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) 2011-2013 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 /* We need to keep a vector of loops */
  22 typedef struct hwloop_info_d *hwloop_info;
  23
  24 /* Information about a loop we have found (or are in the process of
  25    finding).  */
  26 struct GTY (()) hwloop_info_d
  27 {
  28   /* loop number, for dumps */
  29   int loop_no;
  30
  31   /* Next loop in the graph. */
  32   hwloop_info next;
  33
  34   /* Vector of blocks only within the loop, including those within
  35      inner loops.  */
  36   vec<basic_block> blocks;
  37
  38   /* Same information in a bitmap.  */
  39   bitmap block_bitmap;
  40
  41   /* Vector of inner loops within this loop.  Includes loops of every
  42      nesting level.  */
  43   vec<hwloop_info> loops;
  44
  45   /* All edges that jump into the loop.  */
  46   vec<edge, va_gc> *incoming;
  47
  48   /* The ports currently using this infrastructure can typically
  49      handle two cases: all incoming edges have the same destination
  50      block, or all incoming edges have the same source block.  These
  51      two members are set to the common source or destination we found,
  52      or NULL if different blocks were found.  If both are NULL the
  53      loop can't be optimized.  */
  54   basic_block incoming_src;
  55   basic_block incoming_dest;
  56
  57   /* First block in the loop.  This is the one branched to by the loop_end
  58      insn.  */
  59   basic_block head;
  60
  61   /* Last block in the loop (the one with the loop_end insn).  */
  62   basic_block tail;
  63
  64   /* The successor block of the loop.  This is the one the loop_end insn
  65      falls into.  */
  66   basic_block successor;
  67
  68   /* The last instruction in the tail.  */
  69   rtx last_insn;
  70
  71   /* The loop_end insn.  */
  72   rtx loop_end;
  73
  74   /* The iteration register.  */
  75   rtx iter_reg;
  76
  77   /* The new label placed at the beginning of the loop. */
  78   rtx start_label;
  79
  80   /* The new label placed at the end of the loop. */
  81   rtx end_label;
  82
  83   /* The length of the loop.  */
  84   int length;
  85
  86   /* The nesting depth of the loop.  Innermost loops are given a depth
  87      of 1.  Only successfully optimized doloops are counted; if an inner
  88      loop was marked as bad, it does not increase the depth of its parent
  89      loop.
  90      This value is valid when the target's optimize function is called.  */
  91   int depth;
  92
  93   /* True if we can't optimize this loop.  */
  94   bool bad;
  95
  96   /* True if we have visited this loop during the optimization phase.  */
  97   bool visited;
  98
  99   /* The following values are collected before calling the target's optimize
 100      function and are not valid earlier.  */
 101
 102   /* Record information about control flow: whether the loop has calls
 103      or asm statements, whether it has edges that jump out of the loop,
 104      or edges that jump within the loop.  */
 105   bool has_call;
 106   bool has_asm;
 107   bool jumps_within;
 108   bool jumps_outof;
 109
 110   /* True if there is an instruction other than the doloop_end which uses the
 111      iteration register.  */
 112   bool iter_reg_used;
 113   /* True if the iteration register lives past the doloop instruction.  */
 114   bool iter_reg_used_outside;
 115
 116   /* Hard registers set at any point in the loop, except for the loop counter
 117      register's set in the doloop_end instruction.  */
 118   HARD_REG_SET regs_set_in_loop;
 119 };
 120
 121 /* A set of hooks to be defined by a target that wants to use the reorg_loops
 122    functionality.
 123
 124    reorg_loops is intended to handle cases where special hardware loop
 125    setup instructions are required before the loop, for example to set
 126    up loop counter registers that are not exposed to the register
 127    allocator, or to inform the hardware about loop bounds.
 128
 129    reorg_loops performs analysis to discover loop_end patterns created
 130    by the earlier loop-doloop pass, and sets up a hwloop_info
 131    structure for each such insn it finds.  It then tries to discover
 132    the basic blocks containing the loop by tracking the lifetime of
 133    the iteration register.
 134
 135    If a valid loop can't be found, the FAIL function is called;
 136    otherwise the OPT function is called for each loop, visiting
 137    innermost loops first and ascending.  */
 138 struct hw_doloop_hooks
 139 {
 140   /* Examine INSN.  If it is a suitable doloop_end pattern, return the
 141      iteration register, which should be a single hard register.
 142      Otherwise, return NULL_RTX.  */
 143   rtx (*end_pattern_reg) (rtx insn);
 144   /* Optimize LOOP.  The target should perform any additional analysis
 145      (e.g. checking that the loop isn't too long), and then perform
 146      its transformations.  Return true if successful, false if the
 147      loop should be marked bad.  If it returns false, the FAIL
 148      function is called.  */
 149   bool (*opt) (hwloop_info loop);
 150   /* Handle a loop that was marked bad for any reason.  This could be
 151      used to split the doloop_end pattern.  */
 152   void (*fail) (hwloop_info loop);
 153 };
 154
 155 extern void reorg_loops (bool, struct hw_doloop_hooks *);