/* Perform doloop optimizations
- Copyright (C) 2004 Free Software Foundation, Inc.
+ Copyright (C) 2004, 2005, 2006, 2007, 2008 Free Software Foundation,
+ Inc.
Based on code by Michael P. Hayes (m.hayes@elec.canterbury.ac.nz)
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
-Software Foundation; either version 2, or (at your option) any later
+Software Foundation; either version 3, or (at your option) any later
version.
GCC is distributed in the hope that it will be useful, but WITHOUT ANY
for more details.
You should have received a copy of the GNU General Public License
-along with GCC; see the file COPYING. If not, write to the Free
-Software Foundation, 59 Temple Place - Suite 330, Boston, MA
-02111-1307, USA. */
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
#include "cfgloop.h"
#include "output.h"
#include "params.h"
+#include "target.h"
/* This module is used to modify loops with a determinable number of
iterations to use special low-overhead looping instructions.
/* Return the loop termination condition for PATTERN or zero
if it is not a decrement and branch jump insn. */
-static rtx
-doloop_condition_get (rtx pattern)
+rtx
+doloop_condition_get (rtx doloop_pat)
{
rtx cmp;
rtx inc;
rtx reg;
+ rtx inc_src;
rtx condition;
+ rtx pattern;
- /* The canonical doloop pattern we expect is:
+ /* The canonical doloop pattern we expect has one of the following
+ forms:
- (parallel [(set (pc) (if_then_else (condition)
- (label_ref (label))
- (pc)))
- (set (reg) (plus (reg) (const_int -1)))
- (additional clobbers and uses)])
+ 1) (parallel [(set (pc) (if_then_else (condition)
+ (label_ref (label))
+ (pc)))
+ (set (reg) (plus (reg) (const_int -1)))
+ (additional clobbers and uses)])
- Some machines (IA-64) make the decrement conditional on
- the condition as well, so we don't bother verifying the
- actual decrement. In summary, the branch must be the
- first entry of the parallel (also required by jump.c),
- and the second entry of the parallel must be a set of
- the loop counter register. */
+ The branch must be the first entry of the parallel (also required
+ by jump.c), and the second entry of the parallel must be a set of
+ the loop counter register. Some targets (IA-64) wrap the set of
+ the loop counter in an if_then_else too.
+
+ 2) (set (reg) (plus (reg) (const_int -1))
+ (set (pc) (if_then_else (reg != 0)
+ (label_ref (label))
+ (pc))). */
+
+ pattern = PATTERN (doloop_pat);
if (GET_CODE (pattern) != PARALLEL)
- return 0;
+ {
+ rtx cond;
+
+ /* We expect the decrement to immediately precede the branch. */
- cmp = XVECEXP (pattern, 0, 0);
- inc = XVECEXP (pattern, 0, 1);
+ if ((PREV_INSN (doloop_pat) == NULL_RTX)
+ || !INSN_P (PREV_INSN (doloop_pat)))
+ return 0;
+
+ cmp = pattern;
+ inc = PATTERN (PREV_INSN (doloop_pat));
+ /* We expect the condition to be of the form (reg != 0) */
+ cond = XEXP (SET_SRC (cmp), 0);
+ if (GET_CODE (cond) != NE || XEXP (cond, 1) != const0_rtx)
+ return 0;
+
+ }
+ else
+ {
+ cmp = XVECEXP (pattern, 0, 0);
+ inc = XVECEXP (pattern, 0, 1);
+ }
/* Check for (set (reg) (something)). */
- if (GET_CODE (inc) != SET || ! REG_P (SET_DEST (inc)))
+ if (GET_CODE (inc) != SET)
return 0;
-
- /* Extract loop counter register. */
reg = SET_DEST (inc);
+ if (! REG_P (reg))
+ return 0;
+
+ /* Check if something = (plus (reg) (const_int -1)).
