[mid-end] Add notes to dataflow insn info when re-emitting (PR92410)

Programming / Compilers / GCC - matmal01 [138bc75d-0d04-0410-961f-82ee72b054a4] - 9 December 2019 12:03 EST

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, and these labels not having 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: Ran regression tests on aarch64-none-linux-gnu cross compiler. Bootstrapped and ran tests on aarch64-none-linux-gnu native.

gcc/ChangeLog:

2019-12-09 Matthew Malcomson

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:

2019-12-09 Matthew Malcomson

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

b2e4a1f1d4e [mid-end] Add notes to dataflow insn info when re-emitting (PR92410)
gcc/ChangeLog | 10 ++++++++++
gcc/bb-reorder.c | 2 ++
gcc/haifa-sched.c | 1 +
gcc/regstat.c | 1 +
gcc/testsuite/ChangeLog | 5 +++++
gcc/testsuite/gcc.dg/torture/pr92410.c | 8 ++++++++
6 files changed, 27 insertions(+)

Upstream: gcc.gnu.org


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