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      1 /* Description of target passes for AVR.
      2    Copyright (C) 2016-2022 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 /* An analysis pass that runs prior to prologue / epilogue generation.
     21    Computes cfun->machine->gasisr.maybe which is used in prologue and
     22    epilogue generation provided -mgas-isr-prologues is on.  */
     23 
     24 INSERT_PASS_BEFORE (pass_thread_prologue_and_epilogue, 1, avr_pass_pre_proep);
     25 
     26 /* This avr-specific pass (re)computes insn notes, in particular REG_DEAD
     27    notes which are used by `avr.cc::reg_unused_after' and branch offset
     28    computations.  These notes must be correct, i.e. there must be no
     29    dangling REG_DEAD notes; otherwise wrong code might result, cf. PR64331.
     30 
     31    DF needs (correct) CFG, hence right before free_cfg is the last
     32    opportunity to rectify notes.  */
     33 
     34 INSERT_PASS_BEFORE (pass_free_cfg, 1, avr_pass_recompute_notes);
     35 
     36 /* casesi uses a SImode switch index which is quite costly as most code will
     37    work on HImode or QImode.  The following pass runs right after .expand and
     38    tries to fix such situations by operating on the original mode.  This
     39    reduces code size and register pressure.
     40 
     41    The assertion is that the code generated by casesi is unaltered and a
     42    a sign-extend or zero-extend from QImode or HImode precedes the casesi
     43    insns withaout any insns in between.  */
     44 
     45 INSERT_PASS_AFTER (pass_expand, 1, avr_pass_casesi);
     46 
     47 /* If-else decision trees generated for switch / case may produce sequences
     48    like
     49 
     50       SREG = compare (reg, val);
     51 	  if (SREG == 0)  goto label1;
     52       SREG = compare (reg, 1 + val);
     53 	  if (SREG >= 0)  goto label2;
     54 
     55    which can be optimized to
     56 
     57       SREG = compare (reg, val);
     58 	  if (SREG == 0)  goto label1;
     59 	  if (SREG >= 0)  goto label2;
     60 
     61    The optimal place for such a pass would be directly after expand, but
     62    it's not possible for a jump insn to target more than one code label.
     63    Hence, run a mini pass right before split2 which introduces REG_CC.  */
     64 
     65 INSERT_PASS_BEFORE (pass_split_after_reload, 1, avr_pass_ifelse);
     66