https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66872
James Almer <jamrial at gmail dot com> changed:
What |Removed |Added
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CC| |jamrial at gmail dot com
--- Comment #1 from James Almer <jamrial at gmail dot com> ---
Ideally, for -mbmi2 (which is enabled with -march=haswell) the compiler should
generate a single bzhi instruction instead, as i mentioned in pr65871.
The generated code for your example would then be
bzhi %esi, %edi, %eax
ret
Also, left shift of negative value is undefined behavior in C. Try compiling
that code with -Wshift-negative-value using gcc trunk.
