On Fri, Aug 12, 2022 at 12:59 PM Richard Biener <rguent...@suse.de> wrote:
>
> With the last re-org I failed to make sure to not add SSA names
> nor supported by ranger into m_imports which then triggers an
> ICE in range_on_path_entry because range_of_expr returns false. I've
> noticed that range_on_path_entry does mightly complicated things
> that don't make sense to me and the commentary might just be
> out of date. For the sake of it I replaced it with range_on_entry
> and statistics show we thread _more_ jumps with that, so better
> not do magic there.
Hang on, hang on. range_on_path_entry was written that way for a
reason. Andrew and I had numerous discussions about this. For that
matter, my first implementation did exactly what you're proposing, but
he had reservations about using range_on_entry, which IIRC he thought
should be removed from the (public) API because it had a tendency to
blow up lookups.
Let's wait for Andrew to chime in on this. If indeed the commentary
is out of date, I would much rather use range_on_entry like you
propose, but he and I have fought many times about this... over
various versions of the path solver :).
For now I would return VARYING in range_on_path_entry if range_of_expr
returns false. We shouldn't be ICEing when we can gracefully handle
things. This gcc_unreachable was there to catch implementation issues
during development.
I would keep your gimple_range_ssa_p check regardless. No sense doing
extra work if we're absolutely sure we won't handle it.
Aldy
>
> Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
>
> Will push if that succeeds.
>
> PR tree-optimization/106593
> * tree-ssa-threadbackward.cc (back_threader::find_paths):
> If the imports from the conditional do not satisfy
> gimple_range_ssa_p don't try to thread anything.
> * gimple-range-path.cc (range_on_path_entry): Just
> call range_on_entry.
> ---
> gcc/gimple-range-path.cc | 33 +--------------------------------
> gcc/tree-ssa-threadbackward.cc | 6 +++++-
> 2 files changed, 6 insertions(+), 33 deletions(-)
>
> diff --git a/gcc/gimple-range-path.cc b/gcc/gimple-range-path.cc
> index b6148eb5bd7..a7d277c31b8 100644
> --- a/gcc/gimple-range-path.cc
> +++ b/gcc/gimple-range-path.cc
> @@ -153,38 +153,7 @@ path_range_query::range_on_path_entry (vrange &r, tree
> name)
> {
> gcc_checking_assert (defined_outside_path (name));
> basic_block entry = entry_bb ();
> -
> - // Prefer to use range_of_expr if we have a statement to look at,
> - // since it has better caching than range_on_edge.
> - gimple *last = last_stmt (entry);
> - if (last)
> - {
> - if (m_ranger->range_of_expr (r, name, last))
> - return;
> - gcc_unreachable ();
> - }
I
> -
> - // If we have no statement, look at all the incoming ranges to the
> - // block. This can happen when we're querying a block with only an
> - // outgoing edge (no statement but the fall through edge), but for
> - // which we can determine a range on entry to the block.
> - Value_Range tmp (TREE_TYPE (name));
> - bool changed = false;
> - r.set_undefined ();
> - for (unsigned i = 0; i < EDGE_COUNT (entry->preds); ++i)
> - {
> - edge e = EDGE_PRED (entry, i);
> - if (e->src != ENTRY_BLOCK_PTR_FOR_FN (cfun)
> - && m_ranger->range_on_edge (tmp, e, name))
> - {
> - r.union_ (tmp);
> - changed = true;
> - }
> - }
> -
> - // Make sure we don't return UNDEFINED by mistake.
> - if (!changed)
> - r.set_varying (TREE_TYPE (name));
> + m_ranger->range_on_entry (r, entry, name);
> }
>
> // Return the range of NAME at the end of the path being analyzed.
> diff --git a/gcc/tree-ssa-threadbackward.cc b/gcc/tree-ssa-threadbackward.cc
> index 0a992213dad..669098e4ec3 100644
> --- a/gcc/tree-ssa-threadbackward.cc
> +++ b/gcc/tree-ssa-threadbackward.cc
> @@ -525,7 +525,11 @@ back_threader::find_paths (basic_block bb, tree name)
> bitmap_clear (m_imports);
> ssa_op_iter iter;
> FOR_EACH_SSA_TREE_OPERAND (name, stmt, iter, SSA_OP_USE)
> - bitmap_set_bit (m_imports, SSA_NAME_VERSION (name));
> + {
> + if (!gimple_range_ssa_p (name))
> + return;
> + bitmap_set_bit (m_imports, SSA_NAME_VERSION (name));
> + }
>
> // Interesting is the set of imports we still not have see
> // the definition of. So while imports only grow, the
> --
> 2.35.3
>
