On 24/10/2022 08:17, Richard Biener wrote:
Can you check why vect_find_stmt_data_reference doesn't trip on the
if (TREE_CODE (DR_REF (dr)) == COMPONENT_REF
&& DECL_BIT_FIELD (TREE_OPERAND (DR_REF (dr), 1)))
{
free_data_ref (dr);
return opt_result::failure_at (stmt,
"not vectorized:"
" statement is an unsupported"
" bitfield access %G", stmt);
}
It used to, which is why this test didn't trigger the error before my
patch, but we lower it to BIT_FIELD_REFs in ifcvt now so it is no longer
a DECL_BIT_FIELD.
But that is a red-herring, if you change the test structure's 'type
Int24 is mod 2**24;' to 'type Int24 is mod 2**32;', thus making the
field we access a normal 32-bit integer, the field no longer is a
DECL_BIT_FIELD and thus my lowering does nothing. However, you will
still get the failure because the field before it is a packed 4-bit
field, making the offset to the field we are accessing less than
BITS_PER_UNIT.
? I think we should amend this check and I guess that
checking multiple_p on DECL_FIELD_BIT_OFFSET should be enough?
That won't work either, unless we do the same walk-through the full
access as we do in get_inner_reference.
Let me elaborate, the 'offending' stmt here is:
_ifc__23 = (*x_7(D))[_1].b.D.3707;
And the struct in question is:
package Loop_Optimization23_Pkg is
type Nibble is mod 2**4;
type Int24 is mod 2**24;
type StructA is record
a : Nibble;
b : Int24;
end record;
pragma Pack(StructA);
type StructB is record
a : Nibble;
b : StructA;
end record;
pragma Pack(StructB);
type ArrayOfStructB is array(0..100) of StructB;
procedure Foo (X : in out ArrayOfStructB);
end Loop_Optimization23_Pkg;
That D.3707 is the 'container'm i.e. the DECL_BIT_FIELD_REPRESENTATIVE
of the original bitfield of type Int24.
So in vect_find_stmt_data_reference , the dr is: (*x_7(D))[_1].b.D.3707 and
TREE_OPERAND (DR_REF (dr), 1): D.3707,
which has DECL_FIELD_BIT_OFFSET: 0
So that check would also pass. However, get_inner_reference, walks the
full access and comes across '.b', the member access for StructA inside
StructB, that has DECL_FIELD_BIT_OFFSET: 4
Which is where we get into trouble. So to catch that here, we would need
to do the same type of walking through all the member accesses, like
get_inner_reference does.
