1300 lines
35 KiB
C
1300 lines
35 KiB
C
/* Loop unrolling and peeling.
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Copyright (C) 2002, 2003, 2004 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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#include "config.h"
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#include "system.h"
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#include "coretypes.h"
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#include "tm.h"
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#include "rtl.h"
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#include "hard-reg-set.h"
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#include "basic-block.h"
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#include "cfgloop.h"
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#include "cfglayout.h"
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#include "params.h"
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#include "output.h"
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#include "expr.h"
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/* This pass performs loop unrolling and peeling. We only perform these
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optimizations on innermost loops (with single exception) because
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the impact on performance is greatest here, and we want to avoid
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unnecessary code size growth. The gain is caused by greater sequentiality
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of code, better code to optimize for further passes and in some cases
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by fewer testings of exit conditions. The main problem is code growth,
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that impacts performance negatively due to effect of caches.
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What we do:
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-- complete peeling of once-rolling loops; this is the above mentioned
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exception, as this causes loop to be cancelled completely and
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does not cause code growth
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-- complete peeling of loops that roll (small) constant times.
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-- simple peeling of first iterations of loops that do not roll much
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(according to profile feedback)
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-- unrolling of loops that roll constant times; this is almost always
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win, as we get rid of exit condition tests.
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-- unrolling of loops that roll number of times that we can compute
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in runtime; we also get rid of exit condition tests here, but there
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is the extra expense for calculating the number of iterations
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-- simple unrolling of remaining loops; this is performed only if we
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are asked to, as the gain is questionable in this case and often
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it may even slow down the code
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For more detailed descriptions of each of those, see comments at
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appropriate function below.
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There is a lot of parameters (defined and described in params.def) that
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control how much we unroll/peel.
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??? A great problem is that we don't have a good way how to determine
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how many times we should unroll the loop; the experiments I have made
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showed that this choice may affect performance in order of several %.
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*/
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static void decide_unrolling_and_peeling (struct loops *, int);
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static void peel_loops_completely (struct loops *, int);
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static void decide_peel_simple (struct loop *, int);
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static void decide_peel_once_rolling (struct loop *, int);
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static void decide_peel_completely (struct loop *, int);
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static void decide_unroll_stupid (struct loop *, int);
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static void decide_unroll_constant_iterations (struct loop *, int);
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static void decide_unroll_runtime_iterations (struct loop *, int);
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static void peel_loop_simple (struct loops *, struct loop *);
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static void peel_loop_completely (struct loops *, struct loop *);
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static void unroll_loop_stupid (struct loops *, struct loop *);
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static void unroll_loop_constant_iterations (struct loops *, struct loop *);
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static void unroll_loop_runtime_iterations (struct loops *, struct loop *);
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/* Unroll and/or peel (depending on FLAGS) LOOPS. */
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void
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unroll_and_peel_loops (struct loops *loops, int flags)
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{
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struct loop *loop, *next;
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bool check;
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/* First perform complete loop peeling (it is almost surely a win,
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and affects parameters for further decision a lot). */
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peel_loops_completely (loops, flags);
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/* Now decide rest of unrolling and peeling. */
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decide_unrolling_and_peeling (loops, flags);
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loop = loops->tree_root;
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while (loop->inner)
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loop = loop->inner;
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/* Scan the loops, inner ones first. */
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while (loop != loops->tree_root)
