glsl2: Add a pass to convert mod(a, b) to b * fract(a/b).

This is used by the Mesa IR backend to implement mod, fixing glsl-fs-mod.

1 files changed, 89 insertions, 0 deletions

diff --git a/src/glsl/ir_mod_to_fract.cpp b/src/glsl/ir_mod_to_fract.cpp
new file mode 100644
index 00000000000..ec1e65092d9
--- /dev/null
+++ b/src/glsl/ir_mod_to_fract.cpp
@@ -0,0 +1,89 @@
+/*
+ * 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_mod_to_floor.cpp
+ *
+ * Breaks an ir_unop_mod expression down to (op1 * fract(op0 / op1))
+ *
+ * Many GPUs don't have a MOD instruction (945 and 965 included), and
+ * if we have to break it down like this anyway, it gives an
+ * opportunity to do things like constant fold the (1.0 / op1) easily.
+ */
+
+#include "ir.h"
+
+class ir_mod_to_fract_visitor : public ir_hierarchical_visitor {
+public:
+   ir_mod_to_fract_visitor()
+   {
+      this->made_progress = false;
+   }
+
+   ir_visitor_status visit_leave(ir_expression *);
+
+   bool made_progress;
+};
+
+bool
+do_mod_to_fract(exec_list *instructions)
+{
+   ir_mod_to_fract_visitor v;
+
+   visit_list_elements(&v, instructions);
+   return v.made_progress;
+}
+
+ir_visitor_status
+ir_mod_to_fract_visitor::visit_leave(ir_expression *ir)
+{
+   if (ir->operation != ir_binop_mod)
+      return visit_continue;
+
+   ir_variable *temp = new(ir) ir_variable(ir->operands[1]->type, "mod_b");
+   this->base_ir->insert_before(temp);
+
+   ir_assignment *assign;
+   ir_rvalue *expr;
+
+   assign = new(ir) ir_assignment(new(ir) ir_dereference_variable(temp),
+				  ir->operands[1], NULL);
+   this->base_ir->insert_before(assign);
+
+   expr = new(ir) ir_expression(ir_binop_div,
+				ir->operands[0]->type,
+				ir->operands[0],
+				new(ir) ir_dereference_variable(temp));
+
+   expr = new(ir) ir_expression(ir_unop_fract,
+				ir->operands[0]->type,
+				expr,
+				NULL);
+
+   ir->operation = ir_binop_mul;
+   ir->operands[0] = new(ir) ir_dereference_variable(temp);
+   ir->operands[1] = expr;
+   this->made_progress = true;
+
+   return visit_continue;
+}