am not sure this real
bug.

[Bug middle-end/50168] __builtin_ctz() and intrinsics __bsr(), __bsf() generate suboptimal code on x86_64

[alkondratenko at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=50168

Aliaksei Kandratsenka  changed:

   What|Removed |Added

 CC||alkondratenko at gmail dot com

--- Comment #10 from Aliaksei Kandratsenka  ---
There is similar issue with bsr and __builtin_clz.

Looks like for __builtin_clz gcc does 31 - . And 31 - __builtin_clz
does gets compiled optimized to plain bsr, but only under --march=haswell or
later amd cpus.

Under earlier cpus it generates 2 redundant 31 - arg computations.

This is easy to play with at: https://godbolt.org/g/o7gNSS

Clang-en doesn't have that same problem (but they have another. Under
-march=haswell they sometimes too strongly prefer lzcnt which returns different
result and thus requires extra computation).