glsl: Inline builtins in a separate pass

Previously, the ir_call functions for builtin functions were replaced
with the inline implementation immediately after being added to the
instruction list. This patch replaces that with a separate pass that
lowers them after the conversion from AST to IR is complete. This will
be useful to be able to insert some handling for the precision lowering
pass before the inlining. This needs to happen because the precision
of the operations in the inlined implementation depends on the highest
precision of all of the arguments to the call.

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3885>

src/compiler/glsl/lower_builtins.cpp

@@ -0,0 +1,64 @@
+/*
+ * Copyright © 2019 Google, Inc.
+ *
+ * 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_builtins.cpp
+ *
+ * Inline calls to builtin functions.
+ */
+
+#include "ir.h"
+#include "ir_optimization.h"
+
+namespace {
+
+class lower_builtins_visitor : public ir_hierarchical_visitor {
+public:
+   lower_builtins_visitor() : progress(false) { }
+   ir_visitor_status visit_leave(ir_call *);
+   bool progress;
+};
+
+}
+
+bool
+lower_builtins(exec_list *instructions)
+{
+   lower_builtins_visitor v;
+   visit_list_elements(&v, instructions);
+   return v.progress;
+}
+
+ir_visitor_status
+lower_builtins_visitor::visit_leave(ir_call *ir)
+{
+   if (!ir->callee->is_builtin())
+      return visit_continue;
+
+   ir->generate_inline(ir);
+   ir->remove();
+
+   this->progress = true;
+
+   return visit_continue;
+}