gcc/hw-doloop.h

   1 /* Code to analyze doloop loops in order for targets to perform late
   2    optimizations converting doloops to other forms of hardware loops.
   3    Copyright (C) 2011-2023 Free Software Foundation, Inc.
   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_HW_DOLOOP_H
  22 #define GCC_HW_DOLOOP_H
  23
  24 /* We need to keep a vector of loops */
  25 typedef struct hwloop_info_d *hwloop_info;
  26
  27 /* Information about a loop we have found (or are in the process of
  28    finding).  */
  29 struct GTY (()) hwloop_info_d
  30 {
  31   /* loop number, for dumps */
  32   int loop_no;
  33
  34   /* Next loop in the graph. */
  35   hwloop_info next;
  36
  37   /* Vector of blocks only within the loop, including those within
  38      inner loops.  */
  39   vec<basic_block> blocks;
  40
  41   /* Same information in a bitmap.  */
  42   bitmap block_bitmap;
  43
  44   /* Vector of inner loops within this loop.  Includes loops of every
  45      nesting level.  */
  46   vec<hwloop_info> loops;
  47
  48   /* All edges that jump into the loop.  */
  49   vec<edge, va_gc> *incoming;
  50
  51   /* The ports currently using this infrastructure can typically
  52      handle two cases: all incoming edges have the same destination
  53      block, or all incoming edges have the same source block.  These
  54      two members are set to the common source or destination we found,
  55      or NULL if different blocks were found.  If both are NULL the
  56      loop can't be optimized.  */
  57   basic_block incoming_src;
  58   basic_block incoming_dest;
  59
  60   /* First block in the loop.  This is the one branched to by the loop_end
  61      insn.  */
  62   basic_block head;
  63
  64   /* Last block in the loop (the one with the loop_end insn).  */
  65   basic_block tail;
  66
  67   /* The successor block of the loop.  This is the one the loop_end insn
  68      falls into.  */
  69   basic_block successor;
  70
  71   /* The last instruction in the tail.  */
  72   rtx_insn *last_insn;
  73
  74   /* The loop_end insn.  */
  75   rtx_insn *loop_end;
  76
  77   /* The iteration register.  */
  78   rtx iter_reg;
  79
  80   /* The new label placed at the beginning of the loop. */
  81   rtx_insn *start_label;
  82
  83   /* The new label placed at the end of the loop. */
  84   rtx end_label;
  85
  86   /* The length of the loop.  */
  87   int length;
  88
  89   /* The nesting depth of the loop.  Innermost loops are given a depth
  90      of 1.  Only successfully optimized doloops are counted; if an inner
  91      loop was marked as bad, it does not increase the depth of its parent
  92      loop.
  93      This value is valid when the target's optimize function is called.  */
  94   int depth;
  95
  96   /* True if we can't optimize this loop.  */
  97   bool bad;
  98
  99   /* True if we have visited this loop during the optimization phase.  */
 100   bool visited;
 101
 102   /* The following values are collected before calling the target's optimize
 103      function and are not valid earlier.  */
 104
 105   /* Record information about control flow: whether the loop has calls
 106      or asm statements, whether it has edges that jump out of the loop,
 107      or edges that jump within the loop.  */
 108   bool has_call;
 109   bool has_asm;
 110   bool jumps_within;
 111   bool jumps_outof;
 112
 113   /* True if there is an instruction other than the doloop_end which uses the
 114      iteration register.  */
 115   bool iter_reg_used;
 116   /* True if the iteration register lives past the doloop instruction.  */
 117   bool iter_reg_used_outside;
 118
 119   /* Hard registers set at any point in the loop, except for the loop counter
 120      register's set in the doloop_end instruction.  */
 121   HARD_REG_SET regs_set_in_loop;
 122 };
 123
 124 /* A set of hooks to be defined by a target that wants to use the reorg_loops
 125    functionality.
 126
 127    reorg_loops is intended to handle cases where special hardware loop
 128    setup instructions are required before the loop, for example to set
 129    up loop counter registers that are not exposed to the register
 130    allocator, or to inform the hardware about loop bounds.
 131
 132    reorg_loops performs analysis to discover loop_end patterns created
 133    by the earlier loop-doloop pass, and sets up a hwloop_info
 134    structure for each such insn it finds.  It then tries to discover
 135    the basic blocks containing the loop by tracking the lifetime of
 136    the iteration register.
 137
 138    If a valid loop can't be found, the FAIL function is called;
 139    otherwise the OPT function is called for each loop, visiting
 140    innermost loops first and ascending.  */
 141 struct hw_doloop_hooks
 142 {
 143   /* Examine INSN.  If it is a suitable doloop_end pattern, return the
 144      iteration register, which should be a single hard register.
 145      Otherwise, return NULL_RTX.  */
 146   rtx (*end_pattern_reg) (rtx_insn *insn);
 147   /* Optimize LOOP.  The target should perform any additional analysis
 148      (e.g. checking that the loop isn't too long), and then perform
 149      its transformations.  Return true if successful, false if the
 150      loop should be marked bad.  If it returns false, the FAIL
 151      function is called.  */
 152   bool (*opt) (hwloop_info loop);
 153   /* Handle a loop that was marked bad for any reason.  This could be
 154      used to split the doloop_end pattern.  */
 155   void (*fail) (hwloop_info loop);
 156 };
 157
 158 extern void reorg_loops (bool, struct hw_doloop_hooks *);
 159
 160 #endif /* GCC_HW_DOLOOP_H */