https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88739
--- Comment #33 from Wilco <wilco at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #32)
> >
> > Index: gcc/expr.c
> > ===================================================================
> > --- gcc/expr.c (revision 267553)
> > +++ gcc/expr.c (working copy)
> > @@ -10562,6 +10562,15 @@ expand_expr_real_1 (tree exp, rtx target
> > infinitely recurse. */
> > gcc_assert (tem != exp);
> >
> > + /* When extracting from non-mode bitsize entities adjust the
> > + bit position for BYTES_BIG_ENDIAN. */
> > + if (INTEGRAL_TYPE_P (TREE_TYPE (tem))
> > + && (TYPE_PRECISION (TREE_TYPE (tem))
> > + < GET_MODE_BITSIZE (as_a <scalar_int_mode> (TYPE_MODE
> > (TREE_TYPE (tem)))))
> > + && BYTES_BIG_ENDIAN)
> > + bitpos += (GET_MODE_BITSIZE (as_a <scalar_int_mode> (TYPE_MODE
> > (TREE_TYPE (tem))))
> > + - TYPE_PRECISION (TREE_TYPE (tem)));
> > +
> > /* If TEM's type is a union of variable size, pass TARGET to the
> > inner
> > computation, since it will need a temporary and TARGET is known
> > to have to do. This occurs in unchecked conversion in Ada. */
>
> Btw, this needs to be amended for WORDS_BIG_ENDIAN of course. I guess
> we might even run into the case that such BIT_FIELD_REF references
> a non-contiguous set of bits... (that's also true for BITS_BIG_ENDIAN !=
> BYTES_BIG_ENDIAN I guess).
Was that meant to be instead or in addition to the tree-ssa-sccvn.c patch? With
both I get:
lsr w20, w1, 2
...
and w1, w20, 65535
With only the expr.c patch it starts to look as expected:
lsr w20, w1, 2
...
lsr w1, w20, 14
And with the latter case the new torture test now passes on big-endian!
