351 lines
11 KiB
C
351 lines
11 KiB
C
/* Natural loop functions
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Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003
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Free Software Foundation, Inc.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 2, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING. If not, write to the Free
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Software Foundation, 59 Temple Place - Suite 330, Boston, MA
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02111-1307, USA. */
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/* Structure to hold decision about unrolling/peeling. */
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enum lpt_dec
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{
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LPT_NONE,
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LPT_PEEL_COMPLETELY,
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LPT_PEEL_SIMPLE,
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LPT_UNROLL_CONSTANT,
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LPT_UNROLL_RUNTIME,
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LPT_UNROLL_STUPID
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};
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struct lpt_decision
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{
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enum lpt_dec decision;
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unsigned times;
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};
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/* Description of loop for simple loop unrolling. */
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struct loop_desc
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{
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int postincr; /* 1 if increment/decrement is done after loop exit condition. */
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rtx stride; /* Value added to VAR in each iteration. */
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rtx var; /* Loop control variable. */
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rtx var_alts; /* List of definitions of its initial value. */
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rtx lim; /* Expression var is compared with. */
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rtx lim_alts; /* List of definitions of its initial value. */
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bool const_iter; /* True if it iterates constant number of times. */
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unsigned HOST_WIDE_INT niter;
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/* Number of iterations if it is constant. */
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bool may_be_zero; /* If we cannot determine that the first iteration will pass. */
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enum rtx_code cond; /* Exit condition. */
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int neg; /* Set to 1 if loop ends when condition is satisfied. */
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edge out_edge; /* The exit edge. */
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edge in_edge; /* And the other one. */
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int n_branches; /* Number of branches inside the loop. */
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};
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/* Structure to hold information for each natural loop. */
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struct loop
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{
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/* Index into loops array. */
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int num;
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/* Basic block of loop header. */
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basic_block header;
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/* Basic block of loop latch. */
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basic_block latch;
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/* Basic block of loop preheader or NULL if it does not exist. */
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basic_block pre_header;
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/* For loop unrolling/peeling decision. */
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struct lpt_decision lpt_decision;
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/* Simple loop description. */
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int simple;
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struct loop_desc desc;
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int has_desc;
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/* Number of loop insns. */
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unsigned ninsns;
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/* Average number of executed insns per iteration. */
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unsigned av_ninsns;
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/* Array of edges along the preheader extended basic block trace.
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The source of the first edge is the root node of preheader
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extended basic block, if it exists. */
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edge *pre_header_edges;
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/* Number of edges along the pre_header extended basic block trace. */
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int num_pre_header_edges;
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/* The first block in the loop. This is not necessarily the same as
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the loop header. */
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basic_block first;
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/* The last block in the loop. This is not necessarily the same as
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the loop latch. */
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basic_block last;
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/* Bitmap of blocks contained within the loop. */
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sbitmap nodes;
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/* Number of blocks contained within the loop. */
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unsigned num_nodes;
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/* Array of edges that enter the loop. */
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edge *entry_edges;
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/* Number of edges that enter the loop. */
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int num_entries;
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/* Array of edges that exit the loop. */
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edge *exit_edges;
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/* Number of edges that exit the loop. */
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int num_exits;
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/* Bitmap of blocks that dominate all exits of the loop. */
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sbitmap exits_doms;
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/* The loop nesting depth. */
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int depth;
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/* Superloops of the loop. */
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struct loop **pred;
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/* The height of the loop (enclosed loop levels) within the loop
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hierarchy tree. */
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int level;
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/* The outer (parent) loop or NULL if outermost loop. */
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struct loop *outer;
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/* The first inner (child) loop or NULL if innermost loop. */
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struct loop *inner;
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/* Link to the next (sibling) loop. */
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struct loop *next;
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/* Loop that is copy of this loop. */
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struct loop *copy;
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/* Non-zero if the loop is invalid (e.g., contains setjmp.). */
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int invalid;
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/* Auxiliary info specific to a pass. */
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void *aux;
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/* The following are currently used by loop.c but they are likely to
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disappear as loop.c is converted to use the CFG. */
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/* Non-zero if the loop has a NOTE_INSN_LOOP_VTOP. */
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rtx vtop;
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/* Non-zero if the loop has a NOTE_INSN_LOOP_CONT.
