https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90204
--- Comment #7 from Hongtao.liu <crazylht at gmail dot com> --- Yes, C++ with NRV optization, so the alignment of <retval>(res) is 4. and the alignment of res is 16 in C. g++/test.i.158t.vect: ../test.i:8:23: note: recording new base alignment for &<retval> alignment: 4 misalignment: 0 gcc/test.i.158t.vect: ../test.i:8:5: note: recording new base alignment for &res alignment: 16 misalignment: 0 When alignment of res is 16, that triggers loop peeling of vectorization. refer to: /* Function vect_enhance_data_refs_alignment This pass will use loop versioning and loop peeling in order to enhance the alignment of data references in the loop. ......... */ That's why there are more than 150 lines of assemble.
