On Thu, Oct 8, 2015 at 6:59 AM, Richard Henderson <r...@redhat.com> wrote: > I started with Armin Rigo's patch, from back in July, > > https://gcc.gnu.org/ml/gcc/2015-07/msg00125.html > > but then wound up changing all of it. To wit: > > (1) If we use more sensible defaults for address spaces, we no longer > require 8 backend functions and 1 new hook. Indeed, basic support for > x86 segmentation via address spaces then requires no overriding of any > hooks. > > (2) In order to do anything useful with x86 segmentation, we need to > acknowledge that the most common usage puts a valid object at %seg:0. > Which means that we do need a new hook to disable several optimizations.
We could of course simply make all but the default address-space fall under -fno-delete-null-pointer-check rules... > (3) I found that usage within glibc really requires a more structured > address space, one with a known mapping to the generic address space. > Thus I introduce __seg_tls, which knows that the segment base is also > stored at %seg:0. > > (4) I attempted to convert the entire tls implementation to use __seg_tls. > I believe this is ultimately the best long-term solution, but I ran into > a number of problems both generically and in the backend that prevented > this from being simple. I've dropped these patches for now. > > (5) However, in the process of attempting (4), I found two problems in > the backend that could affect any use of address spaces: the movabs > patterns and string expansions. > > > r~ > > > Richard Henderson (9): > Change default of non-overlapping address space conversion > Relax ADDR_SPACE_GENERIC_P checks for default address space hooks > i386: Handle address spaces in movabs patterns > i386: Disallow address spaces with string insns > i386: Add address spaces for fs/gs segments > i386: Replace ix86_address_seg with addr_space_t > i386: Add address space for tls > Add TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID > Fix PR 66768 > > gcc/config/i386/i386-c.c | 8 + > gcc/config/i386/i386-protos.h | 8 +- > gcc/config/i386/i386.c | 296 > +++++++++++++++++++-------- > gcc/config/i386/i386.h | 3 +- > gcc/config/i386/i386.md | 91 +++++--- > gcc/config/i386/predicates.md | 8 +- > gcc/config/i386/rdos.h | 2 +- > gcc/doc/tm.texi | 5 + > gcc/doc/tm.texi.in | 2 + > gcc/expr.c | 30 +-- > gcc/fold-const.c | 6 +- > gcc/gimple.c | 12 +- > gcc/target.def | 9 + > gcc/targhooks.c | 48 ++--- > gcc/targhooks.h | 1 + > gcc/testsuite/gcc.target/i386/addr-space-1.c | 11 + > gcc/tree-ssa-address.c | 2 +- > 17 files changed, 385 insertions(+), 157 deletions(-) > create mode 100644 gcc/testsuite/gcc.target/i386/addr-space-1.c > > -- > 2.4.3 >
