From 554fd8c5195424bdbcabf5de30fdc183aba391bd Mon Sep 17 00:00:00 2001 From: upstream source tree Date: Sun, 15 Mar 2015 20:14:05 -0400 Subject: obtained gcc-4.6.4.tar.bz2 from upstream website; verified gcc-4.6.4.tar.bz2.sig; imported gcc-4.6.4 source tree from verified upstream tarball. downloading a git-generated archive based on the 'upstream' tag should provide you with a source tree that is binary identical to the one extracted from the above tarball. if you have obtained the source via the command 'git clone', however, do note that line-endings of files in your working directory might differ from line-endings of the respective files in the upstream repository. --- gcc/tree-ssa-phiprop.c | 434 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 434 insertions(+) create mode 100644 gcc/tree-ssa-phiprop.c (limited to 'gcc/tree-ssa-phiprop.c') diff --git a/gcc/tree-ssa-phiprop.c b/gcc/tree-ssa-phiprop.c new file mode 100644 index 000000000..a38e6962f --- /dev/null +++ b/gcc/tree-ssa-phiprop.c @@ -0,0 +1,434 @@ +/* Backward propagation of indirect loads through PHIs. + Copyright (C) 2007, 2008, 2009, 2010 Free Software Foundation, Inc. + Contributed by Richard Guenther + +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 +. */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "tm.h" +#include "tree.h" +#include "tm_p.h" +#include "basic-block.h" +#include "timevar.h" +#include "tree-pretty-print.h" +#include "gimple-pretty-print.h" +#include "tree-flow.h" +#include "tree-pass.h" +#include "tree-dump.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 + + 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 + D.2080_5 = &this_1(D)->a0; + ... + + # b_18 = PHI + ... + + # b_21 = PHI + 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.2115_14 = b; + D.2125_17 = MIN_EXPR ; + D.2119_16 = this_1(D)->a0; + D.2124_32 = MIN_EXPR ; + D.2076_33 = MAX_EXPR ; + + 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); + SSA_NAME_DEF_STMT (res) = 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 = create_tmp_reg (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))); + gcc_assert (is_gimple_reg (new_var)); + add_referenced_var (new_var); + new_var = make_ssa_name (new_var, tmp); + gimple_assign_set_lhs (tmp, new_var); + 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> + :; + p_3 = p_2; + z_2 = *p_3; + and converts it to + # z_2 = PHI + :; + 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; + bool one_invariant = false; + + 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); + if (TREE_CODE (arg) == ADDR_EXPR + && is_gimple_min_invariant (arg)) + one_invariant = true; + } + + /* If we neither have an address of a decl nor can reuse a previously + inserted load, do not hoist anything. */ + if (!one_invariant + && !type) + return false; + + /* 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; + + /* 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, heap) *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); + + 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_EACH_VEC_ELT (basic_block, 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 (); + + VEC_free (basic_block, heap, bbs); + free (phivn); + + return 0; +} + +static bool +gate_phiprop (void) +{ + return flag_tree_phiprop; +} + +struct gimple_opt_pass pass_phiprop = +{ + { + GIMPLE_PASS, + "phiprop", /* name */ + gate_phiprop, /* gate */ + tree_ssa_phiprop, /* execute */ + NULL, /* sub */ + NULL, /* next */ + 0, /* static_pass_number */ + TV_TREE_PHIPROP, /* tv_id */ + PROP_cfg | PROP_ssa, /* properties_required */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + 0, /* todo_flags_start */ + TODO_dump_func + | TODO_ggc_collect + | TODO_update_ssa + | TODO_verify_ssa /* todo_flags_finish */ + } +}; -- cgit v1.2.3