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glsl: Don't require gl_Position to be written in GLSL 1.40. 

Fixes piglit glsl-1.40/execution/tf-no-position.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
This commit is contained in:
Eric Anholt 2012-03-19 22:43:27 -07:00
parent 0bc4407744
commit f1c1c9eabe
1 changed files with 30 additions and 5 deletions
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35
src/glsl/linker.cpp
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@ -258,11 +258,36 @@ validate_vertex_shader_executable(struct gl_shader_program *prog,
if (shader == NULL)
return true;
find_assignment_visitor find("gl_Position");
find.run(shader->ir);
if (!find.variable_found()) {
linker_error(prog, "vertex shader does not write to `gl_Position'\n");
return false;
/* From the GLSL 1.10 spec, page 48:
*
* "The variable gl_Position is available only in the vertex
* language and is intended for writing the homogeneous vertex
* position. All executions of a well-formed vertex shader
* executable must write a value into this variable. [...] The
* variable gl_Position is available only in the vertex
* language and is intended for writing the homogeneous vertex
* position. All executions of a well-formed vertex shader
* executable must write a value into this variable."
*
* while in GLSL 1.40 this text is changed to:
*
* "The variable gl_Position is available only in the vertex
* language and is intended for writing the homogeneous vertex
* position. It can be written at any time during shader
* execution. It may also be read back by a vertex shader
* after being written. This value will be used by primitive
* assembly, clipping, culling, and other fixed functionality
* operations, if present, that operate on primitives after
* vertex processing has occurred. Its value is undefined if
* the vertex shader executable does not write gl_Position."
*/
if (prog->Version < 140) {
find_assignment_visitor find("gl_Position");
find.run(shader->ir);
if (!find.variable_found()) {
linker_error(prog, "vertex shader does not write to `gl_Position'\n");
return false;
}
}
prog->Vert.ClipDistanceArraySize = 0;