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{
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if (loop->next)
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{
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next = loop->next;
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while (next->inner)
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next = next->inner;
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}
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else
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next = loop->outer;
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check = true;
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/* And perform the appropriate transformations. */
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switch (loop->lpt_decision.decision)
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{
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case LPT_PEEL_COMPLETELY:
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/* Already done. */
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abort ();
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case LPT_PEEL_SIMPLE:
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peel_loop_simple (loops, loop);
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break;
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case LPT_UNROLL_CONSTANT:
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unroll_loop_constant_iterations (loops, loop);
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break;
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case LPT_UNROLL_RUNTIME:
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unroll_loop_runtime_iterations (loops, loop);
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break;
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case LPT_UNROLL_STUPID:
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unroll_loop_stupid (loops, loop);
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break;
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case LPT_NONE:
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check = false;
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break;
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default:
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abort ();
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}
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if (check)
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{
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#ifdef ENABLE_CHECKING
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verify_dominators (CDI_DOMINATORS);
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verify_loop_structure (loops);
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#endif
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}
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loop = next;
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}
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iv_analysis_done ();
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}
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/* Check whether exit of the LOOP is at the end of loop body. */
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static bool
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loop_exit_at_end_p (struct loop *loop)
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{
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struct niter_desc *desc = get_simple_loop_desc (loop);
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rtx insn;
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if (desc->in_edge->dest != loop->latch)
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return false;
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/* Check that the latch is empty. */
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FOR_BB_INSNS (loop->latch, insn)
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{
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if (INSN_P (insn))
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return false;
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}
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return true;
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}
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/* Check whether to peel LOOPS (depending on FLAGS) completely and do so. */
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static void
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peel_loops_completely (struct loops *loops, int flags)
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{
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struct loop *loop, *next;
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loop = loops->tree_root;
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while (loop->inner)
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loop = loop->inner;
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while (loop != loops->tree_root)
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{
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if (loop->next)
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{
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next = loop->next;
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while (next->inner)
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next = next->inner;
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}
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else
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next = loop->outer;
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loop->lpt_decision.decision = LPT_NONE;
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if (dump_file)
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fprintf (dump_file,
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"\n;; *** Considering loop %d for complete peeling ***\n",
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loop->num);
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loop->ninsns = num_loop_insns (loop);
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decide_peel_once_rolling (loop, flags);
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if (loop->lpt_decision.decision == LPT_NONE)
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decide_peel_completely (loop, flags);
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if (loop->lpt_decision.decision == LPT_PEEL_COMPLETELY)
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{
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peel_loop_completely (loops, loop);
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#ifdef ENABLE_CHECKING
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verify_dominators (CDI_DOMINATORS);
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verify_loop_structure (loops);
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#endif
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}
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loop = next;
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}
