2124 lines
65 KiB
C++
2124 lines
65 KiB
C++
/* Loop interchange.
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Copyright (C) 2017-2022 Free Software Foundation, Inc.
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Contributed by ARM Ltd.
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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
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under the terms of the GNU General Public License as published by the
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Free Software Foundation; either version 3, or (at your option) any
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later version.
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GCC is distributed in the hope that it will be useful, but WITHOUT
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ANY 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 COPYING3. If not see
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<http://www.gnu.org/licenses/>. */
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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 "backend.h"
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#include "is-a.h"
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#include "tree.h"
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#include "gimple.h"
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#include "tree-pass.h"
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#include "ssa.h"
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#include "gimple-pretty-print.h"
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#include "fold-const.h"
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#include "gimplify.h"
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#include "gimple-iterator.h"
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#include "gimplify-me.h"
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#include "cfgloop.h"
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#include "tree-ssa.h"
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#include "tree-scalar-evolution.h"
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#include "tree-ssa-loop-manip.h"
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#include "tree-ssa-loop-niter.h"
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#include "tree-ssa-loop-ivopts.h"
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#include "tree-ssa-dce.h"
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#include "tree-data-ref.h"
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#include "tree-vectorizer.h"
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/* This pass performs loop interchange: for example, the loop nest
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for (int j = 0; j < N; j++)
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for (int k = 0; k < N; k++)
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for (int i = 0; i < N; i++)
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c[i][j] = c[i][j] + a[i][k]*b[k][j];
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is transformed to
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for (int i = 0; i < N; i++)
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for (int j = 0; j < N; j++)
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for (int k = 0; k < N; k++)
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c[i][j] = c[i][j] + a[i][k]*b[k][j];
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This pass implements loop interchange in the following steps:
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1) Find perfect loop nest for each innermost loop and compute data
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dependence relations for it. For above example, loop nest is
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<loop_j, loop_k, loop_i>.
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2) From innermost to outermost loop, this pass tries to interchange
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each loop pair. For above case, it firstly tries to interchange
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<loop_k, loop_i> and loop nest becomes <loop_j, loop_i, loop_k>.
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Then it tries to interchange <loop_j, loop_i> and loop nest becomes
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<loop_i, loop_j, loop_k>. The overall effect is to move innermost
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loop to the outermost position. For loop pair <loop_i, loop_j>
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to be interchanged, we:
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3) Check if data dependence relations are valid for loop interchange.
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4) Check if both loops can be interchanged in terms of transformation.
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5) Check if interchanging the two loops is profitable.
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6) Interchange the two loops by mapping induction variables.
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This pass also handles reductions in loop nest. So far we only support
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simple reduction of inner loop and double reduction of the loop nest. */
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/* Maximum number of stmts in each loop that should be interchanged. */
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#define MAX_NUM_STMT (param_loop_interchange_max_num_stmts)
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/* Maximum number of data references in loop nest. */
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#define MAX_DATAREFS (param_loop_max_datarefs_for_datadeps)
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/* Comparison ratio of access stride between inner/outer loops to be
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interchanged. This is the minimum stride ratio for loop interchange
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to be profitable. */
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#define OUTER_STRIDE_RATIO (param_loop_interchange_stride_ratio)
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/* The same as above, but we require higher ratio for interchanging the
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innermost two loops. */
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#define INNER_STRIDE_RATIO ((OUTER_STRIDE_RATIO) + 1)
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/* Comparison ratio of stmt cost between inner/outer loops. Loops won't
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be interchanged if outer loop has too many stmts. */
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#define STMT_COST_RATIO (3)
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/* Vector of strides that DR accesses in each level loop of a loop nest. */
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#define DR_ACCESS_STRIDE(dr) ((vec<tree> *) dr->aux)
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/* Structure recording loop induction variable. */
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typedef struct induction
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{
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/* IV itself. */
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tree var;
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/* IV's initializing value, which is the init arg of the IV PHI node. */
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tree init_val;
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/* IV's initializing expr, which is (the expanded result of) init_val. */
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tree init_expr;
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/* IV's step. */
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tree step;
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} *induction_p;
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/* Enum type for loop reduction variable. */
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enum reduction_type
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{
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UNKNOWN_RTYPE = 0,
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SIMPLE_RTYPE,
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DOUBLE_RTYPE
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};
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/* Structure recording loop reduction variable. */
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typedef struct reduction
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{
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/* Reduction itself. */
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tree var;
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/* PHI node defining reduction variable. */
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gphi *phi;
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/* Init and next variables of the reduction. */
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tree init;
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tree next;
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/* Lcssa PHI node if reduction is used outside of its definition loop. */
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gphi *lcssa_phi;
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/* Stmts defining init and next. */
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gimple *producer;
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gimple *consumer;
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/* If init is loaded from memory, this is the loading memory reference. */
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tree init_ref;
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/* If reduction is finally stored to memory, this is the stored memory
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reference. */
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tree fini_ref;
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enum reduction_type type;
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} *reduction_p;
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/* Dump reduction RE. */
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static void
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dump_reduction (reduction_p re)
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{
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if (re->type == SIMPLE_RTYPE)
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fprintf (dump_file, " Simple reduction: ");
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else if (re->type == DOUBLE_RTYPE)
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fprintf (dump_file, " Double reduction: ");
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else
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fprintf (dump_file, " Unknown reduction: ");
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print_gimple_stmt (dump_file, re->phi, 0);
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}
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/* Dump LOOP's induction IV. */
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static void
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dump_induction (class loop *loop, induction_p iv)
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{
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fprintf (dump_file, " Induction: ");
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print_generic_expr (dump_file, iv->var, TDF_SLIM);
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fprintf (dump_file, " = {");
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print_generic_expr (dump_file, iv->init_expr, TDF_SLIM);
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fprintf (dump_file, ", ");
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print_generic_expr (dump_file, iv->step, TDF_SLIM);
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fprintf (dump_file, "}_%d\n", loop->num);
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}
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/* Loop candidate for interchange. */
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class loop_cand
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{
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public:
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loop_cand (class loop *, class loop *);
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~loop_cand ();
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reduction_p find_reduction_by_stmt (gimple *);
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void classify_simple_reduction (reduction_p);
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bool analyze_iloop_reduction_var (tree);
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bool analyze_oloop_reduction_var (loop_cand *, tree);
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bool analyze_induction_var (tree, tree);
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bool analyze_carried_vars (loop_cand *);
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bool analyze_lcssa_phis (void);
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bool can_interchange_p (loop_cand *);
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void undo_simple_reduction (reduction_p, bitmap);
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/* The loop itself. */
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class loop *m_loop;
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/* The outer loop for interchange. It equals to loop if this loop cand
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itself represents the outer loop. */
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class loop *m_outer;
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/* Vector of induction variables in loop. */
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vec<induction_p> m_inductions;
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/* Vector of reduction variables in loop. */
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vec<reduction_p> m_reductions;
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/* Lcssa PHI nodes of this loop. */
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vec<gphi *> m_lcssa_nodes;
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/* Single exit edge of this loop. */
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edge m_exit;
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/* Basic blocks of this loop. */
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basic_block *m_bbs;
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/* Number of stmts of this loop. Inner loops' stmts are not included. */
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int m_num_stmts;
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/* Number of constant initialized simple reduction. */
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int m_const_init_reduc;
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};
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/* Constructor. */
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loop_cand::loop_cand (class loop *loop, class loop *outer)
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: m_loop (loop), m_outer (outer), m_exit (single_exit (loop)),
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m_bbs (get_loop_body (loop)), m_num_stmts (0), m_const_init_reduc (0)
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{
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m_inductions.create (3);
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m_reductions.create (3);
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m_lcssa_nodes.create (3);
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}
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/* Destructor. */
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loop_cand::~loop_cand ()
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{
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induction_p iv;
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for (unsigned i = 0; m_inductions.iterate (i, &iv); ++i)
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free (iv);
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reduction_p re;
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for (unsigned i = 0; m_reductions.iterate (i, &re); ++i)
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free (re);
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m_inductions.release ();
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m_reductions.release ();
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m_lcssa_nodes.release ();
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free (m_bbs);
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}
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/* Return single use stmt of VAR in LOOP, otherwise return NULL. */
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static gimple *
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single_use_in_loop (tree var, class loop *loop)
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{
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gimple *stmt, *res = NULL;
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use_operand_p use_p;
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imm_use_iterator iterator;
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FOR_EACH_IMM_USE_FAST (use_p, iterator, var)
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{
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stmt = USE_STMT (use_p);
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if (is_gimple_debug (stmt))
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continue;
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if (!flow_bb_inside_loop_p (loop, gimple_bb (stmt)))
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continue;
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if (res)
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return NULL;
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res = stmt;
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}
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return res;
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}
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/* Return true if E is unsupported in loop interchange, i.e, E is a complex
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edge or part of irreducible loop. */
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static inline bool
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unsupported_edge (edge e)
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{
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return (e->flags & (EDGE_COMPLEX | EDGE_IRREDUCIBLE_LOOP));
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}
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/* Return the reduction if STMT is one of its lcssa PHI, producer or consumer
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stmt. */
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reduction_p
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loop_cand::find_reduction_by_stmt (gimple *stmt)
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{
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gphi *phi = dyn_cast <gphi *> (stmt);
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reduction_p re;
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for (unsigned i = 0; m_reductions.iterate (i, &re); ++i)
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if ((phi != NULL && phi == re->lcssa_phi)
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|| (stmt == re->producer || stmt == re->consumer))
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return re;
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return NULL;
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}
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/* Return true if current loop_cand be interchanged. ILOOP is not NULL if
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current loop_cand is outer loop in loop nest. */
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bool
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loop_cand::can_interchange_p (loop_cand *iloop)
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{
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/* For now we only support at most one reduction. */
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unsigned allowed_reduction_num = 1;
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/* Only support reduction if the loop nest to be interchanged is the
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innermostin two loops. */
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if ((iloop == NULL && m_loop->inner != NULL)
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|| (iloop != NULL && iloop->m_loop->inner != NULL))
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allowed_reduction_num = 0;
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if (m_reductions.length () > allowed_reduction_num
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|| (m_reductions.length () == 1
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&& m_reductions[0]->type == UNKNOWN_RTYPE))
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return false;
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/* Only support lcssa PHI node which is for reduction. */
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if (m_lcssa_nodes.length () > allowed_reduction_num)
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return false;
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/* Check if basic block has any unsupported operation. Note basic blocks
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of inner loops are not checked here. */
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for (unsigned i = 0; i < m_loop->num_nodes; i++)
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{
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basic_block bb = m_bbs[i];
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gphi_iterator psi;
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gimple_stmt_iterator gsi;
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/* Skip basic blocks of inner loops. */
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if (bb->loop_father != m_loop)
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continue;
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for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
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{
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gimple *stmt = gsi_stmt (gsi);
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if (is_gimple_debug (stmt))
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continue;
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if (gimple_has_side_effects (stmt))
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return false;
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m_num_stmts++;
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if (gcall *call = dyn_cast <gcall *> (stmt))
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{
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/* In basic block of outer loop, the call should be cheap since
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it will be moved to inner loop. */
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if (iloop != NULL
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&& !gimple_inexpensive_call_p (call))
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return false;
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continue;
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}
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if (!iloop || !gimple_vuse (stmt))
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continue;
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/* Support stmt accessing memory in outer loop only if it is for
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inner loop's reduction. */
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if (iloop->find_reduction_by_stmt (stmt))
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continue;
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tree lhs;
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/* Support loop invariant memory reference if it's only used once by
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inner loop. */
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/* ??? How's this checking for invariantness? */
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if (gimple_assign_single_p (stmt)
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&& (lhs = gimple_assign_lhs (stmt)) != NULL_TREE
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&& TREE_CODE (lhs) == SSA_NAME
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&& single_use_in_loop (lhs, iloop->m_loop))
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continue;
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return false;
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}
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/* Check if loop has too many stmts. */
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if (m_num_stmts > MAX_NUM_STMT)
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return false;
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/* Allow PHI nodes in any basic block of inner loop, PHI nodes in outer
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loop's header, or PHI nodes in dest bb of inner loop's exit edge. */
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if (!iloop || bb == m_loop->header
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|| bb == iloop->m_exit->dest)
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continue;
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/* Don't allow any other PHI nodes. */
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for (psi = gsi_start_phis (bb); !gsi_end_p (psi); gsi_next (&psi))
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if (!virtual_operand_p (PHI_RESULT (psi.phi ())))
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return false;
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}
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return true;
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}
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/* Programmers and optimizers (like loop store motion) may optimize code:
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for (int i = 0; i < N; i++)
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for (int j = 0; j < N; j++)
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a[i] += b[j][i] * c[j][i];
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into reduction:
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for (int i = 0; i < N; i++)
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{
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// producer. Note sum can be intitialized to a constant.
