On Sat, Sep 19, 2026 at 05:49:50AM -0700, Andrea Pinski wrote:
> 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?
I also added dg-require-effective-target int128 and ran the new test for
- aarch64-unknown-linux-gnu
- powerpc64le-unknown-linux-gnu
- s390x-ibm-linux-gnu
- x86_64-pc-linux-gnu
Pushed as r17-4477-g5dc4ab23e0d.
Cheers,
Stefan
>
> 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
> >
