glsl: fix derived cs variables

There are two issues with the current implementation. First, it relies
on the layout(local_size_*) happening in the same shader as the main
function, and secondly it doesn't work for variable group sizes.

In both cases, the simplest fix is to move the setup of these derived
values to a later time, similar to how the gl_VertexID workarounds are
done. There already exist system values defined for both of the derived
values, so we use them unconditionally, and lower them after linking is
performed.

While we're at it, we move to using gl_LocalGroupSizeARB instead of
gl_WorkGroupSize for variable group sizes.

Also the dead code elimination avoidance can be removed, since there
can be situations where gl_LocalGroupSizeARB is needed but has not been
inserted for the shader with main function. As a result, the lowering
code has to insert its own copies of the system values if needed.

Reported-by: Stephane Chevigny <[email protected]>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103393
Cc: [email protected]
Signed-off-by: Ilia Mirkin <[email protected]>
Reviewed-by: Jordan Justen <[email protected]>
Reviewed-by: Samuel Pitoiset <[email protected]>

8 files changed, 243 insertions, 118 deletions

diff --git a/src/compiler/glsl/builtin_variables.cpp b/src/compiler/glsl/builtin_variables.cpp
index ea2d897cc8e..00bc99dd619 100644
--- a/src/compiler/glsl/builtin_variables.cpp
+++ b/src/compiler/glsl/builtin_variables.cpp
@@ -1295,15 +1295,10 @@ builtin_variable_generator::generate_cs_special_vars()
                        uvec3_t, "gl_LocalGroupSizeARB");
    }
 
-   if (state->ctx->Const.LowerCsDerivedVariables) {
-      add_variable("gl_GlobalInvocationID", uvec3_t, ir_var_auto, 0);
-      add_variable("gl_LocalInvocationIndex", uint_t, ir_var_auto, 0);
-   } else {
-      add_system_value(SYSTEM_VALUE_GLOBAL_INVOCATION_ID,
-                       uvec3_t, "gl_GlobalInvocationID");
-      add_system_value(SYSTEM_VALUE_LOCAL_INVOCATION_INDEX,
-                       uint_t, "gl_LocalInvocationIndex");
-   }
+   add_system_value(SYSTEM_VALUE_GLOBAL_INVOCATION_ID,
+                    uvec3_t, "gl_GlobalInvocationID");
+   add_system_value(SYSTEM_VALUE_LOCAL_INVOCATION_INDEX,
+                    uint_t, "gl_LocalInvocationIndex");
 }
 
