In scheduling passes, notes are removed with `remove_notes` before the
scheduling is done, and added back in with `reemit_notes` once the
scheduling has been decided.

This process leaves the notes in the RTL chain with different insn uid's
than were there before.  Having different UID's (larger than the
previous ones) means that DF_INSN_INFO_GET(insn) will access outside of
the allocated array.

This has been seen in the `regstat_bb_compute_calls_crossed` function.
This patch adds an assert to the `regstat_bb_compute_calls_crossed`
function so that bad accesses here are caught instead of going
unnoticed, and then avoids the problem.

We avoid the problem by ensuring that new notes added by `reemit_notes` have an
insn record given to them.  This is done by adding a call to
`df_insn_create_insn_record` on each note added in `reemit_notes`.
`df_insn_create_insn_record` leaves this new record zeroed out, which appears
to be fine for notes (e.g. `df_bb_refs_record` already does not set
anything except the luid for notes, and notes have no dataflow information to
record).

We add the testcase that Martin found here
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92410#c2 .
This testcase fails with the "regstat.c" change, and then succeeds with the
"haifa-sched.c" change.

There is a similar problem with labels, that the `gcc_assert` catches
when running regression tests in gcc.dg/fold-eqandshift-1.c and
gcc.c-torture/compile/pr32482.c.
This is due to the `cfg_layout_finalize` call in `bb-reorder.c` emitting
new labels for the start of the newly created basic blocks. These labels are
not given a dataflow df_insn_info member.

We solve this by manually calling `df_recompute_luids` on each basic
block once this pass has finished.

Testing done:
  Bootstrapped and regression test on aarch64-none-linux-gnu native.

gcc/ChangeLog:

2019-11-12  Matthew Malcomson  <matthew.malcomson@arm.com>

	PR middle-end/92410
	* bb-reorder.c (pass_reorder_blocks::execute): Recompute
	dataflow luids once basic blocks have been reordered.
	* haifa-sched.c (reemit_notes): Create df insn record for each
	new note.
	* regstat.c (regstat_bb_compute_calls_crossed): Assert every
	insn has an insn record before trying to use it.

gcc/testsuite/ChangeLog:

2019-11-12  Matthew Malcomson  <matthew.malcomson@arm.com>

	PR middle-end/92410
	* gcc.dg/torture/pr92410.c: New test.



###############     Attachment also inlined for ease of reply    ###############


diff --git a/gcc/bb-reorder.c b/gcc/bb-reorder.c
index 0ac39140c6ce3db8499f99cd8f483218888de61b..4943f97a2cfccc7ab7c4834fff2c81f62fc5b738 100644
--- a/gcc/bb-reorder.c
+++ b/gcc/bb-reorder.c
@@ -2662,6 +2662,8 @@ pass_reorder_blocks::execute (function *fun)
       bb->aux = bb->next_bb;
   cfg_layout_finalize ();
 
+  FOR_EACH_BB_FN (bb, fun)
+    df_recompute_luids (bb);
   return 0;
 }
 
diff --git a/gcc/haifa-sched.c b/gcc/haifa-sched.c
index 41cf1f362e8c34d009b0a310ff5b9a9ffb613631..2e1a84f1325d54ece1cf3c6f0bab607099c71d27 100644
--- a/gcc/haifa-sched.c
+++ b/gcc/haifa-sched.c
@@ -5433,6 +5433,7 @@ reemit_notes (rtx_insn *insn)
 
 	  last = emit_note_before (note_type, last);
 	  remove_note (insn, note);
+	  df_insn_create_insn_record (last);
 	}
     }
 }
diff --git a/gcc/regstat.c b/gcc/regstat.c
index 4da9b7cc523cde113df931226ea56310b659e619..c6cefb117d7330cc1b9787c37083e05e2acda2d2 100644
--- a/gcc/regstat.c
+++ b/gcc/regstat.c
@@ -324,6 +324,7 @@ regstat_bb_compute_calls_crossed (unsigned int bb_index, bitmap live)
 
   FOR_BB_INSNS_REVERSE (bb, insn)
     {
+      gcc_assert (INSN_UID (insn) < DF_INSN_SIZE ());
       struct df_insn_info *insn_info = DF_INSN_INFO_GET (insn);
       unsigned int regno;
 
diff --git a/gcc/testsuite/gcc.dg/torture/pr92410.c b/gcc/testsuite/gcc.dg/torture/pr92410.c
new file mode 100644
index 0000000000000000000000000000000000000000..628e329782260ef36f26506bfbc0d36a93b33f41
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr92410.c
@@ -0,0 +1,8 @@
+/* PR middle-end/92410  */
+/* { dg-do compile } */
+int v;
+
+int a() {
+  ;
+  return v;
+}