------- Comment #2 from rguenth at gcc dot gnu dot org 2009-01-26 11:15 ------- This happens because ivcanon introduces an induction variable that counts from 2000 to 1. This "confuses" data-ref analysis and we get
base_address: a_24(D) offset from base address: (<unnamed-signed:64>) ((<unnamed-unsigned:64>) pretmp.28_148 * 16000) constant offset from base address: -15996 step: 8 aligned to: 128 base_object: IMAGPART_EXPR <(*a_24(D))[0]> symbol tag: SMT.12 notice the negative constant offset from base address. This in turn confuses the vectorizer alignment analysis - but only because the alignment of the base object is known. We hit (with misalign == -15996, alignment == 16) /* Modulo alignment. */ misalign = size_binop (TRUNC_MOD_EXPR, misalign, alignment); if (!host_integerp (misalign, 1)) { /* Negative or overflowed misalignment value. */ if (vect_print_dump_info (REPORT_DETAILS)) fprintf (vect_dump, "unexpected misalign value"); return false; } and the modulo is -12. Now, I wonder why we do not just use alignment + misalign in that case. I have a patch. -- rguenth at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- AssignedTo|unassigned at gcc dot gnu |rguenth at gcc dot gnu dot |dot org |org Status|NEW |ASSIGNED Last reconfirmed|2009-01-25 17:33:10 |2009-01-26 11:15:23 date| | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38968