 
@@ -1474,84 +1469,3 @@ _mesa_glsl_initialize_variables(exec_list *instructions,
       break;
    }
 }
-
-
-/**
- * Initialize compute shader variables with values that are derived from other
- * compute shader variable.
- */
-static void
-initialize_cs_derived_variables(gl_shader *shader,
-                                ir_function_signature *const main_sig)
-{
-   assert(shader->Stage == MESA_SHADER_COMPUTE);
-
-   ir_variable *gl_GlobalInvocationID =
-      shader->symbols->get_variable("gl_GlobalInvocationID");
-   assert(gl_GlobalInvocationID);
-   ir_variable *gl_WorkGroupID =
-      shader->symbols->get_variable("gl_WorkGroupID");
-   assert(gl_WorkGroupID);
-   ir_variable *gl_WorkGroupSize =
-      shader->symbols->get_variable("gl_WorkGroupSize");
-   if (gl_WorkGroupSize == NULL) {
-      void *const mem_ctx = ralloc_parent(shader->ir);
-      gl_WorkGroupSize = new(mem_ctx) ir_variable(glsl_type::uvec3_type,
-                                                  "gl_WorkGroupSize",
-                                                  ir_var_auto);
-      gl_WorkGroupSize->data.how_declared = ir_var_declared_implicitly;
-      gl_WorkGroupSize->data.read_only = true;
-      shader->ir->push_head(gl_WorkGroupSize);
-   }
-   ir_variable *gl_LocalInvocationID =
-      shader->symbols->get_variable("gl_LocalInvocationID");
-   assert(gl_LocalInvocationID);
-
-   /* gl_GlobalInvocationID =
-    *    gl_WorkGroupID * gl_WorkGroupSize + gl_LocalInvocationID
-    */
-   ir_instruction *inst =
-      assign(gl_GlobalInvocationID,
-             add(mul(gl_WorkGroupID, gl_WorkGroupSize),
-                 gl_LocalInvocationID));
-   main_sig->body.push_head(inst);
-
-   /* gl_LocalInvocationIndex =
-    *    gl_LocalInvocationID.z * gl_WorkGroupSize.x * gl_WorkGroupSize.y +
-    *    gl_LocalInvocationID.y * gl_WorkGroupSize.x +
-    *    gl_LocalInvocationID.x;
-    */
-   ir_expression *index_z =
-      mul(mul(swizzle_z(gl_LocalInvocationID), swizzle_x(gl_WorkGroupSize)),
-          swizzle_y(gl_WorkGroupSize));
-   ir_expression *index_y =
-      mul(swizzle_y(gl_LocalInvocationID), swizzle_x(gl_WorkGroupSize));
-   ir_expression *index_y_plus_z = add(index_y, index_z);
-   operand index_x(swizzle_x(gl_LocalInvocationID));
-   ir_expression *index_x_plus_y_plus_z = add(index_y_plus_z, index_x);
-   ir_variable *gl_LocalInvocationIndex =
-      shader->symbols->get_variable("gl_LocalInvocationIndex");
-   assert(gl_LocalInvocationIndex);
-   inst = assign(gl_LocalInvocationIndex, index_x_plus_y_plus_z);
-   main_sig->body.push_head(inst);
-}
-
-
-/**
- * Initialize builtin variables with values based on other builtin variables.
- * These are initialized in the main function.
- */
-void
-_mesa_glsl_initialize_derived_variables(struct gl_context *ctx,
-                                        gl_shader *shader)
-{
-   /* We only need to set CS variables currently. */
-   if (shader->Stage == MESA_SHADER_COMPUTE &&
-       ctx->Const.LowerCsDerivedVariables) {
-      ir_function_signature *const main_sig =
-         _mesa_get_main_function_signature(shader->symbols);
-
-      if (main_sig != NULL)
-         initialize_cs_derived_variables(shader, main_sig);
-   }
-}
diff --git a/src/compiler/glsl/glsl_parser_extras.cpp b/src/compiler/glsl/glsl_parser_extras.cpp
index 764c05ad802..51d835bc535 100644
--- a/src/compiler/glsl/glsl_parser_extras.cpp
+++ b/src/compiler/glsl/glsl_parser_extras.cpp
@@ -2009,8 +2009,6 @@ opt_shader_and_create_symbol_table(struct gl_context *ctx,
          break;
       }
    }
-
-   _mesa_glsl_initialize_derived_variables(ctx, shader);
 }
 
 void
diff --git a/src/compiler/glsl/ir.h b/src/compiler/glsl/ir.h
index 27eafe8e22b..070d7b3ffdd 100644
--- a/src/compiler/glsl/ir.h
+++ b/src/compiler/glsl/ir.h
@@ -2413,10 +2413,6 @@ _mesa_glsl_initialize_variables(exec_list *instructions,
 				struct _mesa_glsl_parse_state *state);
 
 extern void
-_mesa_glsl_initialize_derived_variables(struct gl_context *ctx,
-                                        gl_shader *shader);
-
-extern void
 reparent_ir(exec_list *list, void *mem_ctx);
 
 extern void
diff --git a/src/compiler/glsl/ir_optimization.h b/src/compiler/glsl/ir_optimization.h
index eb3ec3b0c7d..f44ddcb05be 100644
--- a/src/compiler/glsl/ir_optimization.h
+++ b/src/compiler/glsl/ir_optimization.h
@@ -166,6 +166,7 @@ void optimize_dead_builtin_variables(exec_list *instructions,
 bool lower_tess_level(gl_linked_shader *shader);
 
 bool lower_vertex_id(gl_linked_shader *shader);
+bool lower_cs_derived(gl_linked_shader *shader);
 bool lower_blend_equation_advanced(gl_linked_shader *shader);
 
 bool lower_subroutine(exec_list *instructions, struct _mesa_glsl_parse_state *state);
diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
index 37983096784..94bd7fb6592 100644
--- a/src/compiler/glsl/linker.cpp
+++ b/src/compiler/glsl/linker.cpp
@@ -2374,6 +2374,9 @@ link_intrastage_shaders(void *mem_ctx,
    if (ctx->Const.VertexID_is_zero_based)
       lower_vertex_id(linked);
 
