Mesa (staging/18.2): intel: decoder: handle 0 sized structs

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Module: Mesa
Branch: staging/18.2
Commit: 09743ed9fcf46f0d8dcc3d4a44d807c4891af132
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=09743ed9fcf46f0d8dcc3d4a44d807c4891af132

Author: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
Date:   Sat Aug 25 18:22:00 2018 +0100

intel: decoder: handle 0 sized structs

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
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
(cherry picked from commit 440a988bd1478bb33dafcbb8575473bc643ae383)

---

 src/intel/common/gen_decoder.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/intel/common/gen_decoder.c b/src/intel/common/gen_decoder.c
index 4316b7a82e..04de7b7bb8 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;
 }
 
@@ -1006,10 +1006,14 @@ gen_field_iterator_next(struct gen_field_iterator *iter)
          iter_start_field(iter, iter->group->next->fields);
 
       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))