code review 12970043: cmd/gc: &x panics if x does

src/cmd/6g/prog.c

 // Copyright 2013 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 "gg.h"
 #include "opt.h"
 
 // Matches real RtoB but can be used in global initializer.
@@ skipping 22 matching lines @@
 // size variants of an operation even if we just use a subset.
 //
 // The table is formatted for 8-space tabs.
 static ProgInfo progtable[ALAST] = {
         [ATYPE]=        {Pseudo | Skip},
         [ATEXT]=        {Pseudo},
         [AFUNCDATA]=    {Pseudo},
         [APCDATA]=      {Pseudo},
         [AUNDEF]=       {OK},
         [AUSEFIELD]=    {OK},
+        [ACHECKNIL]=    {LeftRead},
 
         // NOP is an internal no-op that also stands
         // for USED and SET annotations, not the Intel opcode.
         [ANOP]=         {LeftRead | RightWrite},
 
         [AADCL]=        {SizeL | LeftRead | RightRdwr | SetCarry | UseCarry},
         [AADCQ]=        {SizeQ | LeftRead | RightRdwr | SetCarry | UseCarry},
         [AADCW]=        {SizeW | LeftRead | RightRdwr | SetCarry | UseCarry},
 
         [AADDB]=        {SizeB | LeftRead | RightRdwr | SetCarry},
@@ skipping 250 matching lines @@
         // Addressing makes some registers used.
         if(p->from.type >= D_INDIR)
                 info->regindex |= RtoB(p->from.type-D_INDIR);
         if(p->from.index != D_NONE)
                 info->regindex |= RtoB(p->from.index);
         if(p->to.type >= D_INDIR)
                 info->regindex |= RtoB(p->to.type-D_INDIR);
         if(p->to.index != D_NONE)
                 info->regindex |= RtoB(p->to.index);
 }