+   if (ctx->Const.LowerCsDerivedVariables)
+      lower_cs_derived(linked);
+
 #ifdef DEBUG
    /* Compute the source checksum. */
    linked->SourceChecksum = 0;
diff --git a/src/compiler/glsl/lower_cs_derived.cpp b/src/compiler/glsl/lower_cs_derived.cpp
new file mode 100644
index 00000000000..f7ec2a48b47
--- /dev/null
+++ b/src/compiler/glsl/lower_cs_derived.cpp
@@ -0,0 +1,234 @@
+/*
+ * Copyright © 2017 Ilia Mirkin
+ *
+ * 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 lower_cs_derived.cpp
+ *
+ * For hardware that does not support the gl_GlobalInvocationID and
+ * gl_LocalInvocationIndex system values, replace them with fresh
+ * globals. Note that we can't rely on gl_WorkGroupSize or
+ * gl_LocalGroupSizeARB being available, since they may only have been defined
+ * in a non-main shader.
+ *
+ * [ This can happen if only a secondary shader has the layout(local_size_*)
+ *   declaration. ]
+ *
+ * This is meant to be run post-linking.
+ */
+
+#include "glsl_symbol_table.h"
+#include "ir_hierarchical_visitor.h"
+#include "ir.h"
+#include "ir_builder.h"
+#include "linker.h"
+#include "program/prog_statevars.h"
+#include "builtin_functions.h"
+
+using namespace ir_builder;
+
+namespace {
+
+class lower_cs_derived_visitor : public ir_hierarchical_visitor {
+public:
+   explicit lower_cs_derived_visitor(gl_linked_shader *shader)
+      : progress(false),
+        shader(shader),
+        local_size_variable(shader->Program->info.cs.local_size_variable),
+        gl_WorkGroupSize(NULL),
+        gl_WorkGroupID(NULL),
+        gl_LocalInvocationID(NULL),
+        gl_GlobalInvocationID(NULL),
+        gl_LocalInvocationIndex(NULL)
+   {
+      main_sig = _mesa_get_main_function_signature(shader->symbols);
+      assert(main_sig);
+   }
+
+   virtual ir_visitor_status visit(ir_dereference_variable *);
+
+   ir_variable *add_system_value(
+         int slot, const glsl_type *type, const char *name);
+   void find_sysvals();
+   void make_gl_GlobalInvocationID();
+   void make_gl_LocalInvocationIndex();
+
+   bool progress;
+
+private:
+   gl_linked_shader *shader;
+   bool local_size_variable;
+   ir_function_signature *main_sig;
+
+   ir_rvalue *gl_WorkGroupSize;
+   ir_variable *gl_WorkGroupID;
+   ir_variable *gl_LocalInvocationID;
+
+   ir_variable *gl_GlobalInvocationID;
+   ir_variable *gl_LocalInvocationIndex;
+};
+
+} /* anonymous namespace */
+
+ir_variable *
+lower_cs_derived_visitor::add_system_value(
+      int slot, const glsl_type *type, const char *name)
+{
+   ir_variable *var = new(shader) ir_variable(type, name, ir_var_system_value);
+   var->data.how_declared = ir_var_declared_implicitly;
+   var->data.read_only = true;
+   var->data.location = slot;
+   var->data.explicit_location = true;
+   var->data.explicit_index = 0;
+   shader->ir->push_head(var);
+
+   return var;
+}
+
+void
+lower_cs_derived_visitor::find_sysvals()
+{
+   if (gl_WorkGroupSize != NULL)
+      return;
+
+   ir_variable *WorkGroupSize;
+   if (local_size_variable)
+      WorkGroupSize = shader->symbols->get_variable("gl_LocalGroupSizeARB");
+   else
+      WorkGroupSize = shader->symbols->get_variable("gl_WorkGroupSize");
+   if (WorkGroupSize)
