On Tue, 31 Aug 2021, guojiufu wrote:
> On 2021-08-30 20:02, Richard Biener wrote:
> > On Mon, 30 Aug 2021, guojiufu wrote:
> >
> >> On 2021-08-30 14:15, Jiufu Guo wrote:
> >> > Hi,
> >> >
> >> > In patch r12-3136, niter->control, niter->bound and niter->cmp are
> >> > derived from number_of_iterations_lt. While for 'until wrap condition',
> >> > the calculation in number_of_iterations_lt is not align the requirements
> >> > on the define of them and requirements in determine_exit_conditions.
> >> >
> >> > This patch calculate niter->control, niter->bound and niter->cmp in
> >> > number_of_iterations_until_wrap.
> >> >
> >> > The ICEs in the PR are pass with this patch.
> >> > Bootstrap and reg-tests pass on ppc64/ppc64le and x86.
> >> > Is this ok for trunk?
> >> >
> >> > BR.
> >> > Jiufu Guo
> >> >
> >> Add ChangeLog:
> >> gcc/ChangeLog:
> >>
> >> 2021-08-30 Jiufu Guo <[email protected]>
> >>
> >> PR tree-optimization/102087
> >> * tree-ssa-loop-niter.c (number_of_iterations_until_wrap):
> >> Set bound/cmp/control for niter.
> >>
> >> gcc/testsuite/ChangeLog:
> >>
> >> 2021-08-30 Jiufu Guo <[email protected]>
> >>
> >> PR tree-optimization/102087
> >> * gcc.dg/vect/pr101145_3.c: Update tests.
> >> * gcc.dg/pr102087.c: New test.
> >>
> >> > ---
> >> > gcc/tree-ssa-loop-niter.c | 14 +++++++++++++-
> >> > gcc/testsuite/gcc.dg/pr102087.c | 25 +++++++++++++++++++++++++
> >> > gcc/testsuite/gcc.dg/vect/pr101145_3.c | 4 +++-
> >> > 3 files changed, 41 insertions(+), 2 deletions(-)
> >> > create mode 100644 gcc/testsuite/gcc.dg/pr102087.c
> >> >
> >> > diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c
> >> > index 7af92d1c893..747f04d3ce0 100644
> >> > --- a/gcc/tree-ssa-loop-niter.c
> >> > +++ b/gcc/tree-ssa-loop-niter.c
> >> > @@ -1482,7 +1482,7 @@ number_of_iterations_until_wrap (class loop *,
> >> > tree type, affine_iv *iv0,
> >> > affine_iv *iv1, class tree_niter_desc
> >> > *niter)
> >> > {
> >> > tree niter_type = unsigned_type_for (type);
> >> > - tree step, num, assumptions, may_be_zero;
> >> > + tree step, num, assumptions, may_be_zero, span;
> >> > wide_int high, low, max, min;
> >> >
> >> > may_be_zero = fold_build2 (LE_EXPR, boolean_type_node, iv1->base,
> >> > iv0->base);
> >> > @@ -1513,6 +1513,8 @@ number_of_iterations_until_wrap (class loop *,
> >> > tree type, affine_iv *iv0,
> >> > low = wi::to_wide (iv0->base);
> >> > else
> >> > low = min;
> >> > +
> >> > + niter->control = *iv1;
> >> > }
> >> > /* {base, -C} < n. */
> >> > else if (tree_int_cst_sign_bit (iv0->step) && integer_zerop
> >> > (iv1->step))
> >> > @@ -1533,6 +1535,8 @@ number_of_iterations_until_wrap (class loop *,
> >> > tree type, affine_iv *iv0,
> >> > high = wi::to_wide (iv1->base);
> >> > else
> >> > high = max;
> >> > +
> >> > + niter->control = *iv0;
> >> > }
> >> > else
> >> > return false;
> >
> > it looks like the above two should already be in effect from the
> > caller (guarding with integer_nozerop)?
>
> I add them just because set these fields in one function.
> Yes, they have been set in caller already, I could remove them here.
>
> >
> >> > @@ -1556,6 +1560,14 @@ number_of_iterations_until_wrap (class loop *,
> >> > tree type, affine_iv *iv0,
> >> > niter->assumptions, assumptions);
> >> >
> >> > niter->control.no_overflow = false;
> >> > + niter->control.base = fold_build2 (MINUS_EXPR, niter_type,
> >> > + niter->control.base,
> >> > niter->control.step);
> >
> > how do we know IVn - STEP doesn't already wrap?
>
> The last IV value is just cross the max/min value of the type
> at the last iteration, then IVn - STEP is the nearest value
> to max(or min) and not wrap.
