https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98877
--- Comment #10 from Andrew Pinski <pinskia at gcc dot gnu.org> --- (In reply to Tamar Christina from comment #9) > While RA should be able to deal with this, > shouldn't we also just lower TBLs in gimple? > > This no reason why this can't be a VEC_PERM_EXPR which would also get the > copies > removed at the gimple level and allows us to optimize this to something else > depending on the index. Yes there is a reason, `out of range` values for VEC_PERM is undefined while tbl is well defined ( If an index is out of range for the table, the result for that lookup is 0.). For tbx, it is well defined also (If an index is out of range for the table, the existing value in the vector element of the destination register is left unchanged. ). I think for VECTOR_CST we can fold it down to VEC_PERM_EXPR if there is no out of bounds value though.
