https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99767
--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:b44ab138b7d4aaa5a9ee7956121ffc94777f6a42 commit r11-8211-gb44ab138b7d4aaa5a9ee7956121ffc94777f6a42 Author: Jakub Jelinek <ja...@redhat.com> Date: Fri Apr 16 11:44:04 2021 +0200 vectorizer: Remove dead scalar .COND_* calls from vectorized loops [PR99767] The following testcase ICEs because disabling of DCE means there are dead stmts in the loop (though, in theory they could become dead only shortly before if-conv through some optimization), ifcvt which goes through all stmts in the loop if-converts them into .COND_DIV etc. internal fn calls in the copy of the loop meant for vectorization only, the loop is successfully vectorized but the particular .COND_* call is not because it isn't a live statement and the scalar .COND_* remains in the IL until expansion where it ICEs because these ifns only support vectors and not scalars. These ifns are similar to .MASK_{LOAD,STORE} in this behavior. One possible fix could be to expand scalar versions of them during expansion, basically undoing what if-conv did to create them, i.e. expand them as the lhs = else; if (mask) { lhs = statement; } or so. For .MASK_LOAD we have code to replace them in vect_transform_loop already though (not needed for .MASK_STORE, as stores should be always live and thus always vectorized), so this patch instead replaces .COND_* similarly to .MASK_LOAD in that loop, with the small difference that lhs = .MASK_LOAD (...); is replaced by lhs = 0; while lhs = .COND_* (..., else_arg); is replaced by lhs = else_arg. The statement must be dead, otherwise it would be vectorized, so I think it is not a big deal we don't turn it back into multiple basic blocks etc. (and it might be not possible to do that at that point). 2021-04-16 Jakub Jelinek <ja...@redhat.com> PR target/99767 * tree-vect-loop.c (vect_transform_loop): Don't remove just dead scalar .MASK_LOAD calls, but also dead .COND_* calls - replace them by their last argument. * gcc.target/aarch64/pr99767.c: New test.
