[Mesa-dev] [PATCH 1/2] intel: decoder: handle 0 sized structs

[Lionel Landwerlin]

Gen7.5 has a BLEND_STATE of size 0 which includes a variable length
group. We did not deal with that very well, leading to an endless
loop.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107544
---
 src/intel/common/gen_decoder.c | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/src/intel/common/gen_decoder.c b/src/intel/common/gen_decoder.c
index ec0a486b101..daaf772a59f 100644
--- a/src/intel/common/gen_decoder.c
+++ b/src/intel/common/gen_decoder.c
@@ -991,7 +991,7 @@ gen_field_iterator_init(struct gen_field_iterator *iter,
    iter->p_bit = p_bit;
 
    int length = gen_group_get_length(iter->group, iter->p);
-   iter->p_end = length > 0 ? &p[length] : NULL;
+   iter->p_end = length >= 0 ? &p[length] : NULL;
    iter->print_colors = print_colors;
 }
 
@@ -1000,16 +1000,32 @@ gen_field_iterator_next(struct gen_field_iterator *iter)
 {
    /* Initial condition */
    if (!iter->field) {
-      if (iter->group->fields)
+      if (iter->group->fields) {
+         /* We have an instruction/struct with at least one field. */
          iter->field = iter->group->fields;
-      else
+      } else if (iter->group->next) {
+         /* We have an instruction/struct with no fields but at least a
+          * group.
+          */
          iter->field = iter->group->next->fields;
+         iter->struct_desc =
+            gen_spec_find_struct(iter->group->spec,
+                                 iter->field->type.gen_struct->name);
+      } else {
+         /* Please fix genxml. */
+         unreachable("Empty struct/instruction");
+         return false;
+      }
 
       bool result = iter_decode_field(iter);
-      if (iter->p_end)
-         assert(result);
+      if (!result && iter->p_end) {
+         /* We're dealing with a non empty struct of length=0 (BLEND_STATE on
+          * Gen 7.5)
+          */
+         assert(iter->group->dw_length == 0);
+      }
 
-      return true;
+      return result;
    }
 
    if (!iter_advance_field(iter))
-- 
2.18.0