[RFA 0/9] Address space support for x86

[Richard Henderson <rth at redhat dot com>]

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.

(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

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