mesa/sso: replace Shader binding point with _Shader

To avoid NULL pointer check a default pipeline object is installed in
_Shader when no program is current

The spec say that UseProgram/UseShaderProgramEXT/ActiveProgramEXT got an
higher priority over the pipeline object. When default program is
uninstall, the pipeline is used if any was bound.

Note: A careful rename need to be done now...

V2: formating improvement

V3 (idr):
* Build fix.  The original patch added calls to _mesa_use_shader_program
  with 4 parameters, but the fourth parameter isn't added to that
  function until a much later patch.  Just drop that parameter for now.
* Trivial reformatting.
* Updated comment of gl_context::_Shader

v4 (idr): Reformat spec quotations to look like spec quotations.  Update
comments describing what gl_context::_Shader can point to.  Bot
suggested by Eric.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>

src/mesa/main/mtypes.h

@@ -2817,6 +2817,9 @@ struct gl_pipeline_shader_state
    /** Currently bound pipeline object. See _mesa_BindProgramPipeline() */
    struct gl_pipeline_object *Current;
 
+   /* Default Object to ensure that _Shader is never NULL */
+   struct gl_pipeline_object *Default;
+
    /** Pipeline objects */
    struct _mesa_HashTable *Objects;
 };
@@ -4123,6 +4126,26 @@ struct gl_context
 
    struct gl_pipeline_shader_state Pipeline; /**< GLSL pipeline shader object state */
    struct gl_pipeline_object Shader; /**< GLSL shader object state */
+
+   /**
+    * Current active shader pipeline state
+    *
+    * Almost all internal users want ::_Shader instead of ::Shader.  The
+    * exceptions are bits of legacy GLSL API that do not know about separate
+    * shader objects.
+    *
+    * If a program is active via \c glUseProgram, this will point to
+    * \c ::Shader.
+    *
+    * If a program pipeline is active via \c glBindProgramPipeline, this will
+    * point to \c ::Pipeline.Current.
+    *
+    * If neither a program nor a program pipeline is active, this will point to
+    * \c ::Pipeline.Default.  This ensures that \c ::_Shader will never be
+    * \c NULL.
+    */
+   struct gl_pipeline_object *_Shader;
+
    struct gl_shader_compiler_options ShaderCompilerOptions[MESA_SHADER_STAGES];
 
    struct gl_query_state Query;  /**< occlusion, timer queries */

src/mesa/main/pipelineobj.c

@@ -94,6 +94,10 @@ _mesa_init_pipeline(struct gl_context *ctx)
    ctx->Pipeline.Objects = _mesa_NewHashTable();
 
    ctx->Pipeline.Current = NULL;
+
+   /* Install a default Pipeline */
+   ctx->Pipeline.Default = _mesa_new_pipeline_object(ctx, 0);
+   _mesa_reference_pipeline_object(ctx, &ctx->_Shader, ctx->Pipeline.Default);
 }
 
 
@@ -117,6 +121,10 @@ _mesa_free_pipeline_data(struct gl_context *ctx)
 {
    _mesa_HashDeleteAll(ctx->Pipeline.Objects, delete_pipelineobj_cb, ctx);
    _mesa_DeleteHashTable(ctx->Pipeline.Objects);
+
+   _mesa_reference_pipeline_object(ctx, &ctx->_Shader, NULL);
+   _mesa_delete_pipeline_object(ctx, ctx->Pipeline.Default);
+
 }
 
 /**

src/mesa/main/shaderapi.c

@@ -44,6 +44,7 @@
 #include "main/hash.h"
 #include "main/hash_table.h"
 #include "main/mtypes.h"
+#include "main/pipelineobj.h"
 #include "main/shaderapi.h"
 #include "main/shaderobj.h"
 #include "main/transformfeedback.h"
@@ -144,6 +145,8 @@ _mesa_free_shader_state(struct gl_context *ctx)
    _mesa_reference_shader_program(ctx, &ctx->Shader.ActiveProgram, NULL);
 
    /* Extended for ARB_separate_shader_objects */
+   _mesa_reference_pipeline_object(ctx, &ctx->_Shader, NULL);
+
    assert(ctx->Shader.RefCount == 1);
    mtx_destroy(&ctx->Shader.Mutex);
 }
@@ -1541,7 +1544,31 @@ _mesa_UseProgram(GLhandleARB program)
       shProg = NULL;
    }
 
