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Commit 29fa95ed by Jeff Law Committed by Jeff Law
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re PR rtl-optimization/39077 (GCSE-optimization causes enormous binary size increase (~20 times !)) 

	* PR rtl-optimization/39077
	* doc/invoke.texi (max-gcse-insertion-ratio): Document.
	* params.h (MAX_GCSE_INSERTION_RATIO): Define.
	* params.def (PARAM_MAX_GCSE_INSERTION_RATIO): Define.
	* lcm.c (pre_edge_lcm): Properly initialize output sbitmaps.
	* gcse.c (prune_insertions_deletions): New function.
	(compute_pre_data): Use it.

From-SVN: r168747
parent 71d12276
Showing with 104 additions and 5 deletions
gcc/ChangeLog
2011-01-13 Jeff Law <law@redhat.com>
* PR rtl-optimization/39077
* doc/invoke.texi (max-gcse-insertion-ratio): Document.
* params.h (MAX_GCSE_INSERTION_RATIO): Define.
* params.def (PARAM_MAX_GCSE_INSERTION_RATIO): Define.
* lcm.c (pre_edge_lcm): Properly initialize output sbitmaps.
* gcse.c (prune_insertions_deletions): New function.
(compute_pre_data): Use it.
2011-01-13 Dodji Seketeli <dodji@redhat.com>
PR debug/PR46973
......
gcc/doc/invoke.texi
@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
@c 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
@c 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
@c Free Software Foundation, Inc.
@c This is part of the GCC manual.
@c For copying conditions, see the file gcc.texi.
......@@ -8227,6 +8227,11 @@ order to perform the global common subexpression elimination
optimization. If more memory than specified is required, the
optimization will not be done.
@item max-gcse-insertion-ratio
If the ratio of expression insertions to deletions is larger than this value
for any expression, then RTL PRE will insert or remove the expression and thus
leave partially redundant computations in the instruction stream. The default value is 20.
@item max-pending-list-length
The maximum number of pending dependencies scheduling will allow
before flushing the current state and starting over. Large functions
......
gcc/gcse.c
/* Global common subexpression elimination/Partial redundancy elimination
and global constant/copy propagation for GNU compiler.
Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
This file is part of GCC.
......@@ -3396,6 +3396,75 @@ prune_expressions (bool pre_p)
sbitmap_free (prune_exprs);
}
/* It may be necessary to insert a large number of insns on edges to
make the existing occurrences of expressions fully redundant. This
routine examines the set of insertions and deletions and if the ratio
of insertions to deletions is too high for a particular expression, then
the expression is removed from the insertion/deletion sets.
N_ELEMS is the number of elements in the hash table. */
static void
prune_insertions_deletions (int n_elems)
{
sbitmap_iterator sbi;
sbitmap prune_exprs;
/* We always use I to iterate over blocks/edges and J to iterate over
expressions. */
unsigned int i, j;
/* Counts for the number of times an expression needs to be inserted and
number of times an expression can be removed as a result. */
int *insertions = GCNEWVEC (int, n_elems);
int *deletions = GCNEWVEC (int, n_elems);
/* Set of expressions which require too many insertions relative to
the number of deletions achieved. We will prune these out of the
insertion/deletion sets. */
prune_exprs = sbitmap_alloc (n_elems);
sbitmap_zero (prune_exprs);
/* Iterate over the edges counting the number of times each expression
needs to be inserted. */
for (i = 0; i < (unsigned) n_edges; i++)
