Ada broken on i686-linux (some progress)

[Jan Hubicka]

> With mainline plus your patch, on x86_64 it gets past the a-ngelfu.adb
> failure but it ICE later in the RTS build:
> 
> ../../xgcc -B../../ -c -g -O2 -fPIC      -W -Wall -gnatpg  g-exctra.adb -o g-exctra.o
> +===========================GNAT BUG DETECTED==============================+
> | 3.5.0 20040909 (experimental) (x86_64-unknown-linux-gnu) GCC error:      |
> | in var_ann, at tree-flow-inline.h:34                                     |
> | Error detected at g-exctra.adb:127:1                                     |
> 
> On x86, it fails mid stage2:
> 
> stage1/xgcc -Bstage1/ -B/home/guerby/work/gcc/install/install-20040909T225159/i686-pc-linux-gnu/bin/ -c -g -O2      -gnatpg -gnata -I- -I. -Iada -I/home/guerby/work/gcc/version-head/gcc/ada /home/guerby/work/gcc/version-head/gcc/ada/g-os_lib.adb -o ada/g-os_lib.o
> /home/guerby/work/gcc/version-head/gcc/ada/g-os_lib.adb: In function `GNAT.OS_LIB.TO_PATH_STRING_ACCESS':
> /home/guerby/work/gcc/version-head/gcc/ada/g-os_lib.adb:2224: error: Definition in block 1 does not dominate use in block 8
> for SSA_NAME: T.2976<D5632>_4
> in statement:
> ivtmp.3319<D6204>_59 = &(*return_val$P_ARRAY<D6188>_31)[2]{lb: T.2976<D5632>_4 sz: 1};

It would be usefull to know the backtraces at least here.  The second
problem looks like yet another tree node sharing problem, so in the case
the failure is within tree-ssa-loop-ivopts, I will try to add more of
unsave_exprs to uses that might result in sharing and lets see if it fix
it.

I dunno what is going wrong in the first case just from the failure
reported.

What is the current situation of ada aware gdb?  I used to have one but
it no longer works on 3.5 GCC produced dwarf and the default in my
instalation just die horribly seeing ada.

Honza