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re PR tree-optimization/80520 (Performance regression from missing if-conversion)

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PR tree-optimization/80520
	* gimple-ssa-split-paths.c (is_feasible_trace): Recognize half
	diamonds that are likely if convertable.

	* gcc.dg/tree-ssa/split-path-5.c: Update expected output.
	* gcc.dg/tree-ssa/split-path-11.c: New test.

From-SVN: r266971
This commit is contained in:
Jeff Law 2018-12-10 21:56:54 -07:00 committed by Jeff Law
parent 72cfde41e5
commit 7b1ff60122
5 changed files with 119 additions and 1 deletions
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6
gcc/ChangeLog
View File

@ -1,3 +1,9 @@
2018-12-10 Jeff Law <law@redhat.com>
PR tree-optimization/80520
* gimple-ssa-split-paths.c (is_feasible_trace): Recognize half
diamonds that are likely if convertable.
2018-12-10 Martin Sebor <msebor@redhat.com>
PR tree-optimization/86196

92
gcc/gimple-ssa-split-paths.c
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@ -203,6 +203,98 @@ is_feasible_trace (basic_block bb)
}
}
/* Canonicalize the form. */
if (num_stmts_in_pred1 == 0 && num_stmts_in_pred2 == 1)
{
std::swap (pred1, pred2);
std::swap (num_stmts_in_pred1, num_stmts_in_pred2);
}
/* Another variant. This one is half-diamond. */
if (num_stmts_in_pred1 == 1 && num_stmts_in_pred2 == 0
&& dominated_by_p (CDI_DOMINATORS, pred1, pred2))
{
gimple *stmt1 = last_and_only_stmt (pred1);
/* The only statement in PRED1 must be an assignment that is
not a good candidate for if-conversion. This may need some
generalization. */
if (stmt1 && gimple_code (stmt1) == GIMPLE_ASSIGN)
{
enum tree_code code1 = gimple_assign_rhs_code (stmt1);
if (!poor_ifcvt_candidate_code (code1))
{
tree lhs1 = gimple_assign_lhs (stmt1);
tree rhs1 = gimple_assign_rhs1 (stmt1);
gimple_stmt_iterator gsi;
for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
{
gimple *phi = gsi_stmt (gsi);
if ((gimple_phi_arg_def (phi, 0) == lhs1
&& gimple_phi_arg_def (phi, 1) == rhs1)
|| (gimple_phi_arg_def (phi, 1) == lhs1
&& gimple_phi_arg_def (phi, 0) == rhs1))
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file,
"Block %d appears to be a join point for "
"if-convertable half-diamond.\n",
bb->index);
return false;
}
}
}
}
}
/* Canonicalize the form. */
if (num_stmts_in_pred1 == 0 && num_stmts_in_pred2 == 1)
{
std::swap (pred1, pred2);
std::swap (num_stmts_in_pred1, num_stmts_in_pred2);
}
/* Another variant. This one is half-diamond. */
if (num_stmts_in_pred1 == 1 && num_stmts_in_pred2 == 0
&& dominated_by_p (CDI_DOMINATORS, pred1, pred2))
{
gimple *stmt1 = last_and_only_stmt (pred1);
/* The only statement in PRED1 must be an assignment that is
not a good candidate for if-conversion. This may need some
generalization. */
if (stmt1 && gimple_code (stmt1) == GIMPLE_ASSIGN)
{
enum tree_code code1 = gimple_assign_rhs_code (stmt1);
if (!poor_ifcvt_candidate_code (code1))
{
tree lhs1 = gimple_assign_lhs (stmt1);
tree rhs1 = gimple_assign_rhs1 (stmt1);
gimple_stmt_iterator gsi;
for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
{
gimple *phi = gsi_stmt (gsi);
if ((gimple_phi_arg_def (phi, 0) == lhs1
&& gimple_phi_arg_def (phi, 1) == rhs1)
|| (gimple_phi_arg_def (phi, 1) == lhs1
&& gimple_phi_arg_def (phi, 0) == rhs1))
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file,
"Block %d appears to be a join point for "
"if-convertable half-diamond.\n",
bb->index);
return false;
}
}
}
}
}
/* If the joiner has no PHIs with useful uses there is zero chance
of CSE/DCE/jump-threading possibilities exposed by duplicating it. */
bool found_useful_phi = false;

6
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,9 @@
2018-12-10 Jeff Law <law@redhat.com>
PR tree-optimization/80520
* gcc.dg/tree-ssa/split-path-5.c: Update expected output.
* gcc.dg/tree-ssa/split-path-11.c: New test.
2018-12-10 Steven G. Kargl <kargl@gcc.gnu.org>
PR fortran/97922

14
gcc/testsuite/gcc.dg/tree-ssa/split-path-11.c Normal file
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@ -0,0 +1,14 @@
/* { dg-do compile } */
/* { dg-options "-O2 -fsplit-paths -fdump-tree-split-paths-details -w" } */
void foo(unsigned long *M)
{
for (unsigned long k = 0; k < 227; ++k)
{
unsigned long y =
((M[k] & 0xffffffff80000000) | (M[k + 1] & 0x7fffffff));
M[k] = (M[k + 397] ^ (y >> 1) ^ ((y & 1) ? 2567483615 : 0));
}
}
/* { dg-final { scan-tree-dump-times "join point for if-convertable half-diamond" 1 "split-paths" } } */

2
gcc/testsuite/gcc.dg/tree-ssa/split-path-5.c
View File

@ -41,4 +41,4 @@ bmhi_init (const char *pattern)
}
}
/* { dg-final { scan-tree-dump-times "Duplicating join block" 1 "split-paths" } } */
/* { dg-final { scan-tree-dump-times "join point for if-convertable half-diamond" 1 "split-paths" } } */