[Mesa-dev] [RFC PATCH V3 03/10] glsl: add new interpolateAt* builtin functions

[Chris Forbes]

V2: - Don't assume everyone wants interpolateAtSample() lowered to
      interpolateAtOffset. It turns out this isn't what we want most
      of the time for i965. Lowering can be added later in an ir pass
      which drivers opt into, rather than bolting it straight into the
      builtin definition.
    - Only expose the interpolateAt* builtins in the fragment language.

Signed-off-by: Chris Forbes <chrisf at ijw.co.nz>
---
 src/glsl/builtin_functions.cpp | 67 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)

diff --git a/src/glsl/builtin_functions.cpp b/src/glsl/builtin_functions.cpp
index 8cb75e5..49eb8a8 100644
--- a/src/glsl/builtin_functions.cpp
+++ b/src/glsl/builtin_functions.cpp
@@ -214,6 +214,14 @@ gpu_shader5(const _mesa_glsl_parse_state *state)
 }
 
 static bool
+fs_gpu_shader5(const _mesa_glsl_parse_state *state)
+{
+   return state->target == fragment_shader &&
+          (state->is_version(400, 0) || state->ARB_gpu_shader5_enable);
+}
+
+
+static bool
 texture_array_lod(const _mesa_glsl_parse_state *state)
 {
    return lod_exists_in_stage(state) &&
@@ -564,6 +572,9 @@ private:
    B1(uaddCarry)
    B1(usubBorrow)
    B1(mulExtended)
+   B1(interpolateAtCentroid)
+   B1(interpolateAtOffset)
+   B1(interpolateAtSample)
 
    ir_function_signature *_atomic_intrinsic(builtin_available_predicate avail);
    ir_function_signature *_atomic_op(const char *intrinsic,
@@ -2092,6 +2103,24 @@ builtin_builder::create_builtins()
                 _mulExtended(glsl_type::uvec3_type),
                 _mulExtended(glsl_type::uvec4_type),
                 NULL);
+   add_function("interpolateAtCentroid",
+                _interpolateAtCentroid(glsl_type::float_type),
+                _interpolateAtCentroid(glsl_type::vec2_type),
+                _interpolateAtCentroid(glsl_type::vec3_type),
+                _interpolateAtCentroid(glsl_type::vec4_type),
+                NULL);
+   add_function("interpolateAtOffset",
+                _interpolateAtOffset(glsl_type::float_type),
+                _interpolateAtOffset(glsl_type::vec2_type),
+                _interpolateAtOffset(glsl_type::vec3_type),
+                _interpolateAtOffset(glsl_type::vec4_type),
+                NULL);
+   add_function("interpolateAtSample",
+                _interpolateAtSample(glsl_type::float_type),
+                _interpolateAtSample(glsl_type::vec2_type),
+                _interpolateAtSample(glsl_type::vec3_type),
+                _interpolateAtSample(glsl_type::vec4_type),
+                NULL);
 
    add_function("atomicCounter",
                 _atomic_op("__intrinsic_atomic_read",
@@ -3970,6 +3999,44 @@ builtin_builder::_mulExtended(const glsl_type *type)
 }
 
 ir_function_signature *
+builtin_builder::_interpolateAtCentroid(const glsl_type *type)
+{
+   ir_variable *interpolant = in_var(type, "interpolant");
+   interpolant->must_be_shader_input = 1;
+   MAKE_SIG(type, fs_gpu_shader5, 1, interpolant);
+
+   body.emit(ret(interpolate_at_centroid(interpolant)));
+
+   return sig;
+}
+
+ir_function_signature *
+builtin_builder::_interpolateAtOffset(const glsl_type *type)
+{
+   ir_variable *interpolant = in_var(type, "interpolant");
+   interpolant->must_be_shader_input = 1;
+   ir_variable *offset = in_var(glsl_type::vec2_type, "offset");
+   MAKE_SIG(type, fs_gpu_shader5, 2, interpolant, offset);
+
+   body.emit(ret(interpolate_at_offset(interpolant, offset)));
+
+   return sig;
+}
+
+ir_function_signature *
+builtin_builder::_interpolateAtSample(const glsl_type *type)
+{
+   ir_variable *interpolant = in_var(type, "interpolant");
+   interpolant->must_be_shader_input = 1;
+   ir_variable *sample_num = in_var(glsl_type::int_type, "sample_num");
+   MAKE_SIG(type, fs_gpu_shader5, 2, interpolant, sample_num);
+
+   body.emit(ret(interpolate_at_sample(interpolant, sample_num)));
+
+   return sig;
+}
+
+ir_function_signature *
 builtin_builder::_atomic_intrinsic(builtin_available_predicate avail)
 {
    ir_variable *counter = in_var(glsl_type::atomic_uint_type, "counter");
-- 
1.8.4.2