On Fri, Jan 14, 2022 at 7:21 PM Alexander Monakov <amona...@ispras.ru> wrote:
>
> When a returns_twice call has an associated abnormal edge, the edge
> corresponds to the "second return" from the call. It wouldn't make sense
> if any executable statements appeared between the call and the
> destination of the edge (they wouldn't be re-executed upon the "second
> return"), so verify that.
OK for next stage1.
Thanks,
Richard.
> gcc/ChangeLog:
>
> * tree-cfg.c (gimple_verify_flow_info): Check placement of
> returns_twice calls.
> ---
> gcc/tree-cfg.c | 33 +++++++++++++++++++++++++++++++++
> 1 file changed, 33 insertions(+)
>
> diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
> index a99f1acb4..70bd31d3d 100644
> --- a/gcc/tree-cfg.c
> +++ b/gcc/tree-cfg.c
> @@ -5644,6 +5644,7 @@ gimple_verify_flow_info (void)
> }
>
> /* Verify that body of basic block BB is free of control flow. */
> + bool seen_nondebug_stmt = false;
> for (; !gsi_end_p (gsi); gsi_next (&gsi))
> {
> gimple *stmt = gsi_stmt (gsi);
> @@ -5664,6 +5665,38 @@ gimple_verify_flow_info (void)
> gimple_label_label (label_stmt), bb->index);
> err = 1;
> }
> +
> + /* Check that no statements appear between a returns_twice call
> + and its associated abnormal edge. */
> + if (gimple_code (stmt) == GIMPLE_CALL
> + && gimple_call_flags (stmt) & ECF_RETURNS_TWICE)
> + {
> + const char *misplaced = NULL;
> + /* TM is an exception: it points abnormal edges just after the
> + call that starts a transaction, i.e. it must end the BB. */
> + if (gimple_call_builtin_p (stmt, BUILT_IN_TM_START))
> + {
> + if (single_succ_p (bb)
> + && bb_has_abnormal_pred (single_succ (bb))
> + && !gsi_one_nondebug_before_end_p (gsi))
> + misplaced = "not last";
> + }
> + else
> + {
> + if (seen_nondebug_stmt
> + && bb_has_abnormal_pred (bb))
> + misplaced = "not first";
> + }
> + if (misplaced)
> + {
> + error ("returns_twice call is %s in basic block %d",
> + misplaced, bb->index);
> + print_gimple_stmt (stderr, stmt, 0, TDF_SLIM);
> + err = 1;
> + }
> + }
> + if (!is_gimple_debug (stmt))
> + seen_nondebug_stmt = true;
> }
>
> gsi = gsi_last_nondebug_bb (bb);
> --
> 2.33.1
>
