On Mon, Nov 05, 2012 at 05:20:46PM +0100, Jan Hubicka wrote: > > Hi, > > > > the patch below disables generation of aggregate jump functions from > > bit-field stores because currently we depend on type size of the value > > to determine the size of the stored value and that does not work with > > bit-fields, making it impossible for IPA-CP to organize them in their > > lattices. > > > > If we ever decide aggregate jump functions for bit-fields are worth > > the hassle, we might remove this limitation by storing and streaming > > the size of the memory reference alongside the offset in the jump > > functions (and IPA-CP lattices). > > > > Bootstrapped and tested on x86_64-linux, needed for the aggregate > > IPA-CP. OK for trunk? > > > > Thanks, > > > > Martin > > > > > > 2012-11-02 Martin Jambor <mjam...@suse.cz> > > > > * ipa-prop.c (determine_known_aggregate_parts): Do not create > > aggregate jump functions for bit-fields. > > > > Index: src/gcc/ipa-prop.c > > =================================================================== > > --- src.orig/gcc/ipa-prop.c > > +++ src/gcc/ipa-prop.c > > @@ -1295,7 +1295,10 @@ determine_known_aggregate_parts (gimple > > > > lhs = gimple_assign_lhs (stmt); > > rhs = gimple_assign_rhs1 (stmt); > > - if (!is_gimple_reg_type (rhs)) > > + if (!is_gimple_reg_type (rhs) > > + || TREE_CODE (lhs) == BIT_FIELD_REF > > + || (TREE_CODE (lhs) == COMPONENT_REF > > + && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1)))) > > I am not sure I understand motivation of this patch properly. First I think > BIT_FIELD_REF can be hidden inside chain of other REFs so you should probably > look into all handled components. What exactly goes wrong when your type size > is bigger than the bitfield? >
I hit an assert in the patch I am about to post (I am writing the changelog right now) I hit an assert checking that stuff does not overlap in IPA-CP aggregate lattices. My initial reaction was that I did not want to deal with bit-fields, unless really necessary ;-) However, that assert can be easily changed to bottomizing the lattice, I will re-test with that and if there are no problems, this patch can be omitted. Thanks, Martin