-   _mesa_use_program(ctx, shProg);
+   /* The "Dependencies on EXT_separate_shader_objects" section of the
+    * ARB_separate_shader_object spec says:
+    *
+    *     "The executable code for an individual shader stage is taken from
+    *     the current program for that stage.  If there is a current program
+    *     object for any shader stage or for uniform updates established by
+    *     UseProgram, UseShaderProgramEXT, or ActiveProgramEXT, the current
+    *     program for that stage (if any) is considered current.  Otherwise,
+    *     if there is a bound program pipeline object ..."
+    */
+   if (program) {
+      /* Attach shader state to the binding point */
+      _mesa_reference_pipeline_object(ctx, &ctx->_Shader, &ctx->Shader);
+      /* Update the program */
+      _mesa_use_program(ctx, shProg);
+   } else {
+      /* Must be done first: detach the progam */
+      _mesa_use_program(ctx, shProg);
+      /* Unattach shader_state binding point */
+      _mesa_reference_pipeline_object(ctx, &ctx->_Shader, ctx->Pipeline.Default);
+      /* If a pipeline was bound, rebind it */
+      if (ctx->Pipeline.Current) {
+         _mesa_BindProgramPipeline(ctx->Pipeline.Current->Name);
+      }
+   }
 }
 
 
@@ -1815,7 +1842,41 @@ _mesa_UseShaderProgramEXT(GLenum type, GLuint program)
       }
    }
 
-   _mesa_use_shader_program(ctx, type, shProg);
+   /* The "Dependencies on EXT_separate_shader_objects" section of the
+    * ARB_separate_shader_object spec says:
+    *
+    *     "The executable code for an individual shader stage is taken from
+    *     the current program for that stage.  If there is a current program
+    *     object for any shader stage or for uniform updates established by
+    *     UseProgram, UseShaderProgramEXT, or ActiveProgramEXT, the current
+    *     program for that stage (if any) is considered current.  Otherwise,
+    *     if there is a bound program pipeline object ..."
+    */
+   if (program) {
+      /* Attach shader state to the binding point */
+      _mesa_reference_pipeline_object(ctx, &ctx->_Shader, &ctx->Shader);
+      /* Update the program */
+      _mesa_use_shader_program(ctx, type, shProg);
+   } else {
+      /* Must be done first: detach the progam */
+      _mesa_use_shader_program(ctx, type, shProg);
+
+      /* Nothing remains current */
+      if (!ctx->Shader.CurrentVertexProgram &&
+          !ctx->Shader.CurrentGeometryProgram &&
+          !ctx->Shader.CurrentFragmentProgram &&
+          !ctx->Shader.ActiveProgram) {
+
+         /* Unattach shader_state binding point */
+         _mesa_reference_pipeline_object(ctx, &ctx->_Shader,
+                                         ctx->Pipeline.Default);
+
+         /* If a pipeline was bound, rebind it */
+         if (ctx->Pipeline.Current) {
+            _mesa_BindProgramPipeline(ctx->Pipeline.Current->Name);
+         }
+      }
+   }
 }
 
 
@@ -1830,7 +1891,37 @@ _mesa_ActiveProgramEXT(GLuint program)
       ? _mesa_lookup_shader_program_err(ctx, program, "glActiveProgramEXT")
       : NULL;
 
-   _mesa_active_program(ctx, shProg, "glActiveProgramEXT");
+   /* The "Dependencies on EXT_separate_shader_objects" section of the
+    * ARB_separate_shader_object spec says:
+    *
+    *     "The executable code for an individual shader stage is taken from
+    *     the current program for that stage.  If there is a current program
+    *     object for any shader stage or for uniform updates established by
+    *     UseProgram, UseShaderProgramEXT, or ActiveProgramEXT, the current
+    *     program for that stage (if any) is considered current.  Otherwise,
+    *     if there is a bound program pipeline object ..."
+    */
+   if (shProg != NULL) {
+      /* Attach shader state to the binding point */
+      _mesa_reference_pipeline_object(ctx, &ctx->_Shader, &ctx->Shader);
+      _mesa_active_program(ctx, shProg, "glActiveProgramEXT");
+   } else {
+      /* Must be done first: unset the current active progam */
+      _mesa_active_program(ctx, shProg, "glActiveProgramEXT");
+
+      /* Nothing remains current */
+      if (!ctx->Shader.CurrentVertexProgram && !ctx->Shader.CurrentGeometryProgram &&
+          !ctx->Shader.CurrentFragmentProgram && !ctx->Shader.ActiveProgram) {
+
+         /* Unattach shader_state binding point */
+         _mesa_reference_pipeline_object(ctx, &ctx->_Shader, ctx->Pipeline.Default);
+         /* If a pipeline was bound, rebind it */
+         if (ctx->Pipeline.Current) {
+            _mesa_BindProgramPipeline(ctx->Pipeline.Current->Name);
+         }
+      }
+   }
+
    return;
 }