430 lines
12 KiB
C
430 lines
12 KiB
C
/* Web construction code for GNU compiler.
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Contributed by Jan Hubicka.
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Copyright (C) 2001-2020 Free Software Foundation, Inc.
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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 under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 3, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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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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/* Simple optimization pass that splits independent uses of each pseudo,
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increasing effectiveness of other optimizations. The optimization can
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serve as an example of use for the dataflow module.
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TODO
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- We may use profile information and ignore infrequent use for the
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purpose of web unifying, inserting the compensation code later to
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implement full induction variable expansion for loops (currently
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we expand only if the induction variable is dead afterward, which
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is often the case). */
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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 "rtl.h"
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#include "df.h"
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#include "insn-config.h"
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#include "recog.h"
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#include "tree-pass.h"
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/* Find the root of unionfind tree (the representative of set). */
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web_entry_base *
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web_entry_base::unionfind_root ()
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{
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web_entry_base *element = this, *element1 = this, *element2;
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while (element->pred ())
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element = element->pred ();
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while (element1->pred ())
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{
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element2 = element1->pred ();
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element1->set_pred (element);
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element1 = element2;
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}
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return element;
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}
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/* Union sets.
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Return true if FIRST and SECOND points to the same web entry structure and
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nothing is done. Otherwise, return false. */
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bool
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unionfind_union (web_entry_base *first, web_entry_base *second)
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{
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first = first->unionfind_root ();
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second = second->unionfind_root ();
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if (first == second)
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return true;
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second->set_pred (first);
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return false;
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}
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struct web_entry : public web_entry_base
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{
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private:
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rtx reg_pvt;
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public:
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rtx reg () { return reg_pvt; }
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void set_reg (rtx r) { reg_pvt = r; }
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};
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/* For INSN, union all defs and uses that are linked by match_dup.
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FUN is the function that does the union. */
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static void
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union_match_dups (rtx_insn *insn, web_entry *def_entry, web_entry *use_entry,
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bool (*fun) (web_entry_base *, web_entry_base *))
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{
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struct df_insn_info *insn_info = DF_INSN_INFO_GET (insn);
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df_ref use_link = DF_INSN_INFO_USES (insn_info);
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df_ref def_link = DF_INSN_INFO_DEFS (insn_info);
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struct web_entry *dup_entry;
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int i;
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extract_insn (insn);
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for (i = 0; i < recog_data.n_dups; i++)
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{
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int op = recog_data.dup_num[i];
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enum op_type type = recog_data.operand_type[op];
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df_ref ref, dupref;
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struct web_entry *entry;
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dup_entry = use_entry;
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for (dupref = use_link; dupref; dupref = DF_REF_NEXT_LOC (dupref))
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if (DF_REF_LOC (dupref) == recog_data.dup_loc[i])
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break;
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if (dupref == NULL && type == OP_INOUT)
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{
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dup_entry = def_entry;
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for (dupref = def_link; dupref; dupref = DF_REF_NEXT_LOC (dupref))
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if (DF_REF_LOC (dupref) == recog_data.dup_loc[i])
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break;
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}
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/* ??? *DUPREF can still be zero, because when an operand matches
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a memory, DF_REF_LOC (use_link[n]) points to the register part
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of the address, whereas recog_data.dup_loc[m] points to the
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entire memory ref, thus we fail to find the duplicate entry,
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even though it is there.
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Example: i686-pc-linux-gnu gcc.c-torture/compile/950607-1.c
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-O3 -fomit-frame-pointer -funroll-loops */
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if (dupref == NULL
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|| DF_REF_REGNO (dupref) < FIRST_PSEUDO_REGISTER)
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continue;
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ref = type == OP_IN ? use_link : def_link;
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entry = type == OP_IN ? use_entry : def_entry;
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for (; ref; ref = DF_REF_NEXT_LOC (ref))
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{
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rtx *l = DF_REF_LOC (ref);
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if (l == recog_data.operand_loc[op])
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break;
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if (l && DF_REF_REAL_LOC (ref) == recog_data.operand_loc[op])
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break;
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}
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if (!ref && type == OP_INOUT)
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{
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entry = use_entry;
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for (ref = use_link; ref; ref = DF_REF_NEXT_LOC (ref))
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{
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rtx *l = DF_REF_LOC (ref);
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if (l == recog_data.operand_loc[op])
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break;
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if (l && DF_REF_REAL_LOC (ref) == recog_data.operand_loc[op])
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break;
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}
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}
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gcc_assert (ref);
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(*fun) (dup_entry + DF_REF_ID (dupref), entry + DF_REF_ID (ref));
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}
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}
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/* For each use, all possible defs reaching it must come in the same
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register, union them.
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FUN is the function that does the union.
