pan/bi: Document constant count invariant

   constants + instructions <= 13

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5260>

diff --git a/src/panfrost/bifrost/compiler.h b/src/panfrost/bifrost/compiler.h
index 43bd8bb..e4d37a8 100644 (file)
--- a/src/panfrost/bifrost/compiler.h
+++ b/src/panfrost/bifrost/compiler.h
@@ -373,7 +373,13 @@ typedef struct {
         /* Corresponds to the usual bit but shifted by a clause */
         bool data_register_write_barrier;
 
-        /* Constants read by this clause. ISA limit. */
+        /* Constants read by this clause. ISA limit. Must satisfy:
+         *
+         *      constant_count + bundle_count <= 13
+         *
+         * Also implicitly constant_count <= bundle_count since a bundle only
+         * reads a single constant.
+         */
         uint64_t constants[8];
         unsigned constant_count;