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int sum = a[i];
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for (int j = 0; j < N; j++)
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{
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sum += b[j][i] * c[j][i];
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}
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// consumer.
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a[i] = sum;
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}
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The result code can't be interchanged without undoing the optimization.
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This function classifies this kind reduction and records information so
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that we can undo the store motion during interchange. */
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void
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loop_cand::classify_simple_reduction (reduction_p re)
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{
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gimple *producer, *consumer;
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/* Check init variable of reduction and how it is initialized. */
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if (TREE_CODE (re->init) == SSA_NAME)
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{
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producer = SSA_NAME_DEF_STMT (re->init);
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re->producer = producer;
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basic_block bb = gimple_bb (producer);
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if (!bb || bb->loop_father != m_outer)
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return;
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if (!gimple_assign_load_p (producer))
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return;
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re->init_ref = gimple_assign_rhs1 (producer);
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}
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else if (CONSTANT_CLASS_P (re->init))
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m_const_init_reduc++;
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else
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return;
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/* Check how reduction variable is used. */
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consumer = single_use_in_loop (PHI_RESULT (re->lcssa_phi), m_outer);
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if (!consumer
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|| !gimple_store_p (consumer))
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return;
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re->fini_ref = gimple_get_lhs (consumer);
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re->consumer = consumer;
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/* Simple reduction with constant initializer. */
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if (!re->init_ref)
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{
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gcc_assert (CONSTANT_CLASS_P (re->init));
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re->init_ref = unshare_expr (re->fini_ref);
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}
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/* Require memory references in producer and consumer are the same so
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that we can undo reduction during interchange. */
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if (re->init_ref && !operand_equal_p (re->init_ref, re->fini_ref, 0))
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return;
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re->type = SIMPLE_RTYPE;
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}
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/* Analyze reduction variable VAR for inner loop of the loop nest to be
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interchanged. Return true if analysis succeeds. */
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bool
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loop_cand::analyze_iloop_reduction_var (tree var)
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{
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gphi *phi = as_a <gphi *> (SSA_NAME_DEF_STMT (var));
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gphi *lcssa_phi = NULL, *use_phi;
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tree init = PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (m_loop));
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tree next = PHI_ARG_DEF_FROM_EDGE (phi, loop_latch_edge (m_loop));
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reduction_p re;
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gimple *stmt, *next_def, *single_use = NULL;
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use_operand_p use_p;
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imm_use_iterator iterator;
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if (TREE_CODE (next) != SSA_NAME)
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return false;
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next_def = SSA_NAME_DEF_STMT (next);
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basic_block bb = gimple_bb (next_def);
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if (!bb || !flow_bb_inside_loop_p (m_loop, bb))
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return false;
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/* In restricted reduction, the var is (and must be) used in defining
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the updated var. The process can be depicted as below:
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var ;; = PHI<init, next>
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v
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+---------------------+
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| reduction operators | <-- other operands
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+---------------------+
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v
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next
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In terms loop interchange, we don't change how NEXT is computed based
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on VAR and OTHER OPERANDS. In case of double reduction in loop nest
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to be interchanged, we don't changed it at all. In the case of simple
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reduction in inner loop, we only make change how VAR/NEXT is loaded or
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stored. With these conditions, we can relax restrictions on reduction
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in a way that reduction operation is seen as black box. In general,
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we can ignore reassociation of reduction operator; we can handle fake
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reductions in which VAR is not even used to compute NEXT. */
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if (! single_imm_use (var, &use_p, &single_use)
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|| ! flow_bb_inside_loop_p (m_loop, gimple_bb (single_use)))
|
|
return false;
|
|
|
|
/* Check the reduction operation. We require a left-associative operation.
|
|
For FP math we also need to be allowed to associate operations. */
|
|
if (gassign *ass = dyn_cast <gassign *> (single_use))
|
|
{
|
|
enum tree_code code = gimple_assign_rhs_code (ass);
|
|
if (! (associative_tree_code (code)
|
|
|| (code == MINUS_EXPR
|
|
&& use_p->use == gimple_assign_rhs1_ptr (ass)))
|
|
|| (FLOAT_TYPE_P (TREE_TYPE (var))
|
|
&& ! flag_associative_math))
|
|
return false;
|
|
}
|
|
else
|
|
return false;
|
|
|
|
/* Handle and verify a series of stmts feeding the reduction op. */
|
|
if (single_use != next_def
|
|
&& !check_reduction_path (dump_user_location_t (), m_loop, phi, next,
|
|
gimple_assign_rhs_code (single_use)))
|
|
return false;
|
|
|
|
/* Only support cases in which INIT is used in inner loop. */
|
|
if (TREE_CODE (init) == SSA_NAME)
|
|
FOR_EACH_IMM_USE_FAST (use_p, iterator, init)
|
|
{
|
|
stmt = USE_STMT (use_p);
|
|
if (is_gimple_debug (stmt))
|
|
continue;
|
|
|
|
if (!flow_bb_inside_loop_p (m_loop, gimple_bb (stmt)))
|
|
return false;
|
|
}
|
|
|
|
FOR_EACH_IMM_USE_FAST (use_p, iterator, next)
|
|
{
|
|
stmt = USE_STMT (use_p);
|
|
if (is_gimple_debug (stmt))
|
|
continue;
|
|
|
|
/* Or else it's used in PHI itself. */
|
|
use_phi = dyn_cast <gphi *> (stmt);
|
|
if (use_phi == phi)
|
|
continue;
|
|
|
|
if (use_phi != NULL
|
|
&& lcssa_phi == NULL
|
|
&& gimple_bb (stmt) == m_exit->dest
|
|
&& PHI_ARG_DEF_FROM_EDGE (use_phi, m_exit) == next)
|
|
lcssa_phi = use_phi;
|
|
else
|
|
return false;
|
|
}
|
|
if (!lcssa_phi)
|
|
return false;
|
|
|
|
re = XCNEW (struct reduction);
|
|
re->var = var;
|
|
re->init = init;
|
|
re->next = next;
|
|
re->phi = phi;
|
|
re->lcssa_phi = lcssa_phi;
|
|
|
|
classify_simple_reduction (re);
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
dump_reduction (re);
|
|
|
|
m_reductions.safe_push (re);
|
|
return true;
|
|
}
|
|
|
|
/* Analyze reduction variable VAR for outer loop of the loop nest to be
|
|
interchanged. ILOOP is not NULL and points to inner loop. For the
|
|
moment, we only support double reduction for outer loop, like:
|
|
|
|
for (int i = 0; i < n; i++)
|
|
{
|
|
int sum = 0;
|
|
|
|
for (int j = 0; j < n; j++) // outer loop
|
|
for (int k = 0; k < n; k++) // inner loop
|
|
sum += a[i][k]*b[k][j];
|
|
|
|
s[i] = sum;
|
|
}
|
|
|
|
Note the innermost two loops are the loop nest to be interchanged.
