gcc/function-abi.h

   1 /* Information about fuunction binary interfaces.
   2    Copyright (C) 2019 Free Software Foundation, Inc.
   3
   4 This file is part of GCC
   5
   6 GCC is free software; you can redistribute it and/or modify it under
   7 the terms of the GNU General Public License as published by the Free
   8 Software Foundation; either version 3, or (at your option) any later
   9 version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING3.  If not see
  18 <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef GCC_FUNCTION_ABI_H
  21 #define GCC_FUNCTION_ABI_H
  22
  23 /* Most targets use the same ABI for all functions in a translation
  24    unit, but some targets support interoperability between several ABIs.
  25    Each such ABI has a unique 0-based identifier, with 0 always being
  26    the default choice of ABI.
  27
  28    NUM_ABI_IDS is the maximum number of such ABIs that GCC can handle at once.
  29    A bitfield with this number of bits can represent any combinaion of the
  30    supported ABIs.  */
  31 const size_t NUM_ABI_IDS = 8;
  32
  33 /* Information about one of the target's predefined ABIs.  */
  34 class predefined_function_abi
  35 {
  36 public:
  37   /* A target-specific identifier for this ABI.  The value must be in
  38      the range [0, NUM_ABI_IDS - 1].  */
  39   unsigned int id () const { return m_id; }
  40
  41   /* True if this ABI has been initialized.  */
  42   bool initialized_p () const { return m_initialized; }
  43
  44   /* Return true if a function call is allowed to alter every bit of
  45      register REGNO, so that the register contains an arbitrary value
  46      on return.  If so, the register cannot hold any part of a value
  47      that is live across a call.  */
  48   bool
  49   clobbers_full_reg_p (unsigned int regno) const
  50   {
  51     return TEST_HARD_REG_BIT (m_full_reg_clobbers, regno);
  52   }
  53
  54   /* Return true if a function call is allowed to alter some or all bits
  55      of register REGNO.
  56
  57      This is true whenever clobbers_full_reg_p (REGNO) is true.  It is
  58      also true if, for example, the ABI says that a call must preserve the
  59      low 32 or 64 bits of REGNO, but can clobber the upper bits of REGNO.
  60      In the latter case, it is possible for REGNO to hold values that
  61      are live across a call, provided that the value occupies only the
  62      call-preserved part of the register.  */
  63   bool
  64   clobbers_at_least_part_of_reg_p (unsigned int regno) const
  65   {
  66     return TEST_HARD_REG_BIT (m_full_and_partial_reg_clobbers, regno);
  67   }
  68
  69   /* Return true if a function call is allowed to clobber at least part
  70      of (reg:MODE REGNO).  If so, it is not possible for the register
  71      as a whole to be live across a call.  */
  72   bool
  73   clobbers_reg_p (machine_mode mode, unsigned int regno) const
  74   {
  75     return overlaps_hard_reg_set_p (m_mode_clobbers[mode], mode, regno);
  76   }
  77
  78   /* Return the set of registers that a function call is allowed to
  79      alter completely, so that the registers contain arbitrary values
  80      on return.  This doesn't include registers that a call can only
  81      partly clobber (as per TARGET_HARD_REGNO_CALL_PART_CLOBBERED).
  82
  83      These registers cannot hold any part of a value that is live across
  84      a call.  */
  85   HARD_REG_SET full_reg_clobbers () const { return m_full_reg_clobbers; }
  86
  87   /* Return the set of registers that a function call is allowed to alter
  88      to some degree.  For example, if an ABI says that a call must preserve
  89      the low 32 or 64 bits of a register R, but can clobber the upper bits
  90      of R, R would be in this set but not in full_reg_clobbers ().
  91
  92      This set is a superset of full_reg_clobbers ().  It is possible for a
  93      register in full_and_partial_reg_clobbers () & ~full_reg_clobbers ()
  94      to contain values that are live across a call, provided that the live
  95      value only occupies the call-preserved part of the register.  */
  96   HARD_REG_SET
  97   full_and_partial_reg_clobbers () const
  98   {
  99     return m_full_and_partial_reg_clobbers;
 100   }
 101
 102   /* Return the set of registers that cannot be used to hold a value of
 103      mode MODE across a function call.  That is:
 104
 105        (reg:REGNO MODE)
 106
 107      might be clobbered by a call whenever:
 108
 109        overlaps_hard_reg_set (mode_clobbers (MODE), MODE, REGNO)
 110
 111      In allocation terms, the registers in the returned set conflict
 112      with any value of mode MODE that is live across a call.  */
 113   HARD_REG_SET
 114   mode_clobbers (machine_mode mode) const
 115   {
 116     return m_mode_clobbers[mode];
 117   }
 118
 119   void initialize (unsigned int, const_hard_reg_set);
 120   void add_full_reg_clobber (unsigned int);
 121
 122 private:
 123   unsigned int m_id : NUM_ABI_IDS;
 124   unsigned int m_initialized : 1;
 125   HARD_REG_SET m_full_reg_clobbers;
 126   HARD_REG_SET m_full_and_partial_reg_clobbers;
 127   HARD_REG_SET m_mode_clobbers[NUM_MACHINE_MODES];
 128 };
 129
 130 /* Describes either a predefined ABI or the ABI of a particular function.
