Re: [PATCH] Set bound/cmp/control for until wrap loop.

[Richard Biener <rguenther@suse.de>]

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  <guojiufu@linux.ibm.com>
> 
>         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  <guojiufu@linux.ibm.com>
> 
>         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)?

> > @@ -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?  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?

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 <rguenther@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)