Re: [PATCH V2] Set bound/cmp/control for until wrap loop.

[Jiufu Guo <guojiufu@linux.ibm.com>]

Jiufu Guo <guojiufu@linux.ibm.com> writes:

I may want to have a gentle ping on this.
https://gcc.gnu.org/pipermail/gcc-patches/2021-September/578680.html

BR,
Jiufu

> Changes on V1:
> * Add more test case
> * Add comment for exit-condition transform
> * Removing duplicate setting on niter->control
>
> This patch reset niter->control, niter->bound and niter->cmp in
> number_of_iterations_until_wrap.
>
> Bootstrap and test pass on ppc64 and x86, and pass the test cases
> in PR.  Is this ok for trunk?
>
> One thing, in this patch, the IVbase is still keep as biasing by 1 step.
>
>
> BR.
> Jiufu Guo
>
> gcc/ChangeLog:
>
> 2021-09-02  Jiufu Guo  <guojiufu@linux.ibm.com>
>
>         PR tree-optimization/102087
>         * tree-ssa-loop-niter.c (number_of_iterations_until_wrap):
>         Update bound/cmp/control for niter.
>
> gcc/testsuite/ChangeLog:
>
> 2021-09-02  Jiufu Guo  <guojiufu@linux.ibm.com>
>
>         PR tree-optimization/102087
>         * gcc.dg/pr102087.c: New test.
>
> ---
>  gcc/tree-ssa-loop-niter.c       | 16 ++++++++++++++-
>  gcc/testsuite/gcc.dg/pr102087.c | 35 +++++++++++++++++++++++++++++++++
>  2 files changed, 50 insertions(+), 1 deletion(-)
>  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..75109407124 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);
> @@ -1557,6 +1557,20 @@ number_of_iterations_until_wrap (class loop *, tree type, affine_iv *iv0,
>  
>    niter->control.no_overflow = false;
>  
> +  /* Update bound and exit condition as:
> +     bound = niter * STEP + (IVbase - STEP).
> +     { IVbase - STEP, +, STEP } != bound
> +     Here, biasing IVbase by 1 step makes 'bound' be the value before wrap.
> +     */
> +  niter->control.base = fold_build2 (MINUS_EXPR, niter_type,
> +				     niter->control.base, niter->control.step);
> +  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..fc60cbda066
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr102087.c
> @@ -0,0 +1,35 @@
> +/* { 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;
> +}
> +
> +char **Gif_ClipImage_gfi_0;
> +int Gif_ClipImage_y, Gif_ClipImage_shift;
> +void
> +Gif_ClipImage ()
> +{
> +  for (; Gif_ClipImage_y >= Gif_ClipImage_shift; Gif_ClipImage_y++)
> +    Gif_ClipImage_gfi_0[Gif_ClipImage_shift]
> +      = Gif_ClipImage_gfi_0[Gif_ClipImage_y];
> +}