http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51895
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2012-01-19
Target Milestone|--- |4.7.0
Ever Confirmed|0 |1
--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-01-19
10:06:38 UTC ---
(In reply to comment #2)
> This starts with eipa_sra. It changes a S argument (which has TImode
> TYPE_MODE) into char [9] (with BLKmode)) and then on both caller and callee
> side we have on one side a BLKmode type and on the other side a BLKmode
> MEM_REF
> with pointer to TImode on the second MEM_REF operand.
> I wonder why it does this, instead of just using type S, and if it really has
> to for some reason, why it can't at least make sure it has the same TYPE_MODE.
> Changing a TImode argument to a BLKmode argument doesn't look at least like a
> good optimization.
>
> Or the bug is in the MEM_REF expansion, which expands a BLKmode MEM_REF into a
> TImode reg:
> bftype = TREE_TYPE (base);
> if (TYPE_MODE (TREE_TYPE (exp)) != BLKmode)
> bftype = TREE_TYPE (exp);
> return expand_expr (build3 (BIT_FIELD_REF, bftype,
> base,
> TYPE_SIZE (TREE_TYPE (exp)),
> bit_offset),
> target, tmode, modifier);
> base here is TImode (x PARM_DECL), but exp is BLKmode, so this returns a
> TImode
> pseudo. Shouldn't it store it into a BLKmode temporary and return that MEM
> instead?
Using a BIT_FIELD_REF looked most convenient. Using extract_bit_field
may also be an option (which I suppose is what the above ends up doing?)
