On Fri, Sep 18, 2026 at 11:50 PM Stefan Schulze Frielinghaus
<[email protected]> wrote:
>
> From: Stefan Schulze Frielinghaus <[email protected]>
>
> When expand_mult handles a constant vector multiplier where the scalar
> operand is a CONST_WIDE_INT, then also look through the vector mode
> while determining the shift amount since here we need the scalar mode.
> Note, when we call later on into expand_shift we need the vector mode,
> i.e., only for the shift amount we need the scalar mode.
>
> I guess it would have been sound to call unconditionally into
> GET_MODE_INNER, i.e., even for scalars (kinda similar as for
> GET_MODE_UNIT_BITSIZE from above), however, I think checking for
> VECTOR_MODE_P here makes the intend explicit.
>
> PR middle-end/127474
>
> gcc/ChangeLog:
>
> * expmed.cc (expand_mult): Look through vector mode.
Ok except for a minor change to the testcase listed below.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/s390/pr127474.c: New test.
> ---
> Bootstrapped and regtested for
> - aarch64-unknown-linux-gnu
> - powerpc64le-unknown-linux-gnu
> - s390x-ibm-linux-gnu
> - x86_64-pc-linux-gnu
> Ok for mainline?
>
> gcc/expmed.cc | 4 +++-
> gcc/testsuite/gcc.target/s390/pr127474.c | 11 +++++++++++
> 2 files changed, 14 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/gcc.target/s390/pr127474.c
>
> diff --git a/gcc/expmed.cc b/gcc/expmed.cc
> index c6494484251..b82c0bb10db 100644
> --- a/gcc/expmed.cc
> +++ b/gcc/expmed.cc
> @@ -3633,7 +3633,9 @@ expand_mult (machine_mode mode, rtx op0, rtx op1, rtx
> target,
> else if (CONST_DOUBLE_AS_INT_P (scalar_op1))
> #endif
> {
> - int shift = wi::exact_log2 (rtx_mode_t (scalar_op1, mode));
> + machine_mode scalar_mode = VECTOR_MODE_P (mode)
> + ? GET_MODE_INNER (mode) : mode;
> + int shift = wi::exact_log2 (rtx_mode_t (scalar_op1, scalar_mode));
> /* Perfect power of 2 (other than 1, which is handled above). */
> if (shift > 0)
> return expand_shift (LSHIFT_EXPR, mode, op0,
> diff --git a/gcc/testsuite/gcc.target/s390/pr127474.c
> b/gcc/testsuite/gcc.target/s390/pr127474.c
> new file mode 100644
> index 00000000000..a5580ee3b6a
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/s390/pr127474.c
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -march=z17" } */
Can you place this in gcc.dg/torture/
and change dg-options to dg-additional-options and make that s390x and
remove -O2?
Thanks,
Andrea
> +
> +/* Previously we ICE'd in expand_mult when dealing with a CONST_WIDE_INT. */
> +
> +typedef __int128 v1ti __attribute__ ((vector_size (16)));
> +
> +v1ti foo (v1ti x)
> +{
> + return x * (v1ti){(__int128)123456789 << 64 | (__int128)123456789};
> +}
> --
> 2.55.0
>
