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re PR middle-end/45705 (Useless store not optimized away)

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2010-09-20  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/45705
	* tree-ssa-dom.c (optimize_stmt): Perform redundant store elimination.

	* gcc.dg/tree-ssa/ssa-dom-dse-1.c: New testcase.

From-SVN: r164434
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Richard Guenther 2010-09-20 14:40:10 +00:00 committed by Richard Biener
parent 5e979df369
commit 565b88862d
4 changed files with 71 additions and 0 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2010-09-20 Richard Guenther <rguenther@suse.de>
PR tree-optimization/45705
* tree-ssa-dom.c (optimize_stmt): Perform redundant store elimination.
2010-09-20 Jakub Jelinek <jakub@redhat.com>
PR rtl-optimization/45695

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2010-09-20 Richard Guenther <rguenther@suse.de>
PR tree-optimization/45705
* gcc.dg/tree-ssa/ssa-dom-dse-1.c: New testcase.
2010-09-20 Michael Matz <matz@suse.de>
PR testsuite/45706

19
gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-dse-1.c Normal file
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@ -0,0 +1,19 @@
/* { dg-do compile } */
/* { dg-options "-O -fdump-tree-optimized" } */
int x;
void
foo (void)
{
if (x == 0)
x = 0;
}
void
bar (int i)
{
if (x == i)
x = i;
}
/* { dg-final { scan-tree-dump-not "x =" "optimized" } } */
/* { dg-final { cleanup-tree-dump "optimized" } } */

42
gcc/tree-ssa-dom.c
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@ -2178,6 +2178,48 @@ optimize_stmt (basic_block bb, gimple_stmt_iterator si)
update_stmt_if_modified (stmt);
eliminate_redundant_computations (&si);
stmt = gsi_stmt (si);
/* Perform simple redundant store elimination. */
if (gimple_assign_single_p (stmt)
&& TREE_CODE (gimple_assign_lhs (stmt)) != SSA_NAME)
{
tree lhs = gimple_assign_lhs (stmt);
tree rhs = gimple_assign_rhs1 (stmt);
tree cached_lhs;
gimple new_stmt;
if (TREE_CODE (rhs) == SSA_NAME)
{
tree tem = SSA_NAME_VALUE (rhs);
if (tem)
rhs = tem;
}
/* Build a new statement with the RHS and LHS exchanged. */
if (TREE_CODE (rhs) == SSA_NAME)
{
gimple defstmt = SSA_NAME_DEF_STMT (rhs);
new_stmt = gimple_build_assign (rhs, lhs);
SSA_NAME_DEF_STMT (rhs) = defstmt;
}
else
new_stmt = gimple_build_assign (rhs, lhs);
gimple_set_vuse (new_stmt, gimple_vuse (stmt));
cached_lhs = lookup_avail_expr (new_stmt, false);
if (cached_lhs
&& rhs == cached_lhs)
{
basic_block bb = gimple_bb (stmt);
int lp_nr = lookup_stmt_eh_lp (stmt);
unlink_stmt_vdef (stmt);
gsi_remove (&si, true);
if (lp_nr != 0)
{
bitmap_set_bit (need_eh_cleanup, bb->index);
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, " Flagged to clear EH edges.\n");
}
return;
}
}
}
/* Record any additional equivalences created by this statement. */