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In USED, we keep the DF_REF_ID of the first uninitialized uses of a
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register, so that all uninitialized uses of the register can be
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combined into a single web. We actually offset it by 2, because
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the values 0 and 1 are reserved for use by entry_register. */
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void
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union_defs (df_ref use, web_entry *def_entry,
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unsigned int *used, web_entry *use_entry,
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bool (*fun) (web_entry_base *, web_entry_base *))
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{
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struct df_insn_info *insn_info = DF_REF_INSN_INFO (use);
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struct df_link *link = DF_REF_CHAIN (use);
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rtx set;
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if (insn_info)
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{
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df_ref eq_use;
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set = single_set (insn_info->insn);
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FOR_EACH_INSN_INFO_EQ_USE (eq_use, insn_info)
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if (use != eq_use
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&& DF_REF_REAL_REG (use) == DF_REF_REAL_REG (eq_use))
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(*fun) (use_entry + DF_REF_ID (use), use_entry + DF_REF_ID (eq_use));
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}
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else
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set = NULL;
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/* Union all occurrences of the same register in reg notes. */
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/* Recognize trivial noop moves and attempt to keep them as noop. */
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if (set
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&& SET_SRC (set) == DF_REF_REG (use)
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&& SET_SRC (set) == SET_DEST (set))
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{
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df_ref def;
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FOR_EACH_INSN_INFO_DEF (def, insn_info)
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if (DF_REF_REAL_REG (use) == DF_REF_REAL_REG (def))
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(*fun) (use_entry + DF_REF_ID (use), def_entry + DF_REF_ID (def));
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}
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/* UD chains of uninitialized REGs are empty. Keeping all uses of
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the same uninitialized REG in a single web is not necessary for
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correctness, since the uses are undefined, but it's wasteful to
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allocate one register or slot for each reference. Furthermore,
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creating new pseudos for uninitialized references in debug insns
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(see PR 42631) causes -fcompare-debug failures. We record the
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number of the first uninitialized reference we found, and merge
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with it any other uninitialized references to the same
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register. */
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if (!link)
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{
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int regno = REGNO (DF_REF_REAL_REG (use));
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if (used[regno])
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(*fun) (use_entry + DF_REF_ID (use), use_entry + used[regno] - 2);
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else
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used[regno] = DF_REF_ID (use) + 2;
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}
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while (link)
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{
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(*fun) (use_entry + DF_REF_ID (use),
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def_entry + DF_REF_ID (link->ref));
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link = link->next;
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}
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/* A READ_WRITE use requires the corresponding def to be in the same
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register. Find it and union. */
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if (DF_REF_FLAGS (use) & DF_REF_READ_WRITE)
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if (insn_info)
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{
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df_ref def;
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FOR_EACH_INSN_INFO_DEF (def, insn_info)
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if (DF_REF_REAL_REG (use) == DF_REF_REAL_REG (def))
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(*fun) (use_entry + DF_REF_ID (use), def_entry + DF_REF_ID (def));
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}
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}
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/* Find the corresponding register for the given entry. */
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static rtx
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entry_register (web_entry *entry, df_ref ref, unsigned int *used)
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{
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web_entry *root;
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rtx reg, newreg;
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/* Find the corresponding web and see if it has been visited. */
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root = (web_entry *)entry->unionfind_root ();
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if (root->reg ())
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return root->reg ();
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/* We are seeing this web for the first time, do the assignment. */
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reg = DF_REF_REAL_REG (ref);
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/* In case the original register is already assigned, generate new
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one. Since we use USED to merge uninitialized refs into a single
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web, we might found an element to be nonzero without our having
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used it. Test for 1, because union_defs saves it for our use,
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and there won't be any use for the other values when we get to
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this point. */
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if (used[REGNO (reg)] != 1)
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newreg = reg, used[REGNO (reg)] = 1;
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else
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{
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newreg = gen_reg_rtx (GET_MODE (reg));
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REG_USERVAR_P (newreg) = REG_USERVAR_P (reg);
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REG_POINTER (newreg) = REG_POINTER (reg);
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REG_ATTRS (newreg) = REG_ATTRS (reg);
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if (dump_file)
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fprintf (dump_file, "Web oldreg=%i newreg=%i\n", REGNO (reg),
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REGNO (newreg));
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}
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root->set_reg (newreg);
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return newreg;
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}
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/* Replace the reference by REG. */
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static void
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replace_ref (df_ref ref, rtx reg)
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{
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rtx oldreg = DF_REF_REAL_REG (ref);
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rtx *loc = DF_REF_REAL_LOC (ref);
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unsigned int uid = DF_REF_INSN_UID (ref);
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if (oldreg == reg)
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return;
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if (dump_file)
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fprintf (dump_file, "Updating insn %i (%i->%i)\n",