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}
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/* Decide whether unroll or peel LOOPS (depending on FLAGS) and how much. */
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static void
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decide_unrolling_and_peeling (struct loops *loops, int flags)
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{
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struct loop *loop = loops->tree_root, *next;
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while (loop->inner)
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loop = loop->inner;
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/* Scan the loops, inner ones first. */
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while (loop != loops->tree_root)
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{
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if (loop->next)
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{
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next = loop->next;
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while (next->inner)
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next = next->inner;
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}
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else
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next = loop->outer;
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loop->lpt_decision.decision = LPT_NONE;
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if (dump_file)
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fprintf (dump_file, "\n;; *** Considering loop %d ***\n", loop->num);
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/* Do not peel cold areas. */
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if (!maybe_hot_bb_p (loop->header))
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{
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if (dump_file)
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fprintf (dump_file, ";; Not considering loop, cold area\n");
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loop = next;
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continue;
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}
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/* Can the loop be manipulated? */
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if (!can_duplicate_loop_p (loop))
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{
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if (dump_file)
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fprintf (dump_file,
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";; Not considering loop, cannot duplicate\n");
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loop = next;
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continue;
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}
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/* Skip non-innermost loops. */
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if (loop->inner)
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{
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if (dump_file)
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fprintf (dump_file, ";; Not considering loop, is not innermost\n");
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loop = next;
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continue;
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}
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loop->ninsns = num_loop_insns (loop);
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loop->av_ninsns = average_num_loop_insns (loop);
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/* Try transformations one by one in decreasing order of
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priority. */
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decide_unroll_constant_iterations (loop, flags);
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if (loop->lpt_decision.decision == LPT_NONE)
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decide_unroll_runtime_iterations (loop, flags);
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if (loop->lpt_decision.decision == LPT_NONE)
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decide_unroll_stupid (loop, flags);
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if (loop->lpt_decision.decision == LPT_NONE)
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decide_peel_simple (loop, flags);
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loop = next;
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}
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}
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/* Decide whether the LOOP is once rolling and suitable for complete
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peeling. */
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static void
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decide_peel_once_rolling (struct loop *loop, int flags ATTRIBUTE_UNUSED)
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{
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struct niter_desc *desc;
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if (dump_file)
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fprintf (dump_file, "\n;; Considering peeling once rolling loop\n");
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/* Is the loop small enough? */
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if ((unsigned) PARAM_VALUE (PARAM_MAX_ONCE_PEELED_INSNS) < loop->ninsns)
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{
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if (dump_file)
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fprintf (dump_file, ";; Not considering loop, is too big\n");
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return;
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}
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/* Check for simple loops. */
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desc = get_simple_loop_desc (loop);
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/* Check number of iterations. */
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if (!desc->simple_p
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|| desc->assumptions
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|| !desc->const_iter
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|| desc->niter != 0)
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{
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if (dump_file)
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fprintf (dump_file,
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";; Unable to prove that the loop rolls exactly once\n");
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return;
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}
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/* Success. */
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if (dump_file)
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fprintf (dump_file, ";; Decided to peel exactly once rolling loop\n");