+ On IA-64, this decrement is wrapped in an if_then_else. */
+ inc_src = SET_SRC (inc);
+ if (GET_CODE (inc_src) == IF_THEN_ELSE)
+ inc_src = XEXP (inc_src, 1);
+ if (GET_CODE (inc_src) != PLUS
+ || XEXP (inc_src, 0) != reg
+ || XEXP (inc_src, 1) != constm1_rtx)
+ return 0;
/* Check for (set (pc) (if_then_else (condition)
(label_ref (label))
/* Extract loop termination condition. */
condition = XEXP (SET_SRC (cmp), 0);
- if ((GET_CODE (condition) != GE && GET_CODE (condition) != NE)
- || GET_CODE (XEXP (condition, 1)) != CONST_INT)
+ /* We expect a GE or NE comparison with 0 or 1. */
+ if ((GET_CODE (condition) != GE
+ && GET_CODE (condition) != NE)
+ || (XEXP (condition, 1) != const0_rtx
+ && XEXP (condition, 1) != const1_rtx))
return 0;
- if (XEXP (condition, 0) == reg)
- return condition;
+ if ((XEXP (condition, 0) == reg)
+ || (GET_CODE (XEXP (condition, 0)) == PLUS
+ && XEXP (XEXP (condition, 0), 0) == reg))
+ {
+ if (GET_CODE (pattern) != PARALLEL)
+ /* The second form we expect:
+
+ (set (reg) (plus (reg) (const_int -1))
+ (set (pc) (if_then_else (reg != 0)
+ (label_ref (label))
+ (pc))).
+
+ is equivalent to the following:
+
+ (parallel [(set (pc) (if_then_else (reg != 1)
+ (label_ref (label))
+ (pc)))
+ (set (reg) (plus (reg) (const_int -1)))
+ (additional clobbers and uses)])
+
+ So we return that form instead.
+ */
+ condition = gen_rtx_fmt_ee (NE, VOIDmode, inc_src, const1_rtx);
- if (GET_CODE (XEXP (condition, 0)) == PLUS
- && XEXP (XEXP (condition, 0), 0) == reg)
return condition;
+ }
/* ??? If a machine uses a funny comparison, we could return a
canonicalized form here. */
insn != NEXT_INSN (BB_END (bb));
insn = NEXT_INSN (insn))
{
- /* A called function may clobber any special registers required for
- low-overhead looping. */
- if (GET_CODE (insn) == CALL_INSN)
+ /* Different targets have different necessities for low-overhead
+ looping. Call the back end for each instruction within the loop
+ to let it decide whether the insn prohibits a low-overhead loop.
+ It will then return the cause for it to emit to the dump file. */
+ const char * invalid = targetm.invalid_within_doloop (insn);
+ if (invalid)
{
if (dump_file)
- fprintf (dump_file, "Doloop: Function call in loop.\n");
- result = false;
- goto cleanup;
- }
-
- /* Some targets (eg, PPC) use the count register for branch on table
- instructions. ??? This should be a target specific check. */
- if (GET_CODE (insn) == JUMP_INSN
- && (GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC
- || GET_CODE (PATTERN (insn)) == ADDR_VEC))
- {
- if (dump_file)
- fprintf (dump_file, "Doloop: Computed branch in the loop.\n");
+ fprintf (dump_file, "Doloop: %s\n", invalid);
result = false;
goto cleanup;
}
return result;
}
-/* Adds test of COND jumping to DEST to the end of BB. */
+/* Adds test of COND jumping to DEST on edge *E and set *E to the new fallthru
+ edge. If the condition is always false, do not do anything. If it is always
+ true, redirect E to DEST and return false. In all other cases, true is
+ returned. */
-static void
-add_test (rtx cond, basic_block bb, basic_block dest)
+static bool
+add_test (rtx cond, edge *e, basic_block dest)
{
rtx seq, jump, label;
enum machine_mode mode;
rtx op0 = XEXP (cond, 0), op1 = XEXP (cond, 1);
enum rtx_code code = GET_CODE (cond);
+ basic_block bb;
mode = GET_MODE (XEXP (cond, 0));
if (mode == VOIDmode)
do_compare_rtx_and_jump (op0, op1, code, 0, mode, NULL_RTX, NULL_RTX, label);
jump = get_last_insn ();
+ if (!jump || !JUMP_P (jump))
+ {
+ /* The condition is always false and the jump was optimized out. */
+ end_sequence ();
+ return true;
+ }
+
+ seq = get_insns ();
+ end_sequence ();
+
+ /* There always is at least the jump insn in the sequence. */
+ gcc_assert (seq != NULL_RTX);
+
+ bb = split_edge_and_insert (*e, seq);
+ *e = single_succ_edge (bb);
+
+ if (any_uncondjump_p (jump))
+ {
+ /* The condition is always true. */
+ delete_insn (jump);
+ redirect_edge_and_branch_force (*e, dest);
+ return false;
+ }
+
JUMP_LABEL (jump) = label;
/* The jump is supposed to handle an unlikely special case. */
- REG_NOTES (jump)
- = gen_rtx_EXPR_LIST (REG_BR_PROB,
- const0_rtx, REG_NOTES (jump));
+ add_reg_note (jump, REG_BR_PROB, const0_rtx);
LABEL_NUSES (label)++;
- seq = get_insns ();
- end_sequence ();
- emit_insn_after (seq, BB_END (bb));
+ make_edge (bb, dest, (*e)->flags & ~EDGE_FALLTHRU);
+ return true;
}
/* Modify the loop to use the low-overhead looping insn where LOOP
describes the loop, DESC describes the number of iterations of the
loop, and DOLOOP_INSN is the low-overhead looping insn to emit at the
end of the loop. CONDITION is the condition separated from the
- DOLOOP_SEQ. */
+ DOLOOP_SEQ. COUNT is the number of iterations of the LOOP.
