Mercurial > hg > CbC > CbC_gcc
diff gcc/config/sh/sh_optimize_sett_clrt.cc @ 111:04ced10e8804
gcc 7
author | kono |
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date | Fri, 27 Oct 2017 22:46:09 +0900 |
parents | |
children | 84e7813d76e9 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/gcc/config/sh/sh_optimize_sett_clrt.cc Fri Oct 27 22:46:09 2017 +0900 @@ -0,0 +1,476 @@ +/* An SH specific RTL pass that tries to optimize clrt and sett insns. + Copyright (C) 2013-2017 Free Software Foundation, Inc. + +This file is part of GCC. + +GCC is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 3, or (at your option) +any later version. + +GCC is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +GNU General Public License for more details. + +You should have received a copy of the GNU General Public License +along with GCC; see the file COPYING3. If not see +<http://www.gnu.org/licenses/>. */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "backend.h" +#include "target.h" +#include "rtl.h" +#include "df.h" +#include "cfgrtl.h" +#include "tree-pass.h" + +#include <vector> +#include <algorithm> + +/* +This pass tries to eliminate unnecessary sett or clrt instructions in cases +where the ccreg value is already known to be the same as the constant set +would set it to. This is done as follows: + +Check every BB's insn and see if it's a sett or clrt. +Once a sett or clrt insn is hit, walk insns and predecessor basic blocks +backwards from that insn and determine all possible ccreg values from all +basic block paths. +Insns that set the ccreg value in some way (simple set, clobber etc) are +recorded. Conditional branches where one edge leads to the sett / clrt insn +are also recorded, since for each edge in the conditional branch the ccreg +value is known constant. +After collecting all possible ccreg values at the sett / clrt insn, check that +all the values are the same. If that value is the same as the sett / clrt +insn would set the ccreg to, the sett / clrt insn can be eliminated. +*/ + + +// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +// Helper functions + +#define log_msg(...)\ + do { if (dump_file != NULL) fprintf (dump_file, __VA_ARGS__); } while (0) + +#define log_insn(i)\ + do { if (dump_file != NULL) print_rtl_single (dump_file, \ + (const_rtx)i); } while (0) + +#define log_rtx(r)\ + do { if (dump_file != NULL) print_rtl (dump_file, (const_rtx)r); } while (0) + +#define log_return(retval, ...)\ + do { if (dump_file != NULL) fprintf (dump_file, __VA_ARGS__); \ + return retval; } while (0) + +#define log_return_void(...)\ + do { if (dump_file != NULL) fprintf (dump_file, __VA_ARGS__); \ + return; } while (0) + +// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +// RTL pass class + +class sh_optimize_sett_clrt : public rtl_opt_pass +{ +public: + sh_optimize_sett_clrt (gcc::context* ctx, const char* name); + virtual ~sh_optimize_sett_clrt (void); + virtual bool gate (function*); + virtual unsigned int execute (function* fun); + +private: + static const pass_data default_pass_data; + + struct ccreg_value + { + // The insn at which the ccreg value was determined. + // Might be NULL if e.g. an unknown value is recorded for an + // empty basic block. + rtx_insn *insn; + + // The basic block where the insn was discovered. + basic_block bb; + + // The value of ccreg. If NULL_RTX, the exact value is not known, but + // the ccreg is changed in some way (e.g. clobbered). + rtx value; + }; + + // Update the mode of