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uid, REGNO (oldreg), REGNO (reg));
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*loc = reg;
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df_insn_rescan (DF_REF_INSN (ref));
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}
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namespace {
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const pass_data pass_data_web =
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{
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RTL_PASS, /* type */
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"web", /* name */
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OPTGROUP_NONE, /* optinfo_flags */
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TV_WEB, /* tv_id */
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0, /* properties_required */
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0, /* properties_provided */
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0, /* properties_destroyed */
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0, /* todo_flags_start */
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TODO_df_finish, /* todo_flags_finish */
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};
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class pass_web : public rtl_opt_pass
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{
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public:
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pass_web (gcc::context *ctxt)
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: rtl_opt_pass (pass_data_web, ctxt)
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{}
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/* opt_pass methods: */
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virtual bool gate (function *) { return (optimize > 0 && flag_web); }
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virtual unsigned int execute (function *);
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}; // class pass_web
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unsigned int
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pass_web::execute (function *fun)
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{
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web_entry *def_entry;
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web_entry *use_entry;
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unsigned int max = max_reg_num ();
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unsigned int *used;
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basic_block bb;
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unsigned int uses_num = 0;
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rtx_insn *insn;
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df_set_flags (DF_NO_HARD_REGS + DF_EQ_NOTES);
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df_set_flags (DF_RD_PRUNE_DEAD_DEFS);
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df_chain_add_problem (DF_UD_CHAIN);
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df_analyze ();
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df_set_flags (DF_DEFER_INSN_RESCAN);
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/* Assign ids to the uses. */
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FOR_ALL_BB_FN (bb, fun)
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FOR_BB_INSNS (bb, insn)
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{
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if (NONDEBUG_INSN_P (insn))
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{
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struct df_insn_info *insn_info = DF_INSN_INFO_GET (insn);
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df_ref use;
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FOR_EACH_INSN_INFO_USE (use, insn_info)
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if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
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DF_REF_ID (use) = uses_num++;
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FOR_EACH_INSN_INFO_EQ_USE (use, insn_info)
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if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
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DF_REF_ID (use) = uses_num++;
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}
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}
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/* Record the number of uses and defs at the beginning of the optimization. */
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def_entry = XCNEWVEC (web_entry, DF_DEFS_TABLE_SIZE ());
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used = XCNEWVEC (unsigned, max);
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use_entry = XCNEWVEC (web_entry, uses_num);
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/* Produce the web. */
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FOR_ALL_BB_FN (bb, fun)
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FOR_BB_INSNS (bb, insn)
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if (NONDEBUG_INSN_P (insn))
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{
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struct df_insn_info *insn_info = DF_INSN_INFO_GET (insn);
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df_ref use;
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union_match_dups (insn, def_entry, use_entry, unionfind_union);
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FOR_EACH_INSN_INFO_USE (use, insn_info)
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if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
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union_defs (use, def_entry, used, use_entry, unionfind_union);
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FOR_EACH_INSN_INFO_EQ_USE (use, insn_info)
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if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
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union_defs (use, def_entry, used, use_entry, unionfind_union);
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}
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/* Update the instruction stream, allocating new registers for split pseudos
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in progress. */
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FOR_ALL_BB_FN (bb, fun)
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FOR_BB_INSNS (bb, insn)
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if (NONDEBUG_INSN_P (insn)
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/* Ignore naked clobber. For example, reg 134 in the second insn
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of the following sequence will not be replaced.
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(insn (clobber (reg:SI 134)))
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(insn (set (reg:SI 0 r0) (reg:SI 134)))
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Thus the later passes can optimize them away. */
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&& GET_CODE (PATTERN (insn)) != CLOBBER)
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{
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struct df_insn_info *insn_info = DF_INSN_INFO_GET (insn);
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df_ref def, use;
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FOR_EACH_INSN_INFO_USE (use, insn_info)
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if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
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replace_ref (use, entry_register (use_entry + DF_REF_ID (use),
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use, used));
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FOR_EACH_INSN_INFO_EQ_USE (use, insn_info)
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if (DF_REF_REGNO (use) >= FIRST_PSEUDO_REGISTER)
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replace_ref (use, entry_register (use_entry + DF_REF_ID (use),
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use, used));
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FOR_EACH_INSN_INFO_DEF (def, insn_info)
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if (DF_REF_REGNO (def) >= FIRST_PSEUDO_REGISTER)
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replace_ref (def, entry_register (def_entry + DF_REF_ID (def),
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def, used));
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}
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free (def_entry);
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free (use_entry);
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free (used);
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return 0;
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}
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} // anon namespace
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rtl_opt_pass *
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make_pass_web (gcc::context *ctxt)
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{
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return new pass_web (ctxt);
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}
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