basic block reordering + java

Mon Sep 24 04:49:00 GMT 2001

> > With basic block reordering, we often see code from gcj that ends in...
> > 
> > .L20:
> > call _Jv_ThrowNullPointerException
> > .L21:
> > call _Jv_ThrowNullPointerException
> > .L22:
> > call _Jv_ThrowNullPointerException
> > .L23:
> > call _Jv_ThrowNullPointerException
> > .L24:
> > call _Jv_ThrowNullPointerException
> > .L25:
> > call _Jv_ThrowNullPointerException
> > .L26:
> > call _Jv_ThrowNullPointerException
> > 
> > Is there an easy way for GCC to merge identical blocks?
> Oh yes, all you need is to modify crossjumping to add fake "noreturn"
> edges and crossjump over them.
> I can try to get that working later, but right now I am quite busy by other
> thinks.
Done.
Hi,
this patch adds support for crossjumping of noreturn calls.
For instance in:
int a,b;
main()
{
 if (a)
 abort ();
 if (b)
 abort ();
}
Only single abort call is emit now.
Bootstrapped/regtested i386
Sat Sep 22 17:08:26 CEST 2001 Jan Hubicka <jh@suse.cz>
	* cfgcleanup.c (try_optimize_cfg): Add fake exit edges for noreturn
	calls when crossjumping.
*** /p2/cfg9/egcs/gcc/cfgcleanup.c	Thu Sep 20 18:33:13 2001
--- cfgcleanup.c	Sat Sep 22 14:19:55 2001
*************** try_optimize_cfg (mode)
*** 1032,1037 ****
--- 1027,1035 ----
 bool changed;
 int iterations = 0;
 
+ if (mode & CLEANUP_CROSSJUMP)
+ add_noreturn_fake_exit_edges ();
+ 
 /* Attempt to merge blocks as made possible by edge removal. If a block
 has only one successor, and the successor has only one predecessor,
 they may be combined. */
*************** try_optimize_cfg (mode)
*** 1162,1167 ****
--- 1160,1169 ----
 changed_overall |= changed;
 }
 while (changed);
+ 
+ if (mode & CLEANUP_CROSSJUMP)
+ remove_fake_edges ();
+ 
 return changed_overall;
 }