glsl: Add lowering pass for shared variable references

In this lowering pass, shared variables are decomposed into intrinsic
calls.

v2:
 * Send mem_ctx as a parameter (Iago)

v3:
 * Shared variables don't have an associated interface block (Iago)
 * Always use 430 packing (Iago)
 * Comment / whitespace cleanup (Iago)

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>

src/glsl/Makefile.sources

@@ -182,6 +182,7 @@ LIBGLSL_FILES = \
 	lower_vector_insert.cpp \
 	lower_vertex_id.cpp \
 	lower_output_reads.cpp \
+	lower_shared_reference.cpp \
 	lower_ubo_reference.cpp \
 	opt_algebraic.cpp \
 	opt_array_splitting.cpp \

src/glsl/ir_optimization.h

@@ -124,6 +124,7 @@ bool lower_const_arrays_to_uniforms(exec_list *instructions);
 bool lower_clip_distance(gl_shader *shader);
 void lower_output_reads(unsigned stage, exec_list *instructions);
 bool lower_packing_builtins(exec_list *instructions, int op_mask);
+void lower_shared_reference(struct gl_shader *shader, unsigned *shared_size);
 void lower_ubo_reference(struct gl_shader *shader);
 void lower_packed_varyings(void *mem_ctx,
                            unsigned locations_used, ir_variable_mode mode,

src/glsl/linker.cpp

@@ -4607,6 +4607,10 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
       if (ctx->Const.ShaderCompilerOptions[i].LowerBufferInterfaceBlocks)
          lower_ubo_reference(prog->_LinkedShaders[i]);
 
+      if (ctx->Const.ShaderCompilerOptions[i].LowerShaderSharedVariables)
+         lower_shared_reference(prog->_LinkedShaders[i],
+                                &prog->Comp.SharedSize);
+
       lower_vector_derefs(prog->_LinkedShaders[i]);
    }
 

