qbe

commit 0f879b9b0245e0b23a11ac65943846d312b3786f
parent a767351bdd80d0ba97599372d9dd9ad571601b2c
Author: Quentin Carbonneaux <quentin.carbonneaux@yale.edu>
Date:   Mon, 17 Aug 2015 21:16:03 -0400

tweak block-border heuristic for reg. allocation

We only allocate a register that has a hint if the
hint register is not used already.  In the max example
it gives a better result and it does not seem to affect
the collatz test.

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

1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/lisc/rega.c b/lisc/rega.c
@@ -324,9 +324,10 @@ rega(Fn *fn)
 					radd(&cur, t, r);
 		for (x=0; x<2; x++)
 			for (t=Tmp0; t<fn->ntmp; t++)
-				if (x==1 || tmp[t].hint!=-1)
 				if (BGET(b->out, t))
 				if (!BGET(cur.b, t))
+				if (x == 1
+				|| ((r=tmp[t].hint) != -1 && !BGET(cur.b, r)))
 					ralloc(&cur, t);
 		/* process instructions */
 		end[n] = cur;