glsl2: Add pass for supporting variable vector indexing in rvalues.

The Mesa IR needs this to support vector indexing correctly, and
hardware backends such as 915 would want this behavior as well.

Fixes glsl-vs-vec4-indexing-2.

src/glsl/Makefile

@@ -47,6 +47,7 @@ CXX_SOURCES = \
 	ir_swizzle_swizzle.cpp \
 	ir_validate.cpp \
 	ir_variable.cpp \
+	ir_vec_index_to_cond_assign.cpp \
 	ir_vec_index_to_swizzle.cpp \
 	linker.cpp \
 	s_expression.cpp

src/glsl/ir_optimization.h

@@ -42,4 +42,5 @@ bool do_function_inlining(exec_list *instructions);
 bool do_if_simplification(exec_list *instructions);
 bool do_mod_to_fract(exec_list *instructions);
 bool do_swizzle_swizzle(exec_list *instructions);
+bool do_vec_index_to_cond_assign(exec_list *instructions);
 bool do_vec_index_to_swizzle(exec_list *instructions);

src/glsl/ir_vec_index_to_cond_assign.cpp

@@ -0,0 +1,197 @@
+/*
+ * 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 ir_vec_index_to_cond_assign.cpp
+ *
+ * Turns indexing into vector types to a series of conditional moves
+ * of each channel's swizzle into a temporary.
+ *
+ * Most GPUs don't have a native way to do this operation, and this
+ * works around that.  For drivers using both this pass and
+ * ir_vec_index_to_swizzle, there's a risk that this pass will happen
+ * before sufficient constant folding to find that the array index is
+ * constant.  However, we hope that other optimization passes,
+ * particularly constant folding of assignment conditions and copy
+ * propagation, will result in the same code in the end.
+ */
+
+#include "ir.h"
+#include "ir_visitor.h"
+#include "ir_optimization.h"
+#include "glsl_types.h"
+
+/**
+ * Visitor class for replacing expressions with ir_constant values.
+ */
+
+class ir_vec_index_to_cond_assign_visitor : public ir_hierarchical_visitor {
+public:
+   ir_vec_index_to_cond_assign_visitor()
+   {
+      progress = false;
+   }
+
+   ir_rvalue *convert_vec_index_to_cond_assign(ir_rvalue *val);
+
+   virtual ir_visitor_status visit_enter(ir_expression *);
+   virtual ir_visitor_status visit_enter(ir_swizzle *);
+   virtual ir_visitor_status visit_enter(ir_assignment *);
+   virtual ir_visitor_status visit_enter(ir_return *);
+   virtual ir_visitor_status visit_enter(ir_call *);
+   virtual ir_visitor_status visit_enter(ir_if *);
+
+   bool progress;
+};
+
+ir_rvalue *
+ir_vec_index_to_cond_assign_visitor::convert_vec_index_to_cond_assign(ir_rvalue *ir)
+{
+   ir_dereference_array *orig_deref = ir->as_dereference_array();
+   ir_assignment *assign;
+   ir_variable *index, *var;
+   ir_dereference *deref;
+   ir_expression *condition;
+   ir_swizzle *swizzle;
+   int i;
+
+   if (!orig_deref)
+      return ir;
+
+   if (orig_deref->array->type->is_matrix() ||
+       orig_deref->array->type->is_array())
+      return ir;
+
+   assert(orig_deref->array_index->type->base_type == GLSL_TYPE_INT);
+
+   /* Store the index to a temporary to avoid reusing its tree. */
+   index = new(base_ir) ir_variable(glsl_type::int_type,
+				    "vec_index_tmp_i");
+   base_ir->insert_before(index);
+   deref = new(base_ir) ir_dereference_variable(index);
+   assign = new(base_ir) ir_assignment(deref, orig_deref->array_index, NULL);
+   base_ir->insert_before(assign);
+
+   /* Temporary where we store whichever value we swizzle out. */
+   var = new(base_ir) ir_variable(ir->type, "vec_index_tmp_v");
+   base_ir->insert_before(var);
+
+   /* Generate a conditional move of each vector element to the temp. */
+   for (i = 0; i < orig_deref->array->type->vector_elements; i++) {
+      deref = new(base_ir) ir_dereference_variable(index);
+      condition = new(base_ir) ir_expression(ir_binop_equal,
+					     glsl_type::bool_type,
+					     deref,
+					     new(base_ir) ir_constant(i));
+
+      /* Just clone the rest of the deref chain when trying to get at the
+       * underlying variable.
+       */
+      deref = (ir_dereference *)orig_deref->array->clone(NULL);
+      swizzle = new(base_ir) ir_swizzle(deref, i, 0, 0, 0, 1);
+
+      deref = new(base_ir) ir_dereference_variable(var);
+      assign = new(base_ir) ir_assignment(deref, swizzle, condition);
+      base_ir->insert_before(assign);
+   }
+
+   this->progress = true;
+   return new(base_ir) ir_dereference_variable(var);
+}
+
+ir_visitor_status
+ir_vec_index_to_cond_assign_visitor::visit_enter(ir_expression *ir)
+{
+   unsigned int i;
+
+   for (i = 0; i < ir->get_num_operands(); i++) {
+      ir->operands[i] = convert_vec_index_to_cond_assign(ir->operands[i]);
+   }
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_vec_index_to_cond_assign_visitor::visit_enter(ir_swizzle *ir)
+{
+   /* Can't be hit from normal GLSL, since you can't swizzle a scalar (which
+    * the result of indexing a vector is.  But maybe at some point we'll end up
+    * using swizzling of scalars for vector construction.
+    */
+   ir->val = convert_vec_index_to_cond_assign(ir->val);
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_vec_index_to_cond_assign_visitor::visit_enter(ir_assignment *ir)
+{
+   /* FINISHME: Handle it on the LHS. */
+   ir->rhs = convert_vec_index_to_cond_assign(ir->rhs);
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_vec_index_to_cond_assign_visitor::visit_enter(ir_call *ir)
+{
+   foreach_iter(exec_list_iterator, iter, *ir) {
+      ir_rvalue *param = (ir_rvalue *)iter.get();
+      ir_rvalue *new_param = convert_vec_index_to_cond_assign(param);
+
+      if (new_param != param) {
+	 param->insert_before(new_param);
+	 param->remove();
+      }
+   }
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_vec_index_to_cond_assign_visitor::visit_enter(ir_return *ir)
+{
+   if (ir->value) {
+      ir->value = convert_vec_index_to_cond_assign(ir->value);
+   }
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_vec_index_to_cond_assign_visitor::visit_enter(ir_if *ir)
+{
+   ir->condition = convert_vec_index_to_cond_assign(ir->condition);
+
+   return visit_continue;
+}
+
+bool
+do_vec_index_to_cond_assign(exec_list *instructions)
+{
+   ir_vec_index_to_cond_assign_visitor v;
+
+   visit_list_elements(&v, instructions);
+
+   return v.progress;
+}

