bootstrap failure with cvs current and --enable-checking

[grahams]

Andreas

This failure isn't new it been failing for me like this since about
the egcs-19991004 snapshot. Bootstraps go fine without enable-checking
but bombs in alias.c with configured for enable-checking.

Notice that the rtx has been garbage collected by GC code, the evidence 
is that the fields in the rtx have values of 0xa5a5a5a5

I sent a message to jeff, rth, and mark about the possible need to add
some ggc-roots in the alias.c code.

When I modified my local tree to register the reg_known_value, reg_base_value,
new_reg_base_value and alias_invariant arrays as ggc_roots I was able to
bootstrap with enable checking enabled.

I'll dig up my modification to alias.c and send them to the gcc-patches list.

Graham