cvs commit: fptools/ghc/compiler/basicTypes MkId.lhs fptools/ghc/compiler/prelude PrelNames.lhs fptools/libraries/base/GHC Base.lhs IOBase.lhs

[Simon Marlow]

simonmar    2003/01/24 06:04:41 PST

  Modified files:
    ghc/compiler/basicTypes MkId.lhs 
    ghc/compiler/prelude PrelNames.lhs 
    libraries/base/GHC   Base.lhs IOBase.lhs 
  Log:
  - Generalise seq to allow an unlifted type in its second argument.  This
    works because seq is *always* inlined and replaced by a case.
  
  - Remove getTag, a wired-in Id with an unfolding, with a definition
    in GHC.Base:
  
  	getTag x = x `seq` dataToTag# x
  
    this is why we required the above generalisation to seq (dataToTag#
    returns an Int#).  See the comments in GHC.Base for more details.
  
  - As a side-effect, this fixes a bug in the interpreter, where the
    compiler optimised away the evaluation of the argument to dataToTag#,
    but the interpreter ended up passing it an unevaluated thunk (nullary
    constructors aren't always evaluated in GHCi, but the simplifier
    assumes they are).  Now, in the interpreter, getTag won't be inlined
    so the compiler can't optimise away the evaluation, and we're saved.
  
    The real bug here is either (a) dataToTag# requires an evaluated
    argument or (b) the interpreter doesn't supply it with one, take your
    pick.
  
  Revision  Changes    Path
  1.107     +4 -23     fptools/ghc/compiler/basicTypes/MkId.lhs
  1.68      +1 -4      fptools/ghc/compiler/prelude/PrelNames.lhs
  1.22      +22 -0     fptools/libraries/base/GHC/Base.lhs
  1.25      +1 -1      fptools/libraries/base/GHC/IOBase.lhs