glsl/linker: Ensure the first stage of an SSO pipeline has input locs assigned

Previously an SSO pipeline containing only a tessellation control shader
and a tessellation evaluation shader would not get locations assigned
for the TCS inputs.  This would lead to assertion failures in some
piglit tests, such as arb_program_interface_query-resource-query.

That piglit test still fails on some tessellation related subtests.
Specifically, these subtests fail:

'GL_PROGRAM_INPUT(tcs) active resources' expected 2 but got 3
'GL_PROGRAM_INPUT(tcs) max length name' expected 12 but got 16
'GL_PROGRAM_INPUT(tcs,tes) active resources' expected 2 but got 3
'GL_PROGRAM_INPUT(tcs,tes) max length name' expected 12 but got 16
'GL_PROGRAM_OUTPUT(tcs) active resources' expected 15 but got 3
'GL_PROGRAM_OUTPUT(tcs) max length name' expected 23 but got 12

Signed-off-by: Ian Romanick <[email protected]>
Reviewed-by: Timothy Arceri <[email protected]>
Cc: [email protected]

1 files changed, 6 insertions, 3 deletions

diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
index 6246944b0b4..de569453ee4 100644
--- a/src/compiler/glsl/linker.cpp
+++ b/src/compiler/glsl/linker.cpp
@@ -4790,7 +4790,7 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
           */
          int next = last;
          for (int i = next - 1; i >= 0; i--) {
-            if (prog->_LinkedShaders[i] == NULL)
+            if (prog->_LinkedShaders[i] == NULL && i != 0)
                continue;
 
             gl_shader *const sh_i = prog->_LinkedShaders[i];
@@ -4806,8 +4806,11 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
                       tfeedback_decls);
 
             /* This must be done after all dead varyings are eliminated. */
-            if (!check_against_output_limit(ctx, prog, sh_i))
-               goto done;
+            if (sh_i != NULL) {
+               if (!check_against_output_limit(ctx, prog, sh_i)) {
+                  goto done;
+               }
+            }
             if (!check_against_input_limit(ctx, prog, sh_next))
                goto done;