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glsl: clean up and fix bug in varying linking rules

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The existing code was very hard to follow and has been the source
of at least 3 bugs in the past year.

The existing code also has a bug for SSO where if we have a
multi-stage SSO for example a tes -> gs program, if we try to use
transform feedback with gs the existing code would look for the
transform feedback varyings in the tes stage and fail as it can't
find them.

V2: Add more code comments, always try to remove unused inputs
to the first stage.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
This commit is contained in:
Timothy Arceri
2016-01-23 09:08:23 +11:00
parent fd0b89ad8d
commit 9dd6a4ea79
1 changed files with 67 additions and 78 deletions
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73
src/compiler/glsl/linker.cpp
View File

@@ -4462,68 +4462,55 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
goto done;
}
/* Linking the stages in the opposite order (from fragment to vertex)
* ensures that inter-shader outputs written to in an earlier stage are
* eliminated if they are (transitively) not used in a later stage.
*/
int next;
if (first < MESA_SHADER_FRAGMENT) {
gl_shader *const sh = prog->_LinkedShaders[last];
if (first != MESA_SHADER_VERTEX) {
/* There was no vertex shader, but we still have to assign varying
* locations for use by tessellation/geometry shader inputs in SSO.
/* If there is no fragment shader we need to set transform feedback.
*
* If the shader is not separable (i.e., prog->SeparateShader is
* false), linking will have already failed when first is not
* MESA_SHADER_VERTEX.
* For SSO we need also need to assign output locations, we assign them
* here because we need to do it for both single stage programs and multi
* stage programs.
*/
if (!assign_varying_locations(ctx, mem_ctx, prog,
NULL, prog->_LinkedShaders[first],
num_tfeedback_decls, tfeedback_decls))
goto done;
}
if (last != MESA_SHADER_FRAGMENT &&
if (last < MESA_SHADER_FRAGMENT &&
(num_tfeedback_decls != 0 || prog->SeparateShader)) {
/* There was no fragment shader, but we still have to assign varying
* locations for use by transform feedback.
*/
if (!assign_varying_locations(ctx, mem_ctx, prog,
sh, NULL,
prog->_LinkedShaders[last], NULL,
num_tfeedback_decls, tfeedback_decls))
goto done;
}
do_dead_builtin_varyings(ctx, sh, NULL,
num_tfeedback_decls, tfeedback_decls);
remove_unused_shader_inputs_and_outputs(prog->SeparateShader, sh,
if (last <= MESA_SHADER_FRAGMENT) {
/* Remove unused varyings from the first/last stage unless SSO */
remove_unused_shader_inputs_and_outputs(prog->SeparateShader,
prog->_LinkedShaders[first],
ir_var_shader_in);
remove_unused_shader_inputs_and_outputs(prog->SeparateShader,
prog->_LinkedShaders[last],
ir_var_shader_out);
}
else if (first == MESA_SHADER_FRAGMENT) {
/* If the program only contains a fragment shader...
*/
gl_shader *const sh = prog->_LinkedShaders[first];
do_dead_builtin_varyings(ctx, NULL, sh,
num_tfeedback_decls, tfeedback_decls);
/* If the program is made up of only a single stage */
if (first == last) {
gl_shader *const sh = prog->_LinkedShaders[last];
if (prog->SeparateShader) {
/* Assign input locations for SSO, output locations are already
* assigned.
*/
if (!assign_varying_locations(ctx, mem_ctx, prog,
NULL /* producer */,
sh /* consumer */,
0 /* num_tfeedback_decls */,
NULL /* tfeedback_decls */))
goto done;
} else {
remove_unused_shader_inputs_and_outputs(false, sh,
ir_var_shader_in);
}
}
next = last;
do_dead_builtin_varyings(ctx, NULL, sh, 0, NULL);
do_dead_builtin_varyings(ctx, sh, NULL, num_tfeedback_decls,
tfeedback_decls);
} else {
/* Linking the stages in the opposite order (from fragment to vertex)
* ensures that inter-shader outputs written to in an earlier stage
* are eliminated if they are (transitively) not used in a later
* stage.
*/
int next = last;
for (int i = next - 1; i >= 0; i--) {
if (prog->_LinkedShaders[i] == NULL)
continue;
@@ -4548,6 +4535,8 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
next = i;
}
}
}
if (!store_tfeedback_info(ctx, prog, num_tfeedback_decls, tfeedback_decls))
goto done;