vc4: Avoid generating a custom shader per level in glGenerateMipmaps().

We were baking in the LOD of the source level to each shader.  Instead,
pass it in as a uniform -- this requires storing it to a temp register,
but that's better than compiling a ton of separate shaders:

total instructions in shared programs: 115032 -> 115036 (0.00%)
instructions in affected programs:     96 -> 100 (4.17%)
LOST:                                  572

1 files changed, 4 insertions, 6 deletions

diff --git a/src/gallium/drivers/vc4/vc4_program.c b/src/gallium/drivers/vc4/vc4_program.c
index 0afd8c6..28b3981 100644
--- a/src/gallium/drivers/vc4/vc4_program.c
+++ b/src/gallium/drivers/vc4/vc4_program.c
@@ -393,8 +393,8 @@ ntq_emit_tex(struct vc4_compile *c, nir_tex_instr *instr)
                 }
         }
 
-        if (c->key->tex[unit].forced_first_level) {
-                lod = qir_uniform_f(c, c->key->tex[unit].forced_first_level);
+        if (c->key->tex[unit].force_first_level) {
+                lod = qir_uniform(c, QUNIFORM_TEXTURE_FIRST_LEVEL, unit);
                 is_txl = true;
                 is_txb = false;
         }
@@ -2353,10 +2353,8 @@ vc4_setup_shared_key(struct vc4_context *vc4, struct vc4_key *key,
                         key->tex[i].compare_func = sampler_state->compare_func;
                         key->tex[i].wrap_s = sampler_state->wrap_s;
                         key->tex[i].wrap_t = sampler_state->wrap_t;
-                        if (vc4_sampler->force_first_level) {
-                                key->tex[i].forced_first_level =
-                                        sampler->u.tex.first_level;
-                        }
+                        key->tex[i].force_first_level =
+                                vc4_sampler->force_first_level;
                 }
         }