gcc46: .././../gcc-4.6-20121123/gcc/rtl.h:2105:31: error: use of undeclared identifier 'FIRST_PSEUDO_REGISTER', rtx x_initial_regno_reg_rtx[FIRST_PSEUDO_REGISTER];

On exactly ONE FreeBSD 10.0-CURRENT box, out of a couple, all the same
OS version (most recent sources/buildworld with CLANG and ports tree
always up to date) I get this nasty error shown below.

I can not reproduce this problem on other machines of the very same
architecture (neither Core2Duo or even up to Ivy Bridge CPUs, if the
-march=native option would cause the problem).

I'm helpless. I replaced gcc46 by now with gcc47, but I can not
update/repair the ports database, since many packages which do not
compile with CLANG neede gcc46 as a dependency and pkgdb -F doesn't work
with the unfinished PKGNG version we use by default now on FreeBSD 10.

Since I'm now convinced, that the error is triggered by some shadowed
problems of that specific box, can someone help and suggest where to
llok after? As I said, I deleted the port lang/gcc46 and replaced it
with lang/gcc47 (but didn't it properly with portupgrade -o). Maybe
there are still remains of the gcc46 leftover. How to finde those and
kill them - if?

Tahnks in advance,

Oliver

[...]
cc -c   -O3 -pipe -fno-strict-aliasing -march=native -march=native
-I/usr/local/include -DIN_GCC   -W -Wall -Wwrite-strings -Wcast-qual
-Wstrict-prototypes -Wmissing-prototypes -Wmissing-format-attribute
-pedantic -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings
-Wold-style-definition -Wc++-compat   -DHAVE_CONFIG_H -DGENERATOR_FILE
-I. -Ibuild -I.././../gcc-4.6-20121123/gcc
-I.././../gcc-4.6-20121123/gcc/build
-I.././../gcc-4.6-20121123/gcc/../include
-I.././../gcc-4.6-20121123/gcc/../libcpp/include -I/usr/local/include
-I.././../gcc-4.6-20121123/gcc/../libdecnumber
-I.././../gcc-4.6-20121123/gcc/../libdecnumber/dpd -I../libdecnumber
-I/usr/local/include \
        -o build/genflags.o .././../gcc-4.6-20121123/gcc/genflags.c
In file included from .././../gcc-4.6-20121123/gcc/genflags.c:28:
.././../gcc-4.6-20121123/gcc/rtl.h:1989:13: warning: ISO C forbids
forward references to 'enum' types [-Wpedantic]
extern enum reg_class reg_preferred_class (int);
            ^
.././../gcc-4.6-20121123/gcc/rtl.h:2105:31: error: use of undeclared
identifier 'FIRST_PSEUDO_REGISTER'
  rtx x_initial_regno_reg_rtx[FIRST_PSEUDO_REGISTER];
                              ^
.././../gcc-4.6-20121123/gcc/rtl.h:2112:31: error: use of undeclared
identifier 'FIRST_PSEUDO_REGISTER'
  rtx x_static_reg_base_value[FIRST_PSEUDO_REGISTER];
                              ^
1 warning and 2 errors generated.
gmake[2]: *** [build/genflags.o] Error 1
gmake[2]: Leaving directory `/usr/ports/lang/gcc46/work/build/gcc'
gmake[1]: *** [all-gcc] Error 2
gmake[1]: Leaving directory `/usr/ports/lang/gcc46/work/build'
gmake: *** [all] Error 2
*** [do-build] Error code 1

Stop in /usr/ports/lang/gcc46.
*** [build] Error code 1

Stop in /usr/ports/lang/gcc46.