#include "config.h"#include "system.h"#include "coretypes.h"#include "tm.h"#include "rtl.h"#include "hard-reg-set.h"#include "obstack.h"#include "basic-block.h"#include "cfgloop.h"#include "expr.h"#include "graphds.h"#include "params.h"
Macros | |
| #define | LOOP_REPR(LOOP) ((LOOP)->num + last_basic_block) |
| #define | BB_REPR(BB) ((BB)->index + 1) |
Functions | |
| bool | just_once_each_iteration_p () |
| bool | mark_irreducible_loops () |
| int | num_loop_insns () |
| int | average_num_loop_insns () |
| gcov_type | expected_loop_iterations_unbounded () |
| unsigned | expected_loop_iterations () |
| unsigned | get_loop_level () |
| static unsigned | seq_cost () |
| void | init_set_costs () |
| unsigned | estimate_reg_pressure_cost (unsigned n_new, unsigned n_old, bool speed, bool call_p) |
| void | mark_loop_exit_edges () |
| edge | single_likely_exit () |
| vec< basic_block > | get_loop_hot_path () |
Variables | |
| struct target_cfgloop | default_target_cfgloop |
Macro Definition Documentation
| #define BB_REPR | ( | BB | ) | ((BB)->index + 1) |
| #define LOOP_REPR | ( | LOOP | ) | ((LOOP)->num + last_basic_block) |
Marks blocks and edges that are part of non-recognized loops; i.e. we throw away all latch edges and mark blocks inside any remaining cycle. Everything is a bit complicated due to fact we do not want to do this for parts of cycles that only "pass" through some loop – i.e. for each cycle, we want to mark blocks that belong directly to innermost loop containing the whole cycle.
LOOPS is the loop tree.
Function Documentation
| int average_num_loop_insns | ( | ) |
Counts number of insns executed on average per iteration LOOP.
Estimates cost of increased register pressure caused by making N_NEW new registers live around the loop. N_OLD is the number of registers live around the loop. If CALL_P is true, also take into account that call-used registers may be clobbered in the loop body, reducing the number of available registers before we spill.
If there is a call in the loop body, the call-clobbered registers are not available for loop invariants.
If we have enough registers, we should use them and not restrict the transformations unnecessarily.
If we are close to running out of registers, try to preserve them.
If we run out of registers, it is very expensive to add another one.
IRA regional allocation deals with high register pressure better. So decrease the cost (to do more accurate the cost calculation for IRA, we need to know how many registers lives through the loop transparently).
| unsigned expected_loop_iterations | ( | ) |
Returns expected number of LOOP iterations. The returned value is bounded by REG_BR_PROB_BASE.
| gcov_type expected_loop_iterations_unbounded | ( | ) |
Returns expected number of iterations of LOOP, according to measured or guessed profile. No bounding is done on the value.
References EDGE_FREQUENCY, FOR_EACH_EDGE, loop::header, loop::latch, basic_block_def::preds, and edge_def::src.
| vec<basic_block> get_loop_hot_path | ( | ) |
Gets basic blocks of a LOOP. Header is the 0-th block, rest is in dfs order against direction of edges from latch. Specially, if header != latch, latch is the 1-st block.
| unsigned get_loop_level | ( | ) |
Returns the maximum level of nesting of subloops of LOOP.
References set_rtx_cost(), and single_set.
| void init_set_costs | ( | void | ) |
Initialize the constants for computing set costs.
Set up the costs for using extra registers:
1) If not many free registers remain, we should prefer having an additional move to decreasing the number of available registers. (TARGET_REG_COST). 2) If no registers are available, we need to spill, which may require storing the old value to memory and loading it back (TARGET_SPILL_COST).
References crtl, emit_move_insn(), end_sequence(), get_insns(), seq_cost(), start_sequence(), target_reg_cost, and target_spill_cost.
| bool just_once_each_iteration_p | ( | ) |
Checks whether BB is executed exactly once in each LOOP iteration.
It must be executed at least once each iteration.
And just once.
But this was not enough. We might have some irreducible loop here.
| bool mark_irreducible_loops | ( | void | ) |
Reset the flags.
Create the edge lists.
Ignore edges to exit.
Ignore latch edges.
Edges inside a single loop should be left where they are. Edges
to subloop headers should lead to representative of the subloop,
but from the same place.
Edges exiting loops should lead from representative
of the son of nearest common ancestor of the loops in that
act lays. Find the strongly connected components.
Mark the irreducible loops.
edge E in graph G is irreducible if it connects two vertices in the
same scc. All edges should lead from a component with higher number to the
one with lower one.
Referenced by analyze_function().
| void mark_loop_exit_edges | ( | void | ) |
Sets EDGE_LOOP_EXIT flag for all loop exits.
| int num_loop_insns | ( | ) |
Counts number of insns inside LOOP.
References FOR_BB_INSNS, get_loop_body(), loop::ninsns, and NONDEBUG_INSN_P.
|
static |
Returns estimate on cost of computing SEQ.
References call_used_regs, fixed_regs, gen_raw_REG(), gen_rtx_MEM(), reg_class_contents, target_avail_regs, target_clobbered_regs, target_res_regs, TEST_HARD_REG_BIT, and validize_mem().
Referenced by init_set_costs().
| edge single_likely_exit | ( | ) |
Return exit edge if loop has only one exit that is likely to be executed on runtime (i.e. it is not EH or leading to noreturn call.
The constant of 5 is set in a way so noreturn calls are ruled out by this test. The static branch prediction algorithm will not assign such a low probability to conditionals for usual reasons.
Variable Documentation
| struct target_cfgloop default_target_cfgloop |
Natural loop analysis code for GNU compiler. Copyright (C) 2002-2013 Free Software Foundation, Inc.
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 3, or (at your option) any later version.
GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see http://www.gnu.org/licenses/.
