[Bug middle-end/51895] [4.7 Regression] ICE in simplify_subreg

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51895

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jamborm at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-01-19 07:33:07 UTC ---
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?