Fix assertion failure if temporary was spilled in all predecessors

Since ce0ab53ed7, we skip over predecessors that spilled the
temporary. However, if all predecessors spilled, then we might not have
an entry in `rl`, triggering an assertion failure in the following loop.

1 files changed, 2 insertions, 0 deletions

diff --git a/rega.c b/rega.c
index 9ceba70..6f1da50 100644
--- a/rega.c
+++ b/rega.c
@@ -591,6 +591,8 @@ rega(Fn *fn)
 					continue;
 				rl[r] = (!rl[r] || rl[r] == x) ? x : -1;
 			}
+			if (rl[r] == 0)
+				rl[r] = -1;
 		}
 
 		npm = 0;