gc: maybe the code is only mostly dead

R=ken2
CC=golang-dev
https://golang.org/cl/2346044

src/cmd/gc/gen.c

@@ -257,17 +257,6 @@ gen(Node *n)
 		break;
 
 	case OIF:
-		if(n->ntest == N || n->ntest->op == OLITERAL) {
-			// drop dead code in if true or if false.
-			// the linker will do it for us in general,
-			// but this avoids writnig to the object file
-			// in a very common case.
-			if(n->ntest == N || n->ntest->val.u.bval)
-				genlist(n->nbody);
-			else
-				genlist(n->nelse);
-			break;
-		}
 		p1 = gjmp(P);			//		goto test
 		p2 = gjmp(P);			// p2:		goto else
 		patch(p1, pc);				// test: