On Thu, 26 Feb 2026, Xi Ruoyao wrote:
> The comment above expand_vector_broadcast() states a precondition that
> the mode of op must be the element mode of vmode. But when
> expand_binop() called expand_vector_broadcast() to broadcast the shift
> amount, it only truncated the shift amount if it's too wide, but no
> action is performed if the shift amount is too narrow.
OK.
Thanks,
Richard.
> PR middle-end/124250
> PR target/123807
>
> gcc/
> * optabs.cc (expand_vector_broadcast): Add a checking assert to
> verify the precondition about the input modes.
> (expand_binop): Extend the shift amount if it's narrower than
> the element of the shifted vector.
>
> gcc/testsuite/
>
> * gcc.c-torture/compile/pr124250.c: New test.
> ---
>
> Bootstrapped and regtested on x86_64-linux-gnu and
> loongarch64-linux-gnu. Ok for trunk?
>
> gcc/optabs.cc | 34 +++++++++++++------
> .../gcc.c-torture/compile/pr124250.c | 8 +++++
> 2 files changed, 31 insertions(+), 11 deletions(-)
> create mode 100644 gcc/testsuite/gcc.c-torture/compile/pr124250.c
>
> diff --git a/gcc/optabs.cc b/gcc/optabs.cc
> index e813cf9b215..249413c7576 100644
> --- a/gcc/optabs.cc
> +++ b/gcc/optabs.cc
> @@ -428,9 +428,9 @@ force_expand_binop (machine_mode mode, optab binoptab,
> return true;
> }
>
> -/* Create a new vector value in VMODE with all elements set to OP. The
> - mode of OP must be the element mode of VMODE. If OP is a constant,
> - then the return value will be a constant. */
> +/* Create a new vector value in VMODE with all elements set to OP. If OP
> + is not a constant, the mode of it must be the element mode of VMODE.
> + If OP is a constant, then the return value will be a constant. */
>
> rtx
> expand_vector_broadcast (machine_mode vmode, rtx op)
> @@ -439,6 +439,8 @@ expand_vector_broadcast (machine_mode vmode, rtx op)
> rtvec vec;
>
> gcc_checking_assert (VECTOR_MODE_P (vmode));
> + gcc_checking_assert (CONST_INT_P (op)
> + || GET_MODE_INNER (vmode) == GET_MODE (op));
>
> if (valid_for_const_vector_p (vmode, op))
> return gen_const_vec_duplicate (vmode, op);
> @@ -1629,15 +1631,25 @@ expand_binop (machine_mode mode, optab binoptab, rtx
> op0, rtx op1,
> if (otheroptab
> && (icode = optab_handler (otheroptab, mode)) != CODE_FOR_nothing)
> {
> - /* The scalar may have been extended to be too wide. Truncate
> - it back to the proper size to fit in the broadcast vector. */
> + /* The scalar may be wider or narrower than the vector element.
> + Truncate or extend it to the proper size to fit in the
> + broadcast vector. */
> scalar_mode inner_mode = GET_MODE_INNER (mode);
> - if (!CONST_INT_P (op1)
> - && (GET_MODE_BITSIZE (as_a <scalar_int_mode> (GET_MODE (op1)))
> - > GET_MODE_BITSIZE (inner_mode)))
> - op1 = force_reg (inner_mode,
> - simplify_gen_unary (TRUNCATE, inner_mode, op1,
> - GET_MODE (op1)));
> + if (!CONST_INT_P (op1))
> + {
> + auto mode1 = as_a <scalar_int_mode> (GET_MODE (op1));
> + int size1 = GET_MODE_BITSIZE (mode1);
> + int inner_size = GET_MODE_BITSIZE (inner_mode);
> +
> + if (size1 != inner_size)
> + {
> + auto unary = size1 > inner_size ? TRUNCATE : ZERO_EXTEND;
> + op1 = force_reg (inner_mode,
> + simplify_gen_unary (unary, inner_mode,
> + op1, mode1));
> + }
> + }
> +
> rtx vop1 = expand_vector_broadcast (mode, op1);
> if (vop1)
> {
> diff --git a/gcc/testsuite/gcc.c-torture/compile/pr124250.c
> b/gcc/testsuite/gcc.c-torture/compile/pr124250.c
> new file mode 100644
> index 00000000000..1435091dc0b
> --- /dev/null
> +++ b/gcc/testsuite/gcc.c-torture/compile/pr124250.c
> @@ -0,0 +1,8 @@
> +typedef long long v2i64 __attribute__ ((vector_size (16), aligned (16)));
> +v2i64 a, b;
> +
> +void
> +test (int l)
> +{
> + a = b >> (-l);
> +}
>
--
Richard Biener <[email protected]>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
