Firrtl compiles too slow with MediumBooms config

[shinezyy]

Recently, I tried to build a medium boom for performance test. It takes 80+ minutes for firrtl to generated the verilog source code. I also built it from this boom-template from scratch without local modification, and ended up with similar results.

The I found that firrtl complie time is related to the size of Load Queue. Following table lists my results:

Load queue entries: Total FIRRTL Compile Time

• 12: 126s
• 13: 187s
• 14: 387s
• 15: ???
• 16: 80+ minites