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loop->lpt_decision.decision = LPT_PEEL_COMPLETELY;
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}
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/* Decide whether the LOOP is suitable for complete peeling. */
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static void
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decide_peel_completely (struct loop *loop, int flags ATTRIBUTE_UNUSED)
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{
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unsigned npeel;
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struct niter_desc *desc;
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if (dump_file)
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fprintf (dump_file, "\n;; Considering peeling completely\n");
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/* Skip non-innermost loops. */
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if (loop->inner)
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{
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if (dump_file)
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fprintf (dump_file, ";; Not considering loop, is not innermost\n");
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return;
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}
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/* Do not peel cold areas. */
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if (!maybe_hot_bb_p (loop->header))
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{
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if (dump_file)
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fprintf (dump_file, ";; Not considering loop, cold area\n");
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return;
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}
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/* Can the loop be manipulated? */
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if (!can_duplicate_loop_p (loop))
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{
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if (dump_file)
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fprintf (dump_file,
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";; Not considering loop, cannot duplicate\n");
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return;
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}
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/* npeel = number of iterations to peel. */
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npeel = PARAM_VALUE (PARAM_MAX_COMPLETELY_PEELED_INSNS) / loop->ninsns;
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if (npeel > (unsigned) PARAM_VALUE (PARAM_MAX_COMPLETELY_PEEL_TIMES))
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npeel = PARAM_VALUE (PARAM_MAX_COMPLETELY_PEEL_TIMES);
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/* Is the loop small enough? */
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if (!npeel)
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{
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if (dump_file)
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fprintf (dump_file, ";; Not considering loop, is too big\n");
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return;
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}
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/* Check for simple loops. */
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desc = get_simple_loop_desc (loop);
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/* Check number of iterations. */
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if (!desc->simple_p
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|| desc->assumptions
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|| !desc->const_iter)
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{
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if (dump_file)
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fprintf (dump_file,
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";; Unable to prove that the loop iterates constant times\n");
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return;
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}
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if (desc->niter > npeel - 1)
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{
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if (dump_file)
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{
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fprintf (dump_file,
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";; Not peeling loop completely, rolls too much (");
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fprintf (dump_file, HOST_WIDEST_INT_PRINT_DEC, desc->niter);
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fprintf (dump_file, " iterations > %d [maximum peelings])\n", npeel);
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}
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return;
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}
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/* Success. */
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if (dump_file)
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fprintf (dump_file, ";; Decided to peel loop completely\n");
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loop->lpt_decision.decision = LPT_PEEL_COMPLETELY;
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}
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/* Peel all iterations of LOOP, remove exit edges and cancel the loop
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completely. The transformation done:
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for (i = 0; i < 4; i++)
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body;
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==>
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i = 0;
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body; i++;
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body; i++;
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body; i++;
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body; i++;
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*/
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static void
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peel_loop_completely (struct loops *loops, struct loop *loop)
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{
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sbitmap wont_exit;
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unsigned HOST_WIDE_INT npeel;
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unsigned n_remove_edges, i;
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edge *remove_edges, ei;
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struct niter_desc *desc = get_simple_loop_desc (loop);
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npeel = desc->niter;
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if (npeel)
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{
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wont_exit = sbitmap_alloc (npeel + 1);
