On Thu, Jun 16, 2011 at 6:09 AM, Richard Guenther <rguent...@suse.de> wrote: > > For some reason I split out sanitizing sizetypes from the > no-undefined-overflow-branch. In fact the following patch tries > to only fix one thing - make unsigned sizetypes no longer sign-extended. > > This has (unfortunately) interesting side-effects, and some of them > have been mitigated by already committed patches during the last half > year. The main remaining issue I run into (and that sort-of blocks > me from persuing this really really ...) is that there is a lot of > code in GCC that assumes it can do modulo arithmetic on HOST_WIDE_INTs > for sizetypes (pointers / offsets in general). Which happens to > be wrong when a HOST_WIDE_INT is wider than sizetype (on -m32 multilib > on x86_64 for example). It happens to work in almost all cases > if we sign-extend from 32bit to 64bit HWI but not when we zero-extend. > I'm not exactly sure how to proceeed here, other than adding fixups > to various places (as seen in the patch below) and hope to catch > all existing errors. [yes, I already tried making all sizetypes > signed, really signed, but that has loads of fallout as well] > > That said, the fact that sizetypes are sign-extended has caused > wrong-code bugs in the past, and TYPE_UNSIGNED is really used > inconsistently. So I think this is definitely worth fixing. > > Eventually a first move would be to (finally) get rid of the > requirement of sizetype offset arguments for POINTER_PLUS_EXPR. > I didn't yet start on that project though. > > I remember the following bootstrapped fine on x86_64-unknown-linux-gnu > at least for C, with a few remaining regressions. I'm trying > a full all-lang bootstrap & regtest now. > > Comments? Questions?
Any expected impacts on x32 branch after this changed is merged? > Thanks, > Richard. > > 2011-06-16 Richard Guenther <rguent...@suse.de> > > * fold-const.c (div_if_zero_remainder): sizetypes no longer > sign-extend. > * stor-layout.c (initialize_sizetypes): Likewise. > * tree-ssa-ccp.c (bit_value_unop_1): Likewise. > (bit_value_binop_1): Likewise. > * tree.c (double_int_to_tree): Likewise. > (double_int_fits_to_tree_p): Likewise. > (force_fit_type_double): Likewise. > (host_integerp): Likewise. > (int_fits_type_p): Likewise. > * expr.c (get_inner_reference): Sign-extend offset. > * tree-ssa-structalias.c (get_constraint_for_ptr_offset): Likewise. > * tree-cfg.c (verify_types_in_gimple_reference): Do not compare > sizes by pointer. > -- H.J.
