https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108724
--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Richard Biener <rgue...@gcc.gnu.org>: https://gcc.gnu.org/g:dc87e1391c55c666c7ff39d4f0dea87666f25468 commit r13-5771-gdc87e1391c55c666c7ff39d4f0dea87666f25468 Author: Richard Biener <rguent...@suse.de> Date: Fri Feb 10 11:07:30 2023 +0100 tree-optimization/108724 - vectorized code getting piecewise expanded This fixes an oversight to when removing the hard limits on using generic vectors for the vectorizer to enable both SLP and BB vectorization to use those. The vectorizer relies on vector lowering to expand plus, minus and negate to bit operations but vector lowering has a hard limit on the minimum number of elements per work item. Vectorizer costs for the testcase at hand work out to vectorize a loop with just two work items per vector and that causes element wise expansion and spilling. The fix for now is to re-instantiate the hard limit, matching what vector lowering does. For the future the way to go is to emit the lowered sequence directly from the vectorizer instead. PR tree-optimization/108724 * tree-vect-stmts.cc (vectorizable_operation): Avoid using word_mode vectors when vector lowering will decompose them to elementwise operations. * gcc.target/i386/pr108724.c: New testcase.
