gallium: add PIPE_CAP_MAX_CONSTANT_BUFFER_SIZE_UINT for UBOs

We plan to report UINT32_MAX for UBOs.

Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16881>

docs/gallium/screen.rst

@@ -636,6 +636,7 @@ The integer capabilities:
 * ``PIPE_CAP_QUERY_SPARSE_TEXTURE_RESIDENCY``: TRUE if shader sparse texture sample instruction could also return the residency information.
 * ``PIPE_CAP_CLAMP_SPARSE_TEXTURE_LOD``: TRUE if shader sparse texture sample instruction support clamp the minimal lod to prevent read from un-committed pages.
 * ``PIPE_CAP_ALLOW_DRAW_OUT_OF_ORDER``: TRUE if the driver allows the "draw out of order" optimization to be enabled. See _mesa_update_allow_draw_out_of_order for more details.
+* ``PIPE_CAP_MAX_CONSTANT_BUFFER_SIZE_UINT``: Maximum bound constant buffer size in bytes. This is unsigned integer with the maximum of 4GB - 1. This applies to all constant buffers used by UBOs, unlike `PIPE_SHADER_CAP_MAX_CONST_BUFFER0_SIZE`, which is specifically for GLSL uniforms.
 
 .. _pipe_capf:
 

src/gallium/auxiliary/util/u_screen.c

@@ -488,6 +488,10 @@ u_pipe_screen_get_param_defaults(struct pipe_screen *pscreen,
    case PIPE_CAP_CLAMP_SPARSE_TEXTURE_LOD:
       return 0;
 
+   case PIPE_CAP_MAX_CONSTANT_BUFFER_SIZE_UINT:
+      return pscreen->get_shader_param(pscreen, PIPE_SHADER_FRAGMENT,
+                                       PIPE_SHADER_CAP_MAX_CONST_BUFFER0_SIZE);
+
    default:
       unreachable("bad PIPE_CAP_*");
    }

src/gallium/include/pipe/p_defines.h

@@ -1007,6 +1007,7 @@ enum pipe_cap
    PIPE_CAP_QUERY_SPARSE_TEXTURE_RESIDENCY,
    PIPE_CAP_CLAMP_SPARSE_TEXTURE_LOD,
    PIPE_CAP_ALLOW_DRAW_OUT_OF_ORDER,
+   PIPE_CAP_MAX_CONSTANT_BUFFER_SIZE_UINT,
 
    PIPE_CAP_LAST,
    /* XXX do not add caps after PIPE_CAP_LAST! */

src/mesa/state_tracker/st_extensions.c

@@ -156,12 +156,7 @@ void st_init_limits(struct pipe_screen *screen,
                         PIPE_CAP_QUADS_FOLLOW_PROVOKING_VERTEX_CONVENTION);
 
    c->MaxUniformBlockSize =
-      screen->get_shader_param(screen, PIPE_SHADER_FRAGMENT,
-                               PIPE_SHADER_CAP_MAX_CONST_BUFFER0_SIZE);
-   /* GL45-CTS.enhanced_layouts.ssb_member_invalid_offset_alignment fails if
-    * this is larger than INT_MAX - 100. Use a nicely aligned limit.
-    */
-   c->MaxUniformBlockSize = MIN2(c->MaxUniformBlockSize, INT_MAX - 127);
+      screen->get_param(screen, PIPE_CAP_MAX_CONSTANT_BUFFER_SIZE_UINT);
 
    if (c->MaxUniformBlockSize < 16384) {
       can_ubo = false;