|
|
Return true if analysis succeeds. */
|
|
|
|
bool
|
|
loop_cand::analyze_oloop_reduction_var (loop_cand *iloop, tree var)
|
|
{
|
|
gphi *phi = as_a <gphi *> (SSA_NAME_DEF_STMT (var));
|
|
gphi *lcssa_phi = NULL, *use_phi;
|
|
tree init = PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (m_loop));
|
|
tree next = PHI_ARG_DEF_FROM_EDGE (phi, loop_latch_edge (m_loop));
|
|
reduction_p re;
|
|
gimple *stmt, *next_def;
|
|
use_operand_p use_p;
|
|
imm_use_iterator iterator;
|
|
|
|
if (TREE_CODE (next) != SSA_NAME)
|
|
return false;
|
|
|
|
next_def = SSA_NAME_DEF_STMT (next);
|
|
basic_block bb = gimple_bb (next_def);
|
|
if (!bb || !flow_bb_inside_loop_p (m_loop, bb))
|
|
return false;
|
|
|
|
/* Find inner loop's simple reduction that uses var as initializer. */
|
|
reduction_p inner_re = NULL;
|
|
for (unsigned i = 0; iloop->m_reductions.iterate (i, &inner_re); ++i)
|
|
if (inner_re->init == var || operand_equal_p (inner_re->init, var, 0))
|
|
break;
|
|
|
|
if (inner_re == NULL
|
|
|| inner_re->type != UNKNOWN_RTYPE
|
|
|| inner_re->producer != phi)
|
|
return false;
|
|
|
|
/* In case of double reduction, outer loop's reduction should be updated
|
|
by inner loop's simple reduction. */
|
|
if (next_def != inner_re->lcssa_phi)
|
|
return false;
|
|
|
|
/* Outer loop's reduction should only be used to initialize inner loop's
|
|
simple reduction. */
|
|
if (! single_imm_use (var, &use_p, &stmt)
|
|
|| stmt != inner_re->phi)
|
|
return false;
|
|
|
|
/* Check this reduction is correctly used outside of loop via lcssa phi. */
|
|
FOR_EACH_IMM_USE_FAST (use_p, iterator, next)
|
|
{
|
|
stmt = USE_STMT (use_p);
|
|
if (is_gimple_debug (stmt))
|
|
continue;
|
|
|
|
/* Or else it's used in PHI itself. */
|
|
use_phi = dyn_cast <gphi *> (stmt);
|
|
if (use_phi == phi)
|
|
continue;
|
|
|
|
if (lcssa_phi == NULL
|
|
&& use_phi != NULL
|
|
&& gimple_bb (stmt) == m_exit->dest
|
|
&& PHI_ARG_DEF_FROM_EDGE (use_phi, m_exit) == next)
|
|
lcssa_phi = use_phi;
|
|
else
|
|
return false;
|
|
}
|
|
if (!lcssa_phi)
|
|
return false;
|
|
|
|
re = XCNEW (struct reduction);
|
|
re->var = var;
|
|
re->init = init;
|
|
re->next = next;
|
|
re->phi = phi;
|
|
re->lcssa_phi = lcssa_phi;
|
|
re->type = DOUBLE_RTYPE;
|
|
inner_re->type = DOUBLE_RTYPE;
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
dump_reduction (re);
|
|
|
|
m_reductions.safe_push (re);
|
|
return true;
|
|
}
|
|
|
|
/* Return true if VAR is induction variable of current loop whose scev is
|
|
specified by CHREC. */
|
|
|
|
bool
|
|
loop_cand::analyze_induction_var (tree var, tree chrec)
|
|
{
|
|
gphi *phi = as_a <gphi *> (SSA_NAME_DEF_STMT (var));
|
|
tree init = PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (m_loop));
|
|
|
|
/* Var is loop invariant, though it's unlikely to happen. */
|
|
if (tree_does_not_contain_chrecs (chrec))
|
|
{
|
|
/* Punt on floating point invariants if honoring signed zeros,
|
|
representing that as + 0.0 would change the result if init
|
|
is -0.0. Similarly for SNaNs it can raise exception. */
|
|
if (HONOR_SIGNED_ZEROS (chrec) || HONOR_SNANS (chrec))
|
|
return false;
|
|
struct induction *iv = XCNEW (struct induction);
|
|
iv->var = var;
|
|
iv->init_val = init;
|
|
iv->init_expr = chrec;
|
|
iv->step = build_zero_cst (TREE_TYPE (chrec));
|
|
m_inductions.safe_push (iv);
|
|
return true;
|
|
}
|
|
|
|
if (TREE_CODE (chrec) != POLYNOMIAL_CHREC
|
|
|| CHREC_VARIABLE (chrec) != (unsigned) m_loop->num
|
|
|| tree_contains_chrecs (CHREC_LEFT (chrec), NULL)
|
|
|| tree_contains_chrecs (CHREC_RIGHT (chrec), NULL))
|
|
return false;
|
|
|
|
struct induction *iv = XCNEW (struct induction);
|
|
iv->var = var;
|
|
iv->init_val = init;
|
|
iv->init_expr = CHREC_LEFT (chrec);
|
|
iv->step = CHREC_RIGHT (chrec);
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
dump_induction (m_loop, iv);
|
|
|
|
m_inductions.safe_push (iv);
|
|
return true;
|
|
}
|
|
|
|
/* Return true if all loop carried variables defined in loop header can
|
|
be successfully analyzed. */
|
|
|
|
bool
|
|
loop_cand::analyze_carried_vars (loop_cand *iloop)
|
|
{
|
|
edge e = loop_preheader_edge (m_outer);
|
|
gphi_iterator gsi;
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
fprintf (dump_file, "\nLoop(%d) carried vars:\n", m_loop->num);
|
|
|
|
for (gsi = gsi_start_phis (m_loop->header); !gsi_end_p (gsi); gsi_next (&gsi))
|
|
{
|
|
gphi *phi = gsi.phi ();
|
|
|
|
tree var = PHI_RESULT (phi);
|
|
if (virtual_operand_p (var))
|
|
continue;
|
|
|
|
tree chrec = analyze_scalar_evolution (m_loop, var);
|
|
chrec = instantiate_scev (e, m_loop, chrec);
|
|
|
|
/* Analyze var as reduction variable. */
|
|
if (chrec_contains_undetermined (chrec)
|
|
|| chrec_contains_symbols_defined_in_loop (chrec, m_outer->num))
|
|
{
|
|
if (iloop && !analyze_oloop_reduction_var (iloop, var))
|
|
return false;
|
|
if (!iloop && !analyze_iloop_reduction_var (var))
|
|
return false;
|
|
}
|
|
/* Analyze var as induction variable. */
|
|
else if (!analyze_induction_var (var, chrec))
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/* Return TRUE if loop closed PHI nodes can be analyzed successfully. */
|
|
|
|
bool
|
|
loop_cand::analyze_lcssa_phis (void)
|
|
{
|
|
gphi_iterator gsi;
|
|
for (gsi = gsi_start_phis (m_exit->dest); !gsi_end_p (gsi); gsi_next (&gsi))
|
|
{
|
|
gphi *phi = gsi.phi ();
|
|
|
|
if (virtual_operand_p (PHI_RESULT (phi)))
|
|
continue;
|
|
|
|
/* TODO: We only support lcssa phi for reduction for now. */
|
|
if (!find_reduction_by_stmt (phi))
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/* CONSUMER is a stmt in BB storing reduction result into memory object.
|
|
When the reduction is intialized from constant value, we need to add
|
|
a stmt loading from the memory object to target basic block in inner
|
|
loop during undoing the reduction. Problem is that memory reference
|
|
may use ssa variables not dominating the target basic block. This
|
|
function finds all stmts on which CONSUMER depends in basic block BB,
|
|
records and returns them via STMTS. */
|
|
|
|
static void
|
|
find_deps_in_bb_for_stmt (gimple_seq *stmts, basic_block bb, gimple *consumer)
|
|
{
|
|
auto_vec<gimple *, 4> worklist;
|
|
use_operand_p use_p;
|
|
ssa_op_iter iter;
|
|
gimple *stmt, *def_stmt;
|
|
gimple_stmt_iterator gsi;
|
|
|
|
/* First clear flag for stmts in bb. */
|
|
for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
|
|
gimple_set_plf (gsi_stmt (gsi), GF_PLF_1, false);
|
|
|
|
/* DFS search all depended stmts in bb and mark flag for these stmts. */
|
|
worklist.safe_push (consumer);
|
|
while (!worklist.is_empty ())
|
|
{
|
|
stmt = worklist.pop ();
|
|
FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
|
|
{
|
|
def_stmt = SSA_NAME_DEF_STMT (USE_FROM_PTR (use_p));
|
|
|
|
if (is_a <gphi *> (def_stmt)
|
|
|| gimple_bb (def_stmt) != bb
|
|
|| gimple_plf (def_stmt, GF_PLF_1))
|
|
continue;
|
|
|
|
worklist.safe_push (def_stmt);
|
|
}
|
|
gimple_set_plf (stmt, GF_PLF_1, true);
|
|
}
|
|
for (gsi = gsi_start_nondebug_bb (bb);
|
|
!gsi_end_p (gsi) && (stmt = gsi_stmt (gsi)) != consumer;)
|
|
{
|
|
/* Move dep stmts to sequence STMTS. */
|
|
if (gimple_plf (stmt, GF_PLF_1))
|
|
{
|
|
gsi_remove (&gsi, false);
|
|
gimple_seq_add_stmt_without_update (stmts, stmt);
|
|
}
|
|
else
|
|
gsi_next_nondebug (&gsi);
|
|
}
|
|
}
|
|
|
|
/* User can write, optimizers can generate simple reduction RE for inner
|
|
loop. In order to make interchange valid, we have to undo reduction by
|
|
moving producer and consumer stmts into the inner loop. For example,
|
|
below code:
|
|
|
|
init = MEM_REF[idx]; //producer
|
|
loop:
|
|
var = phi<init, next>
|
|
next = var op ...
|
|
reduc_sum = phi<next>
|
|
MEM_REF[idx] = reduc_sum //consumer
|
|
|
|
is transformed into:
|
|
|
|
loop:
|
|
new_var = MEM_REF[idx]; //producer after moving
|
|
next = new_var op ...
