[Mesa-dev] [PATCH] mesa: allocate transform_feedback_info::Outputs array dynamically

[Christoph Bumiller]

The nvc0 gallium driver is advertising 128 MAX_INTERLEAVED_COMPS
which made it always assert in the linker when TFB was used since
the Outputs array was smaller than that maximum.

NOTE: This is a candidate for the 8.0 branch.
---
 src/glsl/linker.cpp    |   57 +++++++++++++++++++++++++++++------------------
 src/mesa/main/mtypes.h |   32 ++++++++++++++------------
 2 files changed, 52 insertions(+), 37 deletions(-)

diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index 0d85aee..1a986ef 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -1388,6 +1388,7 @@ public:
    static bool is_same(const tfeedback_decl &x, const tfeedback_decl &y);
    bool assign_location(struct gl_context *ctx, struct gl_shader_program *prog,
                         ir_variable *output_var);
+   bool accumulate_num_outputs(struct gl_shader_program *prog, unsigned *count);
    bool store(struct gl_context *ctx, struct gl_shader_program *prog,
               struct gl_transform_feedback_info *info, unsigned buffer,
 	      unsigned varying) const;
@@ -1624,16 +1625,9 @@ tfeedback_decl::assign_location(struct gl_context *ctx,
 }
 
 
-/**
- * Update gl_transform_feedback_info to reflect this tfeedback_decl.
- *
- * If an error occurs, the error is reported through linker_error() and false
- * is returned.
- */
 bool
-tfeedback_decl::store(struct gl_context *ctx, struct gl_shader_program *prog,
-                      struct gl_transform_feedback_info *info,
-                      unsigned buffer, unsigned varying) const
+tfeedback_decl::accumulate_num_outputs(struct gl_shader_program *prog,
+                                       unsigned *count)
 {
    if (!this->is_assigned()) {
       /* From GL_EXT_transform_feedback:
@@ -1648,6 +1642,27 @@ tfeedback_decl::store(struct gl_context *ctx, struct gl_shader_program *prog,
       return false;
    }
 
+   unsigned translated_size = this->size;
+   if (this->is_clip_distance_mesa)
+      translated_size = (translated_size + 3) / 4;
+
+   *count += translated_size * this->matrix_columns;
+
+   return true;
+}
+
+
+/**
+ * Update gl_transform_feedback_info to reflect this tfeedback_decl.
+ *
+ * If an error occurs, the error is reported through linker_error() and false
+ * is returned.
+ */
+bool
+tfeedback_decl::store(struct gl_context *ctx, struct gl_shader_program *prog,
+                      struct gl_transform_feedback_info *info,
+                      unsigned buffer, unsigned varying) const
+{
    /* From GL_EXT_transform_feedback:
     *   A program will fail to link if:
     *
@@ -1663,19 +1678,6 @@ tfeedback_decl::store(struct gl_context *ctx, struct gl_shader_program *prog,
       return false;
    }
 
-   /* Verify that the checks on MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS
-    * and MAX_TRANSFORM_FEEDBACK_SEPARATE_COMPONENTS are sufficient to prevent
-    * overflow of info->Outputs[].  In worst case we generate one entry in
-    * Outputs[] per component so a conservative check is to verify that the
-    * size of the array is greater than or equal to both
-    * MAX_TRANSFORM_FEEDBACK_INTERLEAVED_COMPONENTS and
-    * MAX_TRANSFORM_FEEDBACK_SEPARATE_COMPONENTS.
-    */
-   assert(Elements(info->Outputs) >=
-          ctx->Const.MaxTransformFeedbackInterleavedComponents);
-   assert(Elements(info->Outputs) >=
-          ctx->Const.MaxTransformFeedbackSeparateComponents);
-
    unsigned translated_size = this->size;
    if (this->is_clip_distance_mesa)
       translated_size = (translated_size + 3) / 4;
@@ -1976,6 +1978,7 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
       prog->TransformFeedback.BufferMode == GL_SEPARATE_ATTRIBS;
 
    ralloc_free(prog->LinkedTransformFeedback.Varyings);
+   ralloc_free(prog->LinkedTransformFeedback.Outputs);
 
    memset(&prog->LinkedTransformFeedback, 0,
           sizeof(prog->LinkedTransformFeedback));
@@ -1988,6 +1991,16 @@ store_tfeedback_info(struct gl_context *ctx, struct gl_shader_program *prog,
 		    struct gl_transform_feedback_varying_info,
 		    num_tfeedback_decls);
 
+   unsigned num_outputs = 0;
+   for (unsigned i = 0; i < num_tfeedback_decls; ++i)
+      if (!tfeedback_decls[i].accumulate_num_outputs(prog, &num_outputs))
+         return false;
+
+   prog->LinkedTransformFeedback.Outputs =
+      rzalloc_array(prog->LinkedTransformFeedback.Outputs,
+                    struct gl_transform_feedback_output,
+                    num_outputs);
+
    for (unsigned i = 0; i < num_tfeedback_decls; ++i) {
       unsigned buffer = separate_attribs_mode ? i : 0;
       if (!tfeedback_decls[i].store(ctx, prog, &prog->LinkedTransformFeedback,
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index 9fdabf9..95450f9 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -1823,6 +1823,22 @@ struct gl_transform_feedback_varying_info {
    GLint Size;
 };
 
+struct gl_transform_feedback_output {
+   unsigned OutputRegister;
+   unsigned OutputBuffer;
+   unsigned NumComponents;
+
+   /** offset (in DWORDs) of this output within the interleaved structure */
+   unsigned DstOffset;
+
+   /**
+    * Offset into the output register of the data to output.  For example,
+    * if NumComponents is 2 and ComponentOffset is 1, then the data to
+    * offset is in the y and z components of the output register.
+    */
+   unsigned ComponentOffset;
+};
+
 /** Post-link transform feedback info. */
 struct gl_transform_feedback_info {
    unsigned NumOutputs;
@@ -1832,21 +1848,7 @@ struct gl_transform_feedback_info {
     */
    unsigned NumBuffers;
 
-   struct {
-      unsigned OutputRegister;
-      unsigned OutputBuffer;
-      unsigned NumComponents;
-
-      /** offset (in DWORDs) of this output within the interleaved structure */
-      unsigned DstOffset;
-
-      /**
-       * Offset into the output register of the data to output.  For example,
-       * if NumComponents is 2 and ComponentOffset is 1, then the data to
-       * offset is in the y and z components of the output register.
-       */
-      unsigned ComponentOffset;
-   } Outputs[MAX_PROGRAM_OUTPUTS];
+   struct gl_transform_feedback_output *Outputs;
 
    /** Transform feedback varyings used for the linking of this shader program.
     *
-- 
1.7.3.4