[GHC] #6084: Add stg_ap_pnnv and related call patterns

[GHC]

#6084: Add stg_ap_pnnv and related call patterns
---------------------------------+------------------------------------------
    Reporter:  SimonMeier        |       Owner:  simonmar        
        Type:  feature request   |      Status:  new             
    Priority:  normal            |   Milestone:  7.8.1           
   Component:  Runtime System    |     Version:  7.4.1           
    Keywords:                    |          Os:  Unknown/Multiple
Architecture:  Unknown/Multiple  |     Failure:  None/Unknown    
  Difficulty:  Unknown           |    Testcase:                  
   Blockedby:                    |    Blocking:                  
     Related:                    |  
---------------------------------+------------------------------------------

Comment(by simonmar):

 A better fix for this just occurred to me.  If we're making a tail-call to
 an unknown function that would require multiple stack frames, we could
 attempt to shortcut it like this (pseudo code):

 {{{
   if (GET_TAG(fun) != 0 && fun->header.info.f.arity == 5) {
      // make a fast call with args in regs
   } else {
      // make the slow call as before
   }
 }}}

 This is more code of course, but the advantage is that it doesn't require
 us to guess which call patterns we need.  It could be enabled with -O2
 only, and only if we're making a call that would need, say, 3 or more
 frames.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6084#comment:6>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler