code review 13334052: cmd/gc: eliminate redundant &x.Field nil checks

src/cmd/gc/walk.c

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 #include        <u.h>
 #include        <libc.h>
 #include        "go.h"
 
 static  Node*   walkprint(Node*, NodeList**, int);
 static  Node*   mapfn(char*, Type*);
@@ skipping 389 matching lines @@
         case OPLUS:
         case OCOM:
         case OREAL:
         case OIMAG:
         case ODOTMETH:
         case ODOTINTER:
                 walkexpr(&n->left, init);
                 goto ret;
 
         case OIND:
-                if(n->left->type->type->width == 0) {
-                        // No actual copy will be generated, so emit an explicit nil check.
-                        n->left = cheapexpr(n->left, init);
-                        checknil(n->left, init);
-                }
                 walkexpr(&n->left, init);
                 goto ret;
 
         case ODOT:
                 usefield(n);
                 walkexpr(&n->left, init);
                 goto ret;
 
         case ODOTPTR:
                 usefield(n);
@@ skipping 3314 matching lines @@
            !candiscardlist(n->ninit) ||
            !candiscardlist(n->nbody) ||
            !candiscardlist(n->nelse) ||
            !candiscardlist(n->list) ||
            !candiscardlist(n->rlist)) {
                 return 0;
         }
 ········
         return 1;
 }