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authorBen Cheng <bccheng@google.com>2014-03-25 22:37:19 -0700
committerBen Cheng <bccheng@google.com>2014-03-25 22:37:19 -0700
commit1bc5aee63eb72b341f506ad058502cd0361f0d10 (patch)
treec607e8252f3405424ff15bc2d00aa38dadbb2518 /gcc-4.9/gcc/tree-ssa-phiprop.c
parent283a0bf58fcf333c58a2a92c3ebbc41fb9eb1fdb (diff)
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Initial checkin of GCC 4.9.0 from trunk (r208799).
Change-Id: I48a3c08bb98542aa215912a75f03c0890e497dba
Diffstat (limited to 'gcc-4.9/gcc/tree-ssa-phiprop.c')
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diff --git a/gcc-4.9/gcc/tree-ssa-phiprop.c b/gcc-4.9/gcc/tree-ssa-phiprop.c
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+/* Backward propagation of indirect loads through PHIs.
+ Copyright (C) 2007-2014 Free Software Foundation, Inc.
+ Contributed by Richard Guenther <rguenther@suse.de>
+
+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/>. */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tm.h"
+#include "tree.h"
+#include "tm_p.h"
+#include "basic-block.h"
+#include "gimple-pretty-print.h"
+#include "tree-ssa-alias.h"
+#include "internal-fn.h"
+#include "tree-eh.h"
+#include "gimple-expr.h"
+#include "is-a.h"
+#include "gimple.h"
+#include "gimplify.h"
+#include "gimple-iterator.h"
+#include "gimple-ssa.h"
+#include "tree-phinodes.h"
+#include "ssa-iterators.h"
+#include "stringpool.h"
+#include "tree-ssanames.h"
+#include "tree-pass.h"
+#include "langhooks.h"
+#include "flags.h"
+
+/* This pass propagates indirect loads through the PHI node for its
+ address to make the load source possibly non-addressable and to
+ allow for PHI optimization to trigger.
+
+ For example the pass changes
+
+ # addr_1 = PHI <&a, &b>
+ tmp_1 = *addr_1;
+
+ to
+
+ # tmp_1 = PHI <a, b>
+
+ but also handles more complex scenarios like
+
+ D.2077_2 = &this_1(D)->a1;
+ ...
+
+ # b_12 = PHI <&c(2), D.2077_2(3)>
+ D.2114_13 = *b_12;
+ ...
+
+ # b_15 = PHI <b_12(4), &b(5)>
+ D.2080_5 = &this_1(D)->a0;
+ ...
+
+ # b_18 = PHI <D.2080_5(6), &c(7)>
+ ...
+
+ # b_21 = PHI <b_15(8), b_18(9)>
+ D.2076_8 = *b_21;
+
+ where the addresses loaded are defined by PHIs itself.
+ The above happens for
+
+ std::max(std::min(a0, c), std::min(std::max(a1, c), b))
+
+ where this pass transforms it to a form later PHI optimization
+ recognizes and transforms it to the simple
+
+ D.2109_10 = this_1(D)->a1;
+ D.2110_11 = c;
+ D.2114_31 = MAX_EXPR <D.2109_10, D.2110_11>;
+ D.2115_14 = b;
+ D.2125_17 = MIN_EXPR <D.2115_14, D.2114_31>;
+ D.2119_16 = this_1(D)->a0;
+ D.2124_32 = MIN_EXPR <D.2110_11, D.2119_16>;
+ D.2076_33 = MAX_EXPR <D.2125_17, D.2124_32>;
+
+ The pass does a dominator walk processing loads using a basic-block
+ local analysis and stores the result for use by transformations on
+ dominated basic-blocks. */
+
+
+/* Structure to keep track of the value of a dereferenced PHI result
+ and the virtual operand used for that dereference. */
+
+struct phiprop_d
+{
+ tree value;
+ tree vuse;
+};
+
+/* Verify if the value recorded for NAME in PHIVN is still valid at