|
|
MEM_REF[idx] = next; //consumer after moving
|
|
|
|
Note if the reduction variable is initialized to constant, like:
|
|
|
|
var = phi<0.0, next>
|
|
|
|
we compute new_var as below:
|
|
|
|
loop:
|
|
tmp = MEM_REF[idx];
|
|
new_var = !first_iteration ? tmp : 0.0;
|
|
|
|
so that the initial const is used in the first iteration of loop. Also
|
|
record ssa variables for dead code elimination in DCE_SEEDS. */
|
|
|
|
void
|
|
loop_cand::undo_simple_reduction (reduction_p re, bitmap dce_seeds)
|
|
{
|
|
gimple *stmt;
|
|
gimple_stmt_iterator from, to = gsi_after_labels (m_loop->header);
|
|
gimple_seq stmts = NULL;
|
|
tree new_var;
|
|
|
|
/* Prepare the initialization stmts and insert it to inner loop. */
|
|
if (re->producer != NULL)
|
|
{
|
|
gimple_set_vuse (re->producer, NULL_TREE);
|
|
update_stmt (re->producer);
|
|
from = gsi_for_stmt (re->producer);
|
|
gsi_remove (&from, false);
|
|
gimple_seq_add_stmt_without_update (&stmts, re->producer);
|
|
new_var = re->init;
|
|
}
|
|
else
|
|
{
|
|
/* Find all stmts on which expression "MEM_REF[idx]" depends. */
|
|
find_deps_in_bb_for_stmt (&stmts, gimple_bb (re->consumer), re->consumer);
|
|
/* Because we generate new stmt loading from the MEM_REF to TMP. */
|
|
tree cond, tmp = copy_ssa_name (re->var);
|
|
stmt = gimple_build_assign (tmp, re->init_ref);
|
|
gimple_seq_add_stmt_without_update (&stmts, stmt);
|
|
|
|
/* Init new_var to MEM_REF or CONST depending on if it is the first
|
|
iteration. */
|
|
induction_p iv = m_inductions[0];
|
|
cond = fold_build2 (NE_EXPR, boolean_type_node, iv->var, iv->init_val);
|
|
new_var = copy_ssa_name (re->var);
|
|
stmt = gimple_build_assign (new_var, COND_EXPR, cond, tmp, re->init);
|
|
gimple_seq_add_stmt_without_update (&stmts, stmt);
|
|
}
|
|
gsi_insert_seq_before (&to, stmts, GSI_SAME_STMT);
|
|
|
|
/* Replace all uses of reduction var with new variable. */
|
|
use_operand_p use_p;
|
|
imm_use_iterator iterator;
|
|
FOR_EACH_IMM_USE_STMT (stmt, iterator, re->var)
|
|
{
|
|
FOR_EACH_IMM_USE_ON_STMT (use_p, iterator)
|
|
SET_USE (use_p, new_var);
|
|
|
|
update_stmt (stmt);
|
|
}
|
|
|
|
/* Move consumer stmt into inner loop, just after reduction next's def. */
|
|
unlink_stmt_vdef (re->consumer);
|
|
release_ssa_name (gimple_vdef (re->consumer));
|
|
gimple_set_vdef (re->consumer, NULL_TREE);
|
|
gimple_set_vuse (re->consumer, NULL_TREE);
|
|
gimple_assign_set_rhs1 (re->consumer, re->next);
|
|
update_stmt (re->consumer);
|
|
from = gsi_for_stmt (re->consumer);
|
|
to = gsi_for_stmt (SSA_NAME_DEF_STMT (re->next));
|
|
gsi_move_after (&from, &to);
|
|
|
|
/* Mark the reduction variables for DCE. */
|
|
bitmap_set_bit (dce_seeds, SSA_NAME_VERSION (re->var));
|
|
bitmap_set_bit (dce_seeds, SSA_NAME_VERSION (PHI_RESULT (re->lcssa_phi)));
|
|
}
|
|
|
|
/* Free DATAREFS and its auxiliary memory. */
|
|
|
|
static void
|
|
free_data_refs_with_aux (vec<data_reference_p> datarefs)
|
|
{
|
|
data_reference_p dr;
|
|
for (unsigned i = 0; datarefs.iterate (i, &dr); ++i)
|
|
if (dr->aux != NULL)
|
|
{
|
|
DR_ACCESS_STRIDE (dr)->release ();
|
|
delete (vec<tree> *) dr->aux;
|
|
}
|
|
|
|
free_data_refs (datarefs);
|
|
}
|
|
|
|
/* Class for loop interchange transformation. */
|
|
|
|
class tree_loop_interchange
|
|
{
|
|
public:
|
|
tree_loop_interchange (vec<class loop *> loop_nest)
|
|
: m_loop_nest (loop_nest), m_niters_iv_var (NULL_TREE),
|
|
m_dce_seeds (BITMAP_ALLOC (NULL)) { }
|
|
~tree_loop_interchange () { BITMAP_FREE (m_dce_seeds); }
|
|
bool interchange (vec<data_reference_p>, vec<ddr_p>);
|
|
|
|
private:
|
|
void update_data_info (unsigned, unsigned, vec<data_reference_p>, vec<ddr_p>);
|
|
bool valid_data_dependences (unsigned, unsigned, vec<ddr_p>);
|
|
void interchange_loops (loop_cand &, loop_cand &);
|
|
void map_inductions_to_loop (loop_cand &, loop_cand &);
|
|
void move_code_to_inner_loop (class loop *, class loop *, basic_block *);
|
|
|
|
/* The whole loop nest in which interchange is ongoing. */
|
|
vec<class loop *> m_loop_nest;
|
|
/* We create new IV which is only used in loop's exit condition check.
|
|
In case of 3-level loop nest interchange, when we interchange the
|
|
innermost two loops, new IV created in the middle level loop does
|
|
not need to be preserved in interchanging the outermost two loops
|
|
later. We record the IV so that it can be skipped. */
|
|
tree m_niters_iv_var;
|
|
/* Bitmap of seed variables for dead code elimination after interchange. */
|
|
bitmap m_dce_seeds;
|
|
};
|
|
|
|
/* Update data refs' access stride and dependence information after loop
|
|
interchange. I_IDX/O_IDX gives indices of interchanged loops in loop
|
|
nest. DATAREFS are data references. DDRS are data dependences. */
|
|
|
|
void
|
|
tree_loop_interchange::update_data_info (unsigned i_idx, unsigned o_idx,
|
|
vec<data_reference_p> datarefs,
|
|
vec<ddr_p> ddrs)
|
|
{
|
|
struct data_reference *dr;
|
|
struct data_dependence_relation *ddr;
|
|
|
|
/* Update strides of data references. */
|
|
for (unsigned i = 0; datarefs.iterate (i, &dr); ++i)
|
|
{
|
|
vec<tree> *stride = DR_ACCESS_STRIDE (dr);
|
|
gcc_assert (stride->length () > i_idx);
|
|
std::swap ((*stride)[i_idx], (*stride)[o_idx]);
|
|
}
|
|
/* Update data dependences. */
|
|
for (unsigned i = 0; ddrs.iterate (i, &ddr); ++i)
|
|
if (DDR_ARE_DEPENDENT (ddr) != chrec_known)
|
|
{
|
|
for (unsigned j = 0; j < DDR_NUM_DIST_VECTS (ddr); ++j)
|
|
{
|
|
lambda_vector dist_vect = DDR_DIST_VECT (ddr, j);
|
|
std::swap (dist_vect[i_idx], dist_vect[o_idx]);
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Check data dependence relations, return TRUE if it's valid to interchange
|
|
two loops specified by I_IDX/O_IDX. Theoretically, interchanging the two
|
|
loops is valid only if dist vector, after interchanging, doesn't have '>'
|
|
as the leftmost non-'=' direction. Practically, this function have been
|
|
conservative here by not checking some valid cases. */
|
|
|
|
bool
|
|
tree_loop_interchange::valid_data_dependences (unsigned i_idx, unsigned o_idx,
|
|
vec<ddr_p> ddrs)
|
|
{
|
|
struct data_dependence_relation *ddr;
|
|
|
|
for (unsigned i = 0; ddrs.iterate (i, &ddr); ++i)
|
|
{
|
|
/* Skip no-dependence case. */
|
|
if (DDR_ARE_DEPENDENT (ddr) == chrec_known)
|
|
continue;
|
|
|
|
for (unsigned j = 0; j < DDR_NUM_DIST_VECTS (ddr); ++j)
|
|
{
|
|
lambda_vector dist_vect = DDR_DIST_VECT (ddr, j);
|
|
unsigned level = dependence_level (dist_vect, m_loop_nest.length ());
|
|
|
|
/* If there is no carried dependence. */
|
|
if (level == 0)
|
|
continue;
|
|
|
|
level --;
|
|
|
|
/* If dependence is not carried by any loop in between the two
|
|
loops [oloop, iloop] to interchange. */
|
|
if (level < o_idx || level > i_idx)
|
|
continue;
|
|
|
|
/* Be conservative, skip case if either direction at i_idx/o_idx
|
|
levels is not '=' or '<'. */
|
|
if ((!DDR_REVERSED_P (ddr) && dist_vect[i_idx] < 0)
|
|
|| (DDR_REVERSED_P (ddr) && dist_vect[i_idx] > 0)
|
|
|| (!DDR_REVERSED_P (ddr) && dist_vect[o_idx] < 0)
|
|
|| (DDR_REVERSED_P (ddr) && dist_vect[o_idx] > 0))
|
|
return false;
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/* Interchange two loops specified by ILOOP and OLOOP. */
|
|
|
|
void
|
|
tree_loop_interchange::interchange_loops (loop_cand &iloop, loop_cand &oloop)
|
|
{
|
|
reduction_p re;
|
|
gimple_stmt_iterator gsi;
|
|
tree i_niters, o_niters, var_after;
|
|
|
|
/* Undo inner loop's simple reduction. */
|
|
for (unsigned i = 0; iloop.m_reductions.iterate (i, &re); ++i)
|
|
if (re->type != DOUBLE_RTYPE)
|
|
{
|
|
if (re->producer)
|
|
reset_debug_uses (re->producer);
|
|
|
|
iloop.undo_simple_reduction (re, m_dce_seeds);
|
|
}
|
|
|
|
/* Only need to reset debug uses for double reduction. */
|
|
for (unsigned i = 0; oloop.m_reductions.iterate (i, &re); ++i)
|
|
{
|
|
gcc_assert (re->type == DOUBLE_RTYPE);
|
|
reset_debug_uses (SSA_NAME_DEF_STMT (re->var));
|
|
reset_debug_uses (SSA_NAME_DEF_STMT (re->next));
|
|
}
|
|
|
|
/* Prepare niters for both loops. */
|
|
class loop *loop_nest = m_loop_nest[0];
|
|
edge instantiate_below = loop_preheader_edge (loop_nest);
|
|
gsi = gsi_last_bb (loop_preheader_edge (loop_nest)->src);
|
|
i_niters = number_of_latch_executions (iloop.m_loop);
|
|
i_niters = analyze_scalar_evolution (loop_outer (iloop.m_loop), i_niters);
|
|
i_niters = instantiate_scev (instantiate_below, loop_outer (iloop.m_loop),
|
|
i_niters);
|
|
i_niters = force_gimple_operand_gsi (&gsi, unshare_expr (i_niters), true,
|
|
NULL_TREE, false, GSI_CONTINUE_LINKING);
|
|
o_niters = number_of_latch_executions (oloop.m_loop);
|
|
if (oloop.m_loop != loop_nest)
|
|
{
|
|
o_niters = analyze_scalar_evolution (loop_outer (oloop.m_loop), o_niters);
|
