linker: Initial bits of the linker

No linking is done yet, but some of the semantic checking is done.

Makefile.am

@@ -51,7 +51,8 @@ glsl_SOURCES = \
 	ir_hierarchical_visitor.h \
 	ir_hierarchical_visitor.cpp \
 	ir_swizzle_swizzle.cpp \
-	ir_vec_index_to_swizzle.cpp
+	ir_vec_index_to_swizzle.cpp \
+	linker.cpp
 
 BUILT_SOURCES = glsl_parser.h glsl_parser.cpp glsl_lexer.cpp
 CLEANFILES = $(BUILT_SOURCES)

linker.cpp

@@ -0,0 +1,214 @@
+/*
+ * Copyright © 2010 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+/**
+ * \file linker.cpp
+ * GLSL linker implementation
+ *
+ * Given a set of shaders that are to be linked to generate a final program,
+ * there are three distinct stages.
+ *
+ * In the first stage shaders are partitioned into groups based on the shader
+ * type.  All shaders of a particular type (e.g., vertex shaders) are linked
+ * together.
+ *
+ *   - Undefined references in each shader are resolve to definitions in
+ *     another shader.
+ *   - Types and qualifiers of uniforms, outputs, and global variables defined
+ *     in multiple shaders with the same name are verified to be the same.
+ *   - Initializers for uniforms and global variables defined
+ *     in multiple shaders with the same name are verified to be the same.
+ *
+ * The result, in the terminology of the GLSL spec, is a set of shader
+ * executables for each processing unit.
+ *
+ * After the first stage is complete, a series of semantic checks are performed
+ * on each of the shader executables.
+ *
+ *   - Each shader executable must define a \c main function.
+ *   - Each vertex shader executable must write to \c gl_Position.
+ *   - Each fragment shader executable must write to either \c gl_FragData or
+ *     \c gl_FragColor.
+ *
+ * In the final stage individual shader executables are linked to create a
+ * complete exectuable.
+ *
+ *   - Types of uniforms defined in multiple shader stages with the same name
+ *     are verified to be the same.
+ *   - Initializers for uniforms defined in multiple shader stages with the
+ *     same name are verified to be the same.
+ *   - Types and qualifiers of outputs defined in one stage are verified to
+ *     be the same as the types and qualifiers of inputs defined with the same
+ *     name in a later stage.
+ *
+ * \author Ian Romanick <ian.d.romanick@intel.com>
+ */
+#include <cstdlib>
+#include <cstdio>
+
+#include "glsl_symbol_table.h"
+#include "glsl_parser_extras.h"
+#include "ir.h"
+#include "program.h"
+
+/**
+ * Visitor that determines whether or not a variable is ever written.
+ */
+class find_assignment_visitor : public ir_hierarchical_visitor {
+public:
+   find_assignment_visitor(const char *name)
+      : name(name), found(false)
+   {
+      /* empty */
+   }
+
+   virtual ir_visitor_status visit_enter(ir_assignment *ir)
+   {
+      ir_variable *const var = ir->lhs->variable_referenced();
+
+      if (strcmp(name, var->name) == 0) {
+	 found = true;
+	 return visit_stop;
+      }
+
+      return visit_continue_with_parent;
+   }
+
+   bool variable_found()
+   {
+      return found;
+   }
+
+private:
+   const char *name;       /**< Find writes to a variable with this name. */
+   bool found;             /**< Was a write to the variable found? */
+};
+
+bool
+validate_vertex_shader_executable(struct glsl_shader *shader)
+{
+   if (shader == NULL)
+      return true;
+
+   if (!shader->symbols->get_function("main")) {
+      printf("error: vertex shader lacks `main'\n");
+      return false;
+   }
+
+   find_assignment_visitor find("gl_Position");
+   find.run(&shader->ir);
+   if (!find.variable_found()) {
+      printf("error: vertex shader does not write to `gl_Position'\n");
+      return false;
+   }
+
+   return true;
+}
+
+
+bool
+validate_fragment_shader_executable(struct glsl_shader *shader)
+{
+   if (shader == NULL)
+      return true;
+
+   if (!shader->symbols->get_function("main")) {
+      printf("error: fragment shader lacks `main'\n");
+      return false;
+   }
+
+   find_assignment_visitor frag_color("gl_FragColor");
+   find_assignment_visitor frag_data("gl_FragData");
+
+   frag_color.run(&shader->ir);
+   frag_data.run(&shader->ir);
+
+   if (!frag_color.variable_found() && !frag_data.variable_found()) {
+      printf("error: fragment shader does not write to `gl_FragColor' or "
+	     "`gl_FragData'\n");
+      return false;
+   }
+
+   if (frag_color.variable_found() && frag_data.variable_found()) {
+      printf("error: fragment shader write to both `gl_FragColor' and "
+	     "`gl_FragData'\n");
+      return false;
+   }
+
+   return true;
+}
+
+
+void
+link_shaders(struct glsl_program *prog)
+{
+   prog->LinkStatus = false;
+   prog->Validated = false;
+   prog->_Used = false;
+
+   /* Separate the shaders into groups based on their type.
+    */
+   struct glsl_shader **vert_shader_list;
+   unsigned num_vert_shaders = 0;
+   struct glsl_shader **frag_shader_list;
+   unsigned num_frag_shaders = 0;
+
+   vert_shader_list = (struct glsl_shader **)
+      malloc(sizeof(struct glsl_shader *) * 2 * prog->NumShaders);
+   frag_shader_list =  &vert_shader_list[prog->NumShaders];
+
+   for (unsigned i = 0; i < prog->NumShaders; i++) {
+      switch (prog->Shaders[i]->Type) {
+      case GL_VERTEX_SHADER:
+	 vert_shader_list[num_vert_shaders] = prog->Shaders[i];
+	 num_vert_shaders++;
+	 break;
+      case GL_FRAGMENT_SHADER:
+	 frag_shader_list[num_frag_shaders] = prog->Shaders[i];
+	 num_frag_shaders++;
+	 break;
+      case GL_GEOMETRY_SHADER:
+	 /* FINISHME: Support geometry shaders. */
+	 assert(prog->Shaders[i]->Type != GL_GEOMETRY_SHADER);
+	 break;
+      }
+   }
+
+   /* FINISHME: Implement intra-stage linking. */
+   assert(num_vert_shaders <= 1);
+   assert(num_frag_shaders <= 1);
+
+   /* Verify that each of the per-target executables is valid.
+    */
+   if (!validate_vertex_shader_executable(vert_shader_list[0])
+       || !validate_fragment_shader_executable(frag_shader_list[0]))
+      goto done;
+
+
+   /* FINISHME: Perform inter-stage linking. */
+
+   prog->LinkStatus = true;
+
+done:
+   free(vert_shader_list);
+}

main.cpp

@@ -214,5 +214,10 @@ main(int argc, char **argv)
       }
    }
 
+   if (status == EXIT_SUCCESS) {
+      link_shaders(&whole_program);
+      status = (whole_program.LinkStatus) ? EXIT_SUCCESS : EXIT_FAILURE;
+   }
+
    return status;
 }

program.h

@@ -64,3 +64,6 @@ struct glsl_program {
    GLboolean _Used;        /**< Ever used for drawing? */
    GLchar *InfoLog;
 };
+
+extern void
+link_shaders(struct glsl_program *prog);