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 <guoji...@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 <guoji...@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)?
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.
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" }
> } */
