On Tue, 7 Feb 2017, Jakub Jelinek wrote:
> Hi!
>
> While looking at the RTL problem when combiner optimizes away
> (x & 0xfffe) % 0xffff into just (x & 0xfffe), I've looked at VRP
> which optimizes that case well (-O2 only, the PR is -O1), but discovered
> that it isn't generic enough, we actually don't need op1 to be constant
> in this case, a range whose (positive) minimum satisfies it can be handled
> the same.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk (or
> shall I defer it for GCC8)?
Ok for trunk if you adjust the function comment accordingly.
Thanks,
Richard.
> 2017-02-07 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/79408
> * tree-vrp.c (simplify_div_or_mod_using_ranges): If op1 is not
> constant, but SSA_NAME with a known integer range, use the minimum
> of that range instead of op1 to determine if modulo can be replaced
> with its first operand.
>
> * gcc.dg/tree-ssa/pr79408.c: New test.
>
> --- gcc/tree-vrp.c.jj 2017-01-30 19:10:50.000000000 +0100
> +++ gcc/tree-vrp.c 2017-02-07 12:33:32.721482609 +0100
> @@ -9241,17 +9241,25 @@ simplify_div_or_mod_using_ranges (gimple
> tree val = NULL;
> tree op0 = gimple_assign_rhs1 (stmt);
> tree op1 = gimple_assign_rhs2 (stmt);
> + tree op1min = op1;
> value_range *vr = get_value_range (op0);
>
> if (rhs_code == TRUNC_MOD_EXPR
> - && TREE_CODE (op1) == INTEGER_CST
> - && tree_int_cst_sgn (op1) == 1
> + && TREE_CODE (op1) == SSA_NAME)
> + {
> + value_range *vr1 = get_value_range (op1);
> + if (range_int_cst_p (vr1))
> + op1min = vr1->min;
> + }
> + if (rhs_code == TRUNC_MOD_EXPR
> + && TREE_CODE (op1min) == INTEGER_CST
> + && tree_int_cst_sgn (op1min) == 1
> && range_int_cst_p (vr)
> - && tree_int_cst_lt (vr->max, op1))
> + && tree_int_cst_lt (vr->max, op1min))
> {
> if (TYPE_UNSIGNED (TREE_TYPE (op0))
> || tree_int_cst_sgn (vr->min) >= 0
> - || tree_int_cst_lt (fold_unary (NEGATE_EXPR, TREE_TYPE (op1), op1),
> - vr->min))
> + || tree_int_cst_lt (fold_unary (NEGATE_EXPR, TREE_TYPE (op1min),
> + op1min), vr->min))
> {
> /* If op0 already has the range op0 % op1 has,
> --- gcc/testsuite/gcc.dg/tree-ssa/pr79408.c.jj 2017-02-07
> 16:30:42.439774777 +0100
> +++ gcc/testsuite/gcc.dg/tree-ssa/pr79408.c 2017-02-07 16:32:37.653282317
> +0100
> @@ -0,0 +1,40 @@
> +/* PR tree-optimization/79408 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +
> +void link_error (void);
> +
> +void
> +foo (unsigned int x, unsigned int y)
> +{
> + if (x > 7312)
> + return;
> + if (y <= 7312)
> + return;
> + if (x % y != x)
> + link_error ();
> +}
> +
> +void
> +bar (int x, int y)
> +{
> + if (x > 7312 || x < 0)
> + return;
> + if (y <= 7312)
> + return;
> + if (x % y != x)
> + link_error ();
> +}
> +
> +void
> +baz (int x, int y)
> +{
> + if (x > 7312 || x < -7312)
> + return;
> + if (y <= 7312)
> + return;
> + if (x % y != x)
> + link_error ();
> +}
> +
> +/* { dg-final { scan-tree-dump-times "link_error" 0 "optimized"} } */
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