>
> > A comment might be
> > good to explain you're turning the simplified exit condition into
> >
> > { IVbase - STEP, +, STEP } != niter * STEP + (IVbase - STEP)
> >
> > which, when mathematically looking at it makes me wonder why there's
> > the seemingly redundant '- STEP' term? Also is NE_EXPR really
> > correct since STEP might be not 1? Only for non equality compares
> > the '- STEP' should matter?
>
> I need to add comments for this. This is a little tricky.
> The last value of the original IV just cross max/min at most one STEP,
> at there wrapping already happen.
> Using "{IVbase, +, STEP} != niter * STEP + IVbase" is not wrong
> in the aspect of exit condition.
>
> But this would not work well with existing code:
> like determine_exit_conditions, which will convert NE_EXP to
> LT_EXPR/GT_EXPR. And so, the '- STEP' is added to adjust the
> IV.base and bound, with '- STEP' the bound will be the last value
> just before wrap.
Hmm. The control IV is documented as
/* The simplified shape of the exit condition. The loop exits if
CONTROL CMP BOUND is false, where CMP is one of NE_EXPR,
LT_EXPR, or GT_EXPR, and step of CONTROL is positive if CMP is
LE_EXPR and negative if CMP is GE_EXPR. This information is used
by loop unrolling. */
affine_iv control;
but determine_exit_conditions seems to assume the IV does not wrap?
In fact determine_exit_conditions seems to just build ->base CMP bound
where bound is the IV bound biased by #unroll * step - step. So how
does biasing by step * 1 help?
Does the control IV wrap in our case?
Richard.
> Thanks again for your review!
>
> BR.
> Jiufu
>
> >
> > Richard.
> >
> >> > + span = fold_build2 (MULT_EXPR, niter_type, niter->niter,
> >> > + fold_convert (niter_type, niter->control.step));
> >> > + niter->bound = fold_build2 (PLUS_EXPR, niter_type, span,
> >> > + fold_convert (niter_type,
> >> > niter->control.base));
> >> > + niter->bound = fold_convert (type, niter->bound);
> >> > + niter->cmp = NE_EXPR;
> >> >
> >> > return true;
> >> > }
> >> > diff --git a/gcc/testsuite/gcc.dg/pr102087.c
> >> > b/gcc/testsuite/gcc.dg/pr102087.c
> >> > new file mode 100644
> >> > index 00000000000..ef1f9f5cba9
> >> > --- /dev/null
> >> > +++ b/gcc/testsuite/gcc.dg/pr102087.c
> >> > @@ -0,0 +1,25 @@
> >> > +/* { dg-do compile } */
> >> > +/* { dg-options "-O3" } */
> >> > +
> >> > +unsigned __attribute__ ((noinline))
> >> > +foo (int *__restrict__ a, int *__restrict__ b, unsigned l, unsigned n)
> >> > +{
> >> > + while (n < ++l)
> >> > + *a++ = *b++ + 1;
> >> > + return l;
> >> > +}
> >> > +
> >> > +volatile int a[1];
> >> > +unsigned b;
> >> > +int c;
> >> > +
> >> > +int
> >> > +check ()
> >> > +{
> >> > + int d;
> >> > + for (; b > 1; b++)
> >> > + for (c = 0; c < 2; c++)
> >> > + for (d = 0; d < 2; d++)
> >> > + a[0];
> >> > + return 0;
> >> > +}
> >> > diff --git a/gcc/testsuite/gcc.dg/vect/pr101145_3.c
> >> > b/gcc/testsuite/gcc.dg/vect/pr101145_3.c
> >> > index 99289afec0b..40cb0240aaa 100644
> >> > --- a/gcc/testsuite/gcc.dg/vect/pr101145_3.c
> >> > +++ b/gcc/testsuite/gcc.dg/vect/pr101145_3.c
> >> > @@ -1,5 +1,6 @@
> >> > /* { dg-require-effective-target vect_int } */
> >> > /* { dg-options "-O3 -fdump-tree-vect-details" } */
> >> > +
> >> > #define TYPE int *
> >> > #define MIN ((TYPE)0)
> >> > #define MAX ((TYPE)((long long)-1))
> >> > @@ -10,4 +11,5 @@
> >> >
> >> > #include "pr101145.inc"
> >> >
> >> > -/* { dg-final { scan-tree-dump-times "vectorized 1 loops" 2 "vect" } }
> >> > */
> >> > +/* pointer size may not be vectorized, checking niter is ok. */
> >> > +/* { dg-final { scan-tree-dump "Symbolic number of iterations is" "vect"
> >> > }
> >> > } */
> >>
>
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
