aco: skip NIR in unreachable merge blocks

NIR removes most of this but undef instructions for loop header phis can
remain. These were harmless because ACO would DCE them itself.

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
CC: <mesa-stable@lists.freedesktop.org>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3658>

diff --git a/src/amd/compiler/aco_instruction_selection.cpp b/src/amd/compiler/aco_instruction_selection.cpp
index 52db7f4a6b3dc3c271345c094962f61695568878..59668fb4bc166e7aa419d45a42a251d519f1b12c 100644 (file)
--- a/src/amd/compiler/aco_instruction_selection.cpp
+++ b/src/amd/compiler/aco_instruction_selection.cpp
@@ -8822,7 +8822,7 @@ static void end_divergent_if(isel_context *ctx, if_context *ic)
    }
 }
 
-static void visit_if(isel_context *ctx, nir_if *if_stmt)
+static bool visit_if(isel_context *ctx, nir_if *if_stmt)
 {
    Temp cond = get_ssa_temp(ctx, if_stmt->condition.ssa);
    Builder bld(ctx->program, ctx->block);
@@ -8915,6 +8915,7 @@ static void visit_if(isel_context *ctx, nir_if *if_stmt)
          ctx->block = ctx->program->insert_block(std::move(BB_endif));
          append_logical_start(ctx->block);
       }
+      return !ctx->cf_info.has_branch;
    } else { /* non-uniform condition */
       /**
        * To maintain a logical and linear CFG without critical edges,
@@ -8950,6 +8951,8 @@ static void visit_if(isel_context *ctx, nir_if *if_stmt)
       visit_cf_list(ctx, &if_stmt->else_list);
 
       end_divergent_if(ctx, &ic);
+
+      return true;
    }
 }
 
@@ -8962,7 +8965,8 @@ static void visit_cf_list(isel_context *ctx,
          visit_block(ctx, nir_cf_node_as_block(node));
          break;
       case nir_cf_node_if:
-         visit_if(ctx, nir_cf_node_as_if(node));
+         if (!visit_if(ctx, nir_cf_node_as_if(node)))
+            return;
          break;
       case nir_cf_node_loop:
          visit_loop(ctx, nir_cf_node_as_loop(node));