https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64277
--- Comment #16 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Ilya Enkovich from comment #13)
> Ranges have to be used for maxiter computations to have consistent analysis
> in complete unroll and vrp. Following patch allows to refine maxiter
> estimation using ranges and avoid warnings.
Looks good to me with...
> diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c
> index 919f5c0..14cce2a 100644
> --- a/gcc/tree-ssa-loop-niter.c
> +++ b/gcc/tree-ssa-loop-niter.c
> @@ -2754,6 +2754,7 @@ record_nonwrapping_iv (struct loop *loop, tree base,
> tree step, gimple stmt,
> {
> tree niter_bound, extreme, delta;
> tree type = TREE_TYPE (base), unsigned_type;
> + tree orig_base = base;
>
> if (TREE_CODE (step) != INTEGER_CST || integer_zerop (step))
> return;
> @@ -2777,7 +2778,14 @@ record_nonwrapping_iv (struct loop *loop, tree base,
> tree step, gimple stmt,
>
> if (tree_int_cst_sign_bit (step))
> {
> + wide_int min, max, highwi = high;
> extreme = fold_convert (unsigned_type, low);
> + if (TREE_CODE (orig_base) == SSA_NAME
> + && !POINTER_TYPE_P (TREE_TYPE (orig_base))
test
INTEGRAL_TYPE_P (TREE_TYPE (orig_base))
instead
> + && SSA_NAME_RANGE_INFO (orig_base)
You can drop this check, get_range_info will return VR_VARYING.
> + && get_range_info (orig_base, &min, &max) == VR_RANGE
> + && wi::gts_p (highwi, max))
I think you can write
&& wi::gts_p (high.to_widest (), max))
and avoid the highwi temporary.
Similar changes below.
> + base = wide_int_to_tree (unsigned_type, max);
> if (TREE_CODE (base) != INTEGER_CST)
> base = fold_convert (unsigned_type, high);
> delta = fold_build2 (MINUS_EXPR, unsigned_type, base, extreme);
> @@ -2785,8 +2793,15 @@ record_nonwrapping_iv (struct loop *loop, tree base,
> tree step, gimple stmt,
> }
> else
> {
> + wide_int min, max, lowwi = low;
> extreme = fold_convert (unsigned_type, high);
> - if (TREE_CODE (base) != INTEGER_CST)
> + if (TREE_CODE (orig_base) == SSA_NAME
> + && !POINTER_TYPE_P (TREE_TYPE (orig_base))
> + && SSA_NAME_RANGE_INFO (orig_base)
> + && get_range_info (orig_base, &min, &max) == VR_RANGE
> + && wi::gts_p (min, lowwi))
> + base = wide_int_to_tree (unsigned_type, min);
> + else if (TREE_CODE (base) != INTEGER_CST)
> base = fold_convert (unsigned_type, low);
> delta = fold_build2 (MINUS_EXPR, unsigned_type, extreme, base);
> }
> diff --git a/gcc/testsuite/gcc.dg/pr64277.c b/gcc/testsuite/gcc.dg/pr64277.c
> new file mode 100644
> index 0000000..0d5ef11
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr64277.c
> @@ -0,0 +1,21 @@
> +/* PR tree-optimization/64277 */
> +/* { dg-do compile } */
> +/* { dg-options "-O3 -Wall -Werror" } */
> +
> +
> +int f1[10];
> +void test1 (short a[], short m, unsigned short l)
> +{
> + int i = l;
> + for (i = i + 5; i < m; i++)
> + f1[i] = a[i]++;
> +}
> +
> +void test2 (short a[], short m, short l)
> +{
> + int i;
> + if (m > 5)
> + m = 5;
> + for (i = m; i > l; i--)
> + f1[i] = a[i]++;
> +}