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sbitmap_ones (wont_exit);
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RESET_BIT (wont_exit, 0);
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if (desc->noloop_assumptions)
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RESET_BIT (wont_exit, 1);
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remove_edges = xcalloc (npeel, sizeof (edge));
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n_remove_edges = 0;
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if (!duplicate_loop_to_header_edge (loop, loop_preheader_edge (loop),
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loops, npeel,
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wont_exit, desc->out_edge, remove_edges, &n_remove_edges,
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DLTHE_FLAG_UPDATE_FREQ))
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abort ();
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free (wont_exit);
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/* Remove the exit edges. */
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for (i = 0; i < n_remove_edges; i++)
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remove_path (loops, remove_edges[i]);
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free (remove_edges);
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}
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ei = desc->in_edge;
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free_simple_loop_desc (loop);
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/* Now remove the unreachable part of the last iteration and cancel
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the loop. */
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remove_path (loops, ei);
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if (dump_file)
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fprintf (dump_file, ";; Peeled loop completely, %d times\n", (int) npeel);
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}
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/* Decide whether to unroll LOOP iterating constant number of times
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and how much. */
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static void
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decide_unroll_constant_iterations (struct loop *loop, int flags)
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{
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unsigned nunroll, nunroll_by_av, best_copies, best_unroll = 0, n_copies, i;
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struct niter_desc *desc;
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if (!(flags & UAP_UNROLL))
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{
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/* We were not asked to, just return back silently. */
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return;
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}
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if (dump_file)
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fprintf (dump_file,
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"\n;; Considering unrolling loop with constant "
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"number of iterations\n");
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/* nunroll = total number of copies of the original loop body in
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unrolled loop (i.e. if it is 2, we have to duplicate loop body once. */
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nunroll = PARAM_VALUE (PARAM_MAX_UNROLLED_INSNS) / loop->ninsns;
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nunroll_by_av
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= PARAM_VALUE (PARAM_MAX_AVERAGE_UNROLLED_INSNS) / loop->av_ninsns;
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if (nunroll > nunroll_by_av)
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nunroll = nunroll_by_av;
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if (nunroll > (unsigned) PARAM_VALUE (PARAM_MAX_UNROLL_TIMES))
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nunroll = PARAM_VALUE (PARAM_MAX_UNROLL_TIMES);
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/* Skip big loops. */
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if (nunroll <= 1)
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{
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if (dump_file)
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fprintf (dump_file, ";; Not considering loop, is too big\n");
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return;
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}
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/* Check for simple loops. */
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desc = get_simple_loop_desc (loop);
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|
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/* Check number of iterations. */
|
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if (!desc->simple_p || !desc->const_iter || desc->assumptions)
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{
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if (dump_file)
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fprintf (dump_file,
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";; Unable to prove that the loop iterates constant times\n");
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return;
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}
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|
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/* Check whether the loop rolls enough to consider. */
|
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if (desc->niter < 2 * nunroll)
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{
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if (dump_file)
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fprintf (dump_file, ";; Not unrolling loop, doesn't roll\n");
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return;
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}
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|
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/* Success; now compute number of iterations to unroll. We alter
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nunroll so that as few as possible copies of loop body are
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necessary, while still not decreasing the number of unrollings
|
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too much (at most by 1). */
|
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best_copies = 2 * nunroll + 10;
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|
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i = 2 * nunroll + 2;
|
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if (i - 1 >= desc->niter)
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i = desc->niter - 2;
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for (; i >= nunroll - 1; i--)
