[Mesa-dev] [PATCH 07/11] nir/cf: Fix dominance metadata in the dead control flow pass.

[Kenneth Graunke]

The NIR control flow modification API churns the block structure,
splitting blocks, stitching them back together, and so on.  Preserving
information about block dominance is hard (and probably not worthwhile).

This patch makes nir_cf_extract() throw away all metadata, like we do
when adding/removing jumps.

We then make the dead control flow pass compute dominance information
right before it uses it.  This is necessary because earlier work by the
pass may have invalidated it.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/glsl/nir/nir_control_flow.c | 3 +++
 src/glsl/nir/nir_opt_dead_cf.c  | 7 ++++---
 2 files changed, 7 insertions(+), 3 deletions(-)

New patch!

diff --git a/src/glsl/nir/nir_control_flow.c b/src/glsl/nir/nir_control_flow.c
index e027766..8ec1252 100644
--- a/src/glsl/nir/nir_control_flow.c
+++ b/src/glsl/nir/nir_control_flow.c
@@ -742,6 +742,9 @@ nir_cf_extract(nir_cf_list *extracted, nir_cursor begin, nir_cursor end)
    extracted->impl = nir_cf_node_get_function(&block_begin->cf_node);
    exec_list_make_empty(&extracted->list);
 
+   /* Dominance and other block-related information is toast. */
+   nir_metadata_preserve(extracted->impl, nir_metadata_none);
+
    nir_cf_node *cf_node = &block_begin->cf_node;
    nir_cf_node *cf_node_end = &block_end->cf_node;
    while (true) {
diff --git a/src/glsl/nir/nir_opt_dead_cf.c b/src/glsl/nir/nir_opt_dead_cf.c
index 317bbc5..0d4819b 100644
--- a/src/glsl/nir/nir_opt_dead_cf.c
+++ b/src/glsl/nir/nir_opt_dead_cf.c
@@ -203,6 +203,10 @@ loop_is_dead(nir_loop *loop)
                                      NULL))
       return false;
 
+   nir_function_impl *impl = nir_cf_node_get_function(&loop->cf_node);
+   nir_metadata_require(impl, nir_metadata_live_variables |
+                              nir_metadata_dominance);
+
    for (nir_block *cur = after->imm_dom; cur != before; cur = cur->imm_dom) {
       nir_foreach_instr(cur, instr) {
          if (!nir_foreach_ssa_def(instr, def_not_live_out, after))
@@ -332,9 +336,6 @@ dead_cf_list(struct exec_list *list, bool *list_ends_in_jump)
 static bool
 opt_dead_cf_impl(nir_function_impl *impl)
 {
-   nir_metadata_require(impl, nir_metadata_live_variables |
-                              nir_metadata_dominance);
-
    bool dummy;
    bool progress = dead_cf_list(&impl->body, &dummy);
 
-- 
2.5.3