[Mesa-dev] [PATCH v2 1/4] glsl: look for multiple variables simultaneously with find_assignment_visitor

Nicolai Hähnle nhaehnle at gmail.com
Mon Jul 3 12:34:32 UTC 2017


From: Nicolai Hähnle <nicolai.haehnle at amd.com>

Save some passes over the IR.

v2: redesign to make the users of find_assignments more readable

Reviewed-by: Ian Romanick <ian.d.romanick at intel.com> (v1)
---
 src/compiler/glsl/linker.cpp | 120 ++++++++++++++++++++++++++++---------------
 1 file changed, 79 insertions(+), 41 deletions(-)

diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
index 15295da..4aa4682 100644
--- a/src/compiler/glsl/linker.cpp
+++ b/src/compiler/glsl/linker.cpp
@@ -83,82 +83,120 @@
 #include "ir_uniform.h"
 #include "builtin_functions.h"
 #include "shader_cache.h"
 
 #include "main/shaderobj.h"
 #include "main/enums.h"
 
 
 namespace {
 
+struct find_variable {
+   const char *name;
+   bool found;
+
+   find_variable(const char *name) : name(name), found(false) {}
+};
+
 /**
  * Visitor that determines whether or not a variable is ever written.
+ *
+ * Use \ref find_assignments for convenience.
  */
 class find_assignment_visitor : public ir_hierarchical_visitor {
 public:
-   find_assignment_visitor(const char *name)
-      : name(name), found(false)
+   find_assignment_visitor(unsigned num_vars,
+                           find_variable * const *vars)
+      : num_variables(num_vars), num_found(0), variables(vars)
    {
-      /* 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;
+      return check_variable_name(var->name);
    }
 
    virtual ir_visitor_status visit_enter(ir_call *ir)
    {
       foreach_two_lists(formal_node, &ir->callee->parameters,
                         actual_node, &ir->actual_parameters) {
          ir_rvalue *param_rval = (ir_rvalue *) actual_node;
          ir_variable *sig_param = (ir_variable *) formal_node;
 
          if (sig_param->data.mode == ir_var_function_out ||
              sig_param->data.mode == ir_var_function_inout) {
             ir_variable *var = param_rval->variable_referenced();
-            if (var && strcmp(name, var->name) == 0) {
-               found = true;
+            if (var && check_variable_name(var->name) == visit_stop)
                return visit_stop;
-            }
          }
       }
 
       if (ir->return_deref != NULL) {
          ir_variable *const var = ir->return_deref->variable_referenced();
 
-         if (strcmp(name, var->name) == 0) {
-            found = true;
+         if (check_variable_name(var->name) == visit_stop)
             return visit_stop;
-         }
       }
 
       return visit_continue_with_parent;
    }
 
-   bool variable_found()
+private:
+   ir_visitor_status check_variable_name(const char *name)
    {
-      return found;
+      for (unsigned i = 0; i < num_variables; ++i) {
+         if (strcmp(variables[i]->name, name) == 0) {
+            if (variables[i]->found) {
+               variables[i]->found = true;
+               if (++num_found >= num_variables)
+                  return visit_stop;
+            }
+            break;
+         }
+      }
+
+      return visit_continue_with_parent;
    }
 
 private:
-   const char *name;       /**< Find writes to a variable with this name. */
-   bool found;             /**< Was a write to the variable found? */
+   unsigned num_variables;
+   unsigned num_found;
+   find_variable * const *variables;
 };
 
+/**
+ * Determine whether or not any of NULL-terminated list of variables is ever
+ * written to.
+ */
+static void
+find_assignments(exec_list *ir, find_variable * const *vars)
+{
+   unsigned num_variables = 0;
+
+   for (find_variable * const *v = vars; *v; ++v)
+      num_variables++;
+
+   find_assignment_visitor visitor(num_variables, vars);
+   visitor.run(ir);
+}
+
+/**
+ * Determine whether or not the given variable is ever written to.
+ */
+static void
+find_assignments(exec_list *ir, find_variable *var)
+{
+   find_assignment_visitor visitor(1, &var);
+   visitor.run(ir);
+}
 
 /**
  * Visitor that determines whether or not a variable is ever read.
  */
 class find_deref_visitor : public ir_hierarchical_visitor {
 public:
    find_deref_visitor(const char *name)
       : name(name), found(false)
    {
       /* empty */
@@ -560,61 +598,62 @@ analyze_clip_cull_usage(struct gl_shader_program *prog,
       /* From section 7.1 (Vertex Shader Special Variables) of the
        * GLSL 1.30 spec:
        *
        *   "It is an error for a shader to statically write both
        *   gl_ClipVertex and gl_ClipDistance."
        *
        * This does not apply to GLSL ES shaders, since GLSL ES defines neither
        * gl_ClipVertex nor gl_ClipDistance. However with
        * GL_EXT_clip_cull_distance, this functionality is exposed in ES 3.0.
        */
-      find_assignment_visitor clip_distance("gl_ClipDistance");
-      find_assignment_visitor cull_distance("gl_CullDistance");
-
-      clip_distance.run(shader->ir);
-      cull_distance.run(shader->ir);
+      find_variable gl_ClipDistance("gl_ClipDistance");
+      find_variable gl_CullDistance("gl_CullDistance");
+      find_variable gl_ClipVertex("gl_ClipVertex");
+      find_variable * const variables[] = {
+         &gl_ClipDistance,
+         &gl_CullDistance,
+         !prog->IsES ? &gl_ClipVertex : NULL,
+         NULL
+      };
+      find_assignments(shader->ir, variables);
 