+ ZERO_EXTEND_P says to zero extend COUNT after the increment of it to
+ word_mode from FROM_MODE. */
static void
doloop_modify (struct loop *loop, struct niter_desc *desc,
- rtx doloop_seq, rtx condition)
+ rtx doloop_seq, rtx condition, rtx count,
+ bool zero_extend_p, enum machine_mode from_mode)
{
rtx counter_reg;
- rtx count, tmp, noloop = NULL_RTX;
+ rtx tmp, noloop = NULL_RTX;
rtx sequence;
rtx jump_insn;
rtx jump_label;
- int nonneg = 0, irr;
+ int nonneg = 0;
bool increment_count;
basic_block loop_end = desc->out_edge->src;
+ enum machine_mode mode;
+ rtx true_prob_val;
jump_insn = BB_END (loop_end);
fputs (" iterations).\n", dump_file);
}
+ /* Get the probability of the original branch. If it exists we would
+ need to update REG_BR_PROB of the new jump_insn. */
+ true_prob_val = find_reg_note (jump_insn, REG_BR_PROB, NULL_RTX);
+
/* Discard original jump to continue loop. The original compare
result may still be live, so it cannot be discarded explicitly. */
delete_insn (jump_insn);
counter_reg = XEXP (condition, 0);
if (GET_CODE (counter_reg) == PLUS)
counter_reg = XEXP (counter_reg, 0);
+ mode = GET_MODE (counter_reg);
- count = desc->niter_expr;
increment_count = false;
switch (GET_CODE (condition))
{
case NE:
/* Currently only NE tests against zero and one are supported. */
- if (XEXP (condition, 1) == const1_rtx)
+ noloop = XEXP (condition, 1);
+ if (noloop != const0_rtx)
{
+ gcc_assert (noloop == const1_rtx);
increment_count = true;
- noloop = const1_rtx;
}
- else if (XEXP (condition, 1) == const0_rtx)
- noloop = const0_rtx;
- else
- abort ();
break;
case GE:
/* Currently only GE tests against zero are supported. */
- if (XEXP (condition, 1) != const0_rtx)
- abort ();
+ gcc_assert (XEXP (condition, 1) == const0_rtx);
noloop = constm1_rtx;
Note that the maximum value loaded is iterations_max - 1. */
if (desc->niter_max
<= ((unsigned HOST_WIDEST_INT) 1
- << (GET_MODE_BITSIZE (GET_MODE (counter_reg)) - 1)))
+ << (GET_MODE_BITSIZE (mode) - 1)))
nonneg = 1;
break;
/* Abort if an invalid doloop pattern has been generated. */
default:
- abort ();
+ gcc_unreachable ();
}
if (increment_count)
- count = simplify_gen_binary (PLUS, desc->mode, count, const1_rtx);
+ count = simplify_gen_binary (PLUS, from_mode, count, const1_rtx);
+
+ if (zero_extend_p)
+ count = simplify_gen_unary (ZERO_EXTEND, word_mode,
+ count, from_mode);
/* Insert initialization of the count register into the loop header. */
start_sequence ();
if (desc->noloop_assumptions)
{
- rtx ass = desc->noloop_assumptions;
+ rtx ass = copy_rtx (desc->noloop_assumptions);
basic_block preheader = loop_preheader_edge (loop)->src;
basic_block set_zero
- = loop_split_edge_with (loop_preheader_edge (loop), NULL_RTX);
+ = split_edge (loop_preheader_edge (loop));
basic_block new_preheader
- = loop_split_edge_with (loop_preheader_edge (loop), NULL_RTX);
- basic_block bb;
+ = split_edge (loop_preheader_edge (loop));
edge te;
- gcov_type cnt;
/* Expand the condition testing the assumptions and if it does not pass,
