[Bug target/77586] [7 Regression] ia64 target fails to build due to ICE triggered by -fself-test

["jsm28 at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77586

--- Comment #3 from Joseph S. Myers <jsm28 at gcc dot gnu.org> ---
Author: jsm28
Date: Mon Oct 10 22:43:07 2016
New Revision: 240955

URL: https://gcc.gnu.org/viewcvs?rev=240955&root=gcc&view=rev
Log:
Always support float128 on ia64 (PR target/77586).

Bug 77586, and previously
<https://gcc.gnu.org/ml/gcc-bugs/2016-08/msg03233.html>, reports
ia64-elf failing to build because of float128_type_node being NULL,
but being used by the back end for __float128.

The global float128_type_node is only available conditionally, if
target hooks indicate TFmode is not only available as a scalar mode
and of the right format, but also supported in libgcc.  The back-end
support, however, expects the type always to be available for
__float128 even if the libgcc support is missing.

Although a target-specific node could be restored in the case where
libgcc support is missing, it seems better to address the missing
libgcc support.  Thus, this patch enables TFmode soft-fp in libgcc
globally for all ia64 targets.  Support for XFmode in libgcc (that is,
for libgcc2.c XFmode functions, not soft-fp) is also enabled for all
ia64 targets so that ia64 no longer needs to define the
TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P hook.

I've confirmed that ia64-elf builds cc1 with this patch and it passes
-fself-test.  I have not otherwise tested the patch.  It's plausible
that ia64-elf and ia64-freebsd might work as-is, but ia64-vms probably
needs further changes, by someone familiar with VMS shared libraries,
to implement an equivalent of ia64/t-softfp-compat in that case
(avoiding conflicts between __divtf3 from soft-fp and the old alias
for __divxf3).

        PR target/77586
gcc:
        * config/ia64/ia64.c (ia64_libgcc_floating_mode_supported_p)
        (TARGET_LIBGCC_FLOATING_MODE_SUPPORTED_P): Remove.
        * config/ia64/elf.h (IA64_NO_LIBGCC_TFMODE): Likewise.
        * config/ia64/freebsd.h (IA64_NO_LIBGCC_TFMODE): Likewise.
        * config/ia64/vms.h (IA64_NO_LIBGCC_XFMODE)
        (IA64_NO_LIBGCC_TFMODE): Likewise.

libgcc:
        * config.host (ia64*-*-elf*, ia64*-*-freebsd*, ia64-hp-*vms*): Use
        soft-fp.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/ia64/elf.h
    trunk/gcc/config/ia64/freebsd.h
    trunk/gcc/config/ia64/ia64.c
    trunk/gcc/config/ia64/vms.h
    trunk/libgcc/ChangeLog
    trunk/libgcc/config.host