mesa: add statevar for atomic counter offsets

some hardware can't do a ssbo offset=4, as required by the atomic->ssbo
lowering pass, so for these cases an offset can be passed for the counter
as a uniform, and the shaders can be adjusted accordingly

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16749>

src/mesa/program/prog_statevars.c

@@ -779,6 +779,13 @@ fetch_state(struct gl_context *ctx, const gl_state_index16 state[],
          COPY_4V(value, ctx->Transform._ClipUserPlane[plane]);
       }
       return;
+
+   case STATE_ATOMIC_COUNTER_OFFSET:
+      {
+         const GLuint counter = (GLuint) state[1];
+         val[0].i = ctx->AtomicBufferBindings[counter].Offset % ctx->Const.ShaderStorageBufferOffsetAlignment;
+      }
+      return;
    }
 }
 
@@ -912,6 +919,10 @@ _mesa_program_state_flags(const gl_state_index16 state[STATE_LENGTH])
    case STATE_CLIP_INTERNAL:
       return _NEW_TRANSFORM | _NEW_PROJECTION;
 
+   /* Needs to return any nonzero value to trigger constant updating */
+   case STATE_ATOMIC_COUNTER_OFFSET:
+      return _NEW_PROGRAM_CONSTANTS;
+
    case STATE_TCS_PATCH_VERTICES_IN:
    case STATE_TES_PATCH_VERTICES_IN:
    case STATE_INTERNAL_DRIVER:
@@ -1192,6 +1203,9 @@ append_token(char *dst, gl_state_index k)
    case STATE_CLIP_INTERNAL:
       append(dst, "clipInternal");
       break;
+   case STATE_ATOMIC_COUNTER_OFFSET:
+      append(dst, "counterOffset");
+      break;
    default:
       /* probably STATE_INTERNAL_DRIVER+i (driver private state) */
       append(dst, "driverState");
@@ -1317,6 +1331,7 @@ _mesa_program_state_string(const gl_state_index16 state[STATE_LENGTH])
    case STATE_LIGHT_POSITION_NORMALIZED:
    case STATE_LIGHT_HALF_VECTOR:
    case STATE_CLIP_INTERNAL:
+   case STATE_ATOMIC_COUNTER_OFFSET:
       append_index(str, state[1], false);
       break;
    case STATE_POINT_SIZE:

src/mesa/program/prog_statevars.h

@@ -140,6 +140,7 @@ typedef enum gl_state_index_ {
    STATE_ADVANCED_BLENDING_MODE,
    STATE_ALPHA_REF,        /* alpha-test reference value */
    STATE_CLIP_INTERNAL,    /* similar to STATE_CLIPPLANE, but in clip-space */
+   STATE_ATOMIC_COUNTER_OFFSET,    /* the byte offset to add to atomic counter bindings */
 
    STATE_INTERNAL_DRIVER,	/* first available state index for drivers (must be last) */