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/* Shorten memrefs pass for RISC-V.
Copyright (C) 2018-2022 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/>. */
#define IN_TARGET_CODE 1
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "rtl.h"
#include "backend.h"
#include "regs.h"
#include "target.h"
#include "memmodel.h"
#include "emit-rtl.h"
#include "df.h"
#include "predict.h"
#include "tree-pass.h"
/* Try to make more use of compressed load and store instructions by replacing
a load/store at address BASE + LARGE_OFFSET with a new load/store at address
NEW BASE + SMALL OFFSET. If NEW BASE is stored in a compressed register, the
load/store can be compressed. Since creating NEW BASE incurs an overhead,
the change is only attempted when BASE is referenced by at least four
load/stores in the same basic block. */
namespace {
const pass_data pass_data_shorten_memrefs =
{
RTL_PASS, /* type */
"shorten_memrefs", /* name */
OPTGROUP_NONE, /* optinfo_flags */
TV_NONE, /* tv_id */
0, /* properties_required */
0, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
0, /* todo_flags_finish */
};
class pass_shorten_memrefs : public rtl_opt_pass
{
public:
pass_shorten_memrefs (gcc::context *ctxt)
: rtl_opt_pass (pass_data_shorten_memrefs, ctxt)
{}
/* opt_pass methods: */
virtual bool gate (function *)
{
return TARGET_RVC && riscv_mshorten_memrefs && optimize > 0;
}
virtual unsigned int execute (function *);
private:
typedef int_hash <HOST_WIDE_INT, 0> regno_hash;
typedef hash_map <regno_hash, int> regno_map;
regno_map * analyze (basic_block bb);
void transform (regno_map *m, basic_block bb);
bool get_si_mem_base_reg (rtx mem, rtx *addr, bool *extend);
}; // class pass_shorten_memrefs
bool
pass_shorten_memrefs::get_si_mem_base_reg (rtx mem, rtx *addr, bool *extend)
{
/* Whether it's sign/zero extended. */
if (GET_CODE (mem) == ZERO_EXTEND || GET_CODE (mem) == SIGN_EXTEND)
{
*extend = true;
mem = XEXP (mem, 0);
}
if (!MEM_P (mem) || GET_MODE (mem) != SImode)
return false;
*addr = XEXP (mem, 0);
return GET_CODE (*addr) == PLUS && REG_P (XEXP (*addr, 0));
}
/* Count how many times each regno is referenced as base address for a memory
access. */
pass_shorten_memrefs::regno_map *
pass_shorten_memrefs::analyze (basic_block bb)
{
regno_map *m = hash_map<regno_hash, int>::create_ggc (10);
rtx_insn *insn;
regstat_init_n_sets_and_refs ();
FOR_BB_INSNS (bb, insn)
{
if (!NONJUMP_INSN_P (insn))
continue;
rtx pat = PATTERN (insn);
if (GET_CODE (pat) != SET)
continue;
/* Analyze stores first then loads. */
for (int i = 0; i < 2; i++)
{
rtx mem = XEXP (pat, i);
rtx addr;
bool extend = false;
if (get_si_mem_base_reg (mem, &addr, &extend))
{
HOST_WIDE_INT regno = REGNO (XEXP (addr, 0));
/* Do not count store zero as these cannot be compressed. */
if (i == 0)
{
if (XEXP (pat, 1) == CONST0_RTX (GET_MODE (XEXP (pat, 1))))
continue;
}
if (REG_N_REFS (regno) < 4)
continue;
m->get_or_insert (regno)++;
}
}
}
regstat_free_n_sets_and_refs ();
return m;
}
/* Convert BASE + LARGE_OFFSET to NEW_BASE + SMALL_OFFSET for each load/store
with a base reg referenced at least 4 times. */
void
pass_shorten_memrefs::transform (regno_map *m, basic_block bb)
{
rtx_insn *insn;
FOR_BB_INSNS (bb, insn)
{
if (!NONJUMP_INSN_P (insn))
continue;
rtx pat = PATTERN (insn);
if (GET_CODE (pat) != SET)
continue;
start_sequence ();
/* Transform stores first then loads. */
for (int i = 0; i < 2; i++)
{
rtx mem = XEXP (pat, i);
rtx addr;
bool extend = false;
if (get_si_mem_base_reg (mem, &addr, &extend))
{
HOST_WIDE_INT regno = REGNO (XEXP (addr, 0));
/* Do not transform store zero as these cannot be compressed. */
if (i == 0)
{
if (XEXP (pat, 1) == CONST0_RTX (GET_MODE (XEXP (pat, 1))))
continue;
}
if (m->get_or_insert (regno) > 3)
{
if (extend)
{
addr
= targetm.legitimize_address (addr, addr,
GET_MODE (XEXP (mem, 0)));
XEXP (XEXP (pat, i), 0)
= replace_equiv_address (XEXP (mem, 0), addr);
}
else
{
addr = targetm.legitimize_address (addr, addr,
GET_MODE (mem));
XEXP (pat, i) = replace_equiv_address (mem, addr);
}
df_insn_rescan (insn);
}
}
}
rtx_insn *seq = get_insns ();
end_sequence ();
emit_insn_before (seq, insn);
}
}
unsigned int
pass_shorten_memrefs::execute (function *fn)
{
basic_block bb;
FOR_ALL_BB_FN (bb, fn)
{
regno_map *m;
if (optimize_bb_for_speed_p (bb))
continue;
m = analyze (bb);
transform (m, bb);
}
return 0;
}
} // anon namespace
rtl_opt_pass *
make_pass_shorten_memrefs (gcc::context *ctxt)
{
return new pass_shorten_memrefs (ctxt);
}
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