http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58872
Yann Droneaud <yann at droneaud dot fr> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |yann at droneaud dot fr --- Comment #2 from Yann Droneaud <yann at droneaud dot fr> --- (In reply to Marc Glisse from comment #1) > What do the arguments of brev mean? > Related to PR 50481. The prototype for the reverse bit string builtin was designed to be useful to reverse bits in a subset of a integer value, starting at "index" with "count" bits. The general use case is likely to reverse all bits in a variable, (uint64_t for example): uint64_t v; __builtin_brev64(v, 0, sizeof(v) * 8); But I thought it might be interesting to have a "more" general purpose builtin. Actually, the builtin arguments for reverse should probably match what's currently available on modern hardware.