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      1 /* Representation of thunks inside symbol table.
      2    Copyright (C) 2003-2022 Free Software Foundation, Inc.
      3    Contributed by Jan Hubicka
      4 
      5 This file is part of GCC.
      6 
      7 GCC is free software; you can redistribute it and/or modify it under
      8 the terms of the GNU General Public License as published by the Free
      9 Software Foundation; either version 3, or (at your option) any later
     10 version.
     11 
     12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
     13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
     14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
     15 for more details.
     16 
     17 You should have received a copy of the GNU General Public License
     18 along with GCC; see the file COPYING3.  If not see
     19 <http://www.gnu.org/licenses/>.  */
     20 
     21 #ifndef GCC_SYMTAB_THUNKS_H
     22 #define GCC_SYMTAB_THUNKS_H
     23 
     24 /* This symbol annotation holds information about thunk.
     25 
     26    Thunks are basically wrappers around methods which are introduced in case
     27    of multiple inheritance in order to adjust the value of the "this" pointer
     28    or of the returned value.
     29 
     30    In the case of this-adjusting thunks, each back-end can override the
     31    can_output_mi_thunk/output_mi_thunk target hooks to generate a minimal thunk
     32    (with a tail call for instance) directly as assembly.  For the default hook
     33    or for the case where the can_output_mi_thunk hooks return false, the thunk
     34    is gimplified and lowered using the regular machinery.  */
     35 
     36 struct GTY(()) thunk_info {
     37   /* Constructor.  */
     38   thunk_info ()
     39     : fixed_offset (0),
     40       virtual_value (0),
     41       indirect_offset (0),
     42       alias (NULL),
     43       this_adjusting (false),
     44       virtual_offset_p (false)
     45   {
     46   }
     47   /* Copy constructor.  */
     48   thunk_info (const thunk_info &t)
     49     : fixed_offset (t.fixed_offset),
     50       virtual_value (t.virtual_value),
     51       indirect_offset (t.indirect_offset),
     52       alias (t.alias),
     53       this_adjusting (t.this_adjusting),
     54       virtual_offset_p (t.virtual_offset_p)
     55   {
     56   }
     57 
     58   /* Compare for equiality.  */
     59   bool
     60   operator==(const thunk_info &other) const
     61   {
     62     return fixed_offset == other.fixed_offset
     63 	   && virtual_value == other.virtual_value
     64 	   && indirect_offset == other.indirect_offset
     65 	   && this_adjusting == other.this_adjusting
     66 	   && virtual_offset_p == other.virtual_offset_p;
     67   }
     68   bool
     69   operator!=(const thunk_info &other) const
     70   {
     71     return !(*this == other);
     72   }
     73   /* Copy operator.  */
     74   thunk_info &
     75   operator=(const thunk_info &other)
     76   {
     77     fixed_offset = other.fixed_offset;
     78     virtual_value = other.virtual_value;
     79     indirect_offset = other.indirect_offset;
     80     alias = other.alias;
     81     this_adjusting = other.this_adjusting;
     82     virtual_offset_p = other.virtual_offset_p;
     83     return *this;
     84   }
     85 
     86   /* Offset used to adjust "this".  */
     87   HOST_WIDE_INT fixed_offset;
     88 
     89   /* Offset in the virtual table to get the offset to adjust "this".  Valid iff
     90      VIRTUAL_OFFSET_P is true.  */
     91   HOST_WIDE_INT virtual_value;
     92 
     93   /* Offset from "this" to get the offset to adjust "this".  Zero means: this
     94      offset is to be ignored.  */
     95   HOST_WIDE_INT indirect_offset;
     96 
     97   /* Thunk target, i.e. the method that this thunk wraps.  Depending on the
     98      TARGET_USE_LOCAL_THUNK_ALIAS_P macro, this may have to be a new alias.  */
     99   tree alias;
    100 
    101   /* Nonzero for a "this" adjusting thunk and zero for a result adjusting
    102      thunk.  */
    103   bool this_adjusting;
    104 
    105   /* If true, this thunk is what we call a virtual thunk.  In this case:
    106      * for this-adjusting thunks, after the FIXED_OFFSET based adjustment is
    107        done, add to the result the offset found in the vtable at:
    108 	 vptr + VIRTUAL_VALUE
    109      * for result-adjusting thunks, the FIXED_OFFSET adjustment is done after
    110        the virtual one.  */
    111   bool virtual_offset_p;
    112 
    113 
    114 
    115   /* Dump thunk_info.  */
    116   void dump (FILE *);
    117 
    118   /* Stream out thunk_info.  */
    119   void stream_out (class lto_simple_output_block *);
    120 
    121   /* Stream in trunk_info.  */
    122   void stream_in (class lto_input_block *);
    123 
    124   hashval_t hash ();
    125 
    126 
    127 
    128   /* Return thunk_info, if available.  */
    129   static thunk_info *get (cgraph_node *node);
    130 
    131   /* Return thunk_info possibly creating new one.  */
    132   static thunk_info *get_create (cgraph_node *node);
    133 
    134   /* Remove thunk_info.  */
    135   static void remove (cgraph_node *node);
    136 
    137   /* Add unprocessed thunk.  */
    138   void register_early (cgraph_node *node);
    139 
    140   /* Attach recorded thunks to cgraph_nodes.  */
    141   static void process_early_thunks ();
    142 
    143   /* Release all thunk_infos.  */
    144   static void release (void);
    145 };
    146 
    147 bool expand_thunk (cgraph_node *, bool, bool);
    148 
    149 /* Return thunk_info, if available.  */
    150 inline thunk_info *
    151 thunk_info::get (cgraph_node *node)
    152 {
    153   if (!symtab->m_thunks)
    154     return NULL;
    155   return symtab->m_thunks->get (node);
    156 }
    157 
    158 /* Remove thunk_info association for NODE.  */
    159 inline void
    160 thunk_info::remove (cgraph_node *node)
    161 {
    162   symtab->m_thunks->remove (node);
    163 }
    164 
    165 /* Free thunk info summaries.  */
    166 inline void
    167 thunk_info::release ()
    168 {
    169   if (symtab->m_thunks)
    170     ggc_delete (symtab->m_thunks);
    171   symtab->m_thunks = NULL;
    172 }
    173 #endif  /* GCC_SYMTAB_THUNKS_H  */
    174