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{
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unsigned exit_mod = desc->niter % (i + 1);
|
|
|
|
if (!loop_exit_at_end_p (loop))
|
|
n_copies = exit_mod + i + 1;
|
|
else if (exit_mod != (unsigned) i
|
|
|| desc->noloop_assumptions != NULL_RTX)
|
|
n_copies = exit_mod + i + 2;
|
|
else
|
|
n_copies = i + 1;
|
|
|
|
if (n_copies < best_copies)
|
|
{
|
|
best_copies = n_copies;
|
|
best_unroll = i;
|
|
}
|
|
}
|
|
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; max_unroll %d (%d copies, initial %d).\n",
|
|
best_unroll + 1, best_copies, nunroll);
|
|
|
|
loop->lpt_decision.decision = LPT_UNROLL_CONSTANT;
|
|
loop->lpt_decision.times = best_unroll;
|
|
|
|
if (dump_file)
|
|
fprintf (dump_file,
|
|
";; Decided to unroll the constant times rolling loop, %d times.\n",
|
|
loop->lpt_decision.times);
|
|
}
|
|
|
|
/* Unroll LOOP with constant number of iterations LOOP->LPT_DECISION.TIMES + 1
|
|
times. The transformation does this:
|
|
|
|
for (i = 0; i < 102; i++)
|
|
body;
|
|
|
|
==>
|
|
|
|
i = 0;
|
|
body; i++;
|
|
body; i++;
|
|
while (i < 102)
|
|
{
|
|
body; i++;
|
|
body; i++;
|
|
body; i++;
|
|
body; i++;
|
|
}
|
|
*/
|
|
static void
|
|
unroll_loop_constant_iterations (struct loops *loops, struct loop *loop)
|
|
{
|
|
unsigned HOST_WIDE_INT niter;
|
|
unsigned exit_mod;
|
|
sbitmap wont_exit;
|
|
unsigned n_remove_edges, i;
|
|
edge *remove_edges;
|
|
unsigned max_unroll = loop->lpt_decision.times;
|
|
struct niter_desc *desc = get_simple_loop_desc (loop);
|
|
bool exit_at_end = loop_exit_at_end_p (loop);
|
|
|
|
niter = desc->niter;
|
|
|
|
if (niter <= max_unroll + 1)
|
|
abort (); /* Should not get here (such loop should be peeled instead). */
|
|
|
|
exit_mod = niter % (max_unroll + 1);
|
|
|
|
wont_exit = sbitmap_alloc (max_unroll + 1);
|
|
sbitmap_ones (wont_exit);
|
|
|
|
remove_edges = xcalloc (max_unroll + exit_mod + 1, sizeof (edge));
|
|
n_remove_edges = 0;
|
|
|
|
if (!exit_at_end)
|
|
{
|
|
/* The exit is not at the end of the loop; leave exit test
|
|
in the first copy, so that the loops that start with test
|
|
of exit condition have continuous body after unrolling. */
|
|
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; Condition on beginning of loop.\n");
|
|
|
|
/* Peel exit_mod iterations. */
|
|
RESET_BIT (wont_exit, 0);
|
|
if (desc->noloop_assumptions)
|
|
RESET_BIT (wont_exit, 1);
|
|
|
|
if (exit_mod)
|
|
{
|
|
if (!duplicate_loop_to_header_edge (loop, loop_preheader_edge (loop),
|
|
loops, exit_mod,
|
|
wont_exit, desc->out_edge,
|
|
remove_edges, &n_remove_edges,
|
|
DLTHE_FLAG_UPDATE_FREQ))
|
|
abort ();
|
|
|
|
desc->noloop_assumptions = NULL_RTX;
|
|
desc->niter -= exit_mod;
|
|
desc->niter_max -= exit_mod;
|
|
}
|
|
|
|
SET_BIT (wont_exit, 1);
|
|
}
|
|
else
|
|
{
|
|
/* Leave exit test in last copy, for the same reason as above if
|
|
the loop tests the condition at the end of loop body. */
|
|
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; Condition on end of loop.\n");
|
|
|
|
/* We know that niter >= max_unroll + 2; so we do not need to care of
|
|
case when we would exit before reaching the loop. So just peel
|
|
exit_mod + 1 iterations. */
|
|
if (exit_mod != max_unroll
|
|
|| desc->noloop_assumptions)
|
|
{
|
|
RESET_BIT (wont_exit, 0);
|
|
if (desc->noloop_assumptions)
|
|
RESET_BIT (wont_exit, 1);
|
|
|
|
if (!duplicate_loop_to_header_edge (loop, loop_preheader_edge (loop),
|
|
loops, exit_mod + 1,
|
|
wont_exit, desc->out_edge, remove_edges, &n_remove_edges,
|
|
DLTHE_FLAG_UPDATE_FREQ))
|
|
abort ();
|
|
|
|
desc->niter -= exit_mod + 1;
|
|
desc->niter_max -= exit_mod + 1;
|
|
desc->noloop_assumptions = NULL_RTX;
|
|
|
|
SET_BIT (wont_exit, 0);
|
|
SET_BIT (wont_exit, 1);
|
|
}
|
|
|
|
RESET_BIT (wont_exit, max_unroll);
|
|
}
|
|
|
|
/* Now unroll the loop. */
|
|
if (!duplicate_loop_to_header_edge (loop, loop_latch_edge (loop),
|
|
loops, max_unroll,
|
|
wont_exit, desc->out_edge, remove_edges, &n_remove_edges,
|
|
DLTHE_FLAG_UPDATE_FREQ))
|
|
abort ();
|
|
|
|
free (wont_exit);
|
|
|
|
if (exit_at_end)
|
|
{
|
|
basic_block exit_block = desc->in_edge->src->rbi->copy;
|
|
/* Find a new in and out edge; they are in the last copy we have made. */
|
|
|
|
if (exit_block->succ->dest == desc->out_edge->dest)
|
|
{
|
|
desc->out_edge = exit_block->succ;
|
|
desc->in_edge = exit_block->succ->succ_next;
|
|
}
|
|
else
|
|
{
|
|
desc->out_edge = exit_block->succ->succ_next;
|
|
desc->in_edge = exit_block->succ;
|
|
}
|
|
}
|
|
|
|
desc->niter /= max_unroll + 1;
|
|
desc->niter_max /= max_unroll + 1;
|
|
desc->niter_expr = GEN_INT (desc->niter);
|
|
|
|
/* Remove the edges. */
|
|
for (i = 0; i < n_remove_edges; i++)
|
|
remove_path (loops, remove_edges[i]);
|
|
free (remove_edges);
|
|
|
|
if (dump_file)
|
|
fprintf (dump_file,
|
|
";; Unrolled loop %d times, constant # of iterations %i insns\n",
|
|
max_unroll, num_loop_insns (loop));
|
|
}
|
|
|
|
/* Decide whether to unroll LOOP iterating runtime computable number of times
|
|
and how much. */
|
|
static void
|
|
decide_unroll_runtime_iterations (struct loop *loop, int flags)
|
|
{
|
|
unsigned nunroll, nunroll_by_av, i;
|
|
struct niter_desc *desc;
|
|
|
|
if (!(flags & UAP_UNROLL))
|
|
{
|
|
/* We were not asked to, just return back silently. */
|
|
return;
|
|
}
|
|
|
|
if (dump_file)
|
|
fprintf (dump_file,
|
|
"\n;; Considering unrolling loop with runtime "
|
|
"computable number of iterations\n");
|
|
|
|
/* nunroll = total number of copies of the original loop body in
|
|
unrolled loop (i.e. if it is 2, we have to duplicate loop body once. */
|
|
nunroll = PARAM_VALUE (PARAM_MAX_UNROLLED_INSNS) / loop->ninsns;
|
|
nunroll_by_av = PARAM_VALUE (PARAM_MAX_AVERAGE_UNROLLED_INSNS) / loop->av_ninsns;
|
|
if (nunroll > nunroll_by_av)
|
|
nunroll = nunroll_by_av;
|
|
if (nunroll > (unsigned) PARAM_VALUE (PARAM_MAX_UNROLL_TIMES))
|
|
nunroll = PARAM_VALUE (PARAM_MAX_UNROLL_TIMES);
|
|
|
|
/* Skip big loops. */
|
|
if (nunroll <= 1)
|
|
{
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; Not considering loop, is too big\n");
|
|
return;
|
|
}
|
|
|
|
/* Check for simple loops. */
|
|
desc = get_simple_loop_desc (loop);
|
|
|
|
/* Check simpleness. */
|
|
if (!desc->simple_p || desc->assumptions)
|
|
{
|
|
if (dump_file)
|
|
fprintf (dump_file,
|
|
";; Unable to prove that the number of iterations "
|
|
"can be counted in runtime\n");
|
|
return;
|
|
}
|
|
|
|
if (desc->const_iter)
|
|
{
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; Loop iterates constant times\n");
|
|
return;
|
|
}
|
|
|
|
/* If we have profile feedback, check whether the loop rolls. */
|
|
if (loop->header->count && expected_loop_iterations (loop) < 2 * nunroll)
|
|
{
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; Not unrolling loop, doesn't roll\n");
|
|
return;
|
|
}
|
|
|
|
/* Success; now force nunroll to be power of 2, as we are unable to
|
|
cope with overflows in computation of number of iterations. */
|
|
for (i = 1; 2 * i <= nunroll; i *= 2)
|
|
continue;
|
|
|
|
loop->lpt_decision.decision = LPT_UNROLL_RUNTIME;
|
|
loop->lpt_decision.times = i - 1;
|
|
|
|
if (dump_file)
|
|
fprintf (dump_file,
|
|
";; Decided to unroll the runtime computable "
|
|
"times rolling loop, %d times.\n",