+ the start of basic block BB. */
+
+static bool
+phivn_valid_p (struct phiprop_d *phivn, tree name, basic_block bb)
+{
+ tree vuse = phivn[SSA_NAME_VERSION (name)].vuse;
+ gimple use_stmt;
+ imm_use_iterator ui2;
+ bool ok = true;
+
+ /* The def stmts of the virtual uses need to be dominated by bb. */
+ gcc_assert (vuse != NULL_TREE);
+
+ FOR_EACH_IMM_USE_STMT (use_stmt, ui2, vuse)
+ {
+ /* If BB does not dominate a VDEF, the value is invalid. */
+ if ((gimple_vdef (use_stmt) != NULL_TREE
+ || gimple_code (use_stmt) == GIMPLE_PHI)
+ && !dominated_by_p (CDI_DOMINATORS, gimple_bb (use_stmt), bb))
+ {
+ ok = false;
+ BREAK_FROM_IMM_USE_STMT (ui2);
+ }
+ }
+
+ return ok;
+}
+
+/* Insert a new phi node for the dereference of PHI at basic_block
+ BB with the virtual operands from USE_STMT. */
+
+static tree
+phiprop_insert_phi (basic_block bb, gimple phi, gimple use_stmt,
+ struct phiprop_d *phivn, size_t n)
+{
+ tree res;
+ gimple new_phi;
+ edge_iterator ei;
+ edge e;
+
+ gcc_assert (is_gimple_assign (use_stmt)
+ && gimple_assign_rhs_code (use_stmt) == MEM_REF);
+
+ /* Build a new PHI node to replace the definition of
+ the indirect reference lhs. */
+ res = gimple_assign_lhs (use_stmt);
+ new_phi = create_phi_node (res, bb);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Inserting PHI for result of load ");
+ print_gimple_stmt (dump_file, use_stmt, 0, 0);
+ }
+
+ /* Add PHI arguments for each edge inserting loads of the
+ addressable operands. */
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ {
+ tree old_arg, new_var;
+ gimple tmp;
+ source_location locus;
+
+ old_arg = PHI_ARG_DEF_FROM_EDGE (phi, e);
+ locus = gimple_phi_arg_location_from_edge (phi, e);
+ while (TREE_CODE (old_arg) == SSA_NAME
+ && (SSA_NAME_VERSION (old_arg) >= n
+ || phivn[SSA_NAME_VERSION (old_arg)].value == NULL_TREE))
+ {
+ gimple def_stmt = SSA_NAME_DEF_STMT (old_arg);
+ old_arg = gimple_assign_rhs1 (def_stmt);
+ locus = gimple_location (def_stmt);
+ }
+
+ if (TREE_CODE (old_arg) == SSA_NAME)
+ {
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " for edge defining ");
+ print_generic_expr (dump_file, PHI_ARG_DEF_FROM_EDGE (phi, e), 0);
+ fprintf (dump_file, " reusing PHI result ");
+ print_generic_expr (dump_file,
+ phivn[SSA_NAME_VERSION (old_arg)].value, 0);
+ fprintf (dump_file, "\n");
+ }
+ /* Reuse a formerly created dereference. */
+ new_var = phivn[SSA_NAME_VERSION (old_arg)].value;
+ }
+ else
+ {
+ tree rhs = gimple_assign_rhs1 (use_stmt);
+ gcc_assert (TREE_CODE (old_arg) == ADDR_EXPR);
+ new_var = make_ssa_name (TREE_TYPE (rhs), NULL);
+ if (!is_gimple_min_invariant (old_arg))
+ old_arg = PHI_ARG_DEF_FROM_EDGE (phi, e);
+ else
+ old_arg = unshare_expr (old_arg);
+ tmp = gimple_build_assign (new_var,
+ fold_build2 (MEM_REF, TREE_TYPE (rhs),
+ old_arg,
+ TREE_OPERAND (rhs, 1)));
+ gimple_set_location (tmp, locus);
+
+ gsi_insert_on_edge (e, tmp);
+ update_stmt (tmp);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, " for edge defining ");
+ print_generic_expr (dump_file, PHI_ARG_DEF_FROM_EDGE (phi, e), 0);
+ fprintf (dump_file, " inserting load ");
+ print_gimple_stmt (dump_file, tmp, 0, 0);
