ir_copy_propagation: New pass to rewrite dereferences to avoid copies.

This is pretty basic.  Right now it only handles pure assignments --
same type on each side, no swizzling, and only within basic blocks.

1 files changed, 136 insertions, 0 deletions

diff --git a/ir_basic_block.cpp b/ir_basic_block.cpp
new file mode 100644
index 0000000000..b10a25c535
--- /dev/null
+++ b/ir_basic_block.cpp
@@ -0,0 +1,136 @@
+/*
+ * 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_basic_block.cpp
+ *
+ * Basic block analysis of instruction streams.
+ */
+
+#include <stdio.h>
+#include "ir.h"
+#include "ir_visitor.h"
+#include "ir_visit_tree.h"
+#include "ir_basic_block.h"
+#include "glsl_types.h"
+
+static void
+has_call_callback(ir_instruction *ir, void *data)
+{
+   bool *has_call = (bool *)data;
+
+   *has_call = *has_call || ir->as_call();
+}
+
+/**
+ * Calls a user function for every basic block in the instruction stream.
+ *
+ * Basic block analysis is pretty easy in our IR thanks to the lack of
+ * unstructured control flow.  We've got:
+ *
+ * ir_loop (for () {}, while () {}, do {} while ())
+ * ir_loop_jump (
+ * ir_if () {}
+ * ir_return
+ * ir_call()
+ *
+ * Note that the basic blocks returned by this don't encompass all
+ * operations performed by the program -- for example, if conditions
+ * don't get returned, nor do the assignments that will be generated
+ * for ir_call parameters.
+ */
+void call_for_basic_blocks(exec_list *instructions,
+			   void (*callback)(ir_instruction *first,
+					    ir_instruction *last))
+{
+   ir_instruction *leader = NULL;
+   ir_instruction *last = NULL;
+
+   foreach_iter(exec_list_iterator, iter, *instructions) {
+      ir_instruction *ir = (ir_instruction *)iter.get();
+      ir_if *ir_if;
+      ir_loop *ir_loop;
+      ir_function *ir_function;
+
+      if (!leader)
+	 leader = ir;
+
+      if ((ir_if = ir->as_if())) {
+	 callback(leader, ir);
+	 leader = NULL;
+
+	 call_for_basic_blocks(&ir_if->then_instructions, callback);
+	 call_for_basic_blocks(&ir_if->else_instructions, callback);
+      } else if ((ir_loop = ir->as_loop())) {
+	 callback(leader, ir);
+	 leader = NULL;
+	 call_for_basic_blocks(&ir_loop->body_instructions, callback);
+      } else if (ir->as_return() || ir->as_call()) {
+	 callback(leader, ir);
+	 leader = NULL;
+      } else if ((ir_function = ir->as_function())) {
+	 /* A function definition doesn't interrupt our basic block
+	  * since execution doesn't go into it.  We should process the
+	  * bodies of its signatures for BBs, though.
+	  *
+	  * Note that we miss an opportunity for producing more
+	  * maximal BBs between the instructions that precede main()
+	  * and the body of main().  Perhaps those instructions ought
+	  * to live inside of main().
+	  */
+	 foreach_iter(exec_list_iterator, fun_iter, *ir_function) {
+	    ir_function_signature *ir_sig;
+
+	    ir_sig = (ir_function_signature *)fun_iter.get();
+
+	    call_for_basic_blocks(&ir_sig->body, callback);
+	 }
+      } else if (ir->as_assignment()) {
+	 bool has_call = false;
+
+	 /* If there's a call in the expression tree being assigned,
+	  * then that ends the BB too.
+	  *
+	  * The assumption is that any consumer of the basic block
+	  * walker is fine with the fact that the call is somewhere in
+	  * the tree even if portions of the tree may be evaluated
+	  * after the call.
+	  *
+	  * A consumer that has an issue with this could not process
+	  * the last instruction of the basic block.  If doing so,
+	  * expression flattener may be useful before using the basic
+	  * block finder to get more maximal basic blocks out.
+	  */
+	 ir_visit_tree(ir, has_call_callback, &has_call);
+
+	 if (has_call) {
+	    callback(leader, ir);
+	    leader = NULL;
+	 }
+      }
+      last = ir;
+   }
+   if (leader) {
+      callback(leader, last);
+   }
+}