src/glsl/lower_shared_reference.cpp

@@ -0,0 +1,348 @@
+/*
+ * Copyright (c) 2015 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 lower_shared_reference.cpp
+ *
+ * IR lower pass to replace dereferences of compute shader shared variables
+ * with intrinsic function calls.
+ *
+ * This relieves drivers of the responsibility of allocating space for the
+ * shared variables in the shared memory region.
+ */
+
+#include "lower_buffer_access.h"
+#include "ir_builder.h"
+#include "main/macros.h"
+#include "util/list.h"
+#include "glsl_parser_extras.h"
+
+using namespace ir_builder;
+
+namespace {
+
+struct var_offset {
+   struct list_head node;
+   const ir_variable *var;
+   unsigned offset;
+};
+
+class lower_shared_reference_visitor :
+      public lower_buffer_access::lower_buffer_access {
+public:
+
+   lower_shared_reference_visitor(struct gl_shader *shader)
+      : list_ctx(ralloc_context(NULL)), shader(shader), shared_size(0u)
+   {
+      list_inithead(&var_offsets);
+   }
+
+   ~lower_shared_reference_visitor()
+   {
+      ralloc_free(list_ctx);
+   }
+
+   enum {
+      shared_load_access,
+      shared_store_access,
+      shared_atomic_access,
+   } buffer_access_type;
+
+   void insert_buffer_access(void *mem_ctx, ir_dereference *deref,
+                             const glsl_type *type, ir_rvalue *offset,
+                             unsigned mask, int channel);
+
+   void handle_rvalue(ir_rvalue **rvalue);
+   ir_visitor_status visit_enter(ir_assignment *ir);
+   void handle_assignment(ir_assignment *ir);
+
+   unsigned get_shared_offset(const ir_variable *);
+
+   ir_call *shared_load(void *mem_ctx, const struct glsl_type *type,
+                        ir_rvalue *offset);
+   ir_call *shared_store(void *mem_ctx, ir_rvalue *deref, ir_rvalue *offset,
+                         unsigned write_mask);
+
+   void *list_ctx;
+   struct gl_shader *shader;
+   struct list_head var_offsets;
+   unsigned shared_size;
+   bool progress;
+};
+
+unsigned
+lower_shared_reference_visitor::get_shared_offset(const ir_variable *var)
+{
+   list_for_each_entry(var_offset, var_entry, &var_offsets, node) {
+      if (var_entry->var == var)
+         return var_entry->offset;
+   }
+
+   struct var_offset *new_entry = rzalloc(list_ctx, struct var_offset);
+   list_add(&new_entry->node, &var_offsets);
+   new_entry->var = var;
+
+   unsigned var_align = var->type->std430_base_alignment(false);
+   new_entry->offset = glsl_align(shared_size, var_align);
+
+   unsigned var_size = var->type->std430_size(false);
+   shared_size = new_entry->offset + var_size;
+
+   return new_entry->offset;
+}
+
+void
+lower_shared_reference_visitor::handle_rvalue(ir_rvalue **rvalue)
+{
+   if (!*rvalue)
+      return;
+
+   ir_dereference *deref = (*rvalue)->as_dereference();
+   if (!deref)
+      return;
+
+   ir_variable *var = deref->variable_referenced();
+   if (!var || var->data.mode != ir_var_shader_shared)
+      return;
+
+   buffer_access_type = shared_load_access;
+
+   void *mem_ctx = ralloc_parent(shader->ir);
+
+   ir_rvalue *offset = NULL;
+   unsigned const_offset = get_shared_offset(var);
+   bool row_major;
+   int matrix_columns;
+   assert(var->get_interface_type() == NULL);
+   const unsigned packing = GLSL_INTERFACE_PACKING_STD430;
+
+   setup_buffer_access(mem_ctx, var, deref,
+                       &offset, &const_offset,
+                       &row_major, &matrix_columns, packing);
+
+   /* Now that we've calculated the offset to the start of the
+    * dereference, walk over the type and emit loads into a temporary.
+    */
+   const glsl_type *type = (*rvalue)->type;
+   ir_variable *load_var = new(mem_ctx) ir_variable(type,
+                                                    "shared_load_temp",
+                                                    ir_var_temporary);
+   base_ir->insert_before(load_var);
+
+   ir_variable *load_offset = new(mem_ctx) ir_variable(glsl_type::uint_type,
+                                                       "shared_load_temp_offset",
+                                                       ir_var_temporary);
+   base_ir->insert_before(load_offset);
+   base_ir->insert_before(assign(load_offset, offset));
+
+   deref = new(mem_ctx) ir_dereference_variable(load_var);
+
+   emit_access(mem_ctx, false, deref, load_offset, const_offset, row_major,
+               matrix_columns, packing, 0);
+
+   *rvalue = deref;
+
+   progress = true;
+}
+
+void
+lower_shared_reference_visitor::handle_assignment(ir_assignment *ir)
+{
+   if (!ir || !ir->lhs)
+      return;
+
+   ir_rvalue *rvalue = ir->lhs->as_rvalue();
+   if (!rvalue)
+      return;
+
+   ir_dereference *deref = ir->lhs->as_dereference();
+   if (!deref)
+      return;
+
+   ir_variable *var = ir->lhs->variable_referenced();
+   if (!var || var->data.mode != ir_var_shader_shared)
+      return;
+
+   buffer_access_type = shared_store_access;
+
+   /* We have a write to a shared variable, so declare a temporary and rewrite
+    * the assignment so that the temporary is the LHS.
+    */
+   void *mem_ctx = ralloc_parent(shader->ir);
+
+   const glsl_type *type = rvalue->type;
+   ir_variable *store_var = new(mem_ctx) ir_variable(type,
+                                                     "shared_store_temp",
+                                                     ir_var_temporary);
+   base_ir->insert_before(store_var);
+   ir->lhs = new(mem_ctx) ir_dereference_variable(store_var);
+
+   ir_rvalue *offset = NULL;
+   unsigned const_offset = get_shared_offset(var);
+   bool row_major;
+   int matrix_columns;
+   assert(var->get_interface_type() == NULL);
+   const unsigned packing = GLSL_INTERFACE_PACKING_STD430;
+
+   setup_buffer_access(mem_ctx, var, deref,
