Mesa (master): nir: Add a safety check that we don't remove dead I/ O vars after lowering.

[Eric Anholt]

Module: Mesa
Branch: master
Commit: d9ce4ac990090b3fa940a662655b61359f296be0
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=d9ce4ac990090b3fa940a662655b61359f296be0

Author: Eric Anholt <eric at anholt.net>
Date:   Mon Oct 16 15:32:30 2017 -0700

nir: Add a safety check that we don't remove dead I/O vars after lowering.

The pass only looks at var load/store intrinsics, not input load/store
intrinsics, so assert that we don't see the other type.

v2: Adjust comment indentation.

Reviewed-by: Timothy Arceri <tarceri at itsqueeze.com>

---

 src/compiler/nir/nir_remove_dead_variables.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/src/compiler/nir/nir_remove_dead_variables.c b/src/compiler/nir/nir_remove_dead_variables.c
index a1fe0de9c6..eff66f92d4 100644
--- a/src/compiler/nir/nir_remove_dead_variables.c
+++ b/src/compiler/nir/nir_remove_dead_variables.c
@@ -28,7 +28,8 @@
 #include "nir.h"
 
 static void
-add_var_use_intrinsic(nir_intrinsic_instr *instr, struct set *live)
+add_var_use_intrinsic(nir_intrinsic_instr *instr, struct set *live,
+                      nir_variable_mode modes)
 {
    unsigned num_vars = nir_intrinsic_infos[instr->intrinsic].num_variables;
 
@@ -47,6 +48,14 @@ add_var_use_intrinsic(nir_intrinsic_instr *instr, struct set *live)
       break;
    }
 
+   /* This pass can't be used on I/O variables after they've been lowered. */
+   case nir_intrinsic_load_input:
+      assert(!(modes & nir_var_shader_in));
+      break;
+   case nir_intrinsic_store_output:
+      assert(!(modes & nir_var_shader_out));
+      break;
+
    default:
       for (unsigned i = 0; i < num_vars; i++) {
          _mesa_set_add(live, instr->variables[i]->var);
@@ -84,7 +93,7 @@ add_var_use_tex(nir_tex_instr *instr, struct set *live)
 }
 
 static void
-add_var_use_shader(nir_shader *shader, struct set *live)
+add_var_use_shader(nir_shader *shader, struct set *live, nir_variable_mode modes)
 {
    nir_foreach_function(function, shader) {
       if (function->impl) {
@@ -92,7 +101,8 @@ add_var_use_shader(nir_shader *shader, struct set *live)
             nir_foreach_instr(instr, block) {
                switch(instr->type) {
                case nir_instr_type_intrinsic:
-                  add_var_use_intrinsic(nir_instr_as_intrinsic(instr), live);
+                  add_var_use_intrinsic(nir_instr_as_intrinsic(instr), live,
+                                        modes);
                   break;
 
                case nir_instr_type_call:
@@ -162,7 +172,7 @@ nir_remove_dead_variables(nir_shader *shader, nir_variable_mode modes)
    struct set *live =
       _mesa_set_create(NULL, _mesa_hash_pointer, _mesa_key_pointer_equal);
 
-   add_var_use_shader(shader, live);
+   add_var_use_shader(shader, live, modes);
 
    if (modes & nir_var_uniform)
       progress = remove_dead_vars(&shader->uniforms, live) || progress;