On Mon, 2 Sep 2024, Jakub Jelinek wrote:
> Hi!
>
> The initial CLZ gimple-range-op.cc implementation handled just the
> case where second argument to .CLZ is equal to prec, but in
> r15-1014 I've added also handling of the -1 case. As the following
> testcase shows, incorrectly though for the case where the first argument
> has [0,0] range. If the second argument is prec, then the result should
> be [prec,prec] and that was handled correctly, but when the second argument
> is -1, the result should be [-1,-1] but instead it was incorrectly computed
> as [prec-1,prec-1] (when second argument is prec, mini is 0 and maxi is
> prec, while when second argument is -1, mini is -1 and maxi is prec-1).
>
> Fixed thusly (the actual handling is then similar to the CTZ [0,0] case),
> bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
> 2024-09-02 Jakub Jelinek <ja...@redhat.com>
>
> PR middle-end/116486
> * gimple-range-op.cc (cfn_clz::fold_range): If lh is [0,0]
> and mini is -1, return [-1,-1] range rather than [prec-1,prec-1].
>
> * gcc.dg/bitint-109.c: New test.
>
> --- gcc/gimple-range-op.cc.jj 2024-08-15 10:18:48.000000000 +0200
> +++ gcc/gimple-range-op.cc 2024-08-31 18:23:14.547269372 +0200
> @@ -972,8 +972,10 @@ cfn_clz::fold_range (irange &r, tree typ
> {
> // If CLZ_DEFINED_VALUE_AT_ZERO is 2 with VALUE of prec,
> // return [prec, prec] or [-1, -1], otherwise ignore the range.
> - if (maxi == prec || mini == -1)
> - mini = maxi;
> + if (maxi == prec)
> + mini = prec;
> + else if (mini == -1)
> + maxi = -1;
> }
> else if (mini >= 0)
> mini = newmini;
> --- gcc/testsuite/gcc.dg/bitint-109.c.jj 2024-08-31 18:25:15.111715665
> +0200
> +++ gcc/testsuite/gcc.dg/bitint-109.c 2024-08-31 18:26:02.015118452 +0200
> @@ -0,0 +1,25 @@
> +/* PR middle-end/116486 */
> +/* { dg-do run { target bitint } } */
> +/* { dg-options "-O2 -fno-tree-ccp" } */
> +
> +unsigned u;
> +
> +#if __BITINT_MAXWIDTH__ >= 129
> +#define N 0x100000000000000000000000000000000uwb
> +#else
> +#define N 0xffffffffffffffffuwb
> +#endif
> +
> +int
> +foo (void)
> +{
> + return __builtin_stdc_first_leading_one (u / N);
> +}
> +
> +int
> +main ()
> +{
> + int x = foo ();
> + if (x)
> + __builtin_abort ();
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