|
o_niters = instantiate_scev (instantiate_below, loop_outer (oloop.m_loop),
|
|
o_niters);
|
|
}
|
|
o_niters = force_gimple_operand_gsi (&gsi, unshare_expr (o_niters), true,
|
|
NULL_TREE, false, GSI_CONTINUE_LINKING);
|
|
|
|
/* Move src's code to tgt loop. This is necessary when src is the outer
|
|
loop and tgt is the inner loop. */
|
|
move_code_to_inner_loop (oloop.m_loop, iloop.m_loop, oloop.m_bbs);
|
|
|
|
/* Map outer loop's IV to inner loop, and vice versa. */
|
|
map_inductions_to_loop (oloop, iloop);
|
|
map_inductions_to_loop (iloop, oloop);
|
|
|
|
/* Create canonical IV for both loops. Note canonical IV for outer/inner
|
|
loop is actually from inner/outer loop. Also we record the new IV
|
|
created for the outer loop so that it can be skipped in later loop
|
|
interchange. */
|
|
create_canonical_iv (oloop.m_loop, oloop.m_exit,
|
|
i_niters, &m_niters_iv_var, &var_after);
|
|
bitmap_set_bit (m_dce_seeds, SSA_NAME_VERSION (var_after));
|
|
create_canonical_iv (iloop.m_loop, iloop.m_exit,
|
|
o_niters, NULL, &var_after);
|
|
bitmap_set_bit (m_dce_seeds, SSA_NAME_VERSION (var_after));
|
|
|
|
/* Scrap niters estimation of interchanged loops. */
|
|
iloop.m_loop->any_upper_bound = false;
|
|
iloop.m_loop->any_likely_upper_bound = false;
|
|
free_numbers_of_iterations_estimates (iloop.m_loop);
|
|
oloop.m_loop->any_upper_bound = false;
|
|
oloop.m_loop->any_likely_upper_bound = false;
|
|
free_numbers_of_iterations_estimates (oloop.m_loop);
|
|
|
|
/* Clear all cached scev information. This is expensive but shouldn't be
|
|
a problem given we interchange in very limited times. */
|
|
scev_reset_htab ();
|
|
|
|
/* ??? The association between the loop data structure and the
|
|
CFG changed, so what was loop N at the source level is now
|
|
loop M. We should think of retaining the association or breaking
|
|
it fully by creating a new loop instead of re-using the "wrong" one. */
|
|
}
|
|
|
|
/* Map induction variables of SRC loop to TGT loop. The function firstly
|
|
creates the same IV of SRC loop in TGT loop, then deletes the original
|
|
IV and re-initialize it using the newly created IV. For example, loop
|
|
nest:
|
|
|
|
for (i = 0; i < N; i++)
|
|
for (j = 0; j < M; j++)
|
|
{
|
|
//use of i;
|
|
//use of j;
|
|
}
|
|
|
|
will be transformed into:
|
|
|
|
for (jj = 0; jj < M; jj++)
|
|
for (ii = 0; ii < N; ii++)
|
|
{
|
|
//use of ii;
|
|
//use of jj;
|
|
}
|
|
|
|
after loop interchange. */
|
|
|
|
void
|
|
tree_loop_interchange::map_inductions_to_loop (loop_cand &src, loop_cand &tgt)
|
|
{
|
|
induction_p iv;
|
|
edge e = tgt.m_exit;
|
|
gimple_stmt_iterator incr_pos = gsi_last_bb (e->src), gsi;
|
|
|
|
/* Map source loop's IV to target loop. */
|
|
for (unsigned i = 0; src.m_inductions.iterate (i, &iv); ++i)
|
|
{
|
|
gimple *use_stmt, *stmt = SSA_NAME_DEF_STMT (iv->var);
|
|
gcc_assert (is_a <gphi *> (stmt));
|
|
|
|
use_operand_p use_p;
|
|
/* Only map original IV to target loop. */
|
|
if (m_niters_iv_var != iv->var)
|
|
{
|
|
/* Map the IV by creating the same one in target loop. */
|
|
tree var_before, var_after;
|
|
tree base = unshare_expr (iv->init_expr);
|
|
tree step = unshare_expr (iv->step);
|
|
create_iv (base, step, SSA_NAME_VAR (iv->var),
|
|
tgt.m_loop, &incr_pos, false, &var_before, &var_after);
|
|
bitmap_set_bit (m_dce_seeds, SSA_NAME_VERSION (var_before));
|
|
bitmap_set_bit (m_dce_seeds, SSA_NAME_VERSION (var_after));
|
|
|
|
/* Replace uses of the original IV var with newly created IV var. */
|
|
imm_use_iterator imm_iter;
|
|
FOR_EACH_IMM_USE_STMT (use_stmt, imm_iter, iv->var)
|
|
{
|
|
FOR_EACH_IMM_USE_ON_STMT (use_p, imm_iter)
|
|
SET_USE (use_p, var_before);
|
|
|
|
update_stmt (use_stmt);
|
|
}
|
|
}
|
|
|
|
/* Mark all uses for DCE. */
|
|
ssa_op_iter op_iter;
|
|
FOR_EACH_PHI_OR_STMT_USE (use_p, stmt, op_iter, SSA_OP_USE)
|
|
{
|
|
tree use = USE_FROM_PTR (use_p);
|
|
if (TREE_CODE (use) == SSA_NAME
|
|
&& ! SSA_NAME_IS_DEFAULT_DEF (use))
|
|
bitmap_set_bit (m_dce_seeds, SSA_NAME_VERSION (use));
|
|
}
|
|
|
|
/* Delete definition of the original IV in the source loop. */
|
|
gsi = gsi_for_stmt (stmt);
|
|
remove_phi_node (&gsi, true);
|
|
}
|
|
}
|
|
|
|
/* Move stmts of outer loop to inner loop. */
|
|
|
|
void
|
|
tree_loop_interchange::move_code_to_inner_loop (class loop *outer,
|
|
class loop *inner,
|
|
basic_block *outer_bbs)
|
|
{
|
|
basic_block oloop_exit_bb = single_exit (outer)->src;
|
|
gimple_stmt_iterator gsi, to;
|
|
|
|
for (unsigned i = 0; i < outer->num_nodes; i++)
|
|
{
|
|
basic_block bb = outer_bbs[i];
|
|
|
|
/* Skip basic blocks of inner loop. */
|
|
if (flow_bb_inside_loop_p (inner, bb))
|
|
continue;
|
|
|
|
/* Move code from header/latch to header/latch. */
|
|
if (bb == outer->header)
|
|
to = gsi_after_labels (inner->header);
|
|
else if (bb == outer->latch)
|
|
to = gsi_after_labels (inner->latch);
|
|
else
|
|
/* Otherwise, simply move to exit->src. */
|
|
to = gsi_last_bb (single_exit (inner)->src);
|
|
|
|
for (gsi = gsi_after_labels (bb); !gsi_end_p (gsi);)
|
|
{
|
|
gimple *stmt = gsi_stmt (gsi);
|
|
|
|
if (oloop_exit_bb == bb
|
|
&& stmt == gsi_stmt (gsi_last_bb (oloop_exit_bb)))
|
|
{
|
|
gsi_next (&gsi);
|
|
continue;
|
|
}
|
|
|
|
if (gimple_vdef (stmt))
|
|
{
|
|
unlink_stmt_vdef (stmt);
|
|
release_ssa_name (gimple_vdef (stmt));
|
|
gimple_set_vdef (stmt, NULL_TREE);
|
|
}
|
|
if (gimple_vuse (stmt))
|
|
{
|
|
gimple_set_vuse (stmt, NULL_TREE);
|
|
update_stmt (stmt);
|
|
}
|
|
|
|
reset_debug_uses (stmt);
|
|
gsi_move_before (&gsi, &to);
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Given data reference DR in LOOP_NEST, the function computes DR's access
|
|
stride at each level of loop from innermost LOOP to outer. On success,
|
|
it saves access stride at each level loop in a vector which is pointed
|
|
by DR->aux. For example:
|
|
|
|
int arr[100][100][100];
|
|
for (i = 0; i < 100; i++) ;(DR->aux)strides[0] = 40000
|
|
for (j = 100; j > 0; j--) ;(DR->aux)strides[1] = 400
|
|
for (k = 0; k < 100; k++) ;(DR->aux)strides[2] = 4
|
|
arr[i][j - 1][k] = 0; */
|
|
|
|
static void
|
|
compute_access_stride (class loop *&loop_nest, class loop *loop,
|
|
data_reference_p dr)
|
|
{
|
|
vec<tree> *strides = new vec<tree> ();
|
|
dr->aux = strides;
|
|
|
|
basic_block bb = gimple_bb (DR_STMT (dr));
|
|
if (!flow_bb_inside_loop_p (loop_nest, bb))
|
|
return;
|
|
while (!flow_bb_inside_loop_p (loop, bb))
|
|
{
|
|
strides->safe_push (build_int_cst (sizetype, 0));
|
|
loop = loop_outer (loop);
|
|
}
|
|
gcc_assert (loop == bb->loop_father);
|
|
|
|
tree ref = DR_REF (dr);
|
|
if (TREE_CODE (ref) == COMPONENT_REF
|
|
&& DECL_BIT_FIELD (TREE_OPERAND (ref, 1)))
|
|
{
|
|
/* We can't take address of bitfields. If the bitfield is at constant
|
|
offset from the start of the struct, just use address of the
|
|
struct, for analysis of the strides that shouldn't matter. */
|
|
if (!TREE_OPERAND (ref, 2)
|
|
|| TREE_CODE (TREE_OPERAND (ref, 2)) == INTEGER_CST)
|
|
ref = TREE_OPERAND (ref, 0);
|
|
/* Otherwise, if we have a bit field representative, use that. */
|
|
else if (DECL_BIT_FIELD_REPRESENTATIVE (TREE_OPERAND (ref, 1))
|
|
!= NULL_TREE)
|
|
{
|
|
tree repr = DECL_BIT_FIELD_REPRESENTATIVE (TREE_OPERAND (ref, 1));
|
|
ref = build3 (COMPONENT_REF, TREE_TYPE (repr), TREE_OPERAND (ref, 0),
|
|
repr, TREE_OPERAND (ref, 2));
|
|
}
|
|
/* Otherwise punt. */
|
|
else
|
|
return;
|
|
}
|
|
tree scev_base = build_fold_addr_expr (ref);
|
|
tree scev = analyze_scalar_evolution (loop, scev_base);
|
|
if (chrec_contains_undetermined (scev))
|
|
return;
|
|
|
|
tree orig_scev = scev;
|
|
do
|
|
{
|
|
scev = instantiate_scev (loop_preheader_edge (loop_nest),
|
|
loop, orig_scev);
|
|
if (! chrec_contains_undetermined (scev))
|
|
break;
|
|
|
|
/* If we couldn't instantiate for the desired nest, shrink it. */
|
|
if (loop_nest == loop)
|
|
return;
|
|
loop_nest = loop_nest->inner;
|
|
} while (1);
|
|
|
|
tree sl = scev;
|
|
class loop *expected = loop;
|
|
while (TREE_CODE (sl) == POLYNOMIAL_CHREC)
|
|
{
|
|
class loop *sl_loop = get_chrec_loop (sl);
|
|
while (sl_loop != expected)
|
|
{
|
|
strides->safe_push (size_int (0));
|
|
expected = loop_outer (expected);
|
|
}
|
|
strides->safe_push (CHREC_RIGHT (sl));
|
|
sl = CHREC_LEFT (sl);
|
|
expected = loop_outer (expected);
|
|
}
|
|
if (! tree_contains_chrecs (sl, NULL))
|
|
while (expected != loop_outer (loop_nest))
|
|
{
|
|
strides->safe_push (size_int (0));
|
|
expected = loop_outer (expected);
|
|
}
|
|
}
|
|
|
|
/* Given loop nest LOOP_NEST with innermost LOOP, the function computes
|
|
access strides with respect to each level loop for all data refs in
|
|
DATAREFS from inner loop to outer loop. On success, it returns the
