On Tue, 4 Jun 2024, Jakub Jelinek wrote:
> Hi!
>
> The function currently incorrectly assumes all the __builtin_clz* and .CLZ
> calls have non-negative result. That is the case of the former which is UB
> on zero and has [0, prec-1] return value otherwise, and is the case of the
> single argument .CLZ as well (again, UB on zero), but for two argument
> .CLZ is the case only if the second argument is also nonnegative (or if we
> know the argument can't be zero, but let's do that just in the ranger IMHO).
>
> The following patch does that.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk and 14?
OK.
Thanks,
Richard.
> For 13 and earlier, we can't use the testcase and the fold-const.cc change
> would need to differentiate between __builtin_clz* vs. .CLZ and in the
> latter case look at CLZ_DEFINED_VALUE_AT_ZERO.
>
> 2024-06-04 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/115337
> * fold-const.cc (tree_call_nonnegative_warnv_p) <CASE_CFN_CLZ>:
> If arg1 is non-NULL, RECURSE on it, otherwise return true.
>
> * gcc.dg/bitint-106.c: New test.
>
> --- gcc/fold-const.cc.jj 2024-04-04 10:47:46.363287718 +0200
> +++ gcc/fold-const.cc 2024-06-04 10:56:57.575425348 +0200
> @@ -15241,7 +15241,6 @@ tree_call_nonnegative_warnv_p (tree type
> CASE_CFN_FFS:
> CASE_CFN_PARITY:
> CASE_CFN_POPCOUNT:
> - CASE_CFN_CLZ:
> CASE_CFN_CLRSB:
> case CFN_BUILT_IN_BSWAP16:
> case CFN_BUILT_IN_BSWAP32:
> @@ -15250,6 +15249,11 @@ tree_call_nonnegative_warnv_p (tree type
> /* Always true. */
> return true;
>
> + CASE_CFN_CLZ:
> + if (arg1)
> + return RECURSE (arg1);
> + return true;
> +
> CASE_CFN_SQRT:
> CASE_CFN_SQRT_FN:
> /* sqrt(-0.0) is -0.0. */
> --- gcc/testsuite/gcc.dg/bitint-106.c.jj 2024-06-04 12:00:59.017079094
> +0200
> +++ gcc/testsuite/gcc.dg/bitint-106.c 2024-06-04 12:00:41.975306632 +0200
> @@ -0,0 +1,29 @@
> +/* PR tree-optimization/115337 */
> +/* { dg-do run { target bitint } } */
> +/* { dg-options "-O2" } */
> +
> +#if __BITINT_MAXWIDTH__ >= 129
> +#define N 128
> +#else
> +#define N 63
> +#endif
> +
> +_BitInt (N) g;
> +int c;
> +
> +void
> +foo (unsigned _BitInt (N + 1) z, _BitInt (N) *ret)
> +{
> + c = __builtin_stdc_first_leading_one (z << N);
> + _BitInt (N) y = *(_BitInt (N) *) __builtin_memset (&g, c, 5);
> + *ret = y;
> +}
> +
> +int
> +main ()
> +{
> + _BitInt (N) x;
> + foo (0, &x);
> + if (c || g || 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)
