code review 5432082: gc: keep pointer to original node in constant rewrites.

src/cmd/gc/unsafe.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"
 
 /*
  * look for
@@ skipping 76 matching lines @@
 
 yes:
         if(args->next != nil)
                 yyerror("extra arguments for %S", s);
 ret:
         // any side effects disappear; ignore init
         val.ctype = CTINT;
         val.u.xval = mal(sizeof(*n->val.u.xval));
         mpmovecfix(val.u.xval, v);
         n = nod(OLITERAL, N, N);
+        n->orig = nn;
         n->val = val;
         n->type = types[TUINTPTR];
+        nn->type = types[TUINTPTR];
         return n;
 }
 
 int
 isunsafebuiltin(Node *n)
 {
         if(n == N || n->op != ONAME || n->sym == S || n->sym->pkg != unsafepkg)
                 return 0;
         if(strcmp(n->sym->name, "Sizeof") == 0)
                 return 1;
         if(strcmp(n->sym->name, "Offsetof") == 0)
                 return 1;
         if(strcmp(n->sym->name, "Alignof") == 0)
                 return 1;
         return 0;
 }