glsl2: Add a pass to convert exp and log to exp2 and log2.

Fixes ir_to_mesa handling of unop_log, which used the weird ARB_vp LOG
opcode that doesn't do what we want.  This also lets the multiplication
coefficients in there get constant-folded, possibly.

Fixes:
glsl-fs-log

1 files changed, 85 insertions, 0 deletions

diff --git a/src/glsl/ir_explog_to_explog2.cpp b/src/glsl/ir_explog_to_explog2.cpp
new file mode 100644
index 00000000000..4fe1daaee91
--- /dev/null
+++ b/src/glsl/ir_explog_to_explog2.cpp
@@ -0,0 +1,85 @@
+/*
+ * 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_explog_to_explog2.cpp
+ *
+ * Many GPUs don't have a base e log or exponent instruction, but they
+ * do have base 2 versions, so this pass converts exp and log to exp2
+ * and log2 operations.
+ */
+
+#include <math.h>
+#include "ir.h"
+#include "glsl_types.h"
+
+class ir_explog_to_explog2_visitor : public ir_hierarchical_visitor {
+public:
+   ir_explog_to_explog2_visitor()
+   {
+      this->progress = false;
+   }
+
+   ir_visitor_status visit_leave(ir_expression *);
+
+   bool progress;
+};
+
+bool
+do_explog_to_explog2(exec_list *instructions)
+{
+   ir_explog_to_explog2_visitor v;
+
+   visit_list_elements(&v, instructions);
+   return v.progress;
+}
+
+ir_visitor_status
+ir_explog_to_explog2_visitor::visit_leave(ir_expression *ir)
+{
+   if (ir->operation == ir_unop_exp) {
+      void *mem_ctx = talloc_parent(ir);
+      ir_constant *log2_e = new(mem_ctx) ir_constant(log2f(M_E));
+
+      ir->operation = ir_unop_exp2;
+      ir->operands[0] = new(mem_ctx) ir_expression(ir_binop_mul,
+						   ir->operands[0]->type,
+						   ir->operands[0],
+						   log2_e);
+      this->progress = true;
+   }
+
+   if (ir->operation == ir_unop_log) {
+      void *mem_ctx = talloc_parent(ir);
+
+      ir->operation = ir_binop_mul;
+      ir->operands[0] = new(mem_ctx) ir_expression(ir_unop_log2,
+						   ir->operands[0]->type,
+						   ir->operands[0],
+						   NULL);
+      ir->operands[1] = new(mem_ctx) ir_constant(1.0f / log2f(M_E));
+      this->progress = true;
+   }
+
+   return visit_continue;
+}