nir: Add gl_PointCoord system value

gl_PointCoord handling needs some special bits set in lima/ppir code
generation. Treating gl_PointCoord as a system value makes it easier
to distinguish from a regular varying.

Signed-off-by: Andreas Baierl <ichgeh@imkreisrum.de>
Reviewed-by: Qiang Yu <yuq825@gmail.com>
Reviewed-by: Eric Anholt <eric@anholt.net>

src/compiler/nir/nir.c

@@ -1957,6 +1957,8 @@ nir_intrinsic_from_system_value(gl_system_value val)
       return nir_intrinsic_load_invocation_id;
    case SYSTEM_VALUE_FRAG_COORD:
       return nir_intrinsic_load_frag_coord;
+   case SYSTEM_VALUE_POINT_COORD:
+      return nir_intrinsic_load_point_coord;
    case SYSTEM_VALUE_FRONT_FACE:
       return nir_intrinsic_load_front_face;
    case SYSTEM_VALUE_SAMPLE_ID:
@@ -2046,6 +2048,8 @@ nir_system_value_from_intrinsic(nir_intrinsic_op intrin)
       return SYSTEM_VALUE_INVOCATION_ID;
    case nir_intrinsic_load_frag_coord:
       return SYSTEM_VALUE_FRAG_COORD;
+   case nir_intrinsic_load_point_coord:
+      return SYSTEM_VALUE_POINT_COORD;
    case nir_intrinsic_load_front_face:
       return SYSTEM_VALUE_FRONT_FACE;
    case nir_intrinsic_load_sample_id:

src/compiler/nir/nir_gather_info.c

@@ -238,6 +238,7 @@ gather_intrinsic_info(nir_intrinsic_instr *instr, nir_shader *shader,
 
    case nir_intrinsic_load_draw_id:
    case nir_intrinsic_load_frag_coord:
+   case nir_intrinsic_load_point_coord:
    case nir_intrinsic_load_front_face:
    case nir_intrinsic_load_vertex_id:
    case nir_intrinsic_load_vertex_id_zero_base:

src/compiler/nir/nir_intrinsics.py

@@ -535,6 +535,7 @@ def system_value(name, dest_comp, indices=[], bit_sizes=[32]):
               bit_sizes=bit_sizes)
 
 system_value("frag_coord", 4)
+system_value("point_coord", 2)
 system_value("front_face", 1, bit_sizes=[1, 32])
 system_value("vertex_id", 1)
 system_value("vertex_id_zero_base", 1)