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A continue statement will generate a branch to NEXT_INSN (cont). */
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rtx cont;
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/* The dominator of cont. */
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rtx cont_dominator;
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/* The NOTE_INSN_LOOP_BEG. */
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rtx start;
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/* The NOTE_INSN_LOOP_END. */
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rtx end;
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/* For a rotated loop that is entered near the bottom,
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this is the label at the top. Otherwise it is zero. */
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rtx top;
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/* Place in the loop where control enters. */
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rtx scan_start;
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/* The position where to sink insns out of the loop. */
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rtx sink;
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/* List of all LABEL_REFs which refer to code labels outside the
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loop. Used by routines that need to know all loop exits, such as
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final_biv_value and final_giv_value.
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This does not include loop exits due to return instructions.
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This is because all bivs and givs are pseudos, and hence must be
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dead after a return, so the presence of a return does not affect
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any of the optimizations that use this info. It is simpler to
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just not include return instructions on this list. */
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rtx exit_labels;
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/* The number of LABEL_REFs on exit_labels for this loop and all
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loops nested inside it. */
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int exit_count;
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};
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/* Flags for state of loop structure. */
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enum
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{
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LOOPS_HAVE_PREHEADERS = 1,
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LOOPS_HAVE_SIMPLE_LATCHES = 2,
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LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4
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};
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/* Structure to hold CFG information about natural loops within a function. */
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struct loops
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{
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/* Number of natural loops in the function. */
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unsigned num;
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/* Maximum nested loop level in the function. */
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unsigned levels;
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/* Array of natural loop descriptors (scanning this array in reverse order
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will find the inner loops before their enclosing outer loops). */
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struct loop *array;
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/* The above array is unused in new loop infrastructure and is kept only for
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purposes of the old loop optimizer. Instead we store just pointers to
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loops here. */
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struct loop **parray;
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/* Pointer to root of loop hierarchy tree. */
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struct loop *tree_root;
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/* Information derived from the CFG. */
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struct cfg
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{
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/* The bitmap vector of dominators or NULL if not computed. */
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dominance_info dom;
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/* The ordering of the basic blocks in a depth first search. */
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int *dfs_order;
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/* The reverse completion ordering of the basic blocks found in a
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depth first search. */
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int *rc_order;
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} cfg;
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/* Headers shared by multiple loops that should be merged. */
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sbitmap shared_headers;
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/* State of loops. */
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int state;
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};
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/* Flags for loop discovery. */
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#define LOOP_TREE 1 /* Build loop hierarchy tree. */
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#define LOOP_PRE_HEADER 2 /* Analyze loop preheader. */
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#define LOOP_ENTRY_EDGES 4 /* Find entry edges. */
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#define LOOP_EXIT_EDGES 8 /* Find exit edges. */
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#define LOOP_EDGES (LOOP_ENTRY_EDGES | LOOP_EXIT_EDGES)
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#define LOOP_ALL 15 /* All of the above */
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/* Loop recognition. */
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extern int flow_loops_find PARAMS ((struct loops *, int flags));
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extern int flow_loops_update PARAMS ((struct loops *, int flags));
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extern void flow_loops_free PARAMS ((struct loops *));
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extern void flow_loops_dump PARAMS ((const struct loops *, FILE *,
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void (*)(const struct loop *,
