https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106458
--- Comment #11 from Richard Biener <rguenth at gcc dot gnu.org> --- The dump difference is easily explained by taming PRE when -ftree-vectorize is on, it's not a "real" difference. When I try with a cc1 cross I see > ./cc1 -quiet t.i -fpreprocessed -O2 -g -std=gnu11 -fgnu89-inline > -fmerge-all-constants -frounding-math -fno-stack-protector -fno-common > -fmath-errno -fno-pie -fopt-info-vec and nothing actually vectorized. Besides the PRE there seems to be a missed DSE at the end (when vectorization is enabled as after the change): # DEBUG BEGIN_STMT memset (&buf.__space.__c, 64, 1024); # DEBUG BEGIN_STMT + sizes[0] = 16; sizes[1] = 1024; sizes[2] = 1040; otherwise I see nothing suspicious in differences in .optimized when comparing -fdump-tree-optimized with/without -fno-tree-vectorize. You could try if -fno-tree-pre reproduces it also before the change.
