compiler: Add a system value for the line coord

The line coord is a coordinate along the axis perpendicular to the line.
It is in the range [0,1] between the two edges of the line. It is
available at least on Broadcom hardware.

Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5624>

src/compiler/nir/nir.c

@@ -2025,6 +2025,8 @@ nir_intrinsic_from_system_value(gl_system_value val)
       return nir_intrinsic_load_frag_coord;
    case SYSTEM_VALUE_POINT_COORD:
       return nir_intrinsic_load_point_coord;
+   case SYSTEM_VALUE_LINE_COORD:
+      return nir_intrinsic_load_line_coord;
    case SYSTEM_VALUE_FRONT_FACE:
       return nir_intrinsic_load_front_face;
    case SYSTEM_VALUE_SAMPLE_ID:
@@ -2122,6 +2124,8 @@ nir_system_value_from_intrinsic(nir_intrinsic_op intrin)
       return SYSTEM_VALUE_FRAG_COORD;
    case nir_intrinsic_load_point_coord:
       return SYSTEM_VALUE_POINT_COORD;
+   case nir_intrinsic_load_line_coord:
+      return SYSTEM_VALUE_LINE_COORD;
    case nir_intrinsic_load_front_face:
       return SYSTEM_VALUE_FRONT_FACE;
    case nir_intrinsic_load_sample_id:

src/compiler/nir/nir_divergence_analysis.c

@@ -314,6 +314,7 @@ visit_intrinsic(nir_intrinsic_instr *instr, struct divergence_state *state)
    case nir_intrinsic_interp_deref_at_vertex:
    case nir_intrinsic_load_tess_coord:
    case nir_intrinsic_load_point_coord:
+   case nir_intrinsic_load_line_coord:
    case nir_intrinsic_load_frag_coord:
    case nir_intrinsic_load_sample_pos:
    case nir_intrinsic_load_vertex_id_zero_base:

src/compiler/nir/nir_gather_info.c

@@ -348,6 +348,7 @@ 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_line_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

@@ -560,6 +560,7 @@ def system_value(name, dest_comp, indices=[], bit_sizes=[32]):
 
 system_value("frag_coord", 4)
 system_value("point_coord", 2)
+system_value("line_coord", 1)
 system_value("front_face", 1, bit_sizes=[1, 32])
 system_value("vertex_id", 1)
 system_value("vertex_id_zero_base", 1)

src/compiler/shader_enums.c

@@ -228,6 +228,7 @@ gl_system_value_name(gl_system_value sysval)
      ENUM(SYSTEM_VALUE_INVOCATION_ID),
      ENUM(SYSTEM_VALUE_FRAG_COORD),
      ENUM(SYSTEM_VALUE_POINT_COORD),
+     ENUM(SYSTEM_VALUE_LINE_COORD),
      ENUM(SYSTEM_VALUE_FRONT_FACE),
      ENUM(SYSTEM_VALUE_SAMPLE_ID),
      ENUM(SYSTEM_VALUE_SAMPLE_POS),

src/compiler/shader_enums.h

@@ -585,6 +585,7 @@ typedef enum
    /*@{*/
    SYSTEM_VALUE_FRAG_COORD,
    SYSTEM_VALUE_POINT_COORD,
+   SYSTEM_VALUE_LINE_COORD, /**< Coord along axis perpendicular to line */
    SYSTEM_VALUE_FRONT_FACE,
    SYSTEM_VALUE_SAMPLE_ID,
    SYSTEM_VALUE_SAMPLE_POS,