> On 7 Feb 2025, at 01:04, Andrew Pinski <quic_apin...@quicinc.com> wrote:
>
> With release checking we get an uninitialization warning
> inside aarch64_split_move because of jump threading for the case of
> `npieces==0`
> but `npieces` is never 0 (but there is no way the compiler can know that.
> So this fixes the issue by adding a `gcc_assert` to the function which asserts
> that `npieces > 0` and fixes the uninitialization warning.
>
> Bootstrapped and tested on aarch64-linux-gnu (with and without
> --enable-checking=release).
>
> The warning:
>
> aarch64.cc: In function 'void aarch64_split_move(rtx, rtx, machine_mode)':
> aarch64.cc:3418:31: error: '*(rtx_def**)((char*)&dst_pieces +
> offsetof(auto_vec<rtx_def*, 4>,auto_vec<rtx_def*, 4>::m_data[0]))' may be
> used uninitialized [-Werror=maybe-uninitialized]
> 3418 | if (reg_overlap_mentioned_p (dst_pieces[0], src))
> | ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~
> aarch64.cc:3408:20: note: 'dst_pieces' declared here
> 3408 | auto_vec<rtx, 4> dst_pieces, src_pieces;
> | ^~~~~~~~~~
>
> PR target/118771
> gcc/ChangeLog:
>
> * config/aarch64/aarch64.cc (aarch64_split_move): Assert that npieces is
> greater than 0.
>
Ok.
Thanks,
Kyrill
> Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
> ---
> gcc/config/aarch64/aarch64.cc | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
> index c1e40200806..f5f23f6ff4b 100644
> --- a/gcc/config/aarch64/aarch64.cc
> +++ b/gcc/config/aarch64/aarch64.cc
> @@ -3407,6 +3407,9 @@ aarch64_split_move (rtx dst, rtx src, machine_mode
> single_mode)
> GET_MODE_SIZE (single_mode)).to_constant ();
> auto_vec<rtx, 4> dst_pieces, src_pieces;
>
> + /* There should be at least one piece. */
> + gcc_assert (npieces > 0);
> +
> for (unsigned int i = 0; i < npieces; ++i)
> {
> auto off = i * GET_MODE_SIZE (single_mode);
> --
> 2.43.0
>