|
|
outermost loop that access strides can be computed successfully for
|
|
all data references. If access strides cannot be computed at least
|
|
for two levels of loop for any data reference, it returns NULL. */
|
|
|
|
static class loop *
|
|
compute_access_strides (class loop *loop_nest, class loop *loop,
|
|
vec<data_reference_p> datarefs)
|
|
{
|
|
unsigned i, j, num_loops = (unsigned) -1;
|
|
data_reference_p dr;
|
|
vec<tree> *stride;
|
|
|
|
class loop *interesting_loop_nest = loop_nest;
|
|
for (i = 0; datarefs.iterate (i, &dr); ++i)
|
|
{
|
|
compute_access_stride (interesting_loop_nest, loop, dr);
|
|
stride = DR_ACCESS_STRIDE (dr);
|
|
if (stride->length () < num_loops)
|
|
{
|
|
num_loops = stride->length ();
|
|
if (num_loops < 2)
|
|
return NULL;
|
|
}
|
|
}
|
|
|
|
for (i = 0; datarefs.iterate (i, &dr); ++i)
|
|
{
|
|
stride = DR_ACCESS_STRIDE (dr);
|
|
if (stride->length () > num_loops)
|
|
stride->truncate (num_loops);
|
|
|
|
for (j = 0; j < (num_loops >> 1); ++j)
|
|
std::swap ((*stride)[j], (*stride)[num_loops - j - 1]);
|
|
}
|
|
|
|
loop = superloop_at_depth (loop, loop_depth (loop) + 1 - num_loops);
|
|
gcc_assert (loop_nest == loop || flow_loop_nested_p (loop_nest, loop));
|
|
return loop;
|
|
}
|
|
|
|
/* Prune access strides for data references in DATAREFS by removing strides
|
|
of loops that isn't in current LOOP_NEST. */
|
|
|
|
static void
|
|
prune_access_strides_not_in_loop (class loop *loop_nest,
|
|
class loop *innermost,
|
|
vec<data_reference_p> datarefs)
|
|
{
|
|
data_reference_p dr;
|
|
unsigned num_loops = loop_depth (innermost) - loop_depth (loop_nest) + 1;
|
|
gcc_assert (num_loops > 1);
|
|
|
|
/* Block remove strides of loops that is not in current loop nest. */
|
|
for (unsigned i = 0; datarefs.iterate (i, &dr); ++i)
|
|
{
|
|
vec<tree> *stride = DR_ACCESS_STRIDE (dr);
|
|
if (stride->length () > num_loops)
|
|
stride->block_remove (0, stride->length () - num_loops);
|
|
}
|
|
}
|
|
|
|
/* Dump access strides for all DATAREFS. */
|
|
|
|
static void
|
|
dump_access_strides (vec<data_reference_p> datarefs)
|
|
{
|
|
data_reference_p dr;
|
|
fprintf (dump_file, "Access Strides for DRs:\n");
|
|
for (unsigned i = 0; datarefs.iterate (i, &dr); ++i)
|
|
{
|
|
fprintf (dump_file, " ");
|
|
print_generic_expr (dump_file, DR_REF (dr), TDF_SLIM);
|
|
fprintf (dump_file, ":\t\t<");
|
|
|
|
vec<tree> *stride = DR_ACCESS_STRIDE (dr);
|
|
unsigned num_loops = stride->length ();
|
|
for (unsigned j = 0; j < num_loops; ++j)
|
|
{
|
|
print_generic_expr (dump_file, (*stride)[j], TDF_SLIM);
|
|
fprintf (dump_file, "%s", (j < num_loops - 1) ? ",\t" : ">\n");
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Return true if it's profitable to interchange two loops whose index
|
|
in whole loop nest vector are I_IDX/O_IDX respectively. The function
|
|
computes and compares three types information from all DATAREFS:
|
|
1) Access stride for loop I_IDX and O_IDX.
|
|
2) Number of invariant memory references with respect to I_IDX before
|
|
and after loop interchange.
|
|
3) Flags indicating if all memory references access sequential memory
|
|
in ILOOP, before and after loop interchange.
|
|
If INNMOST_LOOP_P is true, the two loops for interchanging are the two
|
|
innermost loops in loop nest. This function also dumps information if
|
|
DUMP_INFO_P is true. */
|
|
|
|
static bool
|
|
should_interchange_loops (unsigned i_idx, unsigned o_idx,
|
|
vec<data_reference_p> datarefs,
|
|
unsigned i_stmt_cost, unsigned o_stmt_cost,
|
|
bool innermost_loops_p, bool dump_info_p = true)
|
|
{
|
|
unsigned HOST_WIDE_INT ratio;
|
|
unsigned i, j, num_old_inv_drs = 0, num_new_inv_drs = 0;
|
|
struct data_reference *dr;
|
|
bool all_seq_dr_before_p = true, all_seq_dr_after_p = true;
|
|
widest_int iloop_strides = 0, oloop_strides = 0;
|
|
unsigned num_unresolved_drs = 0;
|
|
unsigned num_resolved_ok_drs = 0;
|
|
unsigned num_resolved_not_ok_drs = 0;
|
|
|
|
if (dump_info_p && dump_file && (dump_flags & TDF_DETAILS))
|
|
fprintf (dump_file, "\nData ref strides:\n\tmem_ref:\t\tiloop\toloop\n");
|
|
|
|
for (i = 0; datarefs.iterate (i, &dr); ++i)
|
|
{
|
|
vec<tree> *stride = DR_ACCESS_STRIDE (dr);
|
|
tree iloop_stride = (*stride)[i_idx], oloop_stride = (*stride)[o_idx];
|
|
|
|
bool subloop_stride_p = false;
|
|
/* Data ref can't be invariant or sequential access at current loop if
|
|
its address changes with respect to any subloops. */
|
|
for (j = i_idx + 1; j < stride->length (); ++j)
|
|
if (!integer_zerop ((*stride)[j]))
|
|
{
|
|
subloop_stride_p = true;
|
|
break;
|
|
}
|
|
|
|
if (integer_zerop (iloop_stride))
|
|
{
|
|
if (!subloop_stride_p)
|
|
num_old_inv_drs++;
|
|
}
|
|
if (integer_zerop (oloop_stride))
|
|
{
|
|
if (!subloop_stride_p)
|
|
num_new_inv_drs++;
|
|
}
|
|
|
|
if (TREE_CODE (iloop_stride) == INTEGER_CST
|
|
&& TREE_CODE (oloop_stride) == INTEGER_CST)
|
|
{
|
|
iloop_strides = wi::add (iloop_strides, wi::to_widest (iloop_stride));
|
|
oloop_strides = wi::add (oloop_strides, wi::to_widest (oloop_stride));
|
|
}
|
|
else if (multiple_of_p (TREE_TYPE (iloop_stride),
|
|
iloop_stride, oloop_stride))
|
|
num_resolved_ok_drs++;
|
|
else if (multiple_of_p (TREE_TYPE (iloop_stride),
|
|
oloop_stride, iloop_stride))
|
|
num_resolved_not_ok_drs++;
|
|
else
|
|
num_unresolved_drs++;
|
|
|
|
/* Data ref can't be sequential access if its address changes in sub
|
|
loop. */
|
|
if (subloop_stride_p)
|
|
{
|
|
all_seq_dr_before_p = false;
|
|
all_seq_dr_after_p = false;
|
|
continue;
|
|
}
|
|
/* Track if all data references are sequential accesses before/after loop
|
|
interchange. Note invariant is considered sequential here. */
|
|
tree access_size = TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (dr)));
|
|
if (all_seq_dr_before_p
|
|
&& ! (integer_zerop (iloop_stride)
|
|
|| operand_equal_p (access_size, iloop_stride, 0)))
|
|
all_seq_dr_before_p = false;
|
|
if (all_seq_dr_after_p
|
|
&& ! (integer_zerop (oloop_stride)
|
|
|| operand_equal_p (access_size, oloop_stride, 0)))
|
|
all_seq_dr_after_p = false;
|
|
}
|
|
|
|
if (dump_info_p && dump_file && (dump_flags & TDF_DETAILS))
|
|
{
|
|
fprintf (dump_file, "\toverall:\t\t");
|
|
print_decu (iloop_strides, dump_file);
|
|
fprintf (dump_file, "\t");
|
|
print_decu (oloop_strides, dump_file);
|
|
fprintf (dump_file, "\n");
|
|
|
|
fprintf (dump_file, "Invariant data ref: before(%d), after(%d)\n",
|
|
num_old_inv_drs, num_new_inv_drs);
|
|
fprintf (dump_file, "All consecutive stride: before(%s), after(%s)\n",
|
|
all_seq_dr_before_p ? "true" : "false",
|
|
all_seq_dr_after_p ? "true" : "false");
|
|
fprintf (dump_file, "OK to interchage with variable strides: %d\n",
|
|
num_resolved_ok_drs);
|
|
fprintf (dump_file, "Not OK to interchage with variable strides: %d\n",
|
|
num_resolved_not_ok_drs);
|
|
fprintf (dump_file, "Variable strides we cannot decide: %d\n",
|
|
num_unresolved_drs);
|
|
fprintf (dump_file, "Stmt cost of inner loop: %d\n", i_stmt_cost);
|
|
fprintf (dump_file, "Stmt cost of outer loop: %d\n", o_stmt_cost);
|
|
}
|
|
|
|
if (num_unresolved_drs != 0 || num_resolved_not_ok_drs != 0)
|
|
return false;
|
|
|
|
/* Stmts of outer loop will be moved to inner loop. If there are two many
|
|
such stmts, it could make inner loop costly. Here we compare stmt cost
|
|
between outer and inner loops. */
|
|
if (i_stmt_cost && o_stmt_cost
|
|
&& num_old_inv_drs + o_stmt_cost > num_new_inv_drs
|
|
&& o_stmt_cost * STMT_COST_RATIO > i_stmt_cost)
|
|
return false;
|
|
|
|
/* We use different stride comparison ratio for interchanging innermost
|
|
two loops or not. The idea is to be conservative in interchange for
|
|
the innermost loops. */
|
|
ratio = innermost_loops_p ? INNER_STRIDE_RATIO : OUTER_STRIDE_RATIO;
|
|
/* Do interchange if it gives better data locality behavior. */
|
|
if (wi::gtu_p (iloop_strides, wi::mul (oloop_strides, ratio)))
|
|
return true;
|
|
if (wi::gtu_p (iloop_strides, oloop_strides))
|
|
{
|
|
/* Or it creates more invariant memory references. */
|
|
if ((!all_seq_dr_before_p || all_seq_dr_after_p)
|
|
&& num_new_inv_drs > num_old_inv_drs)
|
|
return true;
|
|
/* Or it makes all memory references sequential. */
|
|
if (num_new_inv_drs >= num_old_inv_drs
|
|
&& !all_seq_dr_before_p && all_seq_dr_after_p)
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
/* Try to interchange inner loop of a loop nest to outer level. */
|
|
|
|
bool
|
|
tree_loop_interchange::interchange (vec<data_reference_p> datarefs,
|
|
vec<ddr_p> ddrs)
|
|
{
|
|
dump_user_location_t loc = find_loop_location (m_loop_nest[0]);
|
|
bool changed_p = false;
|
|
/* In each iteration we try to interchange I-th loop with (I+1)-th loop.
