code review 5966075: cmd/gc: inline slice[arr,str] in the frontend (mostly).

src/cmd/6g/gsubr.c

 // Derived from Inferno utils/6c/txt.c
 // http://code.google.com/p/inferno-os/source/browse/utils/6c/txt.c
 //
 //      Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
 //      Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
 //      Portions Copyright © 1997-1999 Vita Nuova Limited
 //      Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
 //      Portions Copyright © 2004,2006 Bruce Ellis
 //      Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
 //      Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
@@ skipping 1039 matching lines @@
                 w = 8;
                 break;
         }
         if(w != 0 && f != N && (af.width > w || at.width > w)) {
                 fatal("bad width: %P (%d, %d)\n", p, af.width, at.width);
         }
 
         return p;
 }
 
+// Generate an instruction referencing *n
+// to force segv on nil pointer dereference.
+void
+checkref(Node *n)
+{
+        Node m;
+
+        if(n->type->type->width < unmappedzero)
+                return;
+
+        regalloc(&m, types[TUINTPTR], n);
+        cgen(n, &m);
+        m.xoffset = 0;
+        m.op = OINDREG;
+        m.type = types[TUINT8];
+        gins(ATESTB, nodintconst(0), &m);
+        regfree(&m);
+}
+
 static void
 checkoffset(Addr *a, int canemitcode)
 {
         Prog *p;
 
         if(a->offset < unmappedzero)
                 return;
         if(!canemitcode)
                 fatal("checkoffset %#llx, cannot emit code", a->offset);
 
@@ skipping 1140 matching lines @@
         naddr(&n2, a, 1);
         goto yes;
 
 yes:
         return 1;
 
 no:
         sudoclean();
         return 0;
 }