[commit: ghc] master: Add case-floating to the float-out pass (9cb20b4)

[Simon Peyton Jones]

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/9cb20b488d4986c122b0461a54bc5c970f9d8502

>---------------------------------------------------------------

commit 9cb20b488d4986c122b0461a54bc5c970f9d8502
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Mon Jun 27 08:54:29 2011 +0100

    Add case-floating to the float-out pass
    
    There are two things in this patch. First, a new feature.
    Given     (case x of I# y -> ...)
    where 'x' is known to be evaluated, the float-out pass
    will float the case outwards towards x's binding.  Of
    course this doesn't happen if 'x' is evaluated because
    of an enclosing case (becuase then the inner case would
    be eliminated) but it *does* happen when x is bound by
    a constructor with a strict field.  This happens in DPH.
    Trac #4081.
    
    The second change is a significant refactoring of the
    way the let-floater works.  Now SetLevels makes a decision
    about whether the let (or case) will move, and records
    that decision in the FloatSpec flag.  This change makes
    the whole caboodle much easier to think about.

 compiler/simplCore/FloatOut.lhs  |  297 +++++++++++++++++++++----------------
 compiler/simplCore/SetLevels.lhs |  302 ++++++++++++++++++++++----------------
 2 files changed, 343 insertions(+), 256 deletions(-)


Diff suppressed because of size. To see it, use:

    git show 9cb20b488d4986c122b0461a54bc5c970f9d8502