On Mon, Jun 6, 2016 at 6:00 PM, Bin Cheng <bin.ch...@arm.com> wrote: > Hi, > GCC now generates duplicated alias check in vectorizer when versioning loops. > In current implementation, DR_OFFSET and DR_INIT are added together too > early when creating structure dr_with_seg_len. This has two disadvantages: > A) structure dr_with_seg_len_pair_t is only canonicalized against > DR_BASE_ADDRESS in function vect_prune_runtime_alias_test_list, while it > should be against DR_OFFSET too; B) When function > vect_prune_runtime_alias_test_list tries to merge aias checks with > consecutive memory references, it can only handle DRs with constant DR_OFFSET > + DR_INIT, as in below code: > /* We consider the case that DR_B1 and DR_B2 are same memrefs, > and DR_A1 and DR_A2 are two consecutive memrefs. */ > //... ... > if (!operand_equal_p (DR_BASE_ADDRESS (dr_a1->dr), > DR_BASE_ADDRESS (dr_a2->dr), > 0) > || !tree_fits_shwi_p (dr_a1->offset) > || !tree_fits_shwi_p (dr_a2->offset)) > continue; > > Both disadvantages result in duplicated/unnecessary alias checks, as well as > bloated condition basic block of loop versioning. > This patch fixes the issue. Bootstrap and test on x86_64 and AArch64. Is it > OK? > Test gfortran.dg/vect/vect-8.f90 failed now. It scans for "vectorized 20 > loops" but with this patch there are more than 20 loops vectorized. The > additional loop wasn't vectorized because # of alias checks exceeded > parameter bound "vect-max-version-for-alias-checks" w/o this patch. > > There are other issues in vectorizer alias checking, I will tackle them in > follow up patches.
Ok. Thanks, Richard. > Thanks, > bin > > 2016-06-03 Bin Cheng <bin.ch...@arm.com> > > * tree-vectorizer.h (struct dr_with_seg_len): Remove class > member OFFSET. > * tree-vect-data-refs.c (operator ==): Handle DR_OFFSET directly, > rather than OFFSET. > (comp_dr_with_seg_len_pair, comp_dr_with_seg_len_pair): Ditto. > (vect_create_cond_for_alias_checks): Ditto. > (vect_prune_runtime_alias_test_list): Also canonicalize pairs > against DR_OFFSET. Handle DR_OFFSET directly when prune alias > checks. > > gcc/testsuite/ChangeLog > 2016-06-03 Bin Cheng <bin.ch...@arm.com> > > * gcc.dg/vect/vect-alias-check-1.c: New test.
