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?)