qbe

commit 6cba2db94922c6542d0de7e4f4d4a2323a6d9981
parent 7e1db6cc659dc701391639a40790645940a53879
Author: Quentin Carbonneaux <quentin.carbonneaux@yale.edu>
Date:   Wed, 16 Mar 2016 10:57:41 -0400

document oddity in seljmp()

Diffstat:
M
lisc/isel.c
 | 
12
++++++++----

1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/lisc/isel.c b/lisc/isel.c
@@ -397,10 +397,14 @@ seljmp(Blk *b, Fn *fn)
 			}
 			return;
 		}
-		if (fn->tmp[r.val].nuse > 1) {
-			b->jmp.type = JXJc + ICne;
-			return;
-		}
+		/* since flags are not tracked in liveness,
+		 * the result of the flag-setting instruction
+		 * has to be marked as live
+		 */
+		if (fn->tmp[r.val].nuse == 1)
+			emit(OCopy, Kw, R, r, R);
+		b->jmp.type = JXJc + ICne;
+		return;
 	}
 	selcmp((Ref[2]){r, CON_Z}, Kw, fn); /* todo, add long branch if non-zero */
 	b->jmp.type = JXJc + ICne;