{
EXECUTE_IF_SET_IN_SBITMAP (pre_insert_map[i], 0, j, sbi)
insertions[j]++;
}
/* Similarly for deletions, but those occur in blocks rather than on
edges. */
for (i = 0; i < (unsigned) last_basic_block; i++)
{
EXECUTE_IF_SET_IN_SBITMAP (pre_delete_map[i], 0, j, sbi)
deletions[j]++;
}
/* Now that we have accurate counts, iterate over the elements in the
hash table and see if any need too many insertions relative to the
number of evaluations that can be removed. If so, mark them in
PRUNE_EXPRS. */
for (j = 0; j < (unsigned) n_elems; j++)
if (deletions[j]
&& ((unsigned) insertions[j] / deletions[j]) > MAX_GCSE_INSERTION_RATIO)
SET_BIT (prune_exprs, j);
/* Now prune PRE_INSERT_MAP and PRE_DELETE_MAP based on PRUNE_EXPRS. */
EXECUTE_IF_SET_IN_SBITMAP (prune_exprs, 0, j, sbi)
{
for (i = 0; i < (unsigned) n_edges; i++)
RESET_BIT (pre_insert_map[i], j);
for (i = 0; i < (unsigned) last_basic_block; i++)
RESET_BIT (pre_delete_map[i], j);
}
sbitmap_free (prune_exprs);
free (insertions);
free (deletions);
}
/* Top level routine to do the dataflow analysis needed by PRE. */
static void
......@@ -3424,6 +3493,8 @@ compute_pre_data (void)
antloc = NULL;
sbitmap_vector_free (ae_kill);
ae_kill = NULL;
prune_insertions_deletions (expr_hash_table.n_elems);
}
/* PRE utilities */
......@@ -5368,3 +5439,4 @@ struct rtl_opt_pass pass_rtl_hoist =
};
#include "gt-gcse.h"
gcc/lcm.c
/* Generic partial redundancy elimination with lazy code motion support.
Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007, 2008,
2010 Free Software Foundation, Inc.
2010, 2011 Free Software Foundation, Inc.
This file is part of GCC.
......@@ -451,6 +451,8 @@ pre_edge_lcm (int n_exprs, sbitmap *transp,
*insert = sbitmap_vector_alloc (num_edges, n_exprs);
*del = sbitmap_vector_alloc (last_basic_block, n_exprs);
sbitmap_vector_zero (*insert, num_edges);
sbitmap_vector_zero (*del, last_basic_block);
compute_insert_delete (edge_list, antloc, later, laterin, *insert, *del);
sbitmap_vector_free (laterin);
......
gcc/params.def
/* params.def - Run-time parameters.
Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
2011
Free Software Foundation, Inc.
Written by Mark Mitchell <mark@codesourcery.com>.
......@@ -214,6 +215,13 @@ DEFPARAM(PARAM_MAX_GCSE_MEMORY,
"The maximum amount of memory to be allocated by GCSE",
50 * 1024 * 1024, 0, 0)
/* The GCSE optimization of an expression will avoided if the ratio of
insertions to deletions is greater than this value. */
DEFPARAM(PARAM_MAX_GCSE_INSERTION_RATIO,
"max-gcse-insertion-ratio",
"The maximum ratio of insertions to deletions of expressions in GCSE",
20, 0, 0)
/* This is the threshold ratio when to perform partial redundancy
elimination after reload. We perform partial redundancy elimination
when the following holds:
......
gcc/params.h
/* params.h - Run-time parameters.
Copyright (C) 2001, 2003, 2004, 2005, 2007, 2008, 2009, 2010
Copyright (C) 2001, 2003, 2004, 2005, 2007, 2008, 2009, 2010, 2011
Free Software Foundation, Inc.
Written by Mark Mitchell <mark@codesourcery.com>.
......@@ -142,6 +142,8 @@ extern void init_param_values (int *params);
PARAM_VALUE (PARAM_MAX_PENDING_LIST_LENGTH)
#define MAX_GCSE_MEMORY \
((size_t) PARAM_VALUE (PARAM_MAX_GCSE_MEMORY))
#define MAX_GCSE_INSERTION_RATIO \
((size_t) PARAM_VALUE (PARAM_MAX_GCSE_INSERTION_RATIO))
#define GCSE_AFTER_RELOAD_PARTIAL_FRACTION \
PARAM_VALUE (PARAM_GCSE_AFTER_RELOAD_PARTIAL_FRACTION)
#define GCSE_AFTER_RELOAD_CRITICAL_FRACTION \
......
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