On Wed, Apr 11, 2018 at 3:15 PM, Bin.Cheng <amker.ch...@gmail.com> wrote: > On Wed, Apr 11, 2018 at 10:46 AM, Richard Biener > <richard.guent...@gmail.com> wrote: >> On Tue, Apr 10, 2018 at 6:28 PM, Bin.Cheng <amker.ch...@gmail.com> wrote: >>> 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? >> >> number_of_iterations_ne_max computes this it seems based on the >> fact that pointer overflow is undefined. This means that 126 is >> as good as any other number given the testcase is undefined... > > Okay, in this case, I simply removed the function with UB in the case. > Is it OK?

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OK. Richard. > Thanks, > bin > > gcc/testsuite > 2018-04-11 Bin Cheng <bin.ch...@arm.com> > > PR testsuite/85190 > * gcc.dg/vect/pr81196.c: Remove function with undefined behavior. > > >> >> Richard. >> >>> 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