 131    In the latter case, the ABI might make use of extra function-specific
 132    information, such as for -fipa-ra.  */
 133 class function_abi
 134 {
 135 public:
 136   /* Initialize the structure for a general function with the given ABI.  */
 137   function_abi (const predefined_function_abi &base_abi)
 138     : m_base_abi (&base_abi),
 139       m_mask (base_abi.full_and_partial_reg_clobbers ()) {}
 140
 141   /* Initialize the structure for a function that has the given ABI and
 142      that is known not to clobber registers outside MASK.  */
 143   function_abi (const predefined_function_abi &base_abi,
 144                 const_hard_reg_set mask)
 145     : m_base_abi (&base_abi), m_mask (mask) {}
 146
 147   /* The predefined ABI from which this ABI is derived.  */
 148   const predefined_function_abi &base_abi () const { return *m_base_abi; }
 149
 150   /* The target-specific identifier of the predefined ABI.  */
 151   unsigned int id () const { return m_base_abi->id (); }
 152
 153   /* See the corresponding predefined_function_abi functions for
 154      details about the following functions.  */
 155
 156   HARD_REG_SET
 157   full_reg_clobbers () const
 158   {
 159     return m_mask & m_base_abi->full_reg_clobbers ();
 160   }
 161
 162   HARD_REG_SET
 163   full_and_partial_reg_clobbers () const
 164   {
 165     return m_mask & m_base_abi->full_and_partial_reg_clobbers ();
 166   }
 167
 168   HARD_REG_SET
 169   mode_clobbers (machine_mode mode) const
 170   {
 171     return m_mask & m_base_abi->mode_clobbers (mode);
 172   }
 173
 174   bool
 175   clobbers_full_reg_p (unsigned int regno) const
 176   {
 177     return (TEST_HARD_REG_BIT (m_mask, regno)
 178             & m_base_abi->clobbers_full_reg_p (regno));
 179   }
 180
 181   bool
 182   clobbers_at_least_part_of_reg_p (unsigned int regno) const
 183   {
 184     return (TEST_HARD_REG_BIT (m_mask, regno)
 185             & m_base_abi->clobbers_at_least_part_of_reg_p (regno));
 186   }
 187
 188   bool
 189   clobbers_reg_p (machine_mode mode, unsigned int regno) const
 190   {
 191     return overlaps_hard_reg_set_p (mode_clobbers (mode), mode, regno);
 192   }
 193
 194   bool
 195   operator== (const function_abi &other) const
 196   {
 197     return m_base_abi == other.m_base_abi && m_mask == other.m_mask;
 198   }
 199
 200   bool
 201   operator!= (const function_abi &other) const
 202   {
 203     return !operator== (other);
 204   }
 205
 206 protected:
 207   const predefined_function_abi *m_base_abi;
 208   HARD_REG_SET m_mask;
 209 };
 210
 211 struct target_function_abi_info
 212 {
 213   /* An array of all the target ABIs that are available in this
 214      translation unit.  Not all entries are used for all targets,
 215      but the structures are relatively small, and using a fixed-size
 216      array avoids extra indirection.
 217
 218      There are various ways of getting an ABI descriptor:
 219
 220      * fndecl_abi (FNDECL) is the ABI of function FNDECL.
 221
 222      * fntype_abi (FNTYPE) is the ABI of a function with type FNTYPE.
 223
 224      * crtl->abi is the ABI of the function that we are currently
 225        compiling to rtl.
 226
 227      * insn_callee_abi (INSN) is the ABI used by the target of call insn INSN.
 228
 229      * eh_edge_abi is the "ABI" used when taking an EH edge from an
 230        exception-throwing statement to an exception handler.  Catching
 231        exceptions from calls can be treated as an abnormal return from
 232        those calls, and this ABI therefore describes the ABI of functions
 233        on such an abnormal return.  Statements that throw non-call
 234        exceptions can be treated as being implicitly wrapped in a call
 235        that has such an abnormal return.
 236
 237        At present, no target needs to support more than one EH ABI.
 238
 239      * function_abis[N] is the ABI with identifier N.  This can be useful
 240        when referring back to ABIs that have been collected by number in
 241        a bitmask, such as after walking function calls in a particular
 242        region of code.
 243
 244      * default_function_abi refers specifically to the target's default
 245        choice of ABI, regardless of which (if any) functions actually
 246        use it.  This ABI and data derived from it do *not* provide
 247        globally conservatively-correct information, so it is only
 248        useful in very specific circumstances.  */
 249   predefined_function_abi x_function_abis[NUM_ABI_IDS];
 250 };
 251
 252 extern target_function_abi_info default_target_function_abi_info;
 253 #if SWITCHABLE_TARGET
 254 extern target_function_abi_info *this_target_function_abi_info;
 255 #else
 256 #define this_target_function_abi_info (&default_target_function_abi_info)
 257 #endif
 258
 259 /* See the comment above x_function_abis for when these macros should be used.
 260    At present, eh_edge_abi is always the default ABI, but that could change
 261    in future if a target needs it to.  */
 262 #define function_abis \
 263   (this_target_function_abi_info->x_function_abis)
 264 #define default_function_abi \
 265   (this_target_function_abi_info->x_function_abis[0])
 266 #define eh_edge_abi default_function_abi
 267
 268 extern const predefined_function_abi &fntype_abi (const_tree);
 269 extern function_abi fndecl_abi (const_tree);
 270 extern function_abi insn_callee_abi (const rtx_insn *);
 271
 272 #endif