glsl: use bitmask of active xfb buffer indices

This allows us to print the correct binding point when not all
buffers declared in the shader are bound.

For example if we use a single buffer:

layout(xfb_buffer=2, offset=0) out vec4 v;

We now print '2' when the buffer is not bound rather than '0'.

Reviewed-by: Dave Airlie <airlied@redhat.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/src/compiler/glsl/link_varyings.cpp b/src/compiler/glsl/link_varyings.cpp
index 8aefb7e..cb0c8ba 100644
--- a/src/compiler/glsl/link_varyings.cpp
+++ b/src/compiler/glsl/link_varyings.cpp
@@ -872,6 +872,11 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
                      unsigned num_tfeedback_decls,
                      tfeedback_decl *tfeedback_decls, bool has_xfb_qualifiers)
 {
+   /* Make sure MaxTransformFeedbackBuffers is less than 32 so the bitmask for
+    * tracking the number of buffers doesn't overflow.
+    */
+   assert(ctx->Const.MaxTransformFeedbackBuffers < 32);
+
    bool separate_attribs_mode =
       prog->TransformFeedback.BufferMode == GL_SEPARATE_ATTRIBS;
 
@@ -904,6 +909,7 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
                     num_outputs);
 
    unsigned num_buffers = 0;
+   unsigned buffers = 0;
 
    if (!has_xfb_qualifiers && separate_attribs_mode) {
       /* GL_SEPARATE_ATTRIBS */
@@ -913,6 +919,7 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
                                        has_xfb_qualifiers))
             return false;
 
+         buffers |= 1 << num_buffers;
          num_buffers++;
       }
    }
@@ -949,6 +956,7 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
          } else {
             buffer = num_buffers;
          }
+         buffers |= 1 << num_buffers;
 
          if (!tfeedback_decls[i].store(ctx, prog,
                                        &prog->LinkedTransformFeedback,
@@ -956,12 +964,11 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
                                        has_xfb_qualifiers))
             return false;
       }
-      num_buffers++;
    }
 
    assert(prog->LinkedTransformFeedback.NumOutputs == num_outputs);
 
-   prog->LinkedTransformFeedback.NumBuffers = num_buffers;
+   prog->LinkedTransformFeedback.ActiveBuffers = buffers;
    return true;
 }