The testcase shows that we fail to clear gimple_call_ctrl_altering_p
when the last abnormal edge goes away, causing an edge insert to
a loop header edge when we have preheaders to split the edge
unnecessarily.
The following addresses this by more aggressively clearing the
flag in cleanup_call_ctrl_altering_flag.
Bootstrapped / tested on x86_64-unknown-linux-gnu, pushed to master.
2020-09-04 Richard Biener <rguent...@suse.de>
PR tree-optimization/96931
* tree-cfgcleanup.c (cleanup_call_ctrl_altering_flag): If
there's a fallthru edge and no abnormal edge the call is
no longer control-altering.
(cleanup_control_flow_bb): Pass down the BB to
cleanup_call_ctrl_altering_flag.
* gcc.dg/pr96931.c: New testcase.
---
gcc/testsuite/gcc.dg/pr96931.c | 19 +++++++++++++++++++
gcc/tree-cfgcleanup.c | 22 ++++++++++++++++++++--
2 files changed, 39 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/pr96931.c
diff --git a/gcc/testsuite/gcc.dg/pr96931.c b/gcc/testsuite/gcc.dg/pr96931.c
new file mode 100644
index 00000000000..94b8a1128ee
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr96931.c
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fpredictive-commoning -fno-tree-loop-im" } */
+
+int bl;
+
+void
+p3 (void);
+
+void __attribute__ ((returns_twice))
+ie (void)
+{
+ p3 ();
+
+ bl = 0;
+ for (;;)
+ ++bl;
+
+ ie ();
+}
diff --git a/gcc/tree-cfgcleanup.c b/gcc/tree-cfgcleanup.c
index 4763cd45a1c..f8169eef781 100644
--- a/gcc/tree-cfgcleanup.c
+++ b/gcc/tree-cfgcleanup.c
@@ -209,7 +209,7 @@ cleanup_control_expr_graph (basic_block bb,
gimple_stmt_iterator gsi)
to updated gimple_call_flags. */
static void
-cleanup_call_ctrl_altering_flag (gimple *bb_end)
+cleanup_call_ctrl_altering_flag (basic_block bb, gimple *bb_end)
{
if (!is_gimple_call (bb_end)
|| !gimple_call_ctrl_altering_p (bb_end))
@@ -220,6 +220,24 @@ cleanup_call_ctrl_altering_flag (gimple *bb_end)
&& !(flags & ECF_LOOPING_CONST_OR_PURE))
|| (flags & ECF_LEAF))
gimple_call_set_ctrl_altering (bb_end, false);
+ else
+ {
+ edge_iterator ei;
+ edge e;
+ bool found = false;
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ if (e->flags & EDGE_FALLTHRU)
+ found = true;
+ else if (e->flags & EDGE_ABNORMAL)
+ {
+ found = false;
+ break;
+ }
+ /* If there's no abnormal edge and a fallthru edge the call
+ isn't control-altering anymore. */
+ if (found)
+ gimple_call_set_ctrl_altering (bb_end, false);
+ }
}
/* Try to remove superfluous control structures in basic block BB. Returns
@@ -243,7 +261,7 @@ cleanup_control_flow_bb (basic_block bb)
stmt = gsi_stmt (gsi);
/* Try to cleanup ctrl altering flag for call which ends bb. */
- cleanup_call_ctrl_altering_flag (stmt);
+ cleanup_call_ctrl_altering_flag (bb, stmt);
if (gimple_code (stmt) == GIMPLE_COND
|| gimple_code (stmt) == GIMPLE_SWITCH)
--
2.26.2
