On Tue, Apr 10, 2018 at 3:58 PM, Bin.Cheng <amker.ch...@gmail.com> wrote: > On Tue, Apr 10, 2018 at 2:26 PM, Jakub Jelinek <ja...@redhat.com> wrote: >> On Tue, Apr 10, 2018 at 09:55:35AM +0000, Bin Cheng wrote: >>> Hi Rainer, could you please help me double check that this solves the issue? >>> >>> Thanks, >>> bin >>> >>> gcc/testsuite >>> 2018-04-10 Bin Cheng <bin.ch...@arm.com> >>> >>> PR testsuite/85190 >>> * gcc.dg/vect/pr81196.c: Adjust pointer for aligned access. >> >>> diff --git a/gcc/testsuite/gcc.dg/vect/pr81196.c >>> b/gcc/testsuite/gcc.dg/vect/pr81196.c >>> index 46d7a9e..15320ae 100644 >>> --- a/gcc/testsuite/gcc.dg/vect/pr81196.c >>> +++ b/gcc/testsuite/gcc.dg/vect/pr81196.c >>> @@ -4,14 +4,14 @@ >>> >>> void f(short*p){ >>> p=(short*)__builtin_assume_aligned(p,64); >>> - short*q=p+256; >>> + short*q=p+255; >>> for(;p!=q;++p,--q){ >>> short t=*p;*p=*q;*q=t; >> >> This is UB then though, because p will never be equal to q.

Hmm, though it's UB in this case, is it OK for niter analysis gives below results? Analyzing # of iterations of loop 1 exit condition [126, + , 18446744073709551615] != 0 bounds on difference of bases: -126 ... -126 result: # of iterations 126, bounded by 126 I don't really follow last piece of code in number_of_iterations_ne: /* Let nsd (step, size of mode) = d. If d does not divide c, the loop is infinite. Otherwise, the number of iterations is (inverse(s/d) * (c/d)) mod (size of mode/d). */ bits = num_ending_zeros (s); bound = build_low_bits_mask (niter_type, (TYPE_PRECISION (niter_type) - tree_to_uhwi (bits))); d = fold_binary_to_constant (LSHIFT_EXPR, niter_type, build_int_cst (niter_type, 1), bits); s = fold_binary_to_constant (RSHIFT_EXPR, niter_type, s, bits); if (!exit_must_be_taken) { /* If we cannot assume that the exit is taken eventually, record the assumptions for divisibility of c. */ assumption = fold_build2 (FLOOR_MOD_EXPR, niter_type, c, d); assumption = fold_build2 (EQ_EXPR, boolean_type_node, assumption, build_int_cst (niter_type, 0)); if (!integer_nonzerop (assumption)) niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node, niter->assumptions, assumption); } c = fold_build2 (EXACT_DIV_EXPR, niter_type, c, d); tmp = fold_build2 (MULT_EXPR, niter_type, c, inverse (s, bound)); niter->niter = fold_build2 (BIT_AND_EXPR, niter_type, tmp, bound); return true; Though infinite niters is mentioned, I don't see it's handled? Thanks, bin > Sorry I already checked in, will try to correct it in another patch. > > Thanks, > bin >> >>> } >>> } >>> void b(short*p){ >>> p=(short*)__builtin_assume_aligned(p,64); >>> - short*q=p+256; >>> + short*q=p+255; >>> for(;p<q;++p,--q){ >>> short t=*p;*p=*q;*q=t; >> >> This one is fine, sure. >> >> Jakub