qbe

commit c62b1754424046fea6abe3413f736a9483fa22a7
parent 0d5b5cefcba8e4ce7e3917628d367331968e7725
Author: Quentin Carbonneaux <quentin.carbonneaux@yale.edu>
Date:   Sun, 16 Aug 2015 17:43:35 -0400

fix two heuristics in rega

There was a typo that made always the same successor
to be selected for register allocation hinting.
Also, I now attempt to prioritize hints over succeccor's
choices as it appears to give slightly better results...

Now that I think about it, the code re-using the most
frequent successor block's assignment might be dead
because all registers have hints if they got assigned
once.  To investigate.

Diffstat:
M
lisc/rega.c
 | 
3
++-

1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/lisc/rega.c b/lisc/rega.c
@@ -311,13 +311,14 @@ rega(Fn *fn)
 		if (b->s1 && b1->loop <= b->s1->loop)
 			b1 = b->s1;
 		if (b->s2 && b1->loop <= b->s2->loop)
-			b1 = b->s1;
+			b1 = b->s2;
 		/* try to reuse the register
 		 * assignment of the most frequent
 		 * successor
 		 */
 		if (b1 != b)
 			for (t=Tmp0; t<fn->ntmp; t++)
+				if (tmp[t].hint == -1)
 				if (BGET(b->out, t))
 				if ((r = rfind(&beg[b1->id], t)) != -1)
 					radd(&cur, t, r);