sibbling calls versus integreate.c

[law@redhat.com]

  In message < 20010808182440.E30815@atrey.karlin.mff.cuni.cz >you write:
  > Hi,
  > this huge, but mechanical pass handles first part of problem with sibbling 
  > calls
  > and optimizations.
  > 
  > As I've sent previously to gcc-bugs, we do use VIRTUAL_INCOMMING_ARGS to st
  > ore
  > arguments in sibcall sequence.  When integreate.c sees the code, it thinks,
  > that the integreated function plays bad games with it's incomming arguments
  > and allocates area on stack where it stores them.
  > 
  > This is wrong, as we still want to access the incomming arugments of the
  > function (not inlined one) to make sibcall sequence and works only because
  > we never actually output the sibcall.
  > 
  > This patch only avoids this bad converison. To get sibcalls out of inlined
  > calls, we need to update considerably the sibcall.c, but I am not going to
  > do that.
  > 
  > I want to avoid bad effects of allocating the extra space on stack - this i
  > ncludes
  > for instance disabling of any other sibcalls in the function because of tes
  > t:
  > 
  > 	  /* See if there are any reasons we can't perform either sibling or
  > 	     tail call optimizations.  We must be careful with stack slots
  > 	     which are live at potential optimization sites.  ??? The first
  > 	     test is overly conservative and should be replaced.  */
  > 	  if (frame_offset
  > 	      /* Can't take address of local var if used by recursive call.  */
  > 	      || current_function_uses_addressof
  > 
  > Bootstrapped/regtested athlon.
Sorry.  I'm not going to approve this because I still don't understand what
you're trying to do here.  

If your goal is to avoid a using a sibcall when the sibcall's argument space
is smaller than the current function's argument space, then there are far
easier ways to do that.

Namely, extend the  CALL_PLACEHOLDER to include the size of the argument
area.  Then include a check in the code to commit to a sibcall which 
prevents using the sibcall sequence if the current function's argument
list is not large enough.
jeff