On Mon, 28 Sep 2026, Tamar Christina wrote:
> When doing profiledbootstrap the compiler fails with -Wuninitialized
> false positive in stageprofile-bubble
>
> This is a false positive as the analyzer seems unable to see that if
> is_a <.., &foo> passes that foo will be initialized.
>
> There didn't seem to be a good "initial" value here that wouldn't be
> confusing so instead I rewrote the check to avoid the out parameter.
>
> Bootstrapped Regtested on aarch64-none-linux-gnu,
> arm-none-linux-gnueabihf, x86_64-pc-linux-gnu
> -m32, -m64
>
> with:
>
> - default bootstrap
> - profiledbootstrap
>
> and no issues.
>
> Ok for master?
>
> Thanks,
> Tamar
>
> gcc/ChangeLog:
>
> PR bootstrap/127635
> * simplify-rtx.cc (simplify_context::simplify_subreg): Avoid is_a<..>
> with ref param.
>
> ---
> diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
> index
> 285826a3fedac7dc95efb27f37b9ef7a7a1ef7e2..7c068814ae7cfa9477bcb370007b05d9649de8a5
> 100644
> --- a/gcc/simplify-rtx.cc
> +++ b/gcc/simplify-rtx.cc
> @@ -8959,10 +8959,15 @@ simplify_context::simplify_subreg (machine_mode
> outermode, rtx op,
> break;
> }
>
> - if (is_a <scalar_int_mode> (outermode, &int_outermode)
> - && is_a <scalar_int_mode> (innermode, &int_innermode)
> - && known_eq (byte, subreg_lowpart_offset (int_outermode,
> int_innermode)))
> + if (SCALAR_INT_MODE_P (outermode)
> + && SCALAR_INT_MODE_P (innermode)
Can you retain is_a <> here, but in it's single-argument form?
OK with that change unless Richard has a better idea.
Richard.
> + && known_eq (byte,
> + subreg_lowpart_offset (as_a <scalar_int_mode> (outermode),
> + as_a <scalar_int_mode> (innermode))))
> {
> + scalar_int_mode int_outermode = as_a <scalar_int_mode> (outermode);
> + scalar_int_mode int_innermode = as_a <scalar_int_mode> (innermode);
> +
> /* Handle polynomial integers. The upper bits of a paradoxical
> subreg are undefined, so this is safe regardless of whether
> we're truncating or extending. */
>
>
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Stefan Gaiser, Jochen Jaser, Abhinav Puri; (HRB 36809, AG Nuernberg)
