An issue for the SC: horrible documentation quality of GCC

[Richard Kenner]

    It seems to be a confusing name, as it doesn't work locally at all.  

Then it what sense is it "local"?  Do you know?

      p1 <-- 100
      p2 <-- p1 + p3
    into
      p1 <-- 100
      p2 <-- 100 + p3

For many machines, the former is better.  CSE has lots of logic to do this
and knows which is better.  What is this code doing, why does it to things
differently than CSE, and how does it interact with CSE?  These are both
questions and things that need to be documented in the code.

I'd expect gcse to only operate on the *start* of a basic block and let
CSE make the decisions *within* the block.  But the code doesn't seem to
do that.  Without the missing documentation, I can't tell if that's a bug
in the code or is the way it was designed to work.