Exploding link time for x86_64 with ld/2.14

[Tyler Bennett]

I am experiencing nearly exponential time growth when compared to 
executable size.  I am comparing performance against an Alpha EV68 
processor also using ld version 2.14.  Both machines are compiling for 
64-bit executables.  While the Alpha grows linearly or better with 
executable size, the Opteron grows to unacceptable link times.

For example, a 30MB executable takes 3 seconds on the Alpha vs. 5 
minutes on the Opteron.  Going to a 100MB executable, the Alpha only 
takes 5-10 seconds while the Opteron explodes to over 2 hours.

The executables are logic simulators with ~10,000 functions, extremely 
large symbol tables, and large static memory space.  While linking, ld 
has the processor pegged and utilizes ~200MB of system memory (for the 
100MB simulation executable).

If anyone has any ideas or needs more information, please let me know.  
In general, the Opteron system I am using exhibits 2-3x the performance 
of the Alpha system it will be replacing; so, you can see why I'm 
surprised by the terrible link performance.

Thank you.