[gcc r14-4405] Avoid left around copies when value-numbering BBs

[gcc r14-4405] Avoid left around copies when value-numbering BBs

[Richard Biener]

https://gcc.gnu.org/g:b583a2940af90d03f535648fef111cb158933f7d

commit r14-4405-gb583a2940af90d03f535648fef111cb158933f7d
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Oct 4 15:25:33 2023 +0200

    Avoid left around copies when value-numbering BBs
    
    The following makes sure to treat values whose definition we didn't
    visit as available since those by definition must dominate the entry
    of the region.  That avoids unpropagated copies after if-conversion
    and resulting SLP discovery fails (which doesn't handle plain copies).
    
            * tree-ssa-sccvn.cc (rpo_elim::eliminate_avail): Not
            visited value numbers are available itself.

Diff:
---
 gcc/tree-ssa-sccvn.cc | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
index e46498568cb..d2aab38c2d2 100644
--- a/gcc/tree-ssa-sccvn.cc
+++ b/gcc/tree-ssa-sccvn.cc
@@ -7688,7 +7688,11 @@ rpo_elim::eliminate_avail (basic_block bb, tree op)
     {
       if (SSA_NAME_IS_DEFAULT_DEF (valnum))
 	return valnum;
-      vn_avail *av = VN_INFO (valnum)->avail;
+      vn_ssa_aux_t valnum_info = VN_INFO (valnum);
+      /* See above.  */
+      if (!valnum_info->visited)
+	return valnum;
+      vn_avail *av = valnum_info->avail;
       if (!av)
 	return NULL_TREE;
       if (av->location == bb->index)