Hi!
delete_insn_and_edges calls purge_dead_edges whenever deleting the last insn
in a bb, whatever it is. If it called it only for mandatory last insns
in the basic block (that may not be followed by DEBUG_INSNs, dunno if that
is control_flow_insn_p or something more complex), that wouldn't be a
problem, but as it calls it on any last insn and can actually do something
in the bb, if such an insn is followed by one more more DEBUG_INSNs and
nothing else in the same bb, we don't call purge_dead_edges with -g and do
call it with -g0.
On the testcase, there are two reg-to-reg moves with REG_EH_REGION notes
(previously memory accesses but simplified and yet not optimized), and the
second is followed by DEBUG_INSNs; the second move is delete_insn_and_edges
and after removing it, for -g0 purge_dead_edges removes the REG_EH_REGION
from the now last insn in the bb (the first reg-to-reg move), while
for -g it isn't called and things diverge from that quickly on.
Fixed by calling purdge_dead_edges even if we remove the last real insn
followed only by DEBUG_INSNs in the same bb.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2020-04-17 Jakub Jelinek <ja...@redhat.com>
PR rtl-optimization/94618
* cfgrtl.c (delete_insn_and_edges): Set purge not just when
insn is the BB_END of its block, but also when it is only followed
by DEBUG_INSNs in its block.
* g++.dg/opt/pr94618.C: New test.
--- gcc/cfgrtl.c.jj 2020-01-12 11:54:36.218416351 +0100
+++ gcc/cfgrtl.c 2020-04-16 17:28:00.792849169 +0200
@@ -230,10 +230,20 @@ delete_insn_and_edges (rtx_insn *insn)
{
bool purge = false;
- if (INSN_P (insn)
- && BLOCK_FOR_INSN (insn)
- && BB_END (BLOCK_FOR_INSN (insn)) == insn)
- purge = true;
+ if (INSN_P (insn) && BLOCK_FOR_INSN (insn))
+ {
+ basic_block bb = BLOCK_FOR_INSN (insn);
+ if (BB_END (bb) == insn)
+ purge = true;
+ else if (DEBUG_INSN_P (BB_END (bb)))
+ for (rtx_insn *dinsn = NEXT_INSN (insn);
+ DEBUG_INSN_P (dinsn); dinsn = NEXT_INSN (dinsn))
+ if (BB_END (bb) == dinsn)
+ {
+ purge = true;
+ break;
+ }
+ }
delete_insn (insn);
if (purge)
return purge_dead_edges (BLOCK_FOR_INSN (insn));
--- gcc/testsuite/g++.dg/opt/pr94618.C.jj 2020-04-16 17:32:45.891637523
+0200
+++ gcc/testsuite/g++.dg/opt/pr94618.C 2020-04-16 17:32:22.715979882 +0200
@@ -0,0 +1,25 @@
+// PR rtl-optimization/94618
+// { dg-do compile { target c++11 } }
+// { dg-options "-O2 -fnon-call-exceptions -fcompare-debug" }
+
+struct S
+{
+ int a, b, c;
+ int foo () noexcept { return a; }
+ int bar () noexcept { return b; }
+ void baz (int);
+ void qux () { if (c) for (int x = foo (); x != bar (); ) baz (x); }
+};
+
+struct T
+{
+ S s;
+ void foo ();
+};
+
+void
+T::foo ()
+{
+ s.qux ();
+ s.qux ();
+}
Jakub
