The EXT_shader_framebuffer_fetch extension defines alternative
language for GLES2 shaders where user-defined fragment outputs are not
allowed. Instead of using inout user-defined fragment outputs the
shader is expected to read from the gl_LastFragData built-in array.
In addition this allows using the same language on desktop GLSL
versions prior to 4.2 that support the deprecated gl_FragData built-in
in preparation for the MESA_shader_framebuffer_fetch desktop GL
extension.
Both legacy and user-defined inout outputs have a common
representation at the GLSL IR level, so it shouldn't make any
difference for optimization passes and back-ends whether the
application is using gl_LastFragData or user-defined outputs, all
they'll see is a variable dereference of a fragment output at a
certain interface location with the fb_fetch_output bit set to one.
---
src/compiler/glsl/builtin_variables.cpp | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/src/compiler/glsl/builtin_variables.cpp
b/src/compiler/glsl/builtin_variables.cpp
index f63dc3a..6a756ed 100644
--- a/src/compiler/glsl/builtin_variables.cpp
+++ b/src/compiler/glsl/builtin_variables.cpp
@@ -1136,6 +1136,16 @@ builtin_variable_generator::generate_fs_special_vars()
array(vec4_t, state->Const.MaxDrawBuffers), "gl_FragData");
}
+ if (state->has_framebuffer_fetch() && !state->is_version(420, 300)) {
+ ir_variable *const var =
+ add_output(FRAG_RESULT_DATA0,
+ array(vec4_t, state->Const.MaxDrawBuffers),
+ "gl_LastFragData");
+ var->data.precision = GLSL_PRECISION_MEDIUM;
+ var->data.read_only = 1;
+ var->data.fb_fetch_output = 1;
+ }
+
if (state->es_shader && state->language_version == 100 &&
state->EXT_blend_func_extended_enable) {
/* We make an assumption here that there will only ever be one
dual-source draw buffer
* In case this assumption is ever proven to be false, make sure to
assert here
--
2.9.0
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