|
|
The overall effect is to push inner loop to outermost level in whole
|
|
loop nest. */
|
|
for (unsigned i = m_loop_nest.length (); i > 1; --i)
|
|
{
|
|
unsigned i_idx = i - 1, o_idx = i - 2;
|
|
|
|
/* Check validity for loop interchange. */
|
|
if (!valid_data_dependences (i_idx, o_idx, ddrs))
|
|
break;
|
|
|
|
loop_cand iloop (m_loop_nest[i_idx], m_loop_nest[o_idx]);
|
|
loop_cand oloop (m_loop_nest[o_idx], m_loop_nest[o_idx]);
|
|
|
|
/* Check if we can do transformation for loop interchange. */
|
|
if (!iloop.analyze_carried_vars (NULL)
|
|
|| !iloop.analyze_lcssa_phis ()
|
|
|| !oloop.analyze_carried_vars (&iloop)
|
|
|| !oloop.analyze_lcssa_phis ()
|
|
|| !iloop.can_interchange_p (NULL)
|
|
|| !oloop.can_interchange_p (&iloop))
|
|
break;
|
|
|
|
/* Outer loop's stmts will be moved to inner loop during interchange.
|
|
If there are many of them, it may make inner loop very costly. We
|
|
need to check number of outer loop's stmts in profit cost model of
|
|
interchange. */
|
|
int stmt_cost = oloop.m_num_stmts;
|
|
/* Count out the exit checking stmt of outer loop. */
|
|
stmt_cost --;
|
|
/* Count out IV's increasing stmt, IVOPTs takes care if it. */
|
|
stmt_cost -= oloop.m_inductions.length ();
|
|
/* Count in the additional load and cond_expr stmts caused by inner
|
|
loop's constant initialized reduction. */
|
|
stmt_cost += iloop.m_const_init_reduc * 2;
|
|
if (stmt_cost < 0)
|
|
stmt_cost = 0;
|
|
|
|
/* Check profitability for loop interchange. */
|
|
if (should_interchange_loops (i_idx, o_idx, datarefs,
|
|
(unsigned) iloop.m_num_stmts,
|
|
(unsigned) stmt_cost,
|
|
iloop.m_loop->inner == NULL))
|
|
{
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
fprintf (dump_file,
|
|
"Loop_pair<outer:%d, inner:%d> is interchanged\n\n",
|
|
oloop.m_loop->num, iloop.m_loop->num);
|
|
|
|
changed_p = true;
|
|
interchange_loops (iloop, oloop);
|
|
/* No need to update if there is no further loop interchange. */
|
|
if (o_idx > 0)
|
|
update_data_info (i_idx, o_idx, datarefs, ddrs);
|
|
}
|
|
else
|
|
{
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
fprintf (dump_file,
|
|
"Loop_pair<outer:%d, inner:%d> is not interchanged\n\n",
|
|
oloop.m_loop->num, iloop.m_loop->num);
|
|
}
|
|
}
|
|
simple_dce_from_worklist (m_dce_seeds);
|
|
|
|
if (changed_p && dump_enabled_p ())
|
|
dump_printf_loc (MSG_OPTIMIZED_LOCATIONS, loc,
|
|
"loops interchanged in loop nest\n");
|
|
|
|
return changed_p;
|
|
}
|
|
|
|
|
|
/* Loop interchange pass. */
|
|
|
|
namespace {
|
|
|
|
const pass_data pass_data_linterchange =
|
|
{
|
|
GIMPLE_PASS, /* type */
|
|
"linterchange", /* name */
|
|
OPTGROUP_LOOP, /* optinfo_flags */
|
|
TV_LINTERCHANGE, /* tv_id */
|
|
PROP_cfg, /* properties_required */
|
|
0, /* properties_provided */
|
|
0, /* properties_destroyed */
|
|
0, /* todo_flags_start */
|
|
0, /* todo_flags_finish */
|
|
};
|
|
|
|
class pass_linterchange : public gimple_opt_pass
|
|
{
|
|
public:
|
|
pass_linterchange (gcc::context *ctxt)
|
|
: gimple_opt_pass (pass_data_linterchange, ctxt)
|
|
{}
|
|
|
|
/* opt_pass methods: */
|
|
opt_pass * clone () { return new pass_linterchange (m_ctxt); }
|
|
virtual bool gate (function *) { return flag_loop_interchange; }
|
|
virtual unsigned int execute (function *);
|
|
|
|
}; // class pass_linterchange
|
|
|
|
|
|
/* Return true if LOOP has proper form for interchange. We check three
|
|
conditions in the function:
|
|
1) In general, a loop can be interchanged only if it doesn't have
|
|
basic blocks other than header, exit and latch besides possible
|
|
inner loop nest. This basically restricts loop interchange to
|
|
below form loop nests:
|
|
|
|
header<---+
|
|
| |
|
|
v |
|
|
INNER_LOOP |
|
|
| |
|
|
v |
|
|
exit--->latch
|
|
|
|
2) Data reference in basic block that executes in different times
|
|
than loop head/exit is not allowed.
|
|
3) Record the innermost outer loop that doesn't form rectangle loop
|
|
nest with LOOP. */
|
|
|
|
static bool
|
|
proper_loop_form_for_interchange (class loop *loop, class loop **min_outer)
|
|
{
|
|
edge e0, e1, exit;
|
|
|
|
/* Don't interchange if loop has unsupported information for the moment. */
|
|
if (loop->safelen > 0
|
|
|| loop->constraints != 0
|
|
|| loop->can_be_parallel
|
|
|| loop->dont_vectorize
|
|
|| loop->force_vectorize
|
|
|| loop->in_oacc_kernels_region
|
|
|| loop->orig_loop_num != 0
|
|
|| loop->simduid != NULL_TREE)
|
|
return false;
|
|
|
|
/* Don't interchange if outer loop has basic block other than header, exit
|
|
and latch. */
|
|
if (loop->inner != NULL
|
|
&& loop->num_nodes != loop->inner->num_nodes + 3)
|
|
return false;
|
|
|
|
if ((exit = single_dom_exit (loop)) == NULL)
|
|
return false;
|
|
|
|
/* Check control flow on loop header/exit blocks. */
|
|
if (loop->header == exit->src
|
|
&& (EDGE_COUNT (loop->header->preds) != 2
|
|
|| EDGE_COUNT (loop->header->succs) != 2))
|
|
return false;
|
|
else if (loop->header != exit->src
|
|
&& (EDGE_COUNT (loop->header->preds) != 2
|
|
|| !single_succ_p (loop->header)
|
|
|| unsupported_edge (single_succ_edge (loop->header))
|
|
|| EDGE_COUNT (exit->src->succs) != 2
|
|
|| !single_pred_p (exit->src)
|
|
|| unsupported_edge (single_pred_edge (exit->src))))
|
|
return false;
|
|
|
|
e0 = EDGE_PRED (loop->header, 0);
|
|
e1 = EDGE_PRED (loop->header, 1);
|
|
if (unsupported_edge (e0) || unsupported_edge (e1)
|
|
|| (e0->src != loop->latch && e1->src != loop->latch)
|
|
|| (e0->src->loop_father == loop && e1->src->loop_father == loop))
|
|
return false;
|
|
|
|
e0 = EDGE_SUCC (exit->src, 0);
|
|
e1 = EDGE_SUCC (exit->src, 1);
|
|
if (unsupported_edge (e0) || unsupported_edge (e1)
|
|
|| (e0->dest != loop->latch && e1->dest != loop->latch)
|
|
|| (e0->dest->loop_father == loop && e1->dest->loop_father == loop))
|
|
return false;
|
|
|
|
/* Don't interchange if any reference is in basic block that doesn't
|
|
dominate exit block. */
|
|
basic_block *bbs = get_loop_body (loop);
|
|
for (unsigned i = 0; i < loop->num_nodes; i++)
|
|
{
|
|
basic_block bb = bbs[i];
|
|
|
|
if (bb->loop_father != loop
|
|
|| bb == loop->header || bb == exit->src
|
|
|| dominated_by_p (CDI_DOMINATORS, exit->src, bb))
|
|
continue;
|
|
|
|
for (gimple_stmt_iterator gsi = gsi_start_nondebug_bb (bb);
|
|
!gsi_end_p (gsi); gsi_next_nondebug (&gsi))
|
|
if (gimple_vuse (gsi_stmt (gsi)))
|
|
{
|
|
free (bbs);
|
|
return false;
|
|
}
|
|
}
|
|
free (bbs);
|
|
|
|
tree niters = number_of_latch_executions (loop);
|
|
niters = analyze_scalar_evolution (loop_outer (loop), niters);
|
|
if (!niters || chrec_contains_undetermined (niters))
|
|
return false;
|
|
|
|
/* Record the innermost outer loop that doesn't form rectangle loop nest. */
|
|
for (loop_p loop2 = loop_outer (loop);
|
|
loop2 && flow_loop_nested_p (*min_outer, loop2);
|
|
loop2 = loop_outer (loop2))
|
|
{
|
|
niters = instantiate_scev (loop_preheader_edge (loop2),
|
|
loop_outer (loop), niters);
|
|
if (!evolution_function_is_invariant_p (niters, loop2->num))
|
|
{
|
|
*min_outer = loop2;
|
|
break;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/* Return true if any two adjacent loops in loop nest [INNERMOST, LOOP_NEST]
|
|
should be interchanged by looking into all DATAREFS. */
|
|
|
|
static bool
|
|
should_interchange_loop_nest (class loop *loop_nest, class loop *innermost,
|
|
vec<data_reference_p> datarefs)
|
|
{
|
|
unsigned idx = loop_depth (innermost) - loop_depth (loop_nest);
|
|
gcc_assert (idx > 0);
|
|
|
|
/* Check if any two adjacent loops should be interchanged. */
|
|
for (class loop *loop = innermost;
|
|
loop != loop_nest; loop = loop_outer (loop), idx--)
|
|
if (should_interchange_loops (idx, idx - 1, datarefs, 0, 0,
|
|
loop == innermost, false))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
/* Given loop nest LOOP_NEST and data references DATAREFS, compute data
|
|
dependences for loop interchange and store it in DDRS. Note we compute
|
|
dependences directly rather than call generic interface so that we can
|
|
return on unknown dependence instantly. */
|
|
|
|
static bool
|
|
tree_loop_interchange_compute_ddrs (vec<loop_p> loop_nest,
