Re: [tree0ssa] Dead const/pure function removal take II

[law at redhat dot com]

In message <20031111203611.GD1729@kam.mff.cuni.cz>, Jan Hubicka writes:
 >> On Tue, 2003-11-11 at 13:42, Jan Hubicka wrote:
 >> > > On Tue, 2003-11-11 at 12:31, Jan Hubicka wrote:
 >> > > 
 >> > > > 	* gimplify.c (gimplify_call_expr):  Unset side effects for
 >> > > > 	pure functions too.
 >> > > > 	* tree-cfg.c (update-call_expr_flags): New function.
 >> > > > 	(remove_useless_stmts_and_vars_1): Use it.
 >> > > > 	(is_ctrl_altering_stmt):  Pure/const calls enver alter.
 >> > > >
 >> > > I can't parse this last entry.
 >> > We was thinking that pure/const call may do nonlocal GOTO and aborted on
 >> > attempt to remove it.
 >> > Perhaps it should say Pure/const calls never alter CFG?
 >> > 
 >> Oh!  enver = never?  Now I get it.  Yes, 'pure/const calls never alter
 >> the CFG' is a bit more clear.
 >
 >This actually brought me into investigating why I needed to fix this to
 >get libgcc built (it should have no nonlocal gotos).
 >It fails because normal goto gets flagged so in gimplification:
 >
 >		/* If this label is in a different context (function), then
 >		   mark it as a nonlocal label and mark its context as
 >		   receiving nonlocal gotos.  */
 >		tree context = decl_function_context (dest);
 >		if (current_function_decl != context)
 >		  {
 >		    NONLOCAL_LABEL (dest) = 1;
 >		    FUNCTION_RECEIVES_NONLOCAL_GOTO (context) = 1;
 >		  }
 >Expand goto checks:
 >  /* Check for a nonlocal goto to a containing function.  */
 >  context = decl_function_context (label);
 >  if (context != 0 && context != current_function_decl)
 >    {
 >So perhaps we need context != 0 too?  HOw it can happen to have context
 >NULL?
The label should have a context -- if something is creating a label
without a proper context, then that's a bug.

jeff