Re: Fix a pretend_args goof in tail calling

[Mark Mitchell <mark at codesourcery dot com>]

Daniel Jacobowitz wrote:

> No, that's not right.  This patch was for a problem found on ARM
> targets, and it is contiguous.  The problem is that the space is
> "pretend".  It's allocated by the called function, not by the caller,
> so it must be cleaned up before we leave this function or the stack
> pointer will be corrupted.  Therefore it can not be used for outgoing
> arguments.

Oh; the problem would be that when the eventual return occurred from the 
sibcalled function, we'd have more stack space allocated than the 
original caller expected.  So, if the original caller pops the 
arguments, it won't pop enough.  If the ABI had the callee pop the args, 
then things would work OK, I guess, because the sibcalled function would 
pop all the space.  Is that right?

> Therefore the existing comment is right.  It could be extended to:
>        /* If this function requires more stack slots than the current
> 	  function, we cannot change it into a sibling call.
> 	  current_function_pretend_args_size is not part of the
> 	  stack allocated by our caller.  */
>
> OK with that change instead?

OK.

--
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com
(916) 791-8304