[PATCH] tree-optimization/106593 - fix ICE with backward threading

[Richard Biener <rguenther@suse.de>]

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out of date.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.

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 ();
-    }
-
-  // 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