|
|
loop->lpt_decision.times);
|
|
}
|
|
|
|
/* Unroll LOOP for that we are able to count number of iterations in runtime
|
|
LOOP->LPT_DECISION.TIMES + 1 times. The transformation does this (with some
|
|
extra care for case n < 0):
|
|
|
|
for (i = 0; i < n; i++)
|
|
body;
|
|
|
|
==>
|
|
|
|
i = 0;
|
|
mod = n % 4;
|
|
|
|
switch (mod)
|
|
{
|
|
case 3:
|
|
body; i++;
|
|
case 2:
|
|
body; i++;
|
|
case 1:
|
|
body; i++;
|
|
case 0: ;
|
|
}
|
|
|
|
while (i < n)
|
|
{
|
|
body; i++;
|
|
body; i++;
|
|
body; i++;
|
|
body; i++;
|
|
}
|
|
*/
|
|
static void
|
|
unroll_loop_runtime_iterations (struct loops *loops, struct loop *loop)
|
|
{
|
|
rtx old_niter, niter, init_code, branch_code, tmp;
|
|
unsigned i, j, p;
|
|
basic_block preheader, *body, *dom_bbs, swtch, ezc_swtch;
|
|
unsigned n_dom_bbs;
|
|
sbitmap wont_exit;
|
|
int may_exit_copy;
|
|
unsigned n_peel, n_remove_edges;
|
|
edge *remove_edges, e;
|
|
bool extra_zero_check, last_may_exit;
|
|
unsigned max_unroll = loop->lpt_decision.times;
|
|
struct niter_desc *desc = get_simple_loop_desc (loop);
|
|
bool exit_at_end = loop_exit_at_end_p (loop);
|
|
|
|
/* Remember blocks whose dominators will have to be updated. */
|
|
dom_bbs = xcalloc (n_basic_blocks, sizeof (basic_block));
|
|
n_dom_bbs = 0;
|
|
|
|
body = get_loop_body (loop);
|
|
for (i = 0; i < loop->num_nodes; i++)
|
|
{
|
|
unsigned nldom;
|
|
basic_block *ldom;
|
|
|
|
nldom = get_dominated_by (CDI_DOMINATORS, body[i], &ldom);
|
|
for (j = 0; j < nldom; j++)
|
|
if (!flow_bb_inside_loop_p (loop, ldom[j]))
|
|
dom_bbs[n_dom_bbs++] = ldom[j];
|
|
|
|
free (ldom);
|
|
}
|
|
free (body);
|
|
|
|
if (!exit_at_end)
|
|
{
|
|
/* Leave exit in first copy (for explanation why see comment in
|
|
unroll_loop_constant_iterations). */
|
|
may_exit_copy = 0;
|
|
n_peel = max_unroll - 1;
|
|
extra_zero_check = true;
|
|
last_may_exit = false;
|
|
}
|
|
else
|
|
{
|
|
/* Leave exit in last copy (for explanation why see comment in
|
|
unroll_loop_constant_iterations). */
|
|
may_exit_copy = max_unroll;
|
|
n_peel = max_unroll;
|
|
extra_zero_check = false;
|
|
last_may_exit = true;
|
|
}
|
|
|
|
/* Get expression for number of iterations. */
|
|
start_sequence ();
|
|
old_niter = niter = gen_reg_rtx (desc->mode);
|
|
tmp = force_operand (copy_rtx (desc->niter_expr), niter);
|
|
if (tmp != niter)
|
|
emit_move_insn (niter, tmp);
|
|
|
|
/* Count modulo by ANDing it with max_unroll; we use the fact that
|
|
the number of unrollings is a power of two, and thus this is correct
|
|
even if there is overflow in the computation. */
|
|
niter = expand_simple_binop (desc->mode, AND,
|
|
niter,
|
|
GEN_INT (max_unroll),
|
|
NULL_RTX, 0, OPTAB_LIB_WIDEN);
|
|
|
|
init_code = get_insns ();
|
|
end_sequence ();
|
|
|
|
/* Precondition the loop. */
|
|
loop_split_edge_with (loop_preheader_edge (loop), init_code);
|
|
|
|
remove_edges = xcalloc (max_unroll + n_peel + 1, sizeof (edge));
|
|
n_remove_edges = 0;
|
|
|
|
wont_exit = sbitmap_alloc (max_unroll + 2);
|
|
|
|
/* Peel the first copy of loop body (almost always we must leave exit test
|
|
here; the only exception is when we have extra zero check and the number
|
|
of iterations is reliable. Also record the place of (possible) extra
|
|
zero check. */
|
|
sbitmap_zero (wont_exit);
|
|
if (extra_zero_check
|
|
&& !desc->noloop_assumptions)
|
|
SET_BIT (wont_exit, 1);
|
|
ezc_swtch = loop_preheader_edge (loop)->src;
|
|
if (!duplicate_loop_to_header_edge (loop, loop_preheader_edge (loop),
|
|
loops, 1,
|
|
wont_exit, desc->out_edge, remove_edges, &n_remove_edges,
|
|
DLTHE_FLAG_UPDATE_FREQ))
|
|
abort ();
|
|
|
|
/* Record the place where switch will be built for preconditioning. */
|
|
swtch = loop_split_edge_with (loop_preheader_edge (loop),
|
|
NULL_RTX);
|
|
|
|
for (i = 0; i < n_peel; i++)
|
|
{
|
|
/* Peel the copy. */
|
|
sbitmap_zero (wont_exit);
|
|
if (i != n_peel - 1 || !last_may_exit)
|
|
SET_BIT (wont_exit, 1);
|
|
if (!duplicate_loop_to_header_edge (loop, loop_preheader_edge (loop),
|
|
loops, 1,
|
|
wont_exit, desc->out_edge, remove_edges, &n_remove_edges,
|
|
DLTHE_FLAG_UPDATE_FREQ))
|
|
abort ();
|
|
|
|
/* Create item for switch. */
|
|
j = n_peel - i - (extra_zero_check ? 0 : 1);
|
|
p = REG_BR_PROB_BASE / (i + 2);
|
|
|
|
preheader = loop_split_edge_with (loop_preheader_edge (loop), NULL_RTX);
|
|
branch_code = compare_and_jump_seq (copy_rtx (niter), GEN_INT (j), EQ,
|
|
block_label (preheader), p, NULL_RTX);
|
|
|
|
swtch = loop_split_edge_with (swtch->pred, branch_code);
|
|
set_immediate_dominator (CDI_DOMINATORS, preheader, swtch);
|
|
swtch->succ->probability = REG_BR_PROB_BASE - p;
|
|
e = make_edge (swtch, preheader,
|
|
swtch->succ->flags & EDGE_IRREDUCIBLE_LOOP);
|
|
e->probability = p;
|
|
}
|
|
|
|
if (extra_zero_check)
|
|
{
|
|
/* Add branch for zero iterations. */
|
|
p = REG_BR_PROB_BASE / (max_unroll + 1);
|
|
swtch = ezc_swtch;
|
|
preheader = loop_split_edge_with (loop_preheader_edge (loop), NULL_RTX);
|
|
branch_code = compare_and_jump_seq (copy_rtx (niter), const0_rtx, EQ,
|
|
block_label (preheader), p, NULL_RTX);
|
|
|
|
swtch = loop_split_edge_with (swtch->succ, branch_code);
|
|
set_immediate_dominator (CDI_DOMINATORS, preheader, swtch);
|
|
swtch->succ->probability = REG_BR_PROB_BASE - p;
|
|
e = make_edge (swtch, preheader,
|
|
swtch->succ->flags & EDGE_IRREDUCIBLE_LOOP);
|
|
e->probability = p;
|
|
}
|
|
|
|
/* Recount dominators for outer blocks. */
|
|
iterate_fix_dominators (CDI_DOMINATORS, dom_bbs, n_dom_bbs);
|
|
|
|
/* And unroll loop. */
|
|
|
|
sbitmap_ones (wont_exit);
|
|
RESET_BIT (wont_exit, may_exit_copy);
|
|
|
|
if (!duplicate_loop_to_header_edge (loop, loop_latch_edge (loop),
|
|
loops, max_unroll,
|
|
wont_exit, desc->out_edge, remove_edges, &n_remove_edges,
|
|
DLTHE_FLAG_UPDATE_FREQ))
|
|
abort ();
|
|
|
|
free (wont_exit);
|
|
|
|
if (exit_at_end)
|
|
{
|
|
basic_block exit_block = desc->in_edge->src->rbi->copy;
|
|
/* Find a new in and out edge; they are in the last copy we have made. */
|
|
|
|
if (exit_block->succ->dest == desc->out_edge->dest)
|
|
{
|
|
desc->out_edge = exit_block->succ;
|
|
desc->in_edge = exit_block->succ->succ_next;
|
|
}
|
|
else
|
|
{
|
|
desc->out_edge = exit_block->succ->succ_next;
|
|
desc->in_edge = exit_block->succ;
|
|
}
|
|
}
|
|
|
|
/* Remove the edges. */
|
|
for (i = 0; i < n_remove_edges; i++)
|
|
remove_path (loops, remove_edges[i]);
|
|
free (remove_edges);
|
|
|
|
/* We must be careful when updating the number of iterations due to
|
|
preconditioning and the fact that the value must be valid at entry
|
|
of the loop. After passing through the above code, we see that
|
|
the correct new number of iterations is this: */
|
|
if (desc->const_iter)
|
|
abort ();
|
|
desc->niter_expr =
|
|
simplify_gen_binary (UDIV, desc->mode, old_niter, GEN_INT (max_unroll + 1));
|
|
desc->niter_max /= max_unroll + 1;
|
|
if (exit_at_end)
|
|
{
|
|
desc->niter_expr =
|
|
simplify_gen_binary (MINUS, desc->mode, desc->niter_expr, const1_rtx);
|
|
desc->noloop_assumptions = NULL_RTX;
|
|
desc->niter_max--;
|
|
}
|
|
|
|
if (dump_file)
|
|
fprintf (dump_file,
|
|
";; Unrolled loop %d times, counting # of iterations "
|
|
"in runtime, %i insns\n",
|
|
max_unroll, num_loop_insns (loop));
