nir/lower_io: Don't use variable to get deref mode

Drivers only use lower_io for modes where pointers don't have a
meaningful value, and dereferences can always be traced back to a
variable. But there can be other modes, like global mode with
VK_EXT_buffer_device_address, where pointers cannot be traced back to a
variable, and lower_io would segfault on loads/stores of these since
nir_deref_instr_get_variable() would return NULL.

Just use the mode on the deref itself to filter out these modes before
we try to get the variable.

Fixes: 118a66df990 ("radv: Use NIR barycentric coordinates")
Reviewed-by: Bas Nieuwenhuizen <[email protected]>

1 files changed, 3 insertions, 2 deletions

diff --git a/src/compiler/nir/nir_lower_io.c b/src/compiler/nir/nir_lower_io.c
index 9275803d6f5..279e6e77b6a 100644
--- a/src/compiler/nir/nir_lower_io.c
+++ b/src/compiler/nir/nir_lower_io.c
@@ -461,8 +461,7 @@ nir_lower_io_block(nir_block *block,
 
       nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
 
-      nir_variable *var = nir_deref_instr_get_variable(deref);
-      nir_variable_mode mode = var->data.mode;
+      nir_variable_mode mode = deref->mode;
 
       if ((state->modes & mode) == 0)
          continue;
@@ -473,6 +472,8 @@ nir_lower_io_block(nir_block *block,
           mode != nir_var_uniform)
          continue;
 
+      nir_variable *var = nir_deref_instr_get_variable(deref);
+
       b->cursor = nir_before_instr(instr);
 
       const bool per_vertex = nir_is_per_vertex_io(var, b->shader->info.stage);