the captured m_ccreg with the specified mode. + void update_ccreg_mode (machine_mode m); + + // Given an insn pattern, check if it sets the ccreg to a constant value + // of either zero or STORE_FLAG_VALUE. If so, return the value rtx, + // NULL_RTX otherwise. + rtx const_setcc_value (rtx pat) const; + + // Given a start insn and its basic block, recursively determine all + // possible ccreg values in all basic block paths that can lead to the + // start insn. + bool find_last_ccreg_values (rtx_insn *start_insn, basic_block bb, + std::vector<ccreg_value>& values_out, + std::vector<basic_block>& prev_visited_bb) const; + + // Given a cbranch insn, its basic block and another basic block, determine + // the value to which the ccreg will be set after jumping/falling through to + // the specified target basic block. + bool sh_cbranch_ccreg_value (rtx_insn *cbranch_insn, + basic_block cbranch_insn_bb, + basic_block branch_target_bb) const; + + // Check whether all of the ccreg values are the same. + static bool all_ccreg_values_equal (const std::vector<ccreg_value>& values); + + // Remove REG_DEAD and REG_UNUSED notes from insns of the specified + // ccreg_value entries. + void remove_ccreg_dead_unused_notes (std::vector<ccreg_value>& values) const; + + // rtx of the ccreg that is obtained from the target. + rtx m_ccreg; +}; + +const pass_data sh_optimize_sett_clrt::default_pass_data = +{ + RTL_PASS, // type + "", // name (overwritten by the constructor) + OPTGROUP_NONE, // optinfo_flags + TV_OPTIMIZE, // tv_id + 0, // properties_required + 0, // properties_provided + 0, // properties_destroyed + 0, // todo_flags_start + 0 // todo_flags_finish +}; + +sh_optimize_sett_clrt::sh_optimize_sett_clrt (gcc::context* ctx, + const char* name) +: rtl_opt_pass (default_pass_data, ctx), + m_ccreg (NULL_RTX) +{ + // Overwrite default name in pass_data base class. + this->name = name; +} + +sh_optimize_sett_clrt::~sh_optimize_sett_clrt (void) +{ +} + +bool +sh_optimize_sett_clrt::gate (function*) +{ + return optimize > 0; +} + +unsigned int +sh_optimize_sett_clrt::execute (function* fun) +{ + unsigned int ccr0 = INVALID_REGNUM; + unsigned int ccr1 = INVALID_REGNUM; + + if (targetm.fixed_condition_code_regs (&ccr0, &ccr1) + && ccr0 != INVALID_REGNUM) + { + // Initially create a reg rtx with VOIDmode. + // When the constant setcc is discovered, the mode is changed + // to the mode that is actually used by the target. + m_ccreg = gen_rtx_REG (VOIDmode, ccr0); + } + + if (m_ccreg == NULL_RTX) + log_return (0, "no ccreg.\n\n"); + + if (STORE_FLAG_VALUE != 1) + log_return (0, "unsupported STORE_FLAG_VALUE %d", STORE_FLAG_VALUE); + + log_msg ("ccreg: "); + log_rtx (m_ccreg); + log_msg (" STORE_FLAG_VALUE = %d\n", STORE_FLAG_VALUE); + + if (!df_regs_ever_live_p (ccr0)) + log_return (0, "ccreg never live\n\n"); + + // Output vector for find_known_ccreg_values. + std::vector<ccreg_value> ccreg_values; + ccreg_values.reserve (32); + + // Something for recording visited basic blocks to avoid infinite recursion. + std::vector<basic_block> visited_bbs; + visited_bbs.reserve (32); + + // Look for insns that set the ccreg to a constant value and see if it can + // be optimized. + basic_block bb; + FOR_EACH_BB_REVERSE_FN (bb, fun) + for (rtx_insn *next_i, *i = NEXT_INSN (BB_HEAD (bb)); + i != NULL_RTX && i != BB_END (bb); i = next_i) + { + next_i = NEXT_INSN (i); + + if (!INSN_P (i) || !NONDEBUG_INSN_P (i)) + continue; + + rtx setcc_val = const_setcc_value (PATTERN (i)); + if (setcc_val != NULL_RTX) + { + update_ccreg_mode (GET_MODE (XEXP (PATTERN (i), 0))); + + log_msg ("\n\nfound const setcc insn in [bb %d]: \n", bb->index); + log_insn (i); + log_msg ("\n"); + + ccreg_values.clear (); + visited_bbs.clear (); + bool ok = find_last_ccreg_values (PREV_INSN (i), bb, ccreg_values, + visited_bbs); + + log_msg ("number of ccreg values collected: %u\n", + (unsigned int)ccreg_values.size ()); + + // If all the collected values are equal and are equal to the + // constant value of the setcc insn, the setcc insn can be + // removed. + if (ok && all_ccreg_values_equal (ccreg_values) + && rtx_equal_p (ccreg_values.front ().value, setcc_val)) + { + log_msg ("all values are "); + log_rtx (setcc_val); + log_msg ("\n"); + + delete_insn (i); + remove_ccreg_dead_unused_notes (ccreg_values); + } + } + } + + log_return (0, "\n\n"); +} + +void +sh_optimize_sett_clrt::update_ccreg_mode (machine_mode m) +{ + if (GET_MODE (m_ccreg) == m) + return; + + PUT_MODE (m_ccreg, m); + log_msg ("updated ccreg mode: "); + log_rtx (m_ccreg); + log_msg ("\n\n"); +} + +rtx +sh_optimize_sett_clrt::const_setcc_value (rtx pat) const +{ + if (GET_CODE (pat) == SET + && REG_P (XEXP (pat, 0)) && REGNO (XEXP (pat, 0)) == REGNO (m_ccreg) + && CONST_INT_P (XEXP (pat, 1)) + && (INTVAL (XEXP (pat, 1)) == 0 + || INTVAL (XEXP (pat, 1)) == STORE_FLAG_VALUE)) + return XEXP (pat, 1); + else + return NULL_RTX; +} + +bool +sh_optimize_sett_clrt +::sh_cbranch_ccreg_value (rtx_insn *cbranch_insn, basic_block cbranch_insn_bb, + basic_block branch_target_bb) const +{ + rtx pc_set_rtx = pc_set (cbranch_insn); + gcc_assert (pc_set_rtx != NULL_RTX); + gcc_assert (branch_target_bb != NULL); + + rtx cond = XEXP (XEXP (pc_set_rtx, 1), 0); + bool branch_if; + + if (GET_CODE (cond) == NE + && REG_P (XEXP (cond, 0)) && REGNO (XEXP (cond, 0)) == REGNO (m_ccreg) + && XEXP (cond, 1) == const0_rtx) + branch_if = true; + + else if (GET_CODE (cond) == EQ + && REG_P (XEXP (cond, 0)) && REGNO (XEXP (cond, 0)) == REGNO (m_ccreg) + && XEXP (cond, 1) == const0_rtx) + branch_if = false; + + else + gcc_unreachable (); + + if (branch_target_bb == BRANCH_EDGE (cbranch_insn_bb)->dest) + return branch_if; + else if (branch_target_bb == FALLTHRU_EDGE (cbranch_insn_bb)->dest) + return !branch_if; + else + gcc_unreachable (); +} + +bool +sh_optimize_sett_clrt +::find_last_ccreg_values (rtx_insn *start_insn, basic_block bb, + std::vector<ccreg_value>& values_out, + std::vector<basic_block>& prev_visited_bb) const +{ + // FIXME: For larger CFGs this will unnecessarily re-visit basic blocks. + // Once a basic block has been visited, the result should be stored in + // some container so that it can be looked up quickly eliminating the + // re-visits. + log_msg ("looking for ccreg values in [bb %d] ", bb->index); + if (!prev_visited_bb.empty ()) + log_msg ("(prev visited [bb %d])", prev_visited_bb.back ()->index); + log_msg ("\n"); + + for (rtx_insn *i = start_insn; i != NULL && i != PREV_INSN (BB_HEAD (bb)); + i = PREV_INSN (i)) + { + if (!INSN_P (i)) + continue; + + if (reg_set_p (m_ccreg, i)) + { + const_rtx set_rtx = set_of (m_ccreg, i); + + ccreg_value v; + v.insn = i; + v.bb = bb; + v.value = set_rtx != NULL_RTX && GET_CODE (set_rtx) == SET + ? XEXP (set_rtx, 1) + : NULL_RTX; + + log_msg ("found setcc in [bb %d] in insn:\n", bb->index); + log_insn (i); + log_msg ("\nccreg value: "); + log_rtx (v.value); + log_msg ("\n"); + + values_out.push_back (v); + return true; + } + + if (any_condjump_p (i) && onlyjump_p (i) && !prev_visited_bb.empty ()) + { + // For a conditional branch the ccreg value will be a known constant + // of either 0 or STORE_FLAG_VALUE after branching/falling through + // to one of the two successor BBs. Record the value for the BB + // where we came from. + log_msg ("found cbranch in [bb %d]:\n", bb->index); + log_insn (i); + + ccreg_value v; + v.insn = i; + v.bb = bb; + v.value = GEN_INT (sh_cbranch_ccreg_value (i, bb, + prev_visited_bb.back ())); + + log_msg (" branches to [bb %d] with ccreg value ", + prev_visited_bb.back ()->index); + log_rtx (v.value); + log_msg ("\n"); + + values_out.push_back (v); + return true; + } + } + + // If here, we've walked up all the insns of the current basic block + // and none of them seems to modify the ccreg. + // In this case, check the predecessor basic blocks. + unsigned int pred_bb_count = 0; + + // If the current basic block is not in the stack of previously visited + // basic blocks yet, we can recursively check the predecessor basic blocks. + // Otherwise we have a loop in the CFG and recursing again will result in + // an infinite loop. + if (std::find (prev_visited_bb.rbegin (), prev_visited_bb.rend (), bb) + == prev_visited_bb.rend ()) + { + prev_visited_bb.push_back (bb); + + for (edge_iterator ei = ei_start (bb->preds); !ei_end_p (ei); + ei_next (&ei)) + { + if (ei_edge (ei)->flags & EDGE_COMPLEX) + log_return (false, "aborting due to complex edge\n"); + + basic_block pred_bb = ei_edge (ei)->src; + pred_bb_count += 1; + if (!find_last_ccreg_values (BB_END (pred_bb), pred_bb, values_out, + prev_visited_bb)) + return false; + } + + prev_visited_bb.pop_back (); + } + else + log_msg ("loop detected for [bb %d]\n", bb->index); + + log_msg ("[bb %d] pred_bb_count = %u\n", bb->index, pred_bb_count); + + if (pred_bb_count == 0) + { + // If we haven't checked a single predecessor basic block, the current + // basic block is probably a leaf block and we don't know the ccreg value. + log_msg ("unknown ccreg value for [bb %d]\n", bb->index); + + ccreg_value v; + v.insn = BB_END (bb); + v.bb = bb; + v.value = NULL_RTX; + + values_out.push_back (v); + } + + return true; +} + +bool +sh_optimize_sett_clrt +::all_ccreg_values_equal (const std::vector<ccreg_value>& values) +{ + if (values.empty ()) + return false; + + rtx last_value = values.front ().value; + + // If the ccreg is modified in the insn but the exact value is not known + // the value rtx might be null. + if (last_value == NULL_RTX) + return false; + + for (std::vector<ccreg_value>::const_iterator i = values.begin (); + i != values.end (); ++i) + if (i->value == NULL_RTX || !rtx_equal_p (last_value, i->value)) + return false; + + return true; +} + +void +sh_optimize_sett_clrt +::remove_ccreg_dead_unused_notes (std::vector<ccreg_value>& values) const +{ + for (std::vector<ccreg_value>::iterator i = values.begin (); + i != values.end (); ++i) + { + if (i->insn == NULL_RTX) + continue; + + rtx n = find_regno_note (i->insn, REG_DEAD, REGNO (m_ccreg)); + if (n != NULL_RTX) + remove_note (i->insn, n); + + n = find_regno_note (i->insn, REG_UNUSED, REGNO (m_ccreg)); + if (n != NULL_RTX) + remove_note (i->insn, n); + } +} + +// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +// This allows instantiating the pass somewhere else without having to pull +// in a header file. +opt_pass* +make_pass_sh_optimize_sett_clrt (gcc::context* ctx, const char* name) +{ + return new sh_optimize_sett_clrt (ctx, name); +}