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From: "stammark at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/96974] [10/11 Regression] ICE in
 vect_get_vector_types_for_stmt compiling for SVE
Date: Mon, 18 Jan 2021 13:32:19 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D96974

--- Comment #5 from Stam Markianos-Wright <stammark at gcc dot gnu.org> ---
(In reply to rsandifo@gcc.gnu.org from comment #4)
> (In reply to Stam Markianos-Wright from comment #3)
> > Just started looking at this. I've narrowed it as the bug appearing with
> > commit 9b75f56d4b7951c60a656396dddd4a65787b95bc.
> >=20
> > I have yet to fire this up in gdb to see what's happening, but one test=
 I
> > did do was to try commenting out the assert that is causing the ICE and=
 it
> > then ran to completion.=20
> >=20
> > So one _total speculation_ would be that with these latest changes that
> > enable groups of different sizes, this condition in the assert is now t=
oo
> > strict:
> >=20
> >=20
> > multiple_p (TYPE_VECTOR_SUBPARTS (nunits_vectype),
> > 	    TYPE_VECTOR_SUBPARTS (*stmt_vectype_out)))
> What are nunits_vectype and *stmt_vectype_out at the point
> that the assert fails?

Hmm so looking at this on commit 9b75f56d4b7951c60a656396dddd4a65787b95bc,
we have:



nunits_vectype is a: vector(SUBPARTS {coeffs =3D {4, 0}}) float

*stmt_vectype_out is a: vector(SUBPARTS {coeffs =3D {8, 0}}) long int

In this case we are checking multiple_p (4, 8) =3D=3D false
(and also group_size =3D=3D 9 here which is expected)



Before the commit we'd get here with:



nunits_vectype is a: vector(SUBPARTS {coeffs =3D {4, 0}}) float

*stmt_vectype_out is a: vector(SUBPARTS {coeffs =3D {2, 0}}) long int

And here we were checking multiple_p (4, 2) =3D=3D true



I'm tempted to try and add a reverse:

        || multiple_p (*stmt_vectype_out, nunits_vectype)

And then regtest, but I probably need to do more reading around to figure o=
ut
what we really should be expecting each case!=