bogus asm on alpha compiling big bison output

["Greg Lindahl" <lindahl at pbm dot com>]

egcs-1.0.1, Redhat 5.0, built it myself with no funny options, LX164

I have a rather large bison parser which works OK on our other systems.
On RH5.0/alpha, I get:

[lindahl@centurion001 mplc]$ g++-egcs
-I/home/localtmp/lindahl/Legion/src/Compiler/mplc
-I/home/localtmp/lindahl/Legion/obj/alpha_linux/g++
-I/home/localtmp/lindahl/Legion/include -w -fpic -DGNU -Dalpha_linux
-I/home/localtmp/lindahl/Legion/include/mplc/local/alpha_linux/gnu/g++
-g -c /home/localtmp/lindahl/Legion/obj/alpha_linux/g++/parser.tab.c
-o /home/localtmp/lindahl/Legion/obj/alpha_linux/g++/parser.o
/usr/lib/bison.simple: In function `int yyparse()':
/usr/lib/bison.simple:692: internal error--unrecognizable insn:
(insn 112872 112869 112873 (set (reg:DI 5 $5)
        (plus:DI (reg:DI 15 $15)
            (const_int 45248))) -1 (nil)
    (nil))
/usr/lib/bison.simple:692: confused by earlier errors, bailing out

If I turn on -O, the optimizer is not bounded in time and space
(cough), I killed it when it hit 100 megabytes of swap. This input
file is only 14,000 lines.

I have a much smaller grammar that compiles successfully.

Do you have any suggestions for reducing this to a bug report you
can actually do something with?