src/glsl/main.cpp

@@ -175,6 +175,7 @@ compile_shader(struct gl_shader *shader)
 	 progress = do_constant_variable_unlinked(shader->ir) || progress;
 	 progress = do_constant_folding(shader->ir) || progress;
 	 progress = do_vec_index_to_swizzle(shader->ir) || progress;
+	 progress = do_vec_index_to_cond_assign(shader->ir) || progress;
 	 progress = do_swizzle_swizzle(shader->ir) || progress;
       } while (progress);
    }

src/mesa/shader/ir_to_mesa.cpp

@@ -1821,7 +1821,13 @@ _mesa_glsl_compile_shader(GLcontext *ctx, struct gl_shader *shader)
 	 progress = do_dead_code_unlinked(state, shader->ir) || progress;
 	 progress = do_constant_variable_unlinked(shader->ir) || progress;
 	 progress = do_constant_folding(shader->ir) || progress;
+
 	 progress = do_vec_index_to_swizzle(shader->ir) || progress;
+	 /* Do this one after the previous to let the easier pass handle
+	  * constant vector indexing.
+	  */
+	 progress = do_vec_index_to_cond_assign(shader->ir) || progress;
+
 	 progress = do_swizzle_swizzle(shader->ir) || progress;
       } while (progress);
    }