reset the count register to 0. */
- add_test (XEXP (ass, 0), preheader, set_zero);
- preheader->succ->flags &= ~EDGE_FALLTHRU;
- cnt = preheader->succ->count;
- preheader->succ->probability = 0;
- preheader->succ->count = 0;
- irr = preheader->succ->flags & EDGE_IRREDUCIBLE_LOOP;
- te = make_edge (preheader, new_preheader, EDGE_FALLTHRU | irr);
- te->probability = REG_BR_PROB_BASE;
- te->count = cnt;
+ redirect_edge_and_branch_force (single_succ_edge (preheader), new_preheader);
set_immediate_dominator (CDI_DOMINATORS, new_preheader, preheader);
set_zero->count = 0;
set_zero->frequency = 0;
- for (ass = XEXP (ass, 1); ass; ass = XEXP (ass, 1))
+ te = single_succ_edge (preheader);
+ for (; ass; ass = XEXP (ass, 1))
+ if (!add_test (XEXP (ass, 0), &te, set_zero))
+ break;
+
+ if (ass)
{
- bb = loop_split_edge_with (te, NULL_RTX);
- te = bb->succ;
- add_test (XEXP (ass, 0), bb, set_zero);
- make_edge (bb, set_zero, irr);
+ /* We reached a condition that is always true. This is very hard to
+ reproduce (such a loop does not roll, and thus it would most
+ likely get optimized out by some of the preceding optimizations).
+ In fact, I do not have any testcase for it. However, it would
+ also be very hard to show that it is impossible, so we must
+ handle this case. */
+ set_zero->count = preheader->count;
+ set_zero->frequency = preheader->frequency;
}
-
- start_sequence ();
- convert_move (counter_reg, noloop, 0);
- sequence = get_insns ();
- end_sequence ();
- emit_insn_after (sequence, BB_END (set_zero));
+
+ if (EDGE_COUNT (set_zero->preds) == 0)
+ {
+ /* All the conditions were simplified to false, remove the
+ unreachable set_zero block. */
+ delete_basic_block (set_zero);
+ }
+ else
+ {
+ /* Reset the counter to zero in the set_zero block. */
+ start_sequence ();
+ convert_move (counter_reg, noloop, 0);
+ sequence = get_insns ();
+ end_sequence ();
+ emit_insn_after (sequence, BB_END (set_zero));
+
+ set_immediate_dominator (CDI_DOMINATORS, set_zero,
+ recompute_dominator (CDI_DOMINATORS,
+ set_zero));
+ }
+
+ set_immediate_dominator (CDI_DOMINATORS, new_preheader,
+ recompute_dominator (CDI_DOMINATORS,
+ new_preheader));
}
/* Some targets (eg, C4x) need to initialize special looping
unsigned level = get_loop_level (loop) + 1;
init = gen_doloop_begin (counter_reg,
desc->const_iter ? desc->niter_expr : const0_rtx,
- desc->niter_max,
+ GEN_INT (desc->niter_max),
GEN_INT (level));
if (init)
{
/* Add a REG_NONNEG note if the actual or estimated maximum number
of iterations is non-negative. */
if (nonneg)
+ add_reg_note (jump_insn, REG_NONNEG, NULL_RTX);
+
+ /* Update the REG_BR_PROB note. */
+ if (true_prob_val)
{
- REG_NOTES (jump_insn)
- = gen_rtx_EXPR_LIST (REG_NONNEG, NULL_RTX, REG_NOTES (jump_insn));
+ /* Seems safer to use the branch probability. */
+ add_reg_note (jump_insn, REG_BR_PROB,
+ GEN_INT (desc->in_edge->probability));
}
}
{
enum machine_mode mode;
rtx doloop_seq, doloop_pat, doloop_reg;
- rtx iterations;
+ rtx iterations, count;
