[Mesa-stable] [PATCH] nir/vars_to_ssa: Rework copy set handling in lower_copies_to_load_store

[Jason Ekstrand]

Previously, we walked through a given deref_node's copies and, after
lowering the copy away, removed it from both the source and destination
copy sets.  This commit changes this to only remove it from the other
node's copy set (not the one we're lowering).  At the end of the loop, we
just throw away the copy set for the node we're lowering since that node no
longer has any copies.  This has two advantages:

 1) It's more efficient because we're doing potentially half as many set
    search operations.

 2) It now properly handles copies from a node to itself.  Perviously, it
    would delete the copy from the set when processing the destinatioon and
    then assert-fail when we couldn't find it for the source.

Cc: "11.0" <mesa-stable at lists.freedesktop.org>
Cc: Timothy Arceri <timothy.arceri at collabora.com>
---
 src/glsl/nir/nir_lower_vars_to_ssa.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/glsl/nir/nir_lower_vars_to_ssa.c b/src/glsl/nir/nir_lower_vars_to_ssa.c
index 5971507..df24510 100644
--- a/src/glsl/nir/nir_lower_vars_to_ssa.c
+++ b/src/glsl/nir/nir_lower_vars_to_ssa.c
@@ -455,7 +455,8 @@ lower_copies_to_load_store(struct deref_node *node,
          struct deref_node *arg_node =
             get_deref_node(copy->variables[i], state);
 
-         if (arg_node == NULL)
+         /* Only bother removing copy entries for other nodes */
+         if (arg_node == NULL || arg_node == node)
             continue;
 
          struct set_entry *arg_entry = _mesa_set_search(arg_node->copies, copy);
@@ -466,6 +467,8 @@ lower_copies_to_load_store(struct deref_node *node,
       nir_instr_remove(&copy->instr);
    }
 
+   node->copies = NULL;
+
    return true;
 }
 
-- 
2.5.0.400.gff86faf