+      gl_WorkGroupSize = new(shader) ir_dereference_variable(WorkGroupSize);
+   gl_WorkGroupID = shader->symbols->get_variable("gl_WorkGroupID");
+   gl_LocalInvocationID = shader->symbols->get_variable("gl_LocalInvocationID");
+
+   /*
+    * These may be missing due to either dead code elimination, or, in the
+    * case of the group size, due to the layout being declared in a non-main
+    * shader. Re-create them.
+    */
+
+   if (!gl_WorkGroupID)
+      gl_WorkGroupID = add_system_value(
+            SYSTEM_VALUE_WORK_GROUP_ID, glsl_type::uvec3_type, "gl_WorkGroupID");
+   if (!gl_LocalInvocationID)
+      gl_LocalInvocationID = add_system_value(
+            SYSTEM_VALUE_LOCAL_INVOCATION_ID, glsl_type::uvec3_type,
+            "gl_LocalInvocationID");
+   if (!WorkGroupSize) {
+      if (local_size_variable) {
+         gl_WorkGroupSize = new(shader) ir_dereference_variable(
+               add_system_value(
+                     SYSTEM_VALUE_LOCAL_GROUP_SIZE, glsl_type::uvec3_type,
+                     "gl_LocalGroupSizeARB"));
+      } else {
+         ir_constant_data data;
+         memset(&data, 0, sizeof(data));
+         for (int i = 0; i < 3; i++)
+            data.u[i] = shader->Program->info.cs.local_size[i];
+         gl_WorkGroupSize = new(shader) ir_constant(glsl_type::uvec3_type, &data);
+      }
+   }
+}
+
+void
+lower_cs_derived_visitor::make_gl_GlobalInvocationID()
+{
+   if (gl_GlobalInvocationID != NULL)
+      return;
+
+   find_sysvals();
+
+   /* gl_GlobalInvocationID =
+    *    gl_WorkGroupID * gl_WorkGroupSize + gl_LocalInvocationID
+    */
+   gl_GlobalInvocationID = new(shader) ir_variable(
+         glsl_type::uvec3_type, "__GlobalInvocationID", ir_var_temporary);
+   shader->ir->push_head(gl_GlobalInvocationID);
+
+   ir_instruction *inst =
+      assign(gl_GlobalInvocationID,
+             add(mul(gl_WorkGroupID, gl_WorkGroupSize->clone(shader, NULL)),
+                 gl_LocalInvocationID));
+   main_sig->body.push_head(inst);
+}
+
+void
+lower_cs_derived_visitor::make_gl_LocalInvocationIndex()
+{
+   if (gl_LocalInvocationIndex != NULL)
+      return;
+
+   find_sysvals();
+
+   /* gl_LocalInvocationIndex =
+    *    gl_LocalInvocationID.z * gl_WorkGroupSize.x * gl_WorkGroupSize.y +
+    *    gl_LocalInvocationID.y * gl_WorkGroupSize.x +
+    *    gl_LocalInvocationID.x;
+    */
+   gl_LocalInvocationIndex = new(shader)
+      ir_variable(glsl_type::uint_type, "__LocalInvocationIndex", ir_var_temporary);
+   shader->ir->push_head(gl_LocalInvocationIndex);
+
+   ir_expression *index_z =
+      mul(mul(swizzle_z(gl_LocalInvocationID), swizzle_x(gl_WorkGroupSize->clone(shader, NULL))),
+          swizzle_y(gl_WorkGroupSize->clone(shader, NULL)));
+   ir_expression *index_y =
+      mul(swizzle_y(gl_LocalInvocationID), swizzle_x(gl_WorkGroupSize->clone(shader, NULL)));
+   ir_expression *index_y_plus_z = add(index_y, index_z);
+   operand index_x(swizzle_x(gl_LocalInvocationID));
+   ir_expression *index_x_plus_y_plus_z = add(index_y_plus_z, index_x);
+   ir_instruction *inst =
+      assign(gl_LocalInvocationIndex, index_x_plus_y_plus_z);
+   main_sig->body.push_head(inst);
+}
+
+ir_visitor_status
+lower_cs_derived_visitor::visit(ir_dereference_variable *ir)
