Hi!
The following testcase fails with -fcompare-debug, the bug used to be latent
since introduction of -fcompare-debug.
The loop at the start of purge_dead_edges behaves differently between -g0
and -g - if the last insn is a DEBUG_INSN, then it skips not just
DEBUG_INSNs but also NOTEs until it finds some other real insn (or bb head),
while with -g0 it will not skip any NOTEs, so if we have
real_insn
note
debug_insn // not present with -g0
then with -g it might remove useless REG_EH_REGION from real_insn, while
with -g0 it will not.
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?
Yet another option would be not skipping NOTE_P in the loop; I couldn't find
in history rationale for why it is done.
2020-05-13 Jakub Jelinek <ja...@redhat.com>
PR debug/95080
* cfgrtl.c (purge_dead_edges): Skip over debug and note insns even
if the last insn is a note.
* g++.dg/opt/pr95080.C: New test.
--- gcc/cfgrtl.c.jj 2020-04-17 10:32:58.589780140 +0200
+++ gcc/cfgrtl.c 2020-05-12 21:02:09.808395583 +0200
@@ -3100,7 +3100,7 @@ purge_dead_edges (basic_block bb)
bool found;
edge_iterator ei;
- if (DEBUG_INSN_P (insn) && insn != BB_HEAD (bb))
+ if ((DEBUG_INSN_P (insn) || NOTE_P (insn)) && insn != BB_HEAD (bb))
do
insn = PREV_INSN (insn);
while ((DEBUG_INSN_P (insn) || NOTE_P (insn)) && insn != BB_HEAD (bb));
--- gcc/testsuite/g++.dg/opt/pr95080.C.jj 2020-05-12 21:01:09.804295824
+0200
+++ gcc/testsuite/g++.dg/opt/pr95080.C 2020-05-12 21:00:52.738551862 +0200
@@ -0,0 +1,41 @@
+// PR debug/95080
+// { dg-do compile }
+// { dg-options "-Og -fcse-follow-jumps -fnon-call-exceptions -fcompare-debug"
}
+
+char *a;
+
+void baz ();
+
+static inline bool
+bar ()
+{
+ int j = a[0] - 1;
+ switch (j)
+ {
+ case 0:
+ case 2:
+ return true;
+ default:
+ return false;
+ }
+}
+
+static inline bool
+foo ()
+{
+ if (bar ())
+ baz ();
+ return 0;
+}
+
+struct S
+{
+ int h;
+ ~S ();
+};
+
+S::~S ()
+{
+ if (a[0] == 0)
+ foo () != h;
+}
Jakub
