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re PR tree-optimization/60098 (DSE fails to DSE errno settings) 

2014-06-04  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/60098
	* tree-ssa-dse.c (dse_possible_dead_store_p): Walk until
	we hit a kill.
	(dse_optimize_stmt): Simplify, now that we found a kill
	earlier.

	* gcc.dg/tree-ssa/ssa-dse-15.c: New testcase.

From-SVN: r211224
This commit is contained in:
Richard Biener 2014-06-04 11:56:34 +00:00 committed by Richard Biener
parent b1259d34e9
commit 0ea48022b8
4 changed files with 74 additions and 47 deletions
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8
gcc/ChangeLog
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@ -1,3 +1,11 @@
2014-06-04 Richard Biener <rguenther@suse.de>
PR tree-optimization/60098
* tree-ssa-dse.c (dse_possible_dead_store_p): Walk until
we hit a kill.
(dse_optimize_stmt): Simplify, now that we found a kill
earlier.
2014-06-04 Richard Biener <rguenther@suse.de>
* tree-ssa-alias.c (stmt_may_clobber_ref_p): Improve handling

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2014-06-04 Richard Biener <rguenther@suse.de>
PR tree-optimization/60098
* gcc.dg/tree-ssa/ssa-dse-15.c: New testcase.
2014-06-04 Richard Biener <rguenther@suse.de>
* gcc.dg/tree-ssa/ssa-dse-16.c: New testcase.

24
gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-15.c Normal file
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@ -0,0 +1,24 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-dse1-details" } */
void *foo (int *p)
{
void *q;
/* We should be able to DSE this store (p may point to errno). */
*p = 0;
q = __builtin_malloc (4);
*p = 0;
return q;
}
int j;
void bar (int *i)
{
/* This store is dead as well. */
j = 1;
*i = 0;
j = 2;
}
/* { dg-final { scan-tree-dump-times "Deleted dead store" 2 "dse1" } } */
/* { dg-final { cleanup-tree-dump "dse1" } } */

84
gcc/tree-ssa-dse.c
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@ -198,10 +198,8 @@ dse_possible_dead_store_p (gimple stmt, gimple *use_stmt)
break;
}
}
/* We deliberately stop on clobbering statements and not only on
killing ones to make walking cheaper. Otherwise we can just
continue walking until both stores have equal reference trees. */
while (!stmt_may_clobber_ref_p (temp, gimple_assign_lhs (stmt)));
/* Continue walking until we reach a kill. */
while (!stmt_kills_ref_p (temp, gimple_assign_lhs (stmt)));
*use_stmt = temp;
@ -248,57 +246,49 @@ dse_optimize_stmt (gimple_stmt_iterator *gsi)
if (!dse_possible_dead_store_p (stmt, &use_stmt))
return;
/* Now we know that use_stmt kills the LHS of stmt. */
/* But only remove *this_2(D) ={v} {CLOBBER} if killed by
another clobber stmt. */
if (gimple_clobber_p (stmt)
&& !gimple_clobber_p (use_stmt))
return;
/* If we have precisely one immediate use at this point and the
stores are to the same memory location or there is a chain of
virtual uses from stmt and the stmt which stores to that same
memory location, then we may have found redundant store. */
if ((gimple_has_lhs (use_stmt)
&& (operand_equal_p (gimple_assign_lhs (stmt),
gimple_get_lhs (use_stmt), 0)))
|| stmt_kills_ref_p (use_stmt, gimple_assign_lhs (stmt)))
basic_block bb;
/* If use_stmt is or might be a nop assignment, e.g. for
struct { ... } S a, b, *p; ...
b = a; b = b;
or
b = a; b = *p; where p might be &b,
or
*p = a; *p = b; where p might be &b,
or
*p = *u; *p = *v; where p might be v, then USE_STMT
acts as a use as well as definition, so store in STMT
is not dead. */
if (stmt != use_stmt
&& ref_maybe_used_by_stmt_p (use_stmt, gimple_assign_lhs (stmt)))
return;
if (dump_file && (dump_flags & TDF_DETAILS))
{
basic_block bb;
/* If use_stmt is or might be a nop assignment, e.g. for
struct { ... } S a, b, *p; ...
b = a; b = b;
or
b = a; b = *p; where p might be &b,
or
*p = a; *p = b; where p might be &b,
or
*p = *u; *p = *v; where p might be v, then USE_STMT
acts as a use as well as definition, so store in STMT
is not dead. */
if (stmt != use_stmt
&& ref_maybe_used_by_stmt_p (use_stmt, gimple_assign_lhs (stmt)))
return;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, " Deleted dead store '");
print_gimple_stmt (dump_file, gsi_stmt (*gsi), dump_flags, 0);
fprintf (dump_file, "'\n");
}
/* Then we need to fix the operand of the consuming stmt. */
unlink_stmt_vdef (stmt);
/* Remove the dead store. */
bb = gimple_bb (stmt);
if (gsi_remove (gsi, true))
bitmap_set_bit (need_eh_cleanup, bb->index);
/* And release any SSA_NAMEs set in this statement back to the
SSA_NAME manager. */
release_defs (stmt);
fprintf (dump_file, " Deleted dead store '");
print_gimple_stmt (dump_file, gsi_stmt (*gsi), dump_flags, 0);
fprintf (dump_file, "'\n");
}
/* Then we need to fix the operand of the consuming stmt. */
unlink_stmt_vdef (stmt);
/* Remove the dead store. */
bb = gimple_bb (stmt);
if (gsi_remove (gsi, true))
bitmap_set_bit (need_eh_cleanup, bb->index);
/* And release any SSA_NAMEs set in this statement back to the
SSA_NAME manager. */
release_defs (stmt);
}
}