+ }
+ }
+
+ add_phi_arg (new_phi, new_var, e, locus);
+ }
+
+ update_stmt (new_phi);
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ print_gimple_stmt (dump_file, new_phi, 0, 0);
+
+ return res;
+}
+
+/* Propagate between the phi node arguments of PHI in BB and phi result
+ users. For now this matches
+ # p_2 = PHI <&x, &y>
+ <Lx>:;
+ p_3 = p_2;
+ z_2 = *p_3;
+ and converts it to
+ # z_2 = PHI <x, y>
+ <Lx>:;
+ Returns true if a transformation was done and edge insertions
+ need to be committed. Global data PHIVN and N is used to track
+ past transformation results. We need to be especially careful here
+ with aliasing issues as we are moving memory reads. */
+
+static bool
+propagate_with_phi (basic_block bb, gimple phi, struct phiprop_d *phivn,
+ size_t n)
+{
+ tree ptr = PHI_RESULT (phi);
+ gimple use_stmt;
+ tree res = NULL_TREE;
+ gimple_stmt_iterator gsi;
+ imm_use_iterator ui;
+ use_operand_p arg_p, use;
+ ssa_op_iter i;
+ bool phi_inserted;
+ tree type = NULL_TREE;
+
+ if (!POINTER_TYPE_P (TREE_TYPE (ptr))
+ || !is_gimple_reg_type (TREE_TYPE (TREE_TYPE (ptr))))
+ return false;
+
+ /* Check if we can "cheaply" dereference all phi arguments. */
+ FOR_EACH_PHI_ARG (arg_p, phi, i, SSA_OP_USE)
+ {
+ tree arg = USE_FROM_PTR (arg_p);
+ /* Walk the ssa chain until we reach a ssa name we already
+ created a value for or we reach a definition of the form
+ ssa_name_n = &var; */
+ while (TREE_CODE (arg) == SSA_NAME
+ && !SSA_NAME_IS_DEFAULT_DEF (arg)
+ && (SSA_NAME_VERSION (arg) >= n
+ || phivn[SSA_NAME_VERSION (arg)].value == NULL_TREE))
+ {
+ gimple def_stmt = SSA_NAME_DEF_STMT (arg);
+ if (!gimple_assign_single_p (def_stmt))
+ return false;
+ arg = gimple_assign_rhs1 (def_stmt);
+ }
+ if (TREE_CODE (arg) != ADDR_EXPR
+ && !(TREE_CODE (arg) == SSA_NAME
+ && SSA_NAME_VERSION (arg) < n
+ && phivn[SSA_NAME_VERSION (arg)].value != NULL_TREE
+ && (!type
+ || types_compatible_p
+ (type, TREE_TYPE (phivn[SSA_NAME_VERSION (arg)].value)))
+ && phivn_valid_p (phivn, arg, bb)))
+ return false;
+ if (!type
+ && TREE_CODE (arg) == SSA_NAME)
+ type = TREE_TYPE (phivn[SSA_NAME_VERSION (arg)].value);
+ }
+
+ /* Find a dereferencing use. First follow (single use) ssa
+ copy chains for ptr. */
+ while (single_imm_use (ptr, &use, &use_stmt)
+ && gimple_assign_ssa_name_copy_p (use_stmt))
+ ptr = gimple_assign_lhs (use_stmt);
+
+ /* Replace the first dereference of *ptr if there is one and if we
+ can move the loads to the place of the ptr phi node. */
+ phi_inserted = false;
+ FOR_EACH_IMM_USE_STMT (use_stmt, ui, ptr)
+ {
+ gimple def_stmt;
+ tree vuse;
+
+ /* Only replace loads in blocks that post-dominate the PHI node. That
+ makes sure we don't end up speculating loads. */
+ if (!dominated_by_p (CDI_POST_DOMINATORS,
+ bb, gimple_bb (use_stmt)))
+ continue;
+
+ /* Check whether this is a load of *ptr. */
+ if (!(is_gimple_assign (use_stmt)
+ && TREE_CODE (gimple_assign_lhs (use_stmt)) == SSA_NAME
+ && gimple_assign_rhs_code (use_stmt) == MEM_REF
+ && TREE_OPERAND (gimple_assign_rhs1 (use_stmt), 0) == ptr
+ && integer_zerop (TREE_OPERAND (gimple_assign_rhs1 (use_stmt), 1))
+ && (!type
