[Mesa-dev] [RFC PATCH 8/5] glsl: add interpolateAtSample builtin

[Chris Forbes]

Signed-off-by: Chris Forbes <chrisf at ijw.co.nz>
---
 src/glsl/builtin_functions.cpp | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/src/glsl/builtin_functions.cpp b/src/glsl/builtin_functions.cpp
index c55115c..b1ff152 100644
--- a/src/glsl/builtin_functions.cpp
+++ b/src/glsl/builtin_functions.cpp
@@ -566,6 +566,7 @@ private:
    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,
@@ -2106,6 +2107,12 @@ builtin_builder::create_builtins()
                 _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",
@@ -4007,6 +4014,29 @@ builtin_builder::_interpolateAtOffset(const glsl_type *type)
 }
 
 ir_function_signature *
+builtin_builder::_interpolateAtSample(const glsl_type *type)
+{
+   ir_variable *interpolant = new(mem_ctx) ir_variable(type, "interpolant", ir_var_shader_in);
+   ir_variable *sample_num = in_var(glsl_type::int_type, "sample_num");
+   MAKE_SIG(type, gpu_shader5, 2, interpolant, sample_num);
+
+   ir_constant_data offset;
+   offset.f[0] = -0.5f;
+   offset.f[1] = -0.5f;
+
+   ir_rvalue *sample_pos = sub(
+         new(mem_ctx) ir_dereference_array(
+            new(mem_ctx) ir_variable(glsl_type::get_array_instance(glsl_type::vec2_type, 0),
+                               "gl_SamplePositionsMESA",
+                               ir_var_uniform),
+         new(mem_ctx) ir_dereference_variable(sample_num)),
+         imm(glsl_type::vec2_type, offset));
+
+   body.emit(ret(interpolate_at_offset(interpolant, sample_pos)));
+   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