pan/bi: Add a varying_index field to bi_texture

So we can get rid of the offset adjusment done in pack_variant()

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7636>

src/panfrost/bifrost/compiler.h

@@ -261,7 +261,7 @@ struct bi_bitwise {
 struct bi_texture {
         /* Constant indices. Indirect would need to be in src[..] like normal,
          * we can reserve some sentinels there for that for future. */
-        unsigned texture_index, sampler_index;
+        unsigned texture_index, sampler_index, varying_index;
 
         /* Should the LOD be computed based on neighboring pixels? Only valid
          * in fragment shaders. */

src/panfrost/bifrost/gen_pack.py

@@ -392,7 +392,7 @@ def pack_derived(pos, exprs, imm_map, body, pack_exprs):
 
 IMMEDIATE_TABLE = {
         'attribute_index': 'bi_get_immediate(ins, 0)',
-        'varying_index': 'bi_get_immediate(ins, 0)',
+        'varying_index': 'ins->texture.varying_index',
         'index': 'ins->load_vary.index',
         'texture_index': 'ins->texture.texture_index',
         'sampler_index': 'ins->texture.sampler_index',
@@ -452,7 +452,7 @@ def pack_variant(opname, states):
     if staging in ["r", "rw"]:
         offset += 1
 
-    offset += len(set(["attribute_index", "varying_index"]) & set([x[0] for x in states[0][1].get("immediates", [])]))
+    offset += len(set(["attribute_index"]) & set([x[0] for x in states[0][1].get("immediates", [])]))
 
     pack_sources(states[0][1].get("srcs", []), common_body, pack_exprs, offset)