llvmpipe/setup: add point size clamping

Fixes
dEQP-GLES2.functional.rasterization.limits.points
dEQP-VK.rasterization.primitive_size.points.point_size*

Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4574>

src/gallium/drivers/llvmpipe/lp_limits.h

@@ -95,4 +95,8 @@
  */
 #define LP_MAX_SETUP_VARIANTS 64
 
+/*
+ * Max point size reported. Cap vertex shader point sizes to this.
+ */
+#define LP_MAX_POINT_WIDTH 255.0f
 #endif /* LP_LIMITS_H */

src/gallium/drivers/llvmpipe/lp_screen.c

@@ -478,7 +478,7 @@ llvmpipe_get_paramf(struct pipe_screen *screen, enum pipe_capf param)
    case PIPE_CAPF_MAX_POINT_WIDTH:
       /* fall-through */
    case PIPE_CAPF_MAX_POINT_WIDTH_AA:
-      return 255.0; /* arbitrary */
+      return LP_MAX_POINT_WIDTH; /* arbitrary */
    case PIPE_CAPF_MAX_TEXTURE_ANISOTROPY:
       return 16.0; /* not actually signficant at this time */
    case PIPE_CAPF_MAX_TEXTURE_LOD_BIAS:

src/gallium/drivers/llvmpipe/lp_setup_point.c

@@ -337,10 +337,13 @@ try_setup_point( struct lp_setup_context *setup,
    /* x/y positions in fixed point */
    const struct lp_setup_variant_key *key = &setup->setup.variant->key;
    const int sizeAttr = setup->psize_slot;
-   const float size
+   float size
       = (setup->point_size_per_vertex && sizeAttr > 0) ? v0[sizeAttr][0]
       : setup->point_size;
 
+   if (size > LP_MAX_POINT_WIDTH)
+      size = LP_MAX_POINT_WIDTH;
+
    /* Yes this is necessary to accurately calculate bounding boxes
     * with the two fill-conventions we support.  GL (normally) ends
     * up needing a bottom-left fill convention, which requires