On February 5, 2019 4:32:29 PM GMT+01:00, Jakub Jelinek <ja...@redhat.com>
wrote:
>Hi!
>
>RTL DCE is called in different modes, sometimes it is allowed to alter
>cfg,
>in other cases it is not. The following testcase ICEs because when it
>is
>not allowed to alter cfg (combiner's df_analyze) we remove a noop move
>that
>was considered to potentially throw and that made a bb unreachable
>(which
>the pass didn't like), but even removing those unreachable bbs would
>ICE
>anyway, as the algorithm is for !can_alter_cfg not really prepared to
>see
>bbs and edges being removed.
>
>So, the following patch does 3 things:
>1) doesn't delete noop moves if they can
> throw and we can't alter cfg or delete dead exceptions
>2) instead of setting must_clean blindly for any CALL_INSNs, it instead
> sets it accurately from delete_insn_and_edges return value
>3) it asserts that if !can_alter_cfg we don't actually have must_clean
>set
>
>Bootstrapped/regtested on powerpc64{,le}-linux, ok for trunk?
OK.
Richard.
>2019-02-05 Jakub Jelinek <ja...@redhat.com>
>
> PR target/89188
> * dce.c (delete_unmarked_insns): Don't remove no-op moves if they
> can throw, non-call exceptions are enabled and we can't delete
> dead exceptions or alter cfg. Set must_clean if
> delete_insn_and_edges returns true, don't set it blindly for calls.
> Assert that delete_unreachable_blocks is called only if can_alter_cfg.
>
> * g++.dg/opt/pr89188.C: New test.
>
>--- gcc/dce.c.jj 2019-02-05 10:04:16.984062429 +0100
>+++ gcc/dce.c 2019-02-05 10:53:47.655584503 +0100
>@@ -584,7 +584,12 @@ delete_unmarked_insns (void)
> rtx turn_into_use = NULL_RTX;
>
> /* Always delete no-op moves. */
>- if (noop_move_p (insn))
>+ if (noop_move_p (insn)
>+ /* Unless the no-op move can throw and we are not allowed
>+ to alter cfg. */
>+ && (!cfun->can_throw_non_call_exceptions
>+ || (cfun->can_delete_dead_exceptions && can_alter_cfg)
>+ || insn_nothrow_p (insn)))
> {
> if (RTX_FRAME_RELATED_P (insn))
> turn_into_use
>@@ -627,12 +632,6 @@ delete_unmarked_insns (void)
> for the destination regs in order to avoid dangling notes. */
> remove_reg_equal_equiv_notes_for_defs (insn);
>
>- /* If a pure or const call is deleted, this may make the cfg
>- have unreachable blocks. We rememeber this and call
>- delete_unreachable_blocks at the end. */
>- if (CALL_P (insn))
>- must_clean = true;
>-
> if (turn_into_use)
> {
> /* Don't remove frame related noop moves if they cary
>@@ -645,12 +644,15 @@ delete_unmarked_insns (void)
> }
> else
> /* Now delete the insn. */
>- delete_insn_and_edges (insn);
>+ must_clean |= delete_insn_and_edges (insn);
> }
>
> /* Deleted a pure or const call. */
> if (must_clean)
>- delete_unreachable_blocks ();
>+ {
>+ gcc_assert (can_alter_cfg);
>+ delete_unreachable_blocks ();
>+ }
> }
>
>
>--- gcc/testsuite/g++.dg/opt/pr89188.C.jj 2019-02-04 14:20:57.714851393
>+0100
>+++ gcc/testsuite/g++.dg/opt/pr89188.C 2019-02-04 14:52:09.988782531
>+0100
>@@ -0,0 +1,5 @@
>+// PR target/89188
>+// { dg-do compile { target c++11 } }
>+// { dg-options "-Og -flive-range-shrinkage -fnon-call-exceptions" }
>+
>+#include "../torture/pr88861.C"
>
> Jakub