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FILE *, int), int));
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extern void flow_loop_dump PARAMS ((const struct loop *, FILE *,
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void (*)(const struct loop *,
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FILE *, int), int));
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extern int flow_loop_scan PARAMS ((struct loops *,
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struct loop *, int));
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extern void flow_loop_free PARAMS ((struct loop *));
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void mark_irreducible_loops PARAMS ((struct loops *));
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/* Loop datastructure manipulation/querying. */
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extern void flow_loop_tree_node_add PARAMS ((struct loop *, struct loop *));
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extern void flow_loop_tree_node_remove PARAMS ((struct loop *));
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extern bool flow_loop_outside_edge_p PARAMS ((const struct loop *, edge));
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extern bool flow_loop_nested_p PARAMS ((const struct loop *,
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const struct loop *));
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extern bool flow_bb_inside_loop_p PARAMS ((const struct loop *,
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const basic_block));
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extern struct loop * find_common_loop PARAMS ((struct loop *, struct loop *));
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extern int num_loop_insns PARAMS ((struct loop *));
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extern int average_num_loop_insns PARAMS ((struct loop *));
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/* Loops & cfg manipulation. */
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extern basic_block *get_loop_body PARAMS ((const struct loop *));
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extern edge *get_loop_exit_edges PARAMS ((const struct loop *, unsigned *));
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extern edge loop_preheader_edge PARAMS ((const struct loop *));
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extern edge loop_latch_edge PARAMS ((const struct loop *));
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extern void add_bb_to_loop PARAMS ((basic_block, struct loop *));
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extern void remove_bb_from_loops PARAMS ((basic_block));
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extern void cancel_loop PARAMS ((struct loops *, struct loop *));
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extern void cancel_loop_tree PARAMS ((struct loops *, struct loop *));
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extern basic_block loop_split_edge_with PARAMS ((edge, rtx, struct loops *));
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extern int fix_loop_placement PARAMS ((struct loop *));
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enum
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{
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CP_SIMPLE_PREHEADERS = 1,
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CP_INSIDE_CFGLAYOUT = 2
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};
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extern void create_preheaders PARAMS ((struct loops *, int));
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extern void force_single_succ_latches PARAMS ((struct loops *));
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extern void verify_loop_structure PARAMS ((struct loops *));
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/* Loop analysis. */
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extern bool simple_loop_p PARAMS ((struct loops *, struct loop *,
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struct loop_desc *));
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extern rtx count_loop_iterations PARAMS ((struct loop_desc *, rtx, rtx));
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extern bool just_once_each_iteration_p PARAMS ((struct loops *,struct loop *,
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basic_block));
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extern unsigned expected_loop_iterations PARAMS ((const struct loop *));
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/* Loop manipulation. */
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extern bool can_duplicate_loop_p PARAMS ((struct loop *loop));
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#define DLTHE_FLAG_UPDATE_FREQ 1 /* Update frequencies in
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duplicate_loop_to_header_edge. */
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extern int duplicate_loop_to_header_edge PARAMS ((struct loop *, edge,
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struct loops *, unsigned,
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sbitmap, edge, edge *,
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unsigned *, int));
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extern struct loop *loopify PARAMS ((struct loops *, edge,
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edge, basic_block));
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extern void unloop PARAMS ((struct loops *, struct loop *));
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extern bool remove_path PARAMS ((struct loops *, edge));
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extern edge split_loop_bb PARAMS ((struct loops *, basic_block,
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rtx));
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/* Loop optimizer initialization. */
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extern struct loops *loop_optimizer_init PARAMS ((FILE *));
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extern void loop_optimizer_finalize PARAMS ((struct loops *, FILE *));
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/* Optimization passes. */
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extern void unswitch_loops PARAMS ((struct loops *));
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enum
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{
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UAP_PEEL = 1, /* Enables loop peeling. */
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UAP_UNROLL = 2, /* Enables peeling of loops if it seems profitable. */
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UAP_UNROLL_ALL = 4 /* Enables peeling of all loops. */
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};
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extern void unroll_and_peel_loops PARAMS ((struct loops *, int));
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