+{
+   if (ir->var->data.mode == ir_var_system_value &&
+       ir->var->data.location == SYSTEM_VALUE_GLOBAL_INVOCATION_ID) {
+      make_gl_GlobalInvocationID();
+      ir->var = gl_GlobalInvocationID;
+      progress = true;
+   }
+
+   if (ir->var->data.mode == ir_var_system_value &&
+       ir->var->data.location == SYSTEM_VALUE_LOCAL_INVOCATION_INDEX) {
+      make_gl_LocalInvocationIndex();
+      ir->var = gl_LocalInvocationIndex;
+      progress = true;
+   }
+
+   return visit_continue;
+}
+
+bool
+lower_cs_derived(gl_linked_shader *shader)
+{
+   if (shader->Stage != MESA_SHADER_COMPUTE)
+      return false;
+
+   lower_cs_derived_visitor v(shader);
+   v.run(shader->ir);
+
+   return v.progress;
+}
diff --git a/src/compiler/glsl/meson.build b/src/compiler/glsl/meson.build
index d1a75eb8c36..76fcafb9910 100644
--- a/src/compiler/glsl/meson.build
+++ b/src/compiler/glsl/meson.build
@@ -124,6 +124,7 @@ files_libglsl = files(
   'lower_buffer_access.cpp',
   'lower_buffer_access.h',
   'lower_const_arrays_to_uniforms.cpp',
+  'lower_cs_derived.cpp',
   'lower_discard.cpp',
   'lower_discard_flow.cpp',
   'lower_distance.cpp',
diff --git a/src/compiler/glsl/opt_dead_builtin_variables.cpp b/src/compiler/glsl/opt_dead_builtin_variables.cpp
index 03e578982b9..0d4e3a8f00a 100644
--- a/src/compiler/glsl/opt_dead_builtin_variables.cpp
+++ b/src/compiler/glsl/opt_dead_builtin_variables.cpp
@@ -62,23 +62,6 @@ optimize_dead_builtin_variables(exec_list *instructions,
        * information, so removing these variables from the user shader will
        * cause problems later.
        *
-       * For compute shaders, gl_GlobalInvocationID has some dependencies, so
-       * we avoid removing these dependencies.
-       *
-       * We also avoid removing gl_GlobalInvocationID at this stage because it
-       * might be used by a linked shader. In this case it still needs to be
-       * initialized by the main function.
-       *
-       *    gl_GlobalInvocationID =
-       *       gl_WorkGroupID * gl_WorkGroupSize + gl_LocalInvocationID
-       *
-       * Similarly, we initialize gl_LocalInvocationIndex in the main function:
-       *
-       *    gl_LocalInvocationIndex =
-       *       gl_LocalInvocationID.z * gl_WorkGroupSize.x * gl_WorkGroupSize.y +
-       *       gl_LocalInvocationID.y * gl_WorkGroupSize.x +
-       *       gl_LocalInvocationID.x;
-       *
        * Matrix uniforms with "Transpose" are not eliminated because there's
        * an optimization pass that can turn references to the regular matrix
        * into references to the transpose matrix.  Eliminating the transpose
@@ -90,11 +73,6 @@ optimize_dead_builtin_variables(exec_list *instructions,
        */
       if (strcmp(var->name, "gl_ModelViewProjectionMatrix") == 0
           || strcmp(var->name, "gl_Vertex") == 0
-          || strcmp(var->name, "gl_WorkGroupID") == 0
-          || strcmp(var->name, "gl_WorkGroupSize") == 0
-          || strcmp(var->name, "gl_LocalInvocationID") == 0
-          || strcmp(var->name, "gl_GlobalInvocationID") == 0
-          || strcmp(var->name, "gl_LocalInvocationIndex") == 0
           || strstr(var->name, "Transpose") != NULL)
          continue;