+                       &offset, &const_offset,
+                       &row_major, &matrix_columns, packing);
+
+   deref = new(mem_ctx) ir_dereference_variable(store_var);
+
+   ir_variable *store_offset = new(mem_ctx) ir_variable(glsl_type::uint_type,
+                                                        "shared_store_temp_offset",
+                                                        ir_var_temporary);
+   base_ir->insert_before(store_offset);
+   base_ir->insert_before(assign(store_offset, offset));
+
+   /* Now we have to write the value assigned to the temporary back to memory */
+   emit_access(mem_ctx, true, deref, store_offset, const_offset, row_major,
+               matrix_columns, packing, ir->write_mask);
+
+   progress = true;
+}
+
+ir_visitor_status
+lower_shared_reference_visitor::visit_enter(ir_assignment *ir)
+{
+   handle_assignment(ir);
+   return rvalue_visit(ir);
+}
+
+void
+lower_shared_reference_visitor::insert_buffer_access(void *mem_ctx,
+                                                     ir_dereference *deref,
+                                                     const glsl_type *type,
+                                                     ir_rvalue *offset,
+                                                     unsigned mask,
+                                                     int channel)
+{
+   if (buffer_access_type == shared_store_access) {
+      ir_call *store = shared_store(mem_ctx, deref, offset, mask);
+      base_ir->insert_after(store);
+   } else {
+      ir_call *load = shared_load(mem_ctx, type, offset);
+      base_ir->insert_before(load);
+      ir_rvalue *value = load->return_deref->as_rvalue()->clone(mem_ctx, NULL);
+      base_ir->insert_before(assign(deref->clone(mem_ctx, NULL),
+                                    value));
+   }
+}
+
+static bool
+compute_shader_enabled(const _mesa_glsl_parse_state *state)
+{
+   return state->stage == MESA_SHADER_COMPUTE;
+}
+
+ir_call *
+lower_shared_reference_visitor::shared_store(void *mem_ctx,
+                                             ir_rvalue *deref,
+                                             ir_rvalue *offset,
+                                             unsigned write_mask)
+{
+   exec_list sig_params;
+
+   ir_variable *offset_ref = new(mem_ctx)
+      ir_variable(glsl_type::uint_type, "offset" , ir_var_function_in);
+   sig_params.push_tail(offset_ref);
+
+   ir_variable *val_ref = new(mem_ctx)
+      ir_variable(deref->type, "value" , ir_var_function_in);
+   sig_params.push_tail(val_ref);
+
+   ir_variable *writemask_ref = new(mem_ctx)
+      ir_variable(glsl_type::uint_type, "write_mask" , ir_var_function_in);
+   sig_params.push_tail(writemask_ref);
+
+   ir_function_signature *sig = new(mem_ctx)
+      ir_function_signature(glsl_type::void_type, compute_shader_enabled);
+   assert(sig);
+   sig->replace_parameters(&sig_params);
+   sig->is_intrinsic = true;
+
+   ir_function *f = new(mem_ctx) ir_function("__intrinsic_store_shared");
+   f->add_signature(sig);
+
+   exec_list call_params;
+   call_params.push_tail(offset->clone(mem_ctx, NULL));
+   call_params.push_tail(deref->clone(mem_ctx, NULL));
+   call_params.push_tail(new(mem_ctx) ir_constant(write_mask));
+   return new(mem_ctx) ir_call(sig, NULL, &call_params);
+}
+
+ir_call *
+lower_shared_reference_visitor::shared_load(void *mem_ctx,
+                                            const struct glsl_type *type,
+                                            ir_rvalue *offset)
+{
+   exec_list sig_params;
+
+   ir_variable *offset_ref = new(mem_ctx)
+      ir_variable(glsl_type::uint_type, "offset_ref" , ir_var_function_in);
+   sig_params.push_tail(offset_ref);
+
+   ir_function_signature *sig =
+      new(mem_ctx) ir_function_signature(type, compute_shader_enabled);
+   assert(sig);
+   sig->replace_parameters(&sig_params);
+   sig->is_intrinsic = true;
+
+   ir_function *f = new(mem_ctx) ir_function("__intrinsic_load_shared");
+   f->add_signature(sig);
+
+   ir_variable *result = new(mem_ctx)
+      ir_variable(type, "shared_load_result", ir_var_temporary);
+   base_ir->insert_before(result);
+   ir_dereference_variable *deref_result = new(mem_ctx)
+      ir_dereference_variable(result);
+
+   exec_list call_params;
+   call_params.push_tail(offset->clone(mem_ctx, NULL));
+
+   return new(mem_ctx) ir_call(sig, deref_result, &call_params);
+}
+
+} /* unnamed namespace */
+
+void
+lower_shared_reference(struct gl_shader *shader, unsigned *shared_size)
+{
+   if (shader->Stage != MESA_SHADER_COMPUTE)
+      return;
+
+   lower_shared_reference_visitor v(shader);
+
+   /* Loop over the instructions lowering references, because we take a deref
+    * of an shared variable array using a shared variable dereference as the
+    * index will produce a collection of instructions all of which have cloned
+    * shared variable dereferences for that array index.
+    */
+   do {
+      v.progress = false;
+      visit_list_elements(&v, shader->ir);
+   } while (v.progress);
+
+   *shared_size = v.shared_size;
+}

src/mesa/main/mtypes.h

@@ -2674,6 +2674,10 @@ struct gl_shader_program
        * local_size_{x,y,z}.  Otherwise undefined.
        */
       unsigned LocalSize[3];
+      /**
+       * Size of shared variables accessed by the compute shader.
+       */
+      unsigned SharedSize;
    } Comp;
 
    /* post-link info: */
@@ -2885,6 +2889,9 @@ struct gl_shader_compiler_options
 
    GLboolean LowerBufferInterfaceBlocks; /**< Lower UBO and SSBO access to intrinsics. */
 
+   GLboolean LowerShaderSharedVariables; /**< Lower compute shader shared
+                                          *   variable access to intrinsics. */
+
    const struct nir_shader_compiler_options *NirOptions;
 };