scc

commit c40ecd533a2317a3db0b29c3ecdc6ffd0d8baeb4
parent 4343d4491f8251b0af5065d3898a2dc7cf8abf2f
Author: Roberto E. Vargas Caballero <k0ga@shike2.com>
Date:   Sat,  5 Sep 2015 19:58:46 +0200

Add more identities for shift operators

Diffstat:
M
cc1/fold.c
 | 
11
+++++++++--

1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/cc1/fold.c b/cc1/fold.c
@@ -423,13 +423,20 @@ identity(int *op, Node *lp, Node *rp)
 		return NULL;
 	case OSHL:
 	case OSHR:
+		/*
+		 * i >> 0 => i    (free right)
+		 * i << 0 => i    (free right)
+		 * 0 >> i => 0    (free right)
+		 * 0 << i => 0    (free right)
+		 */
+		if (iszeror | iszerol)
+			goto free_right;
+		return NULL;
 	case OBXOR:
 	case OADD:
 	case OBOR:
 	case OSUB:
 		/*
-		 * i >> 0 => i
-		 * i << 0 => i
 		 * i + 0  => i
 		 * i - 0  => i
 		 * i | 0  => i