|
|
vec<data_reference_p> datarefs,
|
|
vec<ddr_p> *ddrs)
|
|
{
|
|
struct data_reference *a, *b;
|
|
class loop *innermost = loop_nest.last ();
|
|
|
|
for (unsigned i = 0; datarefs.iterate (i, &a); ++i)
|
|
{
|
|
bool a_outer_p = gimple_bb (DR_STMT (a))->loop_father != innermost;
|
|
for (unsigned j = i + 1; datarefs.iterate (j, &b); ++j)
|
|
if (DR_IS_WRITE (a) || DR_IS_WRITE (b))
|
|
{
|
|
bool b_outer_p = gimple_bb (DR_STMT (b))->loop_father != innermost;
|
|
/* Don't support multiple write references in outer loop. */
|
|
if (a_outer_p && b_outer_p && DR_IS_WRITE (a) && DR_IS_WRITE (b))
|
|
return false;
|
|
|
|
ddr_p ddr = initialize_data_dependence_relation (a, b, loop_nest);
|
|
ddrs->safe_push (ddr);
|
|
compute_affine_dependence (ddr, loop_nest[0]);
|
|
|
|
/* Give up if ddr is unknown dependence or classic direct vector
|
|
is not available. */
|
|
if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know
|
|
|| (DDR_ARE_DEPENDENT (ddr) == NULL_TREE
|
|
&& DDR_NUM_DIR_VECTS (ddr) == 0))
|
|
return false;
|
|
|
|
/* If either data references is in outer loop of nest, we require
|
|
no dependence here because the data reference need to be moved
|
|
into inner loop during interchange. */
|
|
if (a_outer_p && b_outer_p
|
|
&& operand_equal_p (DR_REF (a), DR_REF (b), 0))
|
|
continue;
|
|
if (DDR_ARE_DEPENDENT (ddr) != chrec_known
|
|
&& (a_outer_p || b_outer_p))
|
|
return false;
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/* Prune DATAREFS by removing any data reference not inside of LOOP. */
|
|
|
|
static inline void
|
|
prune_datarefs_not_in_loop (class loop *loop, vec<data_reference_p> datarefs)
|
|
{
|
|
unsigned i, j;
|
|
struct data_reference *dr;
|
|
|
|
for (i = 0, j = 0; datarefs.iterate (i, &dr); ++i)
|
|
{
|
|
if (flow_bb_inside_loop_p (loop, gimple_bb (DR_STMT (dr))))
|
|
datarefs[j++] = dr;
|
|
else
|
|
{
|
|
if (dr->aux)
|
|
{
|
|
DR_ACCESS_STRIDE (dr)->release ();
|
|
delete (vec<tree> *) dr->aux;
|
|
}
|
|
free_data_ref (dr);
|
|
}
|
|
}
|
|
datarefs.truncate (j);
|
|
}
|
|
|
|
/* Find and store data references in DATAREFS for LOOP nest. If there's
|
|
difficult data reference in a basic block, we shrink the loop nest to
|
|
inner loop of that basic block's father loop. On success, return the
|
|
outer loop of the result loop nest. */
|
|
|
|
static class loop *
|
|
prepare_data_references (class loop *loop, vec<data_reference_p> *datarefs)
|
|
{
|
|
class loop *loop_nest = loop;
|
|
vec<data_reference_p> *bb_refs;
|
|
basic_block bb, *bbs = get_loop_body_in_dom_order (loop);
|
|
|
|
for (unsigned i = 0; i < loop->num_nodes; i++)
|
|
bbs[i]->aux = NULL;
|
|
|
|
/* Find data references for all basic blocks. Shrink loop nest on difficult
|
|
data reference. */
|
|
for (unsigned i = 0; loop_nest && i < loop->num_nodes; ++i)
|
|
{
|
|
bb = bbs[i];
|
|
if (!flow_bb_inside_loop_p (loop_nest, bb))
|
|
continue;
|
|
|
|
bb_refs = new vec<data_reference_p> ();
|
|
if (find_data_references_in_bb (loop, bb, bb_refs) == chrec_dont_know)
|
|
{
|
|
loop_nest = bb->loop_father->inner;
|
|
if (loop_nest && !loop_nest->inner)
|
|
loop_nest = NULL;
|
|
|
|
free_data_refs (*bb_refs);
|
|
delete bb_refs;
|
|
}
|
|
else if (bb_refs->is_empty ())
|
|
{
|
|
bb_refs->release ();
|
|
delete bb_refs;
|
|
}
|
|
else
|
|
bb->aux = bb_refs;
|
|
}
|
|
|
|
/* Collect all data references in loop nest. */
|
|
for (unsigned i = 0; i < loop->num_nodes; i++)
|
|
{
|
|
bb = bbs[i];
|
|
if (!bb->aux)
|
|
continue;
|
|
|
|
bb_refs = (vec<data_reference_p> *) bb->aux;
|
|
if (loop_nest && flow_bb_inside_loop_p (loop_nest, bb))
|
|
{
|
|
datarefs->safe_splice (*bb_refs);
|
|
bb_refs->release ();
|
|
}
|
|
else
|
|
free_data_refs (*bb_refs);
|
|
|
|
delete bb_refs;
|
|
bb->aux = NULL;
|
|
}
|
|
free (bbs);
|
|
|
|
return loop_nest;
|
|
}
|
|
|
|
/* Given innermost LOOP, return true if perfect loop nest can be found and
|
|
data dependences can be computed. If succeed, record the perfect loop
|
|
nest in LOOP_NEST; record all data references in DATAREFS and record all
|
|
data dependence relations in DDRS.
|
|
|
|
We do support a restricted form of imperfect loop nest, i.e, loop nest
|
|
with load/store in outer loop initializing/finalizing simple reduction
|
|
of the innermost loop. For such outer loop reference, we require that
|
|
it has no dependence with others sinve it will be moved to inner loop
|
|
in interchange. */
|
|
|
|
static bool
|
|
prepare_perfect_loop_nest (class loop *loop, vec<loop_p> *loop_nest,
|
|
vec<data_reference_p> *datarefs, vec<ddr_p> *ddrs)
|
|
{
|
|
class loop *start_loop = NULL, *innermost = loop;
|
|
class loop *outermost = loops_for_fn (cfun)->tree_root;
|
|
|
|
/* Find loop nest from the innermost loop. The outermost is the innermost
|
|
outer*/
|
|
while (loop->num != 0 && loop->inner == start_loop
|
|
&& flow_loop_nested_p (outermost, loop))
|
|
{
|
|
if (!proper_loop_form_for_interchange (loop, &outermost))
|
|
break;
|
|
|
|
start_loop = loop;
|
|
/* If this loop has sibling loop, the father loop won't be in perfect
|
|
loop nest. */
|
|
if (loop->next != NULL)
|
|
break;
|
|
|
|
loop = loop_outer (loop);
|
|
}
|
|
if (!start_loop || !start_loop->inner)
|
|
return false;
|
|
|
|
/* Prepare the data reference vector for the loop nest, pruning outer
|
|
loops we cannot handle. */
|
|
start_loop = prepare_data_references (start_loop, datarefs);
|
|
if (!start_loop
|
|
/* Check if there is no data reference. */
|
|
|| datarefs->is_empty ()
|
|
/* Check if there are too many of data references. */
|
|
|| (int) datarefs->length () > MAX_DATAREFS)
|
|
return false;
|
|
|
|
/* Compute access strides for all data references, pruning outer
|
|
loops we cannot analyze refs in. */
|
|
start_loop = compute_access_strides (start_loop, innermost, *datarefs);
|
|
if (!start_loop)
|
|
return false;
|
|
|
|
/* Check if any interchange is profitable in the loop nest. */
|
|
if (!should_interchange_loop_nest (start_loop, innermost, *datarefs))
|
|
return false;
|
|
|
|
/* Check if data dependences can be computed for loop nest starting from
|
|
start_loop. */
|
|
loop = start_loop;
|
|
do {
|
|
loop_nest->truncate (0);
|
|
|
|
if (loop != start_loop)
|
|
prune_datarefs_not_in_loop (start_loop, *datarefs);
|
|
|
|
if (find_loop_nest (start_loop, loop_nest)
|
|
&& tree_loop_interchange_compute_ddrs (*loop_nest, *datarefs, ddrs))
|
|
{
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
fprintf (dump_file,
|
|
"\nConsider loop interchange for loop_nest<%d - %d>\n",
|
|
start_loop->num, innermost->num);
|
|
|
|
if (loop != start_loop)
|
|
prune_access_strides_not_in_loop (start_loop, innermost, *datarefs);
|
|
|
|
if (dump_file && (dump_flags & TDF_DETAILS))
|
|
dump_access_strides (*datarefs);
|
|
|
|
return true;
|
|
}
|
|
|
|
free_dependence_relations (*ddrs);
|
|
*ddrs = vNULL;
|
|
/* Try to compute data dependences with the outermost loop stripped. */
|
|
loop = start_loop;
|
|
start_loop = start_loop->inner;
|
|
} while (start_loop && start_loop->inner);
|
|
|
|
return false;
|
|
}
|
|
|
|
/* Main entry for loop interchange pass. */
|
|
|
|
unsigned int
|
|
pass_linterchange::execute (function *fun)
|
|
{
|
|
if (number_of_loops (fun) <= 2)
|
|
return 0;
|
|
|
|
bool changed_p = false;
|
|
for (auto loop : loops_list (cfun, LI_ONLY_INNERMOST))
|
|
{
|
|
vec<loop_p> loop_nest = vNULL;
|
|
vec<data_reference_p> datarefs = vNULL;
|
|
vec<ddr_p> ddrs = vNULL;
|
|
if (prepare_perfect_loop_nest (loop, &loop_nest, &datarefs, &ddrs))
|
|
{
|
|
tree_loop_interchange loop_interchange (loop_nest);
|
|
changed_p |= loop_interchange.interchange (datarefs, ddrs);
|
|
}
|
|
free_dependence_relations (ddrs);
|
|
free_data_refs_with_aux (datarefs);
|
|
loop_nest.release ();
|
|
}
|
|
|
|
if (changed_p)
|
|
{
|
|
unsigned todo = TODO_update_ssa_only_virtuals;
|
|
todo |= loop_invariant_motion_in_fun (cfun, false);
|
|
scev_reset ();
|
|
return todo;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
} // anon namespace
|
|
|
|
gimple_opt_pass *
|
|
make_pass_linterchange (gcc::context *ctxt)
|
|
{
|
|
return new pass_linterchange (ctxt);
|
|
}
|