Hi!
On the following testcase, if the IL before reassoc would be:
...
<bb 4> [local count: 354334800]:
if (x_3(D) == 2)
goto <bb 7>; [34.00%]
else
goto <bb 5>; [66.00%]
<bb 5> [local count: 233860967]:
if (x_3(D) == 3)
goto <bb 7>; [34.00%]
else
goto <bb 6>; [66.00%]
<bb 6> [local count: 79512730]:
<bb 7> [local count: 1073741824]:
# prephitmp_7 = PHI <1(3), 1(4), 1(5), 1(2), 0(6)>
then we'd optimize it properly, but as bb 5-7 is instead:
<bb 5> [local count: 233860967]:
if (x_3(D) == 3)
goto <bb 6>; [34.00%]
else
goto <bb 7>; [66.00%]
<bb 6> [local count: 79512730]:
<bb 7> [local count: 1073741824]:
# prephitmp_7 = PHI <1(3), 1(4), 0(5), 1(2), 1(6)>
(i.e. the true/false edges on the last bb with condition swapped
and ditto for the phi args), we don't recognize it. If bb 6
is empty, there should be no functional difference between the two IL
representations.
This patch handles those special cases.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2020-08-06 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/96480
* tree-ssa-reassoc.c (suitable_cond_bb): Add TEST_SWAPPED_P argument.
If TEST_BB ends in cond and has one edge to *OTHER_BB and another
through an empty bb to that block too, if PHI args don't match, retry
them through the other path from TEST_BB.
(maybe_optimize_range_tests): Adjust callers. Handle such LAST_BB
through inversion of the condition.
* gcc.dg/tree-ssa/pr96480.c: New test.
--- gcc/tree-ssa-reassoc.c.jj 2020-07-30 15:04:38.000000000 +0200
+++ gcc/tree-ssa-reassoc.c 2020-08-06 11:19:30.942825436 +0200
@@ -4127,11 +4127,14 @@ final_range_test_p (gimple *stmt)
of TEST_BB, and *OTHER_BB is either NULL and filled by the routine,
or compared with to find a common basic block to which all conditions
branch to if true resp. false. If BACKWARD is false, TEST_BB should
- be the only predecessor of BB. */
+ be the only predecessor of BB. *TEST_SWAPPED_P is set to true if
+ TEST_BB is a bb ending in condition where the edge to non-*OTHER_BB
+ block points to an empty block that falls through into *OTHER_BB and
+ the phi args match that path. */
static bool
suitable_cond_bb (basic_block bb, basic_block test_bb, basic_block *other_bb,
- bool backward)
+ bool *test_swapped_p, bool backward)
{
edge_iterator ei, ei2;
edge e, e2;
@@ -4196,6 +4199,7 @@ suitable_cond_bb (basic_block bb, basic_
/* Now check all PHIs of *OTHER_BB. */
e = find_edge (bb, *other_bb);
e2 = find_edge (test_bb, *other_bb);
+ retry:;
for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi); gsi_next (&gsi))
{
gphi *phi = gsi.phi ();
@@ -4221,11 +4225,52 @@ suitable_cond_bb (basic_block bb, basic_
else
{
gimple *test_last = last_stmt (test_bb);
- if (gimple_code (test_last) != GIMPLE_COND
- && gimple_phi_arg_def (phi, e2->dest_idx)
- == gimple_assign_lhs (test_last)
- && (integer_zerop (gimple_phi_arg_def (phi, e->dest_idx))
- || integer_onep (gimple_phi_arg_def (phi, e->dest_idx))))
+ if (gimple_code (test_last) == GIMPLE_COND)
+ {
+ if (backward ? e2->src != test_bb : e->src != bb)
+ return false;
+
+ /* For last_bb, handle also:
+ if (x_3(D) == 3)
+ goto <bb 6>; [34.00%]
+ else
+ goto <bb 7>; [66.00%]
+
+ <bb 6> [local count: 79512730]:
+