       /* From the ARB_cull_distance spec:
        *
        * It is a compile-time or link-time error for the set of shaders forming
        * a program to statically read or write both gl_ClipVertex and either
        * gl_ClipDistance or gl_CullDistance.
        *
        * This does not apply to GLSL ES shaders, since GLSL ES doesn't define
        * gl_ClipVertex.
        */
       if (!prog->IsES) {
-         find_assignment_visitor clip_vertex("gl_ClipVertex");
-
-         clip_vertex.run(shader->ir);
-
-         if (clip_vertex.variable_found() && clip_distance.variable_found()) {
+         if (gl_ClipVertex.found && gl_ClipDistance.found) {
             linker_error(prog, "%s shader writes to both `gl_ClipVertex' "
                          "and `gl_ClipDistance'\n",
                          _mesa_shader_stage_to_string(shader->Stage));
             return;
          }
-         if (clip_vertex.variable_found() && cull_distance.variable_found()) {
+         if (gl_ClipVertex.found && gl_CullDistance.found) {
             linker_error(prog, "%s shader writes to both `gl_ClipVertex' "
                          "and `gl_CullDistance'\n",
                          _mesa_shader_stage_to_string(shader->Stage));
             return;
          }
       }
 
-      if (clip_distance.variable_found()) {
+      if (gl_ClipDistance.found) {
          ir_variable *clip_distance_var =
                 shader->symbols->get_variable("gl_ClipDistance");
          assert(clip_distance_var);
          *clip_distance_array_size = clip_distance_var->type->length;
       }
-      if (cull_distance.variable_found()) {
+      if (gl_CullDistance.found) {
          ir_variable *cull_distance_var =
                 shader->symbols->get_variable("gl_CullDistance");
          assert(cull_distance_var);
          *cull_distance_array_size = cull_distance_var->type->length;
       }
       /* From the ARB_cull_distance spec:
        *
        * It is a compile-time or link-time error for the set of shaders forming
        * a program to have the sum of the sizes of the gl_ClipDistance and
        * gl_CullDistance arrays to be larger than
@@ -669,23 +708,23 @@ validate_vertex_shader_executable(struct gl_shader_program *prog,
     *      after being written. This value will be used by primitive
     *      assembly, clipping, culling, and other fixed functionality
     *      operations, if present, that operate on primitives after
     *      vertex processing has occurred. Its value is undefined if
     *      the vertex shader executable does not write gl_Position."
     *
     * All GLSL ES Versions are similar to GLSL 1.40--failing to write to
     * gl_Position is not an error.
     */
    if (prog->data->Version < (prog->IsES ? 300 : 140)) {
-      find_assignment_visitor find("gl_Position");
-      find.run(shader->ir);
-      if (!find.variable_found()) {
+      find_variable gl_Position("gl_Position");
+      find_assignments(shader->ir, &gl_Position);
+      if (!gl_Position.found) {
         if (prog->IsES) {
           linker_warning(prog,
                          "vertex shader does not write to `gl_Position'. "
                          "Its value is undefined. \n");
         } else {
           linker_error(prog,
                        "vertex shader does not write to `gl_Position'. \n");
         }
          return;
       }
@@ -715,27 +754,26 @@ validate_tess_eval_shader_executable(struct gl_shader_program *prog,
  *
  * \param shader  Fragment shader executable to be verified
  */
 void
 validate_fragment_shader_executable(struct gl_shader_program *prog,
                                     struct gl_linked_shader *shader)
 {
    if (shader == NULL)
       return;
 
-   find_assignment_visitor frag_color("gl_FragColor");
-   find_assignment_visitor frag_data("gl_FragData");
-
-   frag_color.run(shader->ir);
-   frag_data.run(shader->ir);
+   find_variable gl_FragColor("gl_FragColor");
+   find_variable gl_FragData("gl_FragData");
+   find_variable * const variables[] = { &gl_FragColor, &gl_FragData, NULL };
+   find_assignments(shader->ir, variables);
 
-   if (frag_color.variable_found() && frag_data.variable_found()) {
+   if (gl_FragColor.found && gl_FragData.found) {
       linker_error(prog,  "fragment shader writes to both "
                    "`gl_FragColor' and `gl_FragData'\n");
    }
 }
 
 /**
  * Verify that a geometry shader executable meets all semantic requirements
  *
  * Also sets prog->Geom.VerticesIn, and info.clip_distance_array_sizeand
  * info.cull_distance_array_size as a side effect.
-- 
2.9.3



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