glsl/ir: add subroutine lowering pass (v2.3)

This lowers the enhanced ir_call using the lookaside table
of subroutines into an if ladder. This initially was done
at the AST level but it caused some ordering issues so a separate
pass was required.

v2: clone return value derefs.
v2.1: update for subroutine->int convert.
v2.2: add a clone for the array index

Reviewed-by: Chris Forbes <chrisf@ijw.co.nz>
Signed-off-by: Dave Airlie <airlied@redhat.com>

src/glsl/Makefile.sources

@@ -154,6 +154,7 @@ LIBGLSL_FILES = \
 	lower_packed_varyings.cpp \
 	lower_named_interface_blocks.cpp \
 	lower_packing_builtins.cpp \
+	lower_subroutine.cpp \
 	lower_tess_level.cpp \
 	lower_texture_projection.cpp \
 	lower_variable_index_to_cond_assign.cpp \

src/glsl/glsl_parser_extras.cpp

@@ -1617,6 +1617,7 @@ _mesa_glsl_compile_shader(struct gl_context *ctx, struct gl_shader *shader,
       struct gl_shader_compiler_options *options =
          &ctx->Const.ShaderCompilerOptions[shader->Stage];
 
+      lower_subroutine(shader->ir, state);
       /* Do some optimization at compile time to reduce shader IR size
        * and reduce later work if the same shader is linked multiple times
        */

src/glsl/ir_optimization.h

@@ -137,6 +137,8 @@ bool lower_tess_level(gl_shader *shader);
 
 bool lower_vertex_id(gl_shader *shader);
 
+bool lower_subroutine(exec_list *instructions, struct _mesa_glsl_parse_state *state);
+
 ir_rvalue *
 compare_index_block(exec_list *instructions, ir_variable *index,
 		    unsigned base, unsigned components, void *mem_ctx);

src/glsl/lower_subroutine.cpp

@@ -0,0 +1,109 @@
+/*
+ * Copyright © 2015 Red Hat
+ *
+ * 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_subroutine.cpp
+ *
+ * lowers subroutines to an if ladder.
+ */
+
+#include "glsl_types.h"
+#include "glsl_parser_extras.h"
+#include "ir.h"
+#include "ir_builder.h"
+
+using namespace ir_builder;
+namespace {
+
+class lower_subroutine_visitor : public ir_hierarchical_visitor {
+public:
+   lower_subroutine_visitor()
+   {
+      this->progress = false;
+   }
+
+   ir_visitor_status visit_leave(ir_call *);
+   bool progress;
+   struct _mesa_glsl_parse_state *state;
+};
+
+}
+
+bool
+lower_subroutine(exec_list *instructions, struct _mesa_glsl_parse_state *state)
+{
+   lower_subroutine_visitor v;
+   v.state = state;
+   visit_list_elements(&v, instructions);
+   return v.progress;
+}
+
+ir_visitor_status
+lower_subroutine_visitor::visit_leave(ir_call *ir)
+{
+   if (!ir->sub_var)
+      return visit_continue;
+
+   void *mem_ctx = ralloc_parent(ir);
+   ir_if *last_branch = NULL;
+   ir_dereference_variable *return_deref = ir->return_deref;
+
+   for (int s = this->state->num_subroutines - 1; s >= 0; s--) {
+      ir_rvalue *var;
+      ir_constant *lc = new(mem_ctx)ir_constant(s);
+      ir_function *fn = this->state->subroutines[s];
+      bool is_compat = false;
+
+      for (int i = 0; i < fn->num_subroutine_types; i++) {
+         if (ir->sub_var->type->without_array() == fn->subroutine_types[i]) {
+            is_compat = true;
+            break;
+         }
+      }
+      if (is_compat == false)
+         continue;
+
+      if (ir->array_idx != NULL)
+         var = new(mem_ctx) ir_dereference_array(ir->sub_var, ir->array_idx->clone(mem_ctx, NULL));
+      else
+         var = new(mem_ctx) ir_dereference_variable(ir->sub_var);
+
+      ir_function_signature *sub_sig =
+         fn->exact_matching_signature(this->state,
+                                      &ir->actual_parameters);
+
+      ir_call *new_call = new(mem_ctx) ir_call(sub_sig, return_deref, &ir->actual_parameters);
+      if (!last_branch)
+         last_branch = if_tree(equal(subr_to_int(var), lc), new_call);
+      else
+         last_branch = if_tree(equal(subr_to_int(var), lc), new_call, last_branch);
+
+      if (s > 0)
+        return_deref = return_deref->clone(mem_ctx, NULL);
+   }
+   if (last_branch)
+      ir->insert_before(last_branch);
+   ir->remove();
+
+   return visit_continue;
+}