rtx iterations_max;
rtx start_label;
rtx condition;
unsigned level, est_niter;
+ int max_cost;
struct niter_desc *desc;
+ unsigned word_mode_size;
+ unsigned HOST_WIDE_INT word_mode_max;
+ bool zero_extend_p = false;
if (dump_file)
fprintf (dump_file, "Doloop: Processing loop %d.\n", loop->num);
return false;
}
+ max_cost
+ = COSTS_N_INSNS (PARAM_VALUE (PARAM_MAX_ITERATIONS_COMPUTATION_COST));
+ if (rtx_cost (desc->niter_expr, SET, optimize_loop_for_speed_p (loop))
+ > max_cost)
+ {
+ if (dump_file)
+ fprintf (dump_file,
+ "Doloop: number of iterations too costly to compute.\n");
+ return false;
+ }
+
+ count = copy_rtx (desc->niter_expr);
iterations = desc->const_iter ? desc->niter_expr : const0_rtx;
iterations_max = GEN_INT (desc->niter_max);
level = get_loop_level (loop) + 1;
doloop_reg = gen_reg_rtx (mode);
doloop_seq = gen_doloop_end (doloop_reg, iterations, iterations_max,
GEN_INT (level), start_label);
- if (! doloop_seq && mode != word_mode)
+
+ word_mode_size = GET_MODE_BITSIZE (word_mode);
+ word_mode_max
+ = ((unsigned HOST_WIDE_INT) 1 << (word_mode_size - 1) << 1) - 1;
+ if (! doloop_seq
+ && mode != word_mode
+ /* Before trying mode different from the one in that # of iterations is
+ computed, we must be sure that the number of iterations fits into
+ the new mode. */
+ && (word_mode_size >= GET_MODE_BITSIZE (mode)
+ || desc->niter_max <= word_mode_max))
{
+ if (word_mode_size > GET_MODE_BITSIZE (mode))
+ {
+ zero_extend_p = true;
+ iterations = simplify_gen_unary (ZERO_EXTEND, word_mode,
+ iterations, mode);
+ iterations_max = simplify_gen_unary (ZERO_EXTEND, word_mode,
+ iterations_max, mode);
+ }
+ else
+ {
+ count = lowpart_subreg (word_mode, count, mode);
+ iterations = lowpart_subreg (word_mode, iterations, mode);
+ iterations_max = lowpart_subreg (word_mode, iterations_max, mode);
+ }
PUT_MODE (doloop_reg, word_mode);
doloop_seq = gen_doloop_end (doloop_reg, iterations, iterations_max,
GEN_INT (level), start_label);
{
while (NEXT_INSN (doloop_pat) != NULL_RTX)
doloop_pat = NEXT_INSN (doloop_pat);
- if (GET_CODE (doloop_pat) == JUMP_INSN)
- doloop_pat = PATTERN (doloop_pat);
- else
+ if (!JUMP_P (doloop_pat))
doloop_pat = NULL_RTX;
}
return false;
}
- doloop_modify (loop, desc, doloop_seq, condition);
+ doloop_modify (loop, desc, doloop_seq, condition, count,
+ zero_extend_p, mode);
return true;
}
-/* This is the main entry point. Process all LOOPS using doloop_optimize. */
+/* This is the main entry point. Process all loops using doloop_optimize. */
void
-doloop_optimize_loops (struct loops *loops)
+doloop_optimize_loops (void)
{
- unsigned i;
+ loop_iterator li;
struct loop *loop;
- for (i = 1; i < loops->num; i++)
+ FOR_EACH_LOOP (li, loop, 0)
{
- loop = loops->parray[i];
- if (!loop)
- continue;
-
doloop_optimize (loop);
}
#ifdef ENABLE_CHECKING
verify_dominators (CDI_DOMINATORS);
- verify_loop_structure (loops);
+ verify_loop_structure ();
#endif
}
#endif /* HAVE_doloop_end */
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