[LLVMdev] testing instruction selection

[reed kotler]

It's kind of troubling that you can't create test cases that start with 
DAG as opposed to bitcode .ll.

It's very tedious sometimes to go through and make sure that you have 
really tested all your patterns and sometimes the compiler changes and 
it stops generating those patterns but may resume generating them later.

So if you make a change at a time when it's not generating them, then 
there are two issues:
1) you can't test them. you might think you did but those patterns are 
not being generated any more
2) later when the patterns reappear, now you have compiler code that has 
never been tested.