On Wed, Jul 23, 2025 at 12:03 AM Richard Biener
<richard.guent...@gmail.com> wrote:
>
> 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?
I tried to describe why changing initializer_constant_valid_p won't
work in the commit message:
> > 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).
Maybe I was not clear enough or there was not enough information there on it.
Thanks,
Andrew Pinski
>
> Richard.
>
> > --
> > 2.43.0
> >