|
|
}
|
|
|
|
/* Decide whether to simply peel LOOP and how much. */
|
|
static void
|
|
decide_peel_simple (struct loop *loop, int flags)
|
|
{
|
|
unsigned npeel;
|
|
struct niter_desc *desc;
|
|
|
|
if (!(flags & UAP_PEEL))
|
|
{
|
|
/* We were not asked to, just return back silently. */
|
|
return;
|
|
}
|
|
|
|
if (dump_file)
|
|
fprintf (dump_file, "\n;; Considering simply peeling loop\n");
|
|
|
|
/* npeel = number of iterations to peel. */
|
|
npeel = PARAM_VALUE (PARAM_MAX_PEELED_INSNS) / loop->ninsns;
|
|
if (npeel > (unsigned) PARAM_VALUE (PARAM_MAX_PEEL_TIMES))
|
|
npeel = PARAM_VALUE (PARAM_MAX_PEEL_TIMES);
|
|
|
|
/* Skip big loops. */
|
|
if (!npeel)
|
|
{
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; Not considering loop, is too big\n");
|
|
return;
|
|
}
|
|
|
|
/* Check for simple loops. */
|
|
desc = get_simple_loop_desc (loop);
|
|
|
|
/* Check number of iterations. */
|
|
if (desc->simple_p && !desc->assumptions && desc->const_iter)
|
|
{
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; Loop iterates constant times\n");
|
|
return;
|
|
}
|
|
|
|
/* Do not simply peel loops with branches inside -- it increases number
|
|
of mispredicts. */
|
|
if (num_loop_branches (loop) > 1)
|
|
{
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; Not peeling, contains branches\n");
|
|
return;
|
|
}
|
|
|
|
if (loop->header->count)
|
|
{
|
|
unsigned niter = expected_loop_iterations (loop);
|
|
if (niter + 1 > npeel)
|
|
{
|
|
if (dump_file)
|
|
{
|
|
fprintf (dump_file, ";; Not peeling loop, rolls too much (");
|
|
fprintf (dump_file, HOST_WIDEST_INT_PRINT_DEC,
|
|
(HOST_WIDEST_INT) (niter + 1));
|
|
fprintf (dump_file, " iterations > %d [maximum peelings])\n",
|
|
npeel);
|
|
}
|
|
return;
|
|
}
|
|
npeel = niter + 1;
|
|
}
|
|
else
|
|
{
|
|
/* For now we have no good heuristics to decide whether loop peeling
|
|
will be effective, so disable it. */
|
|
if (dump_file)
|
|
fprintf (dump_file,
|
|
";; Not peeling loop, no evidence it will be profitable\n");
|
|
return;
|
|
}
|
|
|
|
/* Success. */
|
|
loop->lpt_decision.decision = LPT_PEEL_SIMPLE;
|
|
loop->lpt_decision.times = npeel;
|
|
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; Decided to simply peel the loop, %d times.\n",
|
|
loop->lpt_decision.times);
|
|
}
|
|
|
|
/* Peel a LOOP LOOP->LPT_DECISION.TIMES times. The transformation:
|
|
while (cond)
|
|
body;
|
|
|
|
==>
|
|
|
|
if (!cond) goto end;
|
|
body;
|
|
if (!cond) goto end;
|
|
body;
|
|
while (cond)
|
|
body;
|
|
end: ;
|
|
*/
|
|
static void
|
|
peel_loop_simple (struct loops *loops, struct loop *loop)
|
|
{
|
|
sbitmap wont_exit;
|
|
unsigned npeel = loop->lpt_decision.times;
|
|
struct niter_desc *desc = get_simple_loop_desc (loop);
|
|
|
|
wont_exit = sbitmap_alloc (npeel + 1);
|
|
sbitmap_zero (wont_exit);
|
|
|
|
if (!duplicate_loop_to_header_edge (loop, loop_preheader_edge (loop),
|
|
loops, npeel, wont_exit, NULL, NULL, NULL,
|
|
DLTHE_FLAG_UPDATE_FREQ))
|
|
abort ();
|
|
|
|
free (wont_exit);
|
|
|
|
if (desc->simple_p)
|
|
{
|
|
if (desc->const_iter)
|
|
{
|
|
desc->niter -= npeel;
|
|
desc->niter_expr = GEN_INT (desc->niter);
|
|
desc->noloop_assumptions = NULL_RTX;
|
|
}
|
|
else
|
|
{
|
|
/* We cannot just update niter_expr, as its value might be clobbered
|
|
inside loop. We could handle this by counting the number into
|
|
temporary just like we do in runtime unrolling, but it does not
|
|
seem worthwhile. */
|
|
free_simple_loop_desc (loop);
|
|
}
|
|
}
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; Peeling loop %d times\n", npeel);
|
|
}
|
|
|
|
/* Decide whether to unroll LOOP stupidly and how much. */
|
|
static void
|
|
decide_unroll_stupid (struct loop *loop, int flags)
|
|
{
|
|
unsigned nunroll, nunroll_by_av, i;
|
|
struct niter_desc *desc;
|
|
|
|
if (!(flags & UAP_UNROLL_ALL))
|
|
{
|
|
/* We were not asked to, just return back silently. */
|
|
return;
|
|
}
|
|
|
|
if (dump_file)
|
|
fprintf (dump_file, "\n;; Considering unrolling loop stupidly\n");
|
|
|
|
/* nunroll = total number of copies of the original loop body in
|
|
unrolled loop (i.e. if it is 2, we have to duplicate loop body once. */
|
|
nunroll = PARAM_VALUE (PARAM_MAX_UNROLLED_INSNS) / loop->ninsns;
|
|
nunroll_by_av
|
|
= PARAM_VALUE (PARAM_MAX_AVERAGE_UNROLLED_INSNS) / loop->av_ninsns;
|
|
if (nunroll > nunroll_by_av)
|
|
nunroll = nunroll_by_av;
|
|
if (nunroll > (unsigned) PARAM_VALUE (PARAM_MAX_UNROLL_TIMES))
|
|
nunroll = PARAM_VALUE (PARAM_MAX_UNROLL_TIMES);
|
|
|
|
/* Skip big loops. */
|
|
if (nunroll <= 1)
|
|
{
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; Not considering loop, is too big\n");
|
|
return;
|
|
}
|
|
|
|
/* Check for simple loops. */
|
|
desc = get_simple_loop_desc (loop);
|
|
|
|
/* Check simpleness. */
|
|
if (desc->simple_p && !desc->assumptions)
|
|
{
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; The loop is simple\n");
|
|
return;
|
|
}
|
|
|
|
/* Do not unroll loops with branches inside -- it increases number
|
|
of mispredicts. */
|
|
if (num_loop_branches (loop) > 1)
|
|
{
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; Not unrolling, contains branches\n");
|
|
return;
|
|
}
|
|
|
|
/* If we have profile feedback, check whether the loop rolls. */
|
|
if (loop->header->count
|
|
&& expected_loop_iterations (loop) < 2 * nunroll)
|
|
{
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; Not unrolling loop, doesn't roll\n");
|
|
return;
|
|
}
|
|
|
|
/* Success. Now force nunroll to be power of 2, as it seems that this
|
|
improves results (partially because of better alignments, partially
|
|
because of some dark magic). */
|
|
for (i = 1; 2 * i <= nunroll; i *= 2)
|
|
continue;
|
|
|
|
loop->lpt_decision.decision = LPT_UNROLL_STUPID;
|
|
loop->lpt_decision.times = i - 1;
|
|
|
|
if (dump_file)
|
|
fprintf (dump_file,
|
|
";; Decided to unroll the loop stupidly, %d times.\n",
|
|
loop->lpt_decision.times);
|
|
}
|
|
|
|
/* Unroll a LOOP LOOP->LPT_DECISION.TIMES times. The transformation:
|
|
while (cond)
|
|
body;
|
|
|
|
==>
|
|
|
|
while (cond)
|
|
{
|
|
body;
|
|
if (!cond) break;
|
|
body;
|
|
if (!cond) break;
|
|
body;
|
|
if (!cond) break;
|
|
body;
|
|
}
|
|
*/
|
|
static void
|
|
unroll_loop_stupid (struct loops *loops, struct loop *loop)
|
|
{
|
|
sbitmap wont_exit;
|
|
unsigned nunroll = loop->lpt_decision.times;
|
|
struct niter_desc *desc = get_simple_loop_desc (loop);
|
|
|
|
wont_exit = sbitmap_alloc (nunroll + 1);
|
|
sbitmap_zero (wont_exit);
|
|
|
|
if (!duplicate_loop_to_header_edge (loop, loop_latch_edge (loop),
|
|
loops, nunroll, wont_exit, NULL, NULL, NULL,
|
|
DLTHE_FLAG_UPDATE_FREQ))
|
|
abort ();
|
|
|
|
free (wont_exit);
|
|
|
|
if (desc->simple_p)
|
|
{
|
|
/* We indeed may get here provided that there are nontrivial assumptions
|
|
for a loop to be really simple. We could update the counts, but the
|
|
problem is that we are unable to decide which exit will be taken
|
|
(not really true in case the number of iterations is constant,
|
|
but noone will do anything with this information, so we do not
|
|
worry about it). */
|
|
desc->simple_p = false;
|
|
}
|
|
|
|
if (dump_file)
|
|
fprintf (dump_file, ";; Unrolled loop %d times, %i insns\n",
|
|
nunroll, num_loop_insns (loop));
|
|
}
|