/* Perform doloop optimizations
- Copyright (C) 2004 Free Software Foundation, Inc.
+ Copyright (C) 2004, 2005, 2006 Free Software Foundation, Inc.
Based on code by Michael P. Hayes (m.hayes@elec.canterbury.ac.nz)
This file is part of GCC.
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. */
+Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA. */
#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
+rtx
doloop_condition_get (rtx pattern)
{
rtx cmp;
rtx inc;
rtx reg;
+ rtx inc_src;
rtx condition;
/* The canonical doloop pattern we expect is:
(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. */
+ Some targets (IA-64) wrap the set of the loop counter in
+ an if_then_else too.
+
+ 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. */
if (GET_CODE (pattern) != PARALLEL)
return 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 (GET_CODE (XEXP (condition, 0)) == PLUS
- && XEXP (XEXP (condition, 0), 0) == reg)
+ if ((XEXP (condition, 0) == reg)
+ || (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
insn != NEXT_INSN (BB_END (bb));
insn = NEXT_INSN (insn))
{
- /* A called function may clobber any special registers required for
- low-overhead looping. */
- if (CALL_P (insn))
- {
- 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 (JUMP_P (insn)
- && (GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC
- || GET_CODE (PATTERN (insn)) == ADDR_VEC))
+ /* 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: 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_P (jump))
+ {
+ /* The condition is always false and the jump was optimized out. */
+ end_sequence ();
+ return true;
+ }
+
+ seq = get_insns ();
+ end_sequence ();
+ bb = loop_split_edge_with (*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));
-
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
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;
{
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;
/* Abort if an invalid doloop pattern has been generated. */
default:
- abort ();
+ gcc_unreachable ();
}
if (increment_count)
= loop_split_edge_with (loop_preheader_edge (loop), NULL_RTX);
basic_block new_preheader
= loop_split_edge_with (loop_preheader_edge (loop), NULL_RTX);
- basic_block bb;
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);
- single_succ_edge (preheader)->flags &= ~EDGE_FALLTHRU;
- cnt = single_succ_edge (preheader)->count;
- single_succ_edge (preheader)->probability = 0;
- single_succ_edge (preheader)->count = 0;
- irr = single_succ_edge (preheader)->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 = single_succ_edge (bb);
- 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. */
+ remove_bb_from_loops (set_zero);
+ 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,
+ recount_dominator (CDI_DOMINATORS,
+ set_zero));
+ }
+
+ set_immediate_dominator (CDI_DOMINATORS, new_preheader,
+ recount_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)
{
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;
return false;
}
+ max_cost
+ = COSTS_N_INSNS (PARAM_VALUE (PARAM_MAX_ITERATIONS_COMPUTATION_COST));
+ if (rtx_cost (desc->niter_expr, SET) > 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);