procyberian/gcc
2
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

tree-ssa-dce.c (simple_dce_from_worklist): Move and rename from tree-ssa-pre.c::remove_dead_inserted_code.

Browse source 
* tree-ssa-dce.c (simple_dce_from_worklist): Move and rename from
	tree-ssa-pre.c::remove_dead_inserted_code.
	* tree-ssa-dce.h: New file.
	* tree-ssa-pre.c (tree-ssa-dce.h): Include new header file.
	(remove_dead_inserted_code): Move and rename to function
	tree-ssa-dce.c::simple_dce_from_worklist.
	(pass_pre::execute): Update use.

From-SVN: r255426
This commit is contained in:
Bin Cheng 2017-12-05 15:42:58 +00:00 • committed by Bin Cheng
parent 0382bcfcda
commit 23ffbafe3a
4 changed files with 90 additions and 59 deletions
Download patch file Download diff file Expand all files Collapse all files

10
gcc/ChangeLog
View file

@ -1,3 +1,13 @@
2017-12-05 Bin Cheng <bin.cheng@arm.com>
* tree-ssa-dce.c (simple_dce_from_worklist): Move and rename from
tree-ssa-pre.c::remove_dead_inserted_code.
* tree-ssa-dce.h: New file.
* tree-ssa-pre.c (tree-ssa-dce.h): Include new header file.
(remove_dead_inserted_code): Move and rename to function
tree-ssa-dce.c::simple_dce_from_worklist.
(pass_pre::execute): Update use.
2017-12-05 Richard Biener <rguenther@suse.de>
PR tree-optimization/83277

52
gcc/tree-ssa-dce.c
View file

@ -1723,3 +1723,55 @@ make_pass_cd_dce (gcc::context *ctxt)
{
return new pass_cd_dce (ctxt);
}
/* A cheap DCE interface. WORKLIST is a list of possibly dead stmts and
is consumed by this function. The function has linear complexity in
the number of dead stmts with a constant factor like the average SSA
use operands number. */
void
simple_dce_from_worklist (bitmap worklist)
{
while (! bitmap_empty_p (worklist))
{
/* Pop item. */
unsigned i = bitmap_first_set_bit (worklist);
bitmap_clear_bit (worklist, i);
tree def = ssa_name (i);
/* Removed by somebody else or still in use. */
if (! def || ! has_zero_uses (def))
continue;
gimple *t = SSA_NAME_DEF_STMT (def);
if (gimple_has_side_effects (t))
continue;
/* Add uses to the worklist. */
ssa_op_iter iter;
use_operand_p use_p;
FOR_EACH_PHI_OR_STMT_USE (use_p, t, iter, SSA_OP_USE)
{
tree use = USE_FROM_PTR (use_p);
if (TREE_CODE (use) == SSA_NAME
&& ! SSA_NAME_IS_DEFAULT_DEF (use))
bitmap_set_bit (worklist, SSA_NAME_VERSION (use));
}
/* Remove stmt. */
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Removing dead stmt:");
print_gimple_stmt (dump_file, t, 0);
}
gimple_stmt_iterator gsi = gsi_for_stmt (t);
if (gimple_code (t) == GIMPLE_PHI)
remove_phi_node (&gsi, true);
else
{
gsi_remove (&gsi, true);
release_defs (t);
}
}
}

22
gcc/tree-ssa-dce.h Normal file
View file

@ -0,0 +1,22 @@
/* Copyright (C) 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/>. */
#ifndef TREE_SSA_DCE_H
#define TREE_SSA_DCE_H
extern void simple_dce_from_worklist (bitmap);
#endif

65
gcc/tree-ssa-pre.c
View file

@ -49,6 +49,7 @@ along with GCC; see the file COPYING3. If not see
#include "dbgcnt.h"
#include "domwalk.h"
#include "tree-ssa-propagate.h"
#include "tree-ssa-dce.h"
#include "tree-cfgcleanup.h"
#include "alias.h"
@ -3995,64 +3996,6 @@ compute_avail (void)
free (worklist);
}
/* Cheap DCE of a known set of possibly dead stmts.
Because we don't follow exactly the standard PRE algorithm, and decide not
to insert PHI nodes sometimes, and because value numbering of casts isn't
perfect, we sometimes end up inserting dead code. This simple DCE-like
pass removes any insertions we made that weren't actually used. */
static void
remove_dead_inserted_code (void)
{
/* ??? Re-use inserted_exprs as worklist not only as initial set.
This may end up removing non-inserted code as well. If we
keep inserted_exprs unchanged we could restrict new worklist
elements to members of inserted_exprs. */
bitmap worklist = inserted_exprs;
while (! bitmap_empty_p (worklist))
{
/* Pop item. */
unsigned i = bitmap_first_set_bit (worklist);
bitmap_clear_bit (worklist, i);
tree def = ssa_name (i);
/* Removed by somebody else or still in use. */
if (! def || ! has_zero_uses (def))
continue;
gimple *t = SSA_NAME_DEF_STMT (def);
if (gimple_has_side_effects (t))
continue;
/* Add uses to the worklist. */
ssa_op_iter iter;
use_operand_p use_p;
FOR_EACH_PHI_OR_STMT_USE (use_p, t, iter, SSA_OP_USE)
{
tree use = USE_FROM_PTR (use_p);
if (TREE_CODE (use) == SSA_NAME
&& ! SSA_NAME_IS_DEFAULT_DEF (use))
bitmap_set_bit (worklist, SSA_NAME_VERSION (use));
}
/* Remove stmt. */
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Removing unnecessary insertion:");
print_gimple_stmt (dump_file, t, 0);
}
gimple_stmt_iterator gsi = gsi_for_stmt (t);
if (gimple_code (t) == GIMPLE_PHI)
remove_phi_node (&gsi, true);
else
{
gsi_remove (&gsi, true);
release_defs (t);
}
}
}
/* Initialize data structures used by PRE. */
@ -4188,7 +4131,11 @@ pass_pre::execute (function *fun)
/* Remove all the redundant expressions. */
todo |= vn_eliminate (inserted_exprs);
remove_dead_inserted_code ();
/* Because we don't follow exactly the standard PRE algorithm, and decide not
to insert PHI nodes sometimes, and because value numbering of casts isn't
perfect, we sometimes end up inserting dead code. This simple DCE-like
pass removes any insertions we made that weren't actually used. */
simple_dce_from_worklist (inserted_exprs);
fini_pre ();