On Tue, Jul 22, 2025 at 7:57 PM Andrew Pinski <quic_apin...@quicinc.com> wrote:
>
> The switch conversion code will generate an array with VLA vector constants
> in it
> in some cases but this does not work as the length of the vector type is not
> known
> at compile time; only the min size is known.
>
> I tried to reject this in initializer_constant_valid_p but code from the C++
> front-end
> will call initializer_constant_valid_p for `vector_arrayx4()` and then will
> cause an ICE
> with g++.target/aarch64/sve/pr116595.C (and
> g++.target/riscv/rvv/autovec/pr116595.C).
>
> Built and tested for aarch64-linux-gnu.
>
> PR tree-optimization/121091
>
> gcc/ChangeLog:
>
> * tree-switch-conversion.cc (switch_conversion::check_final_bb):
> Reject vector types which
> have a non-constant number of elements.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/aarch64/sve/pr121091-1.c: New test.
>
> Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
> ---
> .../gcc.target/aarch64/sve/pr121091-1.c | 25 +++++++++++++++++++
> gcc/tree-switch-conversion.cc | 3 +++
> 2 files changed, 28 insertions(+)
> create mode 100644 gcc/testsuite/gcc.target/aarch64/sve/pr121091-1.c
>
> diff --git a/gcc/testsuite/gcc.target/aarch64/sve/pr121091-1.c
> b/gcc/testsuite/gcc.target/aarch64/sve/pr121091-1.c
> new file mode 100644
> index 00000000000..ea2e5ce6b6a
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/sve/pr121091-1.c
> @@ -0,0 +1,25 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2" } */
> +
> +/* PR tree-optimization/121091 */
> +/* Switch conversion would convert this
> + into static constant array but since
> + svbool_t is a VLA type, it can't be
> + stored in a constant pool. */
> +
> +#include "arm_sve.h"
> +
> +svbool_t e(int mode, svbool_t pg) {
> + switch (mode) {
> + case 0:
> + pg = svptrue_pat_b16(SV_VL6);
> + break;
> + case 1:
> + pg = svpfalse_b();
> + break;
> + case 2:
> + pg = svptrue_pat_b16(SV_VL2);
> + break;
> + }
> + return pg;
> +}
> diff --git a/gcc/tree-switch-conversion.cc b/gcc/tree-switch-conversion.cc
> index d0882879e61..dc9f67bd272 100644
> --- a/gcc/tree-switch-conversion.cc
> +++ b/gcc/tree-switch-conversion.cc
> @@ -636,6 +636,9 @@ switch_conversion::check_final_bb ()
> val = gimple_phi_arg_def (phi, i);
> if (!is_gimple_ip_invariant (val))
> reason = "non-invariant value from a case";
> + else if (VECTOR_TYPE_P (TREE_TYPE (val))
> + && !TYPE_VECTOR_SUBPARTS (TREE_TYPE (val)).is_constant
> ())
> + reason = "VLA vector type";
OK with me, but then I see ...
> else
> {
> reloc = initializer_constant_valid_p (val, TREE_TYPE (val));
... this and wonder why initializer_constant_valid_p says a VLA vector
constant is valid?
Richard.
> --
> 2.43.0
>
