https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96733
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |jakub at gcc dot gnu.org,
| |redi at gcc dot gnu.org
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I'm afraid there is nothing that the compiler can do to optimize the
clamp_builtin into similar code to clamp_minmax, because the optimizer doesn't
know an important restriction on std::clamp
- "The behavior is undefined if the value of lo is greater than hi".
In the IL this isn't expressed in any way, and when the compiler sees
(__val < __lo) ? __lo : (__hi < __val) ? __hi : __val
it can only optimize (for -Ofast) the (__hi < __val) ? __hi : __val part into
min (__hi, __val), but as it needs to assume e.g. __lo could be 10 and __hi 5,
it can't emit max.
