We lower gl_GlobalInvocationID based on the extension spec formula:
gl_GlobalInvocationID =
gl_WorkGroupID * gl_WorkGroupSize + gl_LocalInvocationID
https://www.opengl.org/registry/specs/ARB/compute_shader.txt
We need to set this variable in main(), even if gl_GlobalInvocationID
is not referenced by the shader. (It may be used by a linked shader.)
Therefore, we can't eliminate these as dead variables.
Signed-off-by: Jordan Justen <jordan.l.jus...@intel.com>
---
src/glsl/opt_dead_builtin_variables.cpp | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/src/glsl/opt_dead_builtin_variables.cpp
b/src/glsl/opt_dead_builtin_variables.cpp
index 0d4e3a8..90b753e 100644
--- a/src/glsl/opt_dead_builtin_variables.cpp
+++ b/src/glsl/opt_dead_builtin_variables.cpp
@@ -62,6 +62,16 @@ optimize_dead_builtin_variables(exec_list *instructions,
* information, so removing these variables from the user shader will
* cause problems later.
*
+ * For compute shaders, gl_GlobalInvocationID has some dependencies, so
+ * we avoid removing these dependencies.
+ *
+ * We also avoid removing gl_GlobalInvocationID at this stage because it
+ * might be used by a linked shader. In this case it still needs to be
+ * initialized by the main function.
+ *
+ * gl_GlobalInvocationID =
+ * gl_WorkGroupID * gl_WorkGroupSize + gl_LocalInvocationID
+ *
* Matrix uniforms with "Transpose" are not eliminated because there's
* an optimization pass that can turn references to the regular matrix
* into references to the transpose matrix. Eliminating the transpose
@@ -73,6 +83,10 @@ optimize_dead_builtin_variables(exec_list *instructions,
*/
if (strcmp(var->name, "gl_ModelViewProjectionMatrix") == 0
|| strcmp(var->name, "gl_Vertex") == 0
+ || strcmp(var->name, "gl_WorkGroupID") == 0
+ || strcmp(var->name, "gl_WorkGroupSize") == 0
+ || strcmp(var->name, "gl_LocalInvocationID") == 0
+ || strcmp(var->name, "gl_GlobalInvocationID") == 0
|| strstr(var->name, "Transpose") != NULL)
continue;
--
2.1.4
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