On Tuesday, February 2, 2016 12:20:01 PM PST Timothy Arceri wrote:
> 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.
>
> Cc: Ilia Mirkin <imir...@alum.mit.edu>
> Cc: Chris Forbes <chr...@ijw.co.nz>
> ---
> src/compiler/glsl/linker.cpp | 137
> ++++++++++++++++++++-----------------------
> 1 file changed, 63 insertions(+), 74 deletions(-)
>
> diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
> index fdfdcaa..09323bb 100644
> --- a/src/compiler/glsl/linker.cpp
> +++ b/src/compiler/glsl/linker.cpp
> @@ -4461,91 +4461,80 @@ 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.
> + /* If there is no fragment shader we need to set transform feedback.
> + *
> + * 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.
> */
> - 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 the shader is not separable (i.e., prog->SeparateShader is
> - * false), linking will have already failed when first is not
> - * MESA_SHADER_VERTEX.
> - */
> - if (!assign_varying_locations(ctx, mem_ctx, prog,
> - NULL, prog->_LinkedShaders[first],
> - num_tfeedback_decls, tfeedback_decls))
> - goto done;
> - }
> -
> - 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,
> - num_tfeedback_decls, tfeedback_decls))
> - goto done;
> - }
> -
> - do_dead_builtin_varyings(ctx, sh, NULL,
> - num_tfeedback_decls, tfeedback_decls);
> + if (last < MESA_SHADER_FRAGMENT &&
> + (num_tfeedback_decls != 0 || prog->SeparateShader)) {
> + if (!assign_varying_locations(ctx, mem_ctx, prog,
> + prog->_LinkedShaders[last], NULL,
> + num_tfeedback_decls, tfeedback_decls))
> + goto done;
> + }
>
> - remove_unused_shader_inputs_and_outputs(prog->SeparateShader, sh,
> + if (last <= MESA_SHADER_FRAGMENT) {I don't understand the point of last <= MESA_SHADER_FRAGMENT here. The only other option is MESA_SHADER_COMPUTE, which has no inputs or outputs, so calling this should be harmless. > + /* 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); I see, assign_varying_locations calls this for internal stages, when there's a producer and consumer - this just calls it for the boundary shaders in the !SSO case. Makes sense. This is much cleaner - nice work! Reviewed-by: Kenneth Graunke <kenn...@whitecape.org>
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