+ <bb 7> [local count: 1073741824]:
+ # prephitmp_7 = PHI <1(3), 1(4), 0(5), 1(2), 1(6)>
+ where bb 7 is *OTHER_BB, but the PHI values from the
+ earlier bbs match the path through the empty bb
+ in between. */
+ edge e3;
+ if (backward)
+ e3 = EDGE_SUCC (test_bb,
+ e2 == EDGE_SUCC (test_bb, 0) ? 1 : 0);
+ else
+ e3 = EDGE_SUCC (bb,
+ e == EDGE_SUCC (bb, 0) ? 1 : 0);
+ if (empty_block_p (e3->dest)
+ && single_succ_p (e3->dest)
+ && single_succ (e3->dest) == *other_bb
+ && single_pred_p (e3->dest)
+ && single_succ_edge (e3->dest)->flags == EDGE_FALLTHRU)
+ {
+ if (backward)
+ e2 = single_succ_edge (e3->dest);
+ else
+ e = single_succ_edge (e3->dest);
+ if (test_swapped_p)
+ *test_swapped_p = true;
+ goto retry;
+ }
+ }
+ else if (gimple_phi_arg_def (phi, e2->dest_idx)
+ == gimple_assign_lhs (test_last)
+ && (integer_zerop (gimple_phi_arg_def (phi,
+ e->dest_idx))
+ || integer_onep (gimple_phi_arg_def (phi,
+ e->dest_idx))))
continue;
}
@@ -4414,7 +4459,7 @@ maybe_optimize_range_tests (gimple *stmt
while (single_pred_p (first_bb))
{
basic_block pred_bb = single_pred (first_bb);
- if (!suitable_cond_bb (pred_bb, first_bb, &other_bb, true))
+ if (!suitable_cond_bb (pred_bb, first_bb, &other_bb, NULL, true))
break;
if (!no_side_effect_bb (first_bb))
break;
@@ -4444,7 +4489,8 @@ maybe_optimize_range_tests (gimple *stmt
&& gimple_code (stmt) == GIMPLE_COND
&& EDGE_COUNT (e->dest->succs) == 2)
{
- if (suitable_cond_bb (first_bb, e->dest, &other_bb, true))
+ if (suitable_cond_bb (first_bb, e->dest, &other_bb,
+ NULL, true))
break;
else
other_bb = NULL;
@@ -4472,7 +4518,7 @@ maybe_optimize_range_tests (gimple *stmt
break;
if (!single_pred_p (e->dest))
break;
- if (!suitable_cond_bb (e->dest, last_bb, &other_bb, false))
+ if (!suitable_cond_bb (e->dest, last_bb, &other_bb, NULL, false))
break;
if (!no_side_effect_bb (e->dest))
break;
@@ -4583,6 +4629,28 @@ maybe_optimize_range_tests (gimple *stmt
bbinfo.safe_push (bb_ent);
continue;
}
+ else if (bb == last_bb)
+ {
+ /* For last_bb, handle also:
+ if (x_3(D) == 3)
+ goto <bb 6>; [34.00%]
+ else
+ goto <bb 7>; [66.00%]
+
+ <bb 6> [local count: 79512730]:
+
+ <bb 7> [local count: 1073741824]:
+ # prephitmp_7 = PHI <1(3), 1(4), 0(5), 1(2), 1(6)>
+ where bb 7 is OTHER_BB, but the PHI values from the
+ earlier bbs match the path through the empty bb
+ in between. */
+ bool test_swapped_p = false;
+ bool ok = suitable_cond_bb (single_pred (last_bb), last_bb,
+ &other_bb, &test_swapped_p, true);
+ gcc_assert (ok);
+ if (test_swapped_p)
+ e = EDGE_SUCC (bb, e == EDGE_SUCC (bb, 0) ? 1 : 0);
+ }
/* Otherwise stmt is GIMPLE_COND. */
code = gimple_cond_code (stmt);
lhs = gimple_cond_lhs (stmt);
--- gcc/testsuite/gcc.dg/tree-ssa/pr96480.c.jj 2020-08-05 16:08:30.625614787
+0200
+++ gcc/testsuite/gcc.dg/tree-ssa/pr96480.c 2020-08-05 16:02:32.498832099
+0200
@@ -0,0 +1,23 @@
+/* PR tree-optimization/96480 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump " = _\[0-9]* <= 3;" "optimized" } } */
+
+int v[4];
+
+int
+foo (int x)
+{
+ int *p;
+ if (x == 0)
+ p = &v[0];
+ else if (x == 1)
+ p = &v[1];
+ else if (x == 2)
+ p = &v[2];
+ else if (x == 3)
+ p = &v[3];
+ else
+ p = &v[4];
+ return p != &v[4];
+}
Jakub
