> Am 04.10.2025 um 11:20 schrieb Jakub Jelinek <[email protected]>:
>
> Hi!
>
> In PR95852 I've added an optimization where next to just pattern
> recognizing r = x * y; r / x != y or r = x * y; r / x == y
> as .MUL_OVERFLOW or negation thereof it also recognizes
> r = x * y; x && (r / x != y) or r = x * y; !x || (r / x == y)
> by optimizing the guarding condition to always true/false.
>
> The problem with that is that some value ranges recorded for
> the SSA_NAMEs in the formerly conditional, now unconditional
> basic block can be invalid.
>
> This patch fixes it by calling reset_flow_sensitive_info_in_bb
> if we optimize the guarding condition.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk
> and after a while to affected release branches?
Ok
Thanks,
Richard
> 2025-10-04 Jakub Jelinek <[email protected]>
>
> PR tree-optimization/122104
> * tree-ssa-math-opts.cc (maybe_optimize_guarding_check): Call
> reset_flow_sensitive_info_in_bb on bb when optimizing out the
> guarding condition.
>
> * gcc.target/i386/pr122104.c: New test.
>
> --- gcc/tree-ssa-math-opts.cc.jj 2025-09-29 15:01:29.865553078 +0200
> +++ gcc/tree-ssa-math-opts.cc 2025-10-03 15:09:36.037066116 +0200
> @@ -3834,6 +3834,7 @@ maybe_optimize_guarding_check (vec<gimpl
> else
> gimple_cond_make_false (zero_cond);
> update_stmt (zero_cond);
> + reset_flow_sensitive_info_in_bb (bb);
> *cfg_changed = true;
> }
>
> --- gcc/testsuite/gcc.target/i386/pr122104.c.jj 2025-10-03
> 15:51:11.332196041 +0200
> +++ gcc/testsuite/gcc.target/i386/pr122104.c 2025-10-03 15:55:39.129458987
> +0200
> @@ -0,0 +1,12 @@
> +/* PR tree-optimization/122104 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-widening_mul-alias" } */
> +/* { dg-final { scan-tree-dump "\\.MUL_OVERFLOW" "widening_mul" } } */
> +/* { dg-final { scan-tree-dump-not "# RANGE \\\[irange\\\] unsigned int
> \\\[1, " "widening_mul" } } */
> +
> +int
> +foo (int x)
> +{
> + int r = (unsigned) x * 35;
> + return x && ((unsigned) r / x) != 35U;
> +}
>
> Jakub
>
