https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115073
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |jakub at gcc dot gnu.org
--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
That is misunderstanding of what C[LT]Z_DEFINED_VALUE_AT_ZERO is.
The builtin has always UB on zero.
If you want to define it for zero, use x ? __builtin_clz (x) : 32 (and the
like) or
__builtin_clzg (x, 32) in the source.
C[LT]Z_DEFINED_VALUE_AT_ZERO returning 2 then makes sure the compiler can fold
those conditionals or builtins into .CLZ internal calls with 2 arguments which
makes it well defined for all inputs.