+ || types_compatible_p
+ (TREE_TYPE (gimple_assign_lhs (use_stmt)), type))
+ /* We cannot replace a load that may throw or is volatile. */
+ && !stmt_can_throw_internal (use_stmt)))
+ continue;
+
+ /* Check if we can move the loads. The def stmt of the virtual use
+ needs to be in a different basic block dominating bb. */
+ vuse = gimple_vuse (use_stmt);
+ def_stmt = SSA_NAME_DEF_STMT (vuse);
+ if (!SSA_NAME_IS_DEFAULT_DEF (vuse)
+ && (gimple_bb (def_stmt) == bb
+ || !dominated_by_p (CDI_DOMINATORS,
+ bb, gimple_bb (def_stmt))))
+ goto next;
+
+ /* Found a proper dereference. Insert a phi node if this
+ is the first load transformation. */
+ if (!phi_inserted)
+ {
+ res = phiprop_insert_phi (bb, phi, use_stmt, phivn, n);
+ type = TREE_TYPE (res);
+
+ /* Remember the value we created for *ptr. */
+ phivn[SSA_NAME_VERSION (ptr)].value = res;
+ phivn[SSA_NAME_VERSION (ptr)].vuse = vuse;
+
+ /* Remove old stmt. The phi is taken care of by DCE, if we
+ want to delete it here we also have to delete all intermediate
+ copies. */
+ gsi = gsi_for_stmt (use_stmt);
+ gsi_remove (&gsi, true);
+
+ phi_inserted = true;
+ }
+ else
+ {
+ /* Further replacements are easy, just make a copy out of the
+ load. */
+ gimple_assign_set_rhs1 (use_stmt, res);
+ update_stmt (use_stmt);
+ }
+
+next:;
+ /* Continue searching for a proper dereference. */
+ }
+
+ return phi_inserted;
+}
+
+/* Main entry for phiprop pass. */
+
+static unsigned int
+tree_ssa_phiprop (void)
+{
+ vec<basic_block> bbs;
+ struct phiprop_d *phivn;
+ bool did_something = false;
+ basic_block bb;
+ gimple_stmt_iterator gsi;
+ unsigned i;
+ size_t n;
+
+ calculate_dominance_info (CDI_DOMINATORS);
+ calculate_dominance_info (CDI_POST_DOMINATORS);
+
+ n = num_ssa_names;
+ phivn = XCNEWVEC (struct phiprop_d, n);
+
+ /* Walk the dominator tree in preorder. */
+ bbs = get_all_dominated_blocks (CDI_DOMINATORS,
+ single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun)));
+ FOR_EACH_VEC_ELT (bbs, i, bb)
+ for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+ did_something |= propagate_with_phi (bb, gsi_stmt (gsi), phivn, n);
+
+ if (did_something)
+ gsi_commit_edge_inserts ();
+
+ bbs.release ();
+ free (phivn);
+
+ free_dominance_info (CDI_POST_DOMINATORS);
+
+ return 0;
+}
+
+static bool
+gate_phiprop (void)
+{
+ return flag_tree_phiprop;
+}
+
+namespace {
+
+const pass_data pass_data_phiprop =
+{
+ GIMPLE_PASS, /* type */
+ "phiprop", /* name */
+ OPTGROUP_NONE, /* optinfo_flags */
+ true, /* has_gate */
+ true, /* has_execute */
+ TV_TREE_PHIPROP, /* tv_id */
+ ( PROP_cfg | PROP_ssa ), /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ ( TODO_update_ssa | TODO_verify_ssa ), /* todo_flags_finish */
+};
+
+class pass_phiprop : public gimple_opt_pass
+{
+public:
+ pass_phiprop (gcc::context *ctxt)
+ : gimple_opt_pass (pass_data_phiprop, ctxt)
+ {}
+
+ /* opt_pass methods: */
+ bool gate () { return gate_phiprop (); }
+ unsigned int execute () { return tree_ssa_phiprop (); }
+
+}; // class pass_phiprop
+
+} // anon namespace
+
+gimple_opt_pass *
+make_pass_phiprop (gcc::context *ctxt)
+{
+ return new pass_phiprop (ctxt);
+}