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, 3 insertions, 1 deletions

diff --git a/src/gallium/drivers/vc4/vc4_qir.h b/src/gallium/drivers/vc4/vc4_qir.h
index 81b55651cec..b8ded30711c 100644
--- a/src/gallium/drivers/vc4/vc4_qir.h
+++ b/src/gallium/drivers/vc4/vc4_qir.h
@@ -246,6 +246,8 @@ enum quniform_contents {
         /** A reference to a texture config parameter 2 cubemap stride uniform */
         QUNIFORM_TEXTURE_CONFIG_P2,
 
+        QUNIFORM_TEXTURE_FIRST_LEVEL,
+
         QUNIFORM_TEXTURE_MSAA_ADDR,
 
         QUNIFORM_UBO_ADDR,
@@ -314,7 +316,7 @@ struct vc4_key {
                                 unsigned compare_func:3;
                                 unsigned wrap_s:3;
                                 unsigned wrap_t:3;
-                                unsigned forced_first_level:8;
+                                bool force_first_level:1;
                         };
                         struct {
                                 uint16_t msaa_width, msaa_height;