draw: fixup draw_find_shader_output

draw_find_shader_output like most of the code in draw used to
depend on position always being at output slot 0. which meant
that any other attribute being at 0 could signify an error.
unfortunately position can be at any of the output slots, thus
other attributes can occupy slot 0 and we need to mark the ones
which were not found by something else. This commit changes
draw_find_shader_output so that it returns -1 if it can't
find the given attribute and adjust the code that depended
on it returning >0 whenever it correctly found an attrib.

Signed-off-by: Zack Rusin <[email protected]>
Reviewed-by: José Fonseca<[email protected]>
Reviewed-by: Brian Paul <[email protected]>
Reviewed-by: Roland Scheidegger <[email protected]>

1 files changed, 4 insertions, 4 deletions

diff --git a/src/gallium/drivers/llvmpipe/lp_state_derived.c b/src/gallium/drivers/llvmpipe/lp_state_derived.c
index 9c5e84722f1..ea24ffcd6b6 100644
--- a/src/gallium/drivers/llvmpipe/lp_state_derived.c
+++ b/src/gallium/drivers/llvmpipe/lp_state_derived.c
@@ -50,7 +50,7 @@ compute_vertex_info(struct llvmpipe_context *llvmpipe)
 {
    const struct lp_fragment_shader *lpfs = llvmpipe->fs;
    struct vertex_info *vinfo = &llvmpipe->vertex_info;
-   unsigned vs_index;
+   int vs_index;
    uint i;
 
    llvmpipe->color_slot[0] = -1;
@@ -99,7 +99,7 @@ compute_vertex_info(struct llvmpipe_context *llvmpipe)
       vs_index = draw_find_shader_output(llvmpipe->draw,
                                          TGSI_SEMANTIC_BCOLOR, i);
 
-      if (vs_index > 0) {
+      if (vs_index >= 0) {
          llvmpipe->bcolor_slot[i] = (int)vinfo->num_attribs;
          draw_emit_vertex_attr(vinfo, EMIT_4F, INTERP_PERSPECTIVE, vs_index);
       }
@@ -111,7 +111,7 @@ compute_vertex_info(struct llvmpipe_context *llvmpipe)
    vs_index = draw_find_shader_output(llvmpipe->draw,
                                       TGSI_SEMANTIC_PSIZE, 0);
 
-   if (vs_index > 0) {
+   if (vs_index >= 0) {
       llvmpipe->psize_slot = vinfo->num_attribs;
       draw_emit_vertex_attr(vinfo, EMIT_4F, INTERP_CONSTANT, vs_index);
    }
@@ -120,7 +120,7 @@ compute_vertex_info(struct llvmpipe_context *llvmpipe)
    vs_index = draw_find_shader_output(llvmpipe->draw,
                                       TGSI_SEMANTIC_VIEWPORT_INDEX,
                                       0);
-   if (vs_index > 0) {
+   if (vs_index >= 0) {
       llvmpipe->viewport_index_slot = vinfo->num_attribs;
       draw_emit_vertex_attr(vinfo, EMIT_